Protocol for combined N-of-1 trials to assess cerebellar neurostimulation for movement disorders in children and young adults with dyskinetic cerebral palsy

Background

Movement and tone disorders in children and young adults with cerebral palsy are a great source of disability. Deep brain stimulation (DBS) of basal ganglia targets has a major role in the treatment of isolated dystonias, but its efficacy in dyskinetic cerebral palsy (DCP) is lower, due to structural basal ganglia and thalamic damage and lack of improvement of comorbid choreoathetosis and spasticity. The cerebellum is an attractive target for DBS in DCP since it is frequently spared from hypoxic ischemic damage, it has a significant role in dystonia network models, and small studies have shown promise of dentate stimulation in improving CP-related movement and tone disorders.

Methods

Ten children and young adults with DCP and disabling movement disorders with or without spasticity will undergo bilateral DBS in the dorsal dentate nucleus, with the most distal contact ending in the superior cerebellar peduncle. We will implant Medtronic Percept, a bidirectional neurostimulator that can sense and store brain activity and deliver DBS therapy. The efficacy of cerebellar DBS in improving quality of life and motor outcomes will be tested by a series of N-of-1 clinical trials. Each N-of-1 trial will consist of three blocks, each consisting of one month of effective stimulation and one month of sham stimulation in a random order with weekly motor and quality of life scales as primary and secondary outcomes. In addition, we will characterize abnormal patterns of cerebellar oscillatory activity measured by local field potentials from the intracranial electrodes related to clinical assessments and wearable monitors. Pre- and 12-month postoperative volumetric structural and functional MRI and diffusion tensor imaging will be used to identify candidate imaging markers of baseline disease severity and response to DBS.

Discussion

Our goal is to test a cerebellar neuromodulation therapy that produces meaningful changes in function and well-being for people with CP, obtain a mechanistic understanding of the underlying brain network disorder, and identify physiological and imaging-based predictors of outcomes useful in planning further studies.

Trial registration

ClinicalTrials.gov NCT06122675, first registered November 7, 2023.

Functional Connectivity Differences in Distinct Dentato-Cortical Networks in Alzheimer's Disease and Mild Cognitive Impairment

Recent research has implicated the cerebellum in Alzheimer's disease (AD), and cerebrocerebellar network connectivity is emerging as a possible contributor to symptom severity. The cerebellar dentate nucleus (DN) has parallel motor and non-motor sub-regions that project to motor and frontal regions of the cerebral cortex, respectively. These distinct dentato-cortical networks have been delineated in the non-human primate and human brain. Importantly, cerebellar regions prone to atrophy in AD are functionally connected to atrophied regions of the cerebral cortex, suggesting that dysfunction perhaps occurs at a network level. Investigating functional connectivity (FC) alterations of the DN is a crucial step in understanding the cerebellum in AD and in mild cognitive impairment (MCI). Inclusion of this latter group stands to provide insights into cerebellar contributions prior to diagnosis of AD. The present study investigated FC differences in dorsal (dDN) and ventral (vDN) DN networks in MCI and AD relative to cognitively normal participants (CN) and relationships between FC and behavior. Our results showed patterns indicating both higher and lower functional connectivity in both dDN and vDN in AD compared to CN. However, connectivity in the AD group was lower when compared to MCI. We argue that these findings suggest that the patterns of higher FC in AD may act as a compensatory mechanism. Additionally, we found associations between the individual networks and behavior. There were significant interactions between dDN connectivity and motor symptoms. However, both DN seeds were associated with cognitive task performance. Together, these results indicate that cerebellar DN networks are impacted in AD, and this may impact behavior. In concert with the growing body of literature implicating the cerebellum in AD, our work further underscores the importance of investigations of this region. We speculate that much like in psychiatric diseases such as schizophrenia, cerebellar dysfunction results in negative impacts on thought and the organization therein. Further, this is consistent with recent arguments that the cerebellum provides crucial scaffolding for cognitive function in aging. Together, our findings stand to inform future clinical work in the diagnosis and understanding of this disease.

Paired DBS and TMS Reveals Dentato-Cortical Facilitation Underlying Upper Extremity Movement in Chronic Stroke Survivors

BACKGROUND

Cerebellum shares robust di-synaptic dentato-thalamo-cortical (DTC) connections with the contralateral motor cortex. Preclinical studies have shown that DTC are excitatory in nature. Structural integrity of DTC is associated with better upper extremity (UE) motor function in people with stroke, indicating DTC are important for cerebellar influences on movement. However, there is a lack of understanding of physiologic influence of DTC in humans, largely due to difficulty in accessing the dentate nucleus.

OBJECTIVE

Characterize DTC physiology using dentate nucleus deep brain stimulation (DBS) combined with transcranial magnetic stimulation (TMS) in stroke.

METHODS

Nine chronic stroke survivors with moderate-to-severe UE impairment (Fugl-Meyer 13-38) underwent a paired DBS-TMS experiment before receiving experimental dentate nucleus DBS in our first-in-human phase I trial (Baker et al., 2023, Nature Medicine). Conditioning DBS pulses were given to dentate nucleus 1 to 10 ms prior to supra-threshold TMS pulses given to ipsilesional motor cortex. Effects were assessed on motor evoked potentials (MEPs). Size of DBS-conditioned MEPs was expressed relative to TMS MEPs, where values >1 indicate facilitation.

RESULTS

Dentate nucleus DBS led to facilitation of MEPs at short-latency intervals (3.5 and 5 ms, P = .049 and .021, respectively), a phenomenon we have termed dentato-cortical facilitation (DCF). Higher DCF was observed among patients with more severe UE impairment. Diffusion tensor imaging revealed microstructure of thalamo-cortical portion of DTC was related to higher corticomotor excitability.

CONCLUSIONS

Our in vivo investigation reveals for the first time in humans the intrinsic excitatory properties of DTC, which can serve as a novel therapeutic target for post-stroke motor recovery.

Magnetic resonance imaging features of cerebellar atrophy pattern after epilepsy

OBJECTIVES

Clinically, it has been found that some patients with epilepsy are accompanied by cerebellar atrophy that is inconsistent with symptoms, but the pattern of cerebellar atrophy after epilepsy and the role of cerebellar atrophy in the mechanism of epilepsy have not been elucidated. This study aims to explore the specific pattern of cerebellar atrophy after epilepsy via analyzing magnetic resonance images in patients with postepileptic cerebellar atrophy.

METHODS

A total of 41 patients with epilepsy, who received the treatment in Xiangya Hospital of Central South University from January 2017 to January 2022 and underwent cranial MRI examination, were selected as the case group. The results of cranial MRI examination of all patients showed cerebellar atrophy. In the same period, 41 cases of physical examination were selected as the control group. General clinical data and cranial MRI results of the 2 groups were collected. The maximum area and signal of dentate nucleus, the maximum width of the brachium pontis, the maximum anterior-posterior diameter of the pontine, and the maximum transverse area of the fourth ventricle were compared between the 2 groups. The indexes with difference were further subjected to logistic regression analysis to clarify the characteristic imaging changes in patients with cerebellar atrophy after epilepsy.

RESULTS

Compared with the control group, the maximum width of the brachium pontis and the maximum anterior-posterior diameter of the pontine were decreased significantly, the maximum transverse area of the fourth ventricle was increased significantly in the case group (all P<0.05). The difference in distribution of the low, equal, and high signal in dentate nucleus between the 2 groups was statistically significant (χ2=43.114, P<0.001), and the difference in the maximum area of dentate nucleus between the 2 groups was not significant (P>0.05). The maximum width of the brachium pontis [odds ratio (OR)=3.327, 95% CI 1.454 to 7.615, P=0.004] and the maximum transverse area of the fourth ventricle (OR=0.987, 95% CI 0.979 to 0.995, P=0.002) were independent factors that distinguished cerebellar atrophy after epilepsy from the normal control, while the anterior-posterior diameter of pontine (OR=1.456, 95% CI 0.906 to 2.339, P>0.05) was not an independent factor that distinguished them.

CONCLUSIONS

In MRI imaging, cerebellar atrophy after epilepsy is manifested as significant atrophy of the brachium pontis, significant enlargement of the fourth ventricle, and increased dentate nucleus signaling while insignificant dentate nucleus atrophy. This particular pattern may be associated with seizures and exacerbated pathological processes.

The Entity of Cerebellar Mutism Syndrome: A Narrative Review Centered on the Etiology, Diagnostics, Prevention, and Therapeutic Options

Cerebellar mutism syndrome (CMS), also known as posterior fossa syndrome, is an entity that entails a constellation of signs and symptoms which are recorded in a limited number of pediatric patients who have been operated on mainly for tumors involving the posterior cranial fossa, and more precisely, the region of the vermis. Medulloblastoma seems to constitute the most commonly recognized pathological substrate, associated with this entity. The most prevalent constituents of this syndrome are noted to be a, often transient, although protracted, language impairment, emotional lability, along with cerebellar and brainstem dysfunction. Apart from that, a definite proportion of involved individuals are affected by irreversible neurological defects and long-lasting neurocognitive impairment. A bulk of literature and evidence based on clinical trials exist, which reflect the continuous effort of the scientific community to highlight all perspectives of this complex phenomenon. There are several circumstances that intervene in our effort to delineate the divergent parameters that constitute the spectrum of this syndrome. In summary, this is implicated by the fact that inconsistent nomenclature, poorly defined diagnostic criteria, and uncertainty regarding risk factors and etiology are all constituents of a non-well-investigated syndrome. Currently, a preliminary consensus exists about the identification of a group of diagnostic prerequisites that are managed as sine qua non, in our aim to document the diagnosis of CMS. These include language impairment and emotional lability, as proposed by the international Board of the Posterior Fossa Society in their consensus statement. It is common concept that midline tumor location, diagnosis of medulloblastoma, younger age at diagnosis, and preoperatively established language impairment should be accepted as the most determinant predisposing conditions for the establishment of this syndrome. A well-recognized pathophysiological explanation of CMS includes disruption of the cerebellar outflow tracts, the cerebellar nuclei, and their efferent projections through the superior cerebellar peduncle. Despite the relative advancement that is recorded regarding the diagnostic section of this disease, no corresponding encouraging results are reported, regarding the available treatment options. On the contrary, it is mainly targeted toward the symptomatic relief of the affected individuals. The basic tenet of our review is centered on the presentation of a report that is dedicated to the definition of CMS etiology, diagnosis, risk factors, clinical presentation, and clinical management. Apart from that, an effort is made that attempts to elucidate the paramount priorities of the scientific forum, which are directed toward the expansion our knowledge in the era of diagnostics, prevention, and therapeutic options for patients suffering from CM, or who are at risk for development of this syndrome.

Cortico-Cerebellar Connectivity Underlying Motor Control in Chronic Poststroke Individuals

The robust, reciprocal anatomic connections between the cerebellum and contralateral sensorimotor cerebral hemisphere underscore the strong physiological interdependence between these two regions in relation to human behavior. Previous studies have shown that damage to sensorimotor cortex can result in a lasting reduction of cerebellar metabolism, the magnitude of which has been linked to poor rehabilitative outcomes. A better understanding of movement-related cerebellar physiology as well as cortico-cerebellar coherence (CCC) in the chronic, poststroke state may be key to developing novel neuromodulatory techniques that promote upper limb motor rehabilitation. As a part of the first in-human phase I trial investigating the effects of deep brain stimulation of the cerebellar dentate nucleus (DN) on chronic poststroke motor rehabilitation, we collected invasive recordings from DN and scalp EEG in participants (both sexes) with middle cerebral artery stroke during a visuo-motor tracking task. We investigated the excitability of ipsilesional cortex, DN, and their interaction as a function of motor impairment and performance. Our results indicate the following: (1) event-related oscillations in the ipsilesional cortex and DN were significantly correlated at movement onset in the low beta band, with moderately and severely impaired participants showing desynchronization and synchronization, respectively; and (2) significant CCC was observed during the isometric hold period in the low beta band, which was critical for maintaining task accuracy. Our findings support a strong coupling between ipsilesional cortex and DN in the low beta band during motor control across all impairment levels, which encourages the exploitation of the cerebello-thalamo-cortical pathway as a neuromodulation target to promote rehabilitation.SIGNIFICANCE STATEMENT Cerebral infarct because of stroke can lead to lasting reduction in cerebellar metabolism, resulting in poor rehabilitative outcomes. Thorough investigation of the cerebellar electrophysiology, as well as cortico-cerebellar connectivity in humans that could provide key insights to facilitate the development of novel neuromodulatory technologies, has been lacking. As a part of the first in-human phase I trial investigating deep brain stimulation of the cerebellar dentate nucleus (DN) for chronic, poststroke motor rehabilitation, we collected invasive recordings from DN and scalp EEG while stroke survivors performed a motor task. Our data indicate strong coupling between ipsilesional sensorimotor cortex and DN in the low beta band across all impairment levels encouraging the exploration of electrical stimulation of the DN.

Baseline Cerebro-Cerebellar Functional Connectivity in Afferent and Efferent Pathways Reveal Dissociable Improvements in Visuomotor Learning

Visuomotor coordination is a complex process involving several brain regions, primarily the cerebellum and motor cortex. Studies have shown inconsistent resting-state functional magnetic resonance imaging (rsfMRI) results in the cerebellar cortex and dentate nucleus of the cerebro-cerebellar connections. Echoing anatomical pathways, these two different cerebellar regions are differentially responsible for afferent and efferent cerebro-cerebellar functional connections. The aim of this study was to measure the baseline resting-state functional connectivity of different cerebellar afferent and efferent pathways and to investigate their relationship to visuomotor learning abilities. We used different cerebellar repetitive transcranial magnetic stimulation (rTMS) frequencies before a pursuit rotor task to influence visuomotor performance. Thirty-eight right-handed participants were included and randomly assigned to three different rTMS frequency groups (1 Hz, 10 Hz and sham) and underwent baseline rsfMRI and pursuit rotor task assessments. We report that greater baseline functional connectivity in the afferent cerebro-cerebellar pathways was associated with greater accuracy improvements. Interestingly, lower baseline functional connectivity in the efferent dentato-thalamo-cortical pathways was associated with greater stability in visuomotor performance, possibly associated with the inhibitory role of the dentate nucleus and caused a reduction in the efferent functional connectivity. The functional dissociation of the cerebellar cortex and dentate nucleus and their connections, suggests that distinct mechanisms in the cerebellum regarding visuomotor learning, which should be investigated in future research.

VTA-projecting cerebellar neurons mediate stress-dependent depression-like behaviors

Although cerebellar alterations have been implicated in stress symptoms, the exact contribution of the cerebellum to stress symptoms remains to be elucidated. Here, we demonstrated the crucial role of cerebellar neurons projecting to the ventral tegmental area (VTA) in the development of chronic stress-induced behavioral alterations in mice. Chronic chemogenetic activation of inhibitory Purkinje cells in crus I suppressed c-Fos expression in the DN and an increase in immobility in the tail suspension test or forced swimming test, which were triggered by chronic stress application. The combination of adeno-associated virus-based circuit mapping and electrophysiological recording identified network connections from crus I to the VTA via the dentate nucleus (DN) of the deep cerebellar nuclei. Furthermore, chronic inhibition of specific neurons in the DN that project to the VTA prevented stressed mice from showing such depression-like behavior, whereas chronic activation of these neurons alone triggered behavioral changes that were comparable with the depression-like behaviors triggered by chronic stress application. Our results indicate that the VTA-projecting cerebellar neurons proactively regulate the development of depression-like behavior, raising the possibility that cerebellum may be an effective target for the prevention of depressive disorders in human.

Apoptosis in the Dentate Nucleus Following Kindling-induced Seizures in Rats

BACKGROUND

Epilepsy is a common neurological disorder characterized by abnormal and recurrent neuronal discharges that result in epileptic seizures. The dentate nuclei of the cerebellum receive excitatory input from different brain regions. Purkinje cell loss due to chronic seizures could lead to decreased inhibition of these excitatory neurons, resulting in the activation of apoptotic cascades in the dentate nucleus.

OBJECTIVE

The present study was designed to determine whether there is a presence of apoptosis (either intrinsic or extrinsic) in the dentate nucleus, the final relay of the cerebellar circuit, following kindling-induced seizures.

METHODS

In order to determine this, seizures were triggered via the amygdaloid kindling model. Following 0, 15, or 45 stimuli, rats were sacrificed, and the cerebellum was extracted. It was posteriorly prepared for the immunohistochemical analysis with cell death biomarkers: TUNEL, Bcl-2, truncated Bid (tBid), Bax, cytochrome C, and cleaved caspase 3 (active form). Our findings reproduce results obtained in other parts of the cerebellum.

RESULTS

We found a decrease of Bcl-2 expression, an anti-apoptotic protein, in the dentate nucleus of kindled rats. We also determined the presence of TUNEL-positive neurons, which confirms the presence of apoptosis in the dentate nucleus. We observed the expression of tBid, Bax, as well as cytochrome C and cleaved caspase-3, the main executor caspase of apoptosis.

CONCLUSION

There is a clear activation of both the intrinsic and extrinsic apoptotic pathways in the cells of the dentate nucleus of the cerebellum of rats subjected to amygdaloid kindling.

Ornidazole-Induced Recurrent Encephalopathy in a Chinese Man: A Rare Case Report and Literature Review

Ornidazole-induced encephalopathy (OIE) is seldom seen in the clinic. In this study, we report a new case of a patient who had taken 1,000 mg ornidazole daily for nearly 4 years because of suspected diarrhea and proctitis and presented with subacute symptoms such as unsteady gait, slurred speech, and psychiatric disorder. These symptoms were significantly relieved 3 days after the patient stopped taking ornidazole. When he took this medicine again, however, similar symptoms occurred 4 months later, which were again reduced after 4 days of drug discontinuation. After the second onset, abnormal signals were identified around the aqueduct of the midbrain, around the fourth ventricle, and in the dentate nuclei of the cerebellum bilaterally. After 9 days of drug discontinuation, lesions disappeared in the magnetic resonance imaging (MRI) results. According to the clinical manifestations, imaging features, and the reduced symptoms after drug withdrawal, we clinically diagnosed the patient with OIE. This paper also reviews the literature on OIE. Only five cases (including our case) have been reported, all of whom presented with cerebellar ataxia and dysarthria and three with additional mental symptoms such as agitation and irritability. All five patients had abnormal lesions in the dentate nucleus of the cerebellum bilaterally, among whom four also had lesions in the corpus callosum and three around the periaqueduct of the midbrain. After withdrawal of ornidazole, the symptoms in all patients vanished or were alleviated, and three of them showed reduced or disappeared lesions in a head MRI reexamination. Overall, OIE has rarely been reported. Our case report and literature review show that the lesions in the cerebellum, corpus callosum, and brainstem can be reversed. The main manifestations of the lesions—cerebellar ataxia, dysarthria, and mental symptoms—quickly weaken or disappear after drug withdrawal, with good prognosis. Nevertheless, clear pathogenesis has yet to be further investigated.

An autopsy case of corticobasal degeneration with inferior olivary hypertrophy

We report autopsy results of a female patient who was confirmed pathologically as having corticobasal degeneration (CBD). This patient presented with progressive gait disturbance at the age of 66 years, and subsequently showed parkinsonism with a right-sided predominance and dementia. She was clinically diagnosed as having possible corticobasal syndrome without palatal myoclonus throughout the disease course. An autopsy at 72 years of age revealed that neuronal loss with gliosis was severe in the substantia nigra and the portion from hippocampal cornu ammonis (CA1) region to the parahippocampal gyrus, and mild-to-moderate in the basal ganglia, thalamus, red nucleus, dentate nucleus, and cerebral cortices, predominantly in the frontal lobe. Myelin pallor was observed in the pyramidal tract of the brainstem and central tegmental tract. Neurodegenerative or axonal degenerative findings were observed predominantly on the left side, except for the dentate nucleus, which was more affected on the right side. The inferior olivary nucleus exhibited hypertrophic degeneration predominantly on the left side. The topography of neurodegeneration was likely to correspond to the dentate nucleus and inferior olivary nucleus. Phosphorylated tau-immunoreactive pretangles, neurofibrillary tangles, coiled bodies, and threads were diffusely observed in the whole brain. The distribution of tau deposits was prominent in the deeper affected lesions of the dentate nucleus and inferior olivary nucleus. Inferior olivary hypertrophy is unusual in patients with CBD. It is highly possible that the neurodegeneration of the inferior olivary nucleus followed that of the dentate nucleus in our patient. Moreover, these results indicate not only the severity of neurodegenerative changes, but also that of tau deposition that could be related to the topography of the projections of the dentato-olivary pathway. Tau propagation and subsequent neurodegeneration along the fiber connections may have occurred. Our results support the possibility that progression of CBD lesions can be mediated by tau propagation.

Case Report: Deep Cerebellar Stimulation for Tremor and Dystonia

Background: The cerebellum plays an important role in the pathogenesis and pathophysiology of movement disorders, including tremor and dystonia. To date, there have been few reports on deep cerebellar stimulation.

Case Report: The patient was a 35-year-old previously healthy man with no history of movement disorders. He developed a tremor and stiffness in his left hand at the age of 27 years, which was diagnosed as a dystonic tremor. We performed right thalamotomy, which resulted in a complete resolution of the tremor; however, the dystonia persisted. Subsequently, the patient developed left foot dystonia with inversion and a newly developed tremor in the right hand and foot. The patient underwent left ventralis intermedius (VIM) deep brain stimulation (VIM-DBS) and left pallidothalamic tract DBS (PTT-DBS). Left VIM-DBS completely resolved the right hand and foot tremor, and PTT-DBS significantly improved the left hand and foot dystonia. Three months postoperatively, the patient developed an infection and wound disruption at the surgical site. We performed palliative surgery for deep cerebellar stimulation via the posterior cranial region, which was not infected. The surgery was performed under general anesthesia with the patient lying in the prone position. Eight contact DBS electrodes were used. The placement of electrodes extended from the superior cerebellar peduncle to the dentate nucleus. Both the right hand and foot tremor improved with right cerebellar stimulation. Further, both the left hand and foot dystonia improved with left cerebellar stimulation. Right and left cerebellar stimulation led to no improvement in the left hand and foot dystonia and right hand and foot tremor, respectively. Stimulation-induced complications observed in the patient included dizziness, dysphagia, and dysarthria. After the surgery, the patient developed hypersalivation and hyperhidrosis in the left side of the body, both of which did not improve with adjustments of stimulation parameters. At the 6-month follow-up, the tremor and dystonia had almost completely resolved.

Conclusion: Deep cerebellar stimulation deserves consideration as a potential treatment for tremor and dystonia.

The clinical and imaging features of cerebrotendinous xanthomatosis: A case report and review of the literature

RATIONALE

Cerebrotendinous xanthomatosis (CTX) is a rare autosomal recessive lipid deposition disorder characterized by systemic signs and neurological dysfunction. The radiological features of CTX are infrequently summarized in the literature.

PATIENT CONCERNS

We described a 40-year-old male patient who repeatedly engaged in wrestling matches and presented with progressive difficulty in walking and reduced balance with egg-sized, hard, smooth, and painless masses in both ankles.

DIAGNOSIS

Neuroimaging examination showed abnormalities both supra- and infratentorially. Bilateral ankle joint magnetic resonance imaging showed bilateral xanthomata of the Achilles tendon. The diagnosis was confirmed by the detection of a sterol 27-hydroxylase gene mutation.

INTERVENTIONS

The patient was treated with chenodeoxycholic acid (250 mg 3 times per day).

OUTCOMES

To date, the patient's bilateral xanthomas of the Achilles tendon have begun to diminish, and his neurological impairment has not deteriorated further but has not yet improved.

LESSONS

We report a rare case of CTX and summarize the clinical and imaging features of this disease. Our findings suggest that the abnormal signals in the dentate nucleus or a long spinal cord lesion involving the central and posterior cord, combined with tendon xanthoma, are important clues for the diagnosis of CTX.

Automated workflow for volumetric assessment of signal intensity ratio on T1-weighted MR images after multiple gadolinium administrations

Purpose: Repeated injections of linear gadolinium-based contrast agent (GBCA) have shown correlations with increased signal intensities (SI) on unenhanced T1-weighted (T1w) images. Assessment is usually performed manually on a single slice and the SI as an average of a freehand region-of-interest is reported. We aim to develop a fully automated software that segments and computes SI ratio of dentate nucleus (DN) to pons (DN/P) and globus pallidus (GP) to thalamus (GP/T) for the assessment of gadolinium presence in the brain after a serial GBCA administrations. Approach: All patients ( N = 113 ) underwent at least eight GBCA enhanced scans. The modal SI in the DN, GP, pons, and thalamus were measured volumetrically on unenhanced T1w images and corrected based on the reference protocol (measurement 1) and compared to the SI-uncorrected-modal-volume (measurement 2), SI-corrected-mean-volume (measurement 3), as well as SI-corrected-modal-single slice (measurement 4) approaches. Results: Automatic processing worked on all 2119 studies (1150 at 1.5 T and 969 at 3 T). DN/P were 1.085 ± 0.048 (1.5 T) and 0.979 ± 0.061 (3 T). GP/T were 1.084 ± 0.039 (1.5 T) and 1.069 ± 0.042 (3 T). Modal DN/P ratios from volumetric assessment at 1.5 T failed to show a statistical difference with or without SI corrections ( p = 0.71 ). All other t -tests demonstrated significant differences (measurement 2, 3, 4 compared to 1, p < 0.001 ). Conclusion: The fully automatic method is an effective powerful tool to streamline the analysis of SI ratios in the deep brain tissues. Divergent SI ratios using different approaches reinforces the need to standardize the measurement for the research in this field.

The switch from Gd-DTPA to Gd-DOTA is not associated with decrease of the T1 signal intensity of the pallidus and dentate in a pediatric population

BACKGROUND

The switch from the linear gadolinium-based contrast agent (GBCA) gadopentate dimeglumine (Gd_DTPA) to the macrocyclic GBCA gadobutrol is associated with a decrease of the T1 signal intensity (SI) in brain gray matter nuclei. The effects of the switch to other macrocyclic GBCAs are not yet established.

PURPOSE

To explore the effects of switching from Gd-DTPA to the macrocyclic GBCA gadoterate meglumine (Gd-DOTA) in pediatric patients.

MATERIAL AND METHODS

We measured the pallidus/middle cerebellar peduncle (MCP) SI ratio and the dentate/MCP SI ratio in pre-contrast sagittal T1-weighted spin-echo images in nine patients who had received ≥6 administrations of Gd-DTPA and then of Gd-DOTA, in 18 patients who had received ≥6 administrations of Gd-DOTA alone, and in nine age-matched controls without prior GBCA administrations. Serial assessment was performed in patients who switched from Gd-DTPA to Gd-DOTA. Finally, the rate of change of pallidal/MCP and dentate/MCP SI ratios between the first and last Gd-DOTA administrations was compared.

RESULTS

The pallidal/MCP and dentate/MCP SI ratios were (P < 0.05) higher in patients with prior Gd-DTPA and Gd-DOTA administrations compared to the controls. After the switch, the pallidal/MCP SI ratio increased in nine patients and the dentate/MCP ratio in seven patients. The rate of change of pallidal/MCP SI ratio after Gd-DOTA was higher (P < 0.01) in patients who had previously received Gd-DTPA (mean 2.89 ± 2.6%) than in patients who had received Gd-DOTA alone (mean 0.53 ± 0.89%).

CONCLUSION

T1 SI in gray matter nuclei does not decrease after switching from Gd-DTPA to Gd-DOTA. The switch effects from Gd-DTPA to each macrocyclic GBCA should be individually evaluated.

The Understanding of Pediatric Akinetic Mutism

Pediatric akinetic mutism syndrome is a clinical disease resulting from cerebellar injury and characterized by the absence of speech or reduced speech, emotional lability, there may also be hypotonia, oropharyngeal dysfunction/dysphagia, bladder and intestinal incontinence, or other behavioral disorders and neurological signals. It is described as the most recurrent complication in children, after posterior fossa tumor surgery, mainly related to cerebellar midline injuries. An increasing number of research and prospective reviews have provided valuable information on cerebellar mutism syndrome in recent years. The purpose of this review was to elucidate the pathophysiological basis and the predictive factors for this syndrome. Most cases of mutism are due to injury cerebellar tracts and cerebellar-cerebral circuits, involving particularly distinct points of the dentate-thalamus-cortical and dentato-rubro-thalamus-cortical. Advanced neuroimaging techniques, such as tractography and perfusion studies, have contributed to demonstrating changes in these pathways in patients with pediatric cerebellar mutism.

Effect of at Least 10 Serial Gadobutrol Administrations on Brain Signal Intensity Ratios on T1-Weighted MRI in Children: A Matched Case-Control Study

BACKGROUND. An association is recognized between linear gadolinium-based contrast agents (GBCAs) and intracranial gadolinium retention in children. The relation between macrocyclic GBCAs and gadolinium retention remains incompletely understood. OBJECTIVE. The purpose of this study was to assess whether 10 or more administrations of the macrocyclic GBCA gadobutrol are associated with increased signal intensity (SI) in the dentate nucleus (DN) and globus pallidus (GP) on unenhanced T1-weighted MRI of children and to explore clinical variables potentially associated with T1 hyperintensity. METHODS. The case group consisted of 25 children (13 boys, 12 girls; mean age, 7 ± 4 years; range, 2-18 years) who underwent at least 10 (mean, 15 ± 6; range, 10-34) contrast-enhanced MRI examinations exclusively with gadobutrol. The control group consisted of 25 age- and sex-matched patients undergoing MRI who had never been exposed to gadolinium. Two observers in consensus using a 3-point scale assessed visual T1 hyperintensity in the DN and GP. One observer placed ROIs on T1-weighted images to mark the DN, GP, middle cerebellar peduncle (MCP), and pulvinar of the thalamus bilaterally to compute mean DN-to-MCP and GP-to-thalamus SI ratios. SI ratios were compared between the macrocyclic GBCA and control groups. In the macrocyclic GBCA group, Pearson correlation analysis was conducted between SI ratios and clinical variables. ROI measurements were repeated by the original reader and an independent reader, and interobserver and intraobserver agreement were computed by means of Lin concordance correlation coefficient (ρ_c). RESULTS. No patient had visual T1 hyperintensity in the DN or GP. No significant difference between the macrocyclic GBCA and control groups was observed for DN-to-MCP SI ratio (0.95 ± 0.05 vs 0.95 ± 0.03; p = .67) or GP-to-thalamus SI ratio (1.05 ± 0.06 vs 1.04 ± 0.06; p = .65). In the macrocyclic GBCA group, no significant correlation was observed between DN-to-MCP SI ratio or GP-to-thalamus SI ratio and age (r = 0.355, p = .08; r = 0.167, p = .42), number of contrast-enhanced MRI examinations (r = 0.247, p = .23; r = 0.203, p = .33), mean time between examinations (r = 0.193, p = .36; r = 0.047, p = .82), or cumulative macrocyclic GBCA dose (r = 0.434, p = .07; r = 0.270, p = .19). Interobserver and intraobserver agreement was substantial for DN-to-MCP SI and GP-to-TH SI ratios (ρ_c = 0.931-0.974). CONCLUSION. Ten or more serial gadobutrol administrations were not associated with T1 hyperintensity in the DN or GP of children. CLINICAL IMPACT. Selection of gadobutrol as an MRI contrast agent may reduce risk of gadolinium retention in children. The findings may help guide practices for GBCA administration to children.

Intrinsic Functional Connectivity of Dentate Nuclei in Autism Spectrum Disorder

Cerebellar abnormalities are commonly reported in autism spectrum disorder (ASD). Dentate nuclei (DNs) are key structures in the anatomical circuits linking the cerebellum to the extracerebellum. Previous resting-state functional connectivity (RsFc) analyses reported DN abnormalities in high-functioning ASD (HF-ASD). This study examined the RsFc of the DN in young adults with HF-ASD compared with healthy controls (HCs) with the aim to expand upon previous findings of DNs in a dataset using advanced, imaging acquisition methods that optimize spatiotemporal resolution and statistical power. Additional seed-to-voxel analyses were carried out using motor and nonmotor DN coordinates reported in previous studies as seeds. We report abnormal dentato-cerebral and dentato-cerebellar functional connectivity in ASD. Our results expand and, in part, replicate previous descriptions of DN RsFc abnormalities in this disorder and reveal correlations between DN-cerebral RsFc and ASD symptom severity.

Cerebellar Neuromodulation for Stroke

Purpose of Review

This paper reviews the current preclinical and clinical evidence for cerebellar deep brain stimulation for stroke rehabilitation.

Recent Findings

We have demonstrated the effectiveness of cerebellar stimulation for stroke rehabilitation in rodent models, which has been reproduced by other groups. Synaptogenesis, neurogenesis, and vicariation of function in the perilesional cortex likely contribute to the mechanistic underpinnings of the effectiveness of this therapy. A Phase I clinical trial investigating dentate nucleus stimulation for improvement of hemiparesis due to stroke is currently underway, and results thus far are encouraging.

Summary

Activation of the rodent cerebellar dentate nucleus promotes functional motor recovery following stroke. Although results of a Phase I clinical trial are pending, substantial preclinical evidence indicates that deep brain stimulation of the dentate nucleus is a promising therapeutic modality.

Deep Cerebellar Transcranial Direct Current Stimulation of the Dentate Nucleus to Facilitate Standing Balance in Chronic Stroke Survivors-A Pilot Study

Objective: Cerebrovascular accidents are the second leading cause of death and the third leading cause of disability worldwide. We hypothesized that cerebellar transcranial direct current stimulation (ctDCS) of the dentate nuclei and the lower-limb representations in the cerebellum can improve functional reach during standing balance in chronic (>6 months’ post-stroke) stroke survivors. Materials and Methods: Magnetic resonance imaging (MRI) based subject-specific electric field was computed across a convenience sample of 10 male chronic (>6 months) stroke survivors and one healthy MRI template to find an optimal bipolar bilateral ctDCS montage to target dentate nuclei and lower-limb representations (lobules VII–IX). Then, in a repeated-measure crossover study on a subset of 5 stroke survivors, we compared 15 min of 2 mA ctDCS based on the effects on successful functional reach (%) during standing balance task. Three-way ANOVA investigated the factors of interest– brain regions, montages, stroke participants, and their interactions. Results: “One-size-fits-all” bipolar ctDCS montage for the clinical study was found to be PO9h–PO10h for dentate nuclei and Exx7–Exx8 for lobules VII–IX with the contralesional anode. PO9h–PO10h ctDCS performed significantly (alpha = 0.05) better in facilitating successful functional reach (%) when compared to Exx7–Exx8 ctDCS. Furthermore, a linear relationship between successful functional reach (%) and electric field strength was found where PO9h–PO10h montage resulted in a significantly (alpha = 0.05) higher electric field strength when compared to Exx7–Exx8 montage for the same 2 mA current. Conclusion: We presented a rational neuroimaging based approach to optimize deep ctDCS of the dentate nuclei and lower limb representations in the cerebellum for post-stroke balance rehabilitation. However, this promising pilot study was limited by “one-size-fits-all” bipolar ctDCS montage as well as a small sample size.

Using deep learning for a diffusion-based segmentation of the dentate nucleus and its benefits over atlas-based methods

The dentate nucleus (DN) is a gray matter structure deep in the cerebellum involved in motor coordination, sensory input integration, executive planning, language, and visuospatial function. The DN is an emerging biomarker of disease, informing studies that advance pathophysiologic understanding of neurodegenerative and related disorders. The main challenge in defining the DN radiologically is that, like many deep gray matter structures, it has poor contrast in T1-weighted magnetic resonance (MR) images and therefore requires specialized MR acquisitions for visualization. Manual tracing of the DN across multiple acquisitions is resource-intensive and does not scale well to large datasets. We describe a technique that automatically segments the DN using deep learning (DL) on common imaging sequences, such as T1-weighted, T2-weighted, and diffusion MR imaging. We trained a DL algorithm that can automatically delineate the DN and provide an estimate of its volume. The automatic segmentation achieved higher agreement to the manual labels compared to template registration, which is the current common practice in DN segmentation or multiatlas segmentation of manual labels. Across all sequences, the FA maps achieved the highest mean Dice similarity coefficient (DSC) of 0.83 compared to T1 imaging ( DSC = 0.76 ), T2 imaging ( DSC = 0.79 ), or a multisequence approach ( DSC = 0.80 ). A single atlas registration approach using the spatially unbiased atlas template of the cerebellum and brainstem template achieved a DSC of 0.23, and multi-atlas segmentation achieved a DSC of 0.33. Overall, we propose a method of delineating the DN on clinical imaging that can reproduce manual labels with higher accuracy than current atlas-based tools.

Cerebrotendinous xanthomatosis - A case report

Cerebrotendinous xanthomatosis (CTX) is a rare autosomal recessive disorder resulting from a defective enzyme in bile acid synthesis pathway leading to neurological, ocular, vascular, and musculoskeletal symptoms from deposition of cholestanol and cholesterol in these tissues. We present clinical and imaging features of a 32-year-old female who presented with mental retardation, gait instability and swelling along posterior aspect of both ankles. Imaging studies were performed which revealed spectrum of CTX findings in brain and tendons. Subsequently the diagnosis was confirmed by biopsy and laboratory tests.

Do the Dento-Thalamic Connections of Genetic Absence Epilepsy Rats from Strasbourg Differ from Those of Control Wistar Rats?

The thalamo-cortical circuit is important in the genesis of absence epilepsy. This circuit can be influenced by connecting pathways from various parts of central nervous system. The aim of the present study is to define the dento-thalamic connections in Wistar animals and compare the results with genetic absence epilepsy rats from Strasbourg (GAERS) using the biotinylated dextran amine (BDA) tracer. We injected BDA into the dentate nucleus of 13 (n = 6 Wistar and n = 7 GAERS) animals. The dento-thalamic connections in the Wistar animals were denser and were connected to a wider range of thalamic nuclei compared with GAERS. The dentate nucleus was bilaterally connected to the central (central medial [CM], paracentral [PC]), ventral (ventral medial [VM], ventral lateral [VL], and ventral posterior lateral [VPL]), and posterior (Po) thalamic nuclei in Wistar animals. The majority of these connections were dense contralaterally and scarce ipsilaterally. Contralateral connections were present with the parafascicular (PF), ventral posterior medial, ventral anterior (VA), and central lateral (CL) thalamic nuclei in Wistar animals. Whereas in GAERS, bilateral connections were observed with the VL and CM. Contralateral connections were present with the PC, VM, VA, and PF thalamic nuclei in GAERS. The CL, VPL, and Po thalamic nucleus connections were not observed in GAERS. The present study showed weak/deficit dento-thalamic connections in GAERS compared with control Wistar animals. The scarce information flow from the dentate nucleus to thalamus in GAERS may have a deficient modulatory role on the thalamus and thus may affect modulation of the thalamo-cortical circuit.

Entrained neuronal activity to periodic visual stimuli in the primate striatum compared with the cerebellum

Rhythmic events recruit neuronal activity in the basal ganglia and cerebellum, but their roles remain elusive. In monkeys attempting to detect a single omission of isochronous visual stimulus, we found that neurons in the caudate nucleus showed increased activity for each stimulus in sequence, while those in the cerebellar dentate nucleus showed decreased activity. Firing modulation in the majority of caudate neurons and all cerebellar neurons was proportional to the stimulus interval, but a quarter of caudate neurons displayed a clear duration tuning. Furthermore, the time course of population activity in the cerebellum well predicted stimulus timing, whereas that in the caudate reflected stochastic variation of response latency. Electrical stimulation to the respective recording sites confirmed a causal role in the detection of stimulus omission. These results suggest that striatal neurons might represent periodic response preparation while cerebellar nuclear neurons may play a role in temporal prediction of periodic events.

Role of cerebellar GABAergic dysfunctions in the origins of essential tremor

Essential tremor (ET) is among the most prevalent movement disorders, but its origins are elusive. The inferior olivary nucleus (ION) has been hypothesized as the prime generator of tremor because of the pacemaker properties of ION neurons, but structural and functional changes in ION are unlikely under ET. Abnormalities have instead been reported in the cerebello-thalamo-cortical network, including dysfunctions of the GABAergic projections from the cerebellar cortex to the dentate nucleus. It remains unclear, though, how tremor would relate to a dysfunction of cerebellar connectivity. To address this question, we built a computational model of the cortico-cerebello-thalamo-cortical loop. We simulated the effects of a progressive loss of GABA_A α₁-receptor subunits and up-regulation of α_2/3-receptor subunits in the dentate nucleus, and correspondingly, we studied the evolution of the firing patterns along the loop. The model closely reproduced experimental evidence for each structure in the loop. It showed that an alteration of amplitudes and decay times of the GABAergic currents to the dentate nucleus can facilitate sustained oscillatory activity at tremor frequency throughout the network as well as a robust bursting activity in the thalamus, which is consistent with observations of thalamic tremor cells in ET patients. Tremor-related oscillations initiated in small neural populations and spread to a larger network as the synaptic dysfunction increased, while thalamic high-frequency stimulation suppressed tremor-related activity in thalamus but increased the oscillation frequency in the olivocerebellar loop. These results suggest a mechanism for tremor generation under cerebellar dysfunction, which may explain the origin of ET.

Impact of nasopharyngeal irradiation and gadolinium administration on changes in T1 signal intensity of the dentate nucleus in nasopharyngeal malignancy patients without intracranial abnormalities

BACKGROUND

Irradiation has been found to increase T₁ signal intensity (SI) of the dentate nucleus (DN) by accelerating the gadolinium deposition in patients after multiple gadolinium-based contrast agent (GBCA) administrations. Several reports have focused on this phenomenon in patients with brain tumors; however, data in patients receiving irradiation with no intracranial abnormalities (NIAs) are lacking.

PURPOSE

To explore how nasopharyngeal irradiation affected SI changes on unenhanced T₁ -weighted imaging (T₁ WI) in the DN in nasopharyngeal malignancy (NPM) patients who presented with NIAs and who had multiple injection doses (IDs) of linear GBCAs.

STUDY TYPE

Single-center, retrospective, case-control study.

POPULATION

In all, 132 subjects: 66 NPM patients, 66 matched controls.

FIELD STRENGTH/SEQUENCE

1.5T and 3T/T₁ WI, T₂ WI, and fluid-attenuated inversion recovery (FLAIR).

ASSESSMENT

Radiation doses (RDs) were calculated by a radiotherapy technician. SIs were measured by a radiologist. The DN-to-cerebellar white matter (CWM) SI ratios and their relative percentage change (R_change ) were compared.

STATISTICAL TESTS

Shapiro-Wilk test, paired t-test, independent t-test, Mann-Whitney U-test, Pearson and Spearman correlation.

RESULTS

DN/CWM _b ratios or R _change from the NPM group were significantly higher than those from the control group (P < 0.001). No significant difference of DN/CWM _a ratios was found between the two groups (P > 0.05). Positive correlations between R _change , DN/CWM _b ratio, and the number of IDs were found in both the NPM and control groups (P < 0.01). The overall changes of DN/CWM _b ratio or R _change between NPM and control groups were higher for the higher-IDs subgroup (≥10) than for the lower-IDs subgroup (<10).

DATA CONCLUSION

Nasopharyngeal irradiation appeared to increase SI in T₁ WI in NPM patients with NIAs and repeated GBCA administrations relative to control patients who also underwent GBCA administrations, especially when IDs ≥10. However, no significant association between R _change and RDs to the DNs was found.

LEVEL OF EVIDENCE

3 Technical Efficacy: Stage 2 J. Magn. Reson. Imaging 2020;51:250-259.

The striking effects of deep cerebellar stimulation on generalized fixed dystonia: case report

Cerebellar neuromodulation could influence the pathological abnormalities of movement disorders through several connections between the cerebellum and the basal ganglia or other cortices. In the present report, the authors demonstrate the effects of cerebellar deep brain stimulation (DBS) on a patient with severe generalized fixed dystonia (FD) that was refractory to bilateral pallidotomy and intrathecal baclofen therapy. A previously healthy 16-year-old girl presented with generalized FD. Bilateral pallidotomy and intrathecal baclofen therapy had failed to resolve her condition, following which she received DBS through the bilateral superior cerebellar peduncle (SCP) and dentate nucleus (DN). Ipsilateral stimulation of the SCP or DN improved the FD, and the ability of DBS administered via the SCP to relax muscles was better than that of DN DBS. A considerable improvement of generalized FD, from a bedridden state to a wheelchair-bound state, was observed in the patient following 6 months of chronic bilateral DBS via the SCP; moreover, the patient was able to move her arms and legs. The findings in the present case suggest that neuromodulation of deep cerebellar structures is a promising treatment for FD that is refractory to conventional treatments.

Longitudinal evaluation of iron concentration and atrophy in the dentate nuclei in friedreich ataxia

BACKGROUND

Friedreich ataxia is a recessively inherited, progressive neurological disease characterized by impaired mitochondrial iron metabolism. The dentate nuclei of the cerebellum are characteristic sites of neurodegeneration in the disease, but little is known of the longitudinal progression of abnormalities in these structures.

METHODS

Using in vivo magnetic resonance imaging, including quantitative susceptibility mapping, we investigated changes in iron concentration and volume in the dentate nuclei in individuals with Friedreich ataxia (n = 20) and healthy controls (n = 18) over a 2-year period.

RESULTS

The longitudinal rate of iron concentration was significantly elevated bilaterally in participants with Friedreich ataxia relative to healthy controls. Atrophy rates did not differ significantly between groups. Change in iron concentration and atrophy both correlated with baseline disease severity or duration, indicating sensitivity of these measures to disease stage. Specifically, atrophy was maximal in individuals early in the disease course, whereas the rate of iron concentration increased with disease progression.

CONCLUSIONS

Progressive dentate nucleus abnormalities are evident in vivo in Friedreich ataxia, and the rates of change of iron concentration and atrophy in these structures are sensitive to the disease stage. The findings are consistent with an increased rate of iron concentration and atrophy early in the disease, followed by iron accumulation and stable volume in later stages. This pattern suggests that iron dysregulation persists after loss of the vulnerable neurons in the dentate. The significant changes observed over a 2-year period highlight the utility of quantitative susceptibility mapping as a longitudinal biomarker and staging tool. © 2019 International Parkinson and Movement Disorder Society.

Progressive T1 Shortening of the Dentate Nucleus in Patients With Multiple Sclerosis: Result of Multiple Administrations of Linear Gadolinium Contrast Agents Versus Intrinsic Disease

OBJECTIVE

The purpose of this article is to study the effect of the administration of multiple IV doses of gadolinium-based contrast agent on the intrinsic T1 hyperintensity in the dentate nucleus and globus pallidus in patients with multiple sclerosis (MS).

MATERIALS AND METHODS

A retrospective review of imaging in patients with relapsing-remitting MS was performed. Images of 20 patients who received four or more doses of gadolinium-based contrast agent were reviewed. Patients received the linear agent gadopentetate dimeglumine before 2011 and the macrocyclic agent gadobutrol from 2011 onward. Dentate nucleus-to-pons and globus pallidus-to-thalamus signal intensity (SI) ratios were evaluated. SI ratios were compared over time with multiple injections of gadolinium. Similar SI ratios were evaluated for six patients who received gadopentetate dimeglumine and then underwent multiple subsequent MRI studies without contrast agent administration.

RESULTS

The increase in the dentate nucleus-to-pons SI ratio after multiple administrations of the linear agent gadopentetate dimeglumine (mean = 1.44; SD = 2.50) was significantly higher than that with the macrocyclic agent gadobutrol (mean = -0.11; SD = 2.33) (p < 0.001). The globus pallidus-to-thalamus and dentate nucleus-to-CSF ratios also increased with multiple contrast injections over time, but the changes were not found to be statistically significant. The increase in SI in the dentate nucleus was not observed in patients who stopped receiving contrast injections, after showing a previous increase over time with gadolinium.

CONCLUSION

In patients with MS, SI within the dentate nucleus and globus pallidus increased on unenhanced T1-weighted images and was significantly greater with the administration of a linear agent than with a macrocyclic agent. This increase in SI over time is likely a reflection of gadolinium deposition and not due to intrinsic disease, as previously postulated.

Human Cerebellar Sub-millimeter Diffusion Imaging Reveals the Motor and Non-motor Topography of the Dentate Nucleus

The reciprocal cortico-cerebellar loops that underlie cerebellar contributions to motor and cognitive behavior form one of the largest systems in the primate brain. Work with non-human primates has shown that the dentate nucleus, the major output nucleus of the cerebellum, contains topographically distinct connections to both motor and non-motor regions, yet there is no evidence for how the cerebellar cortex connects to the dentate nuclei in humans. Here we used in-vivo sub-millimeter diffusion imaging to characterize this fundamental component of the cortico-cerebellar loop, and identified a pattern of superior motor and infero-lateral non-motor connectivity strikingly similar to that proposed by animal work. Crucially, we also present first evidence that the dominance for motor connectivity observed in non-human primates may be significantly reduced in man - a finding that is in accordance with the proposed increase in cerebellar contributions to higher cognitive behavior over the course of primate evolution.

Claustral neurons are vulnerable to ischemic insults in cardiac arrest encephalopathy

Cardiac arrest encephalopathy is the major cause of global brain ischemia which is the main cause of death in these cases. Morphological assessment of the ischemic changes is important to prove the extent of the brain injury and its effects. Selective vulnerability is the common form of ischemic injury in these cases and commonly affects the CA1 of hippocampus, cerebral cortex in watershed zone and Purkinje cells of the cerebellum. In this retrospective study, we reviewed the clinical and pathological data for the 135 retrieved cases and only 16/135 cases met the selection criteria (i.e. confirmed cardiac arrest episode with known survival time, autopsy performed in less than 24 hours after death, compatible gray matter ischemic changes with the survival period, and no pathological changes of other diseases that could confound the result). We found that the claustrum is the most sensitive area for ischemic changes. This represents a novel finding, as up to our knowledge, the neurons of the claustrum have not been considered before as common area to show selective vulnerability. In the 3 cases with a short survival (6-9 hours), the hippocampus showed no or mild ischemic changes and as such was not a good area for assessment of global ischemia. Another unexplained novel finding was prominent vacuolar changes predominantly around both sides of the gray-white matter junction of the cerebellar dentate nucleus and focally inside the dentate nucleus.

Implications of Lateral Cerebellum in Proactive Control of Saccades

Although several lines of evidence establish the involvement of the medial and vestibular parts of the cerebellum in the adaptive control of eye movements, the role of the lateral hemisphere of the cerebellum in eye movements remains unclear. Ascending projections from the lateral cerebellum to the frontal and parietal association cortices via the thalamus are consistent with a role of these pathways in higher-order oculomotor control. In support of this, previous functional imaging studies and recent analyses in subjects with cerebellar lesions have indicated a role for the lateral cerebellum in volitional eye movements such as anti-saccades. To elucidate the underlying mechanisms, we recorded from single neurons in the dentate nucleus of the cerebellum in monkeys performing anti-saccade/pro-saccade tasks. We found that neurons in the posterior part of the dentate nucleus showed higher firing rates during the preparation of anti-saccades compared with pro-saccades. When the animals made erroneous saccades to the visual stimuli in the anti-saccade trials, the firing rate during the preparatory period decreased. Furthermore, local inactivation of the recording sites with muscimol moderately increased the proportion of error trials, while successful anti-saccades were more variable and often had shorter latency during inactivation. Thus, our results show that neuronal activity in the cerebellar dentate nucleus causally regulates anti-saccade performance. Neuronal signals from the lateral cerebellum to the frontal cortex might modulate the proactive control signals in the corticobasal ganglia circuitry that inhibit early reactive responses and possibly optimize the speed and accuracy of anti-saccades.

SIGNIFICANCE STATEMENT

Although the lateral cerebellum is interconnected with the cortical eye fields via the thalamus and the pons, its role in eye movements remains unclear. We found that neurons in the caudal part of the lateral (dentate) nucleus of the cerebellum showed the increased firing rate during the preparation of anti-saccades. Inactivation of the recording sites modestly elevated the rate of erroneous saccades to the visual stimuli in the anti-saccade trials, while successful anti-saccades during inactivation tended to have a shorter latency. Our data indicate that neuronal signals in the lateral cerebellum may proactively regulate anti-saccade generation through the pathways to the frontal cortex, and may inhibit early reactive responses and regulate the accuracy of anti-saccades.

Sodium MRI of T1 High Signal Intensity in the Dentate Nucleus due to Gadolinium Deposition in Multiple Sclerosis

BACKGROUND AND PURPOSE

Recently, several studies reported increased signal intensity (SI) of the dentate nucleus (DN) on unenhanced T1-weighted magnetic resonance imaging (MRI) as a possible consequence of multiple applications of gadolinium-based contrast agents. The aim of this study was to investigate with sodium (²³ Na) MRI possible tissue abnormalities of the DN in multiple sclerosis (MS) patients.

METHODS

Sodium and conventional MRI were performed on a clinical 3T scanner. Total sodium concentrations (TSCs) of the DN, as well as DN-to-pons and DN-to-cerebellum SI ratios on unenhanced T1-weighted MRI were calculated.

RESULTS

A total of 18 subjects (6/18 normal controls, 12/18 MS patients [6/12 with T1 hyperintense DN]) were investigated. There was no significant difference of TSC values of the DN in MS patients with a T1-hyperintense DN (33.70 ± 2.14 mM) compared to MS patients without those signal abnormalities (33.29 ± 1.67 mM; P = .67) or to healthy controls (33.14 ± 1.12; P = .32).

CONCLUSIONS

Normal sodium signal in the T1-hyperintense DN in MS patients may point to relative tissue integrity despite gadolinium deposition in this area.

Metronidazole-induced encephalopathy associated with treatment for liver abscesses

Metronidazole‐induced encephalopathy (MIE) is a rare condition in Japan. We report the case of a patient with MIE who presented with abducens paralysis and ataxia without underlying risk factors. A history of metronidazole (MNZ) administration and rapid improvement after MNZ discontinuation are important in making this diagnosis, and characteristic findings of magnetic resonance imaging support the diagnosis. MIE is expected to become common in Japan as the use of MNZ increases because of expanded insurance coverage. Therefore, MIE needs to be recognized as a differential diagnosis of the central nervous symptoms in patients taking MNZ.

Longitudinal Assessment of Dentate Nuclei Relaxometry during Massive Gadobutrol Exposure

We report the assessment of Dentate Nuclei (DN) R1 (1/T₁) and R2* (1/T2*) values in a patient with relapsing-remitting Multiple Sclerosis, exposed to 22 standard (0.1 mmol/kg) doses of gadobutrol, who underwent eight relaxometric MR measurements within 2 years. DN R1 did not significantly increase nor correlated with cumulative gadobutrol administration, even after a total dose of 130 ml. Likewise, DN R2* relaxometry remained unchanged. In conclusion, massive gadobutrol exposure did not induce significant DN relaxometry changes.

Synaptic pathology in the cerebellar dentate nucleus in chronic multiple sclerosis

In multiple sclerosis, cerebellar symptoms are associated with clinical impairment and an increased likelihood of progressive course. Cortical atrophy and synaptic dysfunction play a prominent role in cerebellar pathology and although the dentate nucleus is a predilection site for lesion development, structural synaptic changes in this region remain largely unexplored. Moreover, the mechanisms leading to synaptic dysfunction have not yet been investigated at an ultrastructural level in multiple sclerosis. Here, we report on synaptic changes of dentate nuclei in post-mortem cerebella of 16 multiple sclerosis patients and eight controls at the histological level as well as an electron microscopy evaluation of afferent synapses of the cerebellar dentate and pontine nuclei of one multiple sclerosis patient and one control. We found a significant reduction of afferent dentate synapses in multiple sclerosis, irrespective of the presence of demyelination, and a close relationship between glial processes and dentate synapses. Ultrastructurally, we show autophagosomes containing degradation products of synaptic vesicles within dendrites, residual bodies within intact-appearing axons and free postsynaptic densities opposed to astrocytic appendages. Our study demonstrates loss of dentate afferent synapses and provides, for the first time, ultrastructural evidence pointing towards neuron-autonomous and neuroglia-mediated mechanisms of synaptic degradation in chronic multiple sclerosis.

Lack of increased signal intensity in the dentate nucleus after repeated administration of a macrocyclic contrast agent in multiple sclerosis: An observational study

Recently, several studies reported increased signal intensity (SI) in the dentate nucleus (DN) after repeated application of gadolinium-based contrast agents (GBCAs), suggesting a deposition of gadolinium in this location. Patients with relapsing-remitting multiple sclerosis (RRMS) frequently show increased permeability of the blood-brain barrier as part of the inflammatory process in the brain parenchyma, which theoretically might increase the risk of gadolinium deposition. In this retrospective study, we investigated a possible increasing SI in the DN after repeated administrations of the macrocyclic contrast agent gadoterate meglumine.Forty-one RRMS patients (33 women, mean age 38 years) with at least 6 prior gadolinium-enhanced examinations (single dose gadoterate meglumine) were identified. A total of 279 unenhanced T1-weighted examinations were analyzed.SI ratio differences did not differ between the first and last MRI examination, neither for the DN-to-pons ratio (P = 0.594) nor for the DN-to-cerebellum ratio (P = 0.847). There was no correlation between the mean DN-to-pons, or between the mean DN-to-cerebellum SI ratio and the number of MRI examinations (P = 0.848 and 0.891), disease duration (P = 0.676 and 0.985), and expanded disability status scale (EDSS) (P = 0.639 and 0.945).We found no signal increases in the DN after a minimum of 6 injections of the macrocyclic GBCA gadoterate meglumine in RRMS patients. This warrants further investigations in regard to the true pathophysiologic basis of intracerebral gadolinium deposition.

Dentate nucleus connectivity in adult patients with multiple sclerosis: functional changes at rest and correlation with clinical features

BACKGROUND AND OBJECTIVE

The dentate nucleus, which is the largest of the cerebellar nuclei, plays a critical role in movement and cognition. The aim of our study was to assess any changes in dentate functional connectivity (FC) in adult relapsing remitting multiple sclerosis (RR-MS) patients and to investigate possible clinical correlates.

MATERIALS AND METHODS

In all, 54 patients and 24 healthy subjects (HS) underwent multimodal magnetic resonance imaging (MRI), including diffusion tensor imaging (DTI), three-dimensional-T1-weighted and resting state (RS) functional images; they also underwent a cognitive evaluation, that is, attention and information processing speed, by means of the Paced Auditory Serial Addition Test (PASAT). Patients were also scored according to Expanded Disability Status Scale (EDSS). RS-MRI data were analysed using FMRIB Software Library (FSL) tools, with the seed-based method to identify dentate FC.

RESULTS

When compared with HS, patients exhibited brain atrophy and widespread DTI abnormalities, as well as greater FC between the dentate nucleus and cortical areas, particularly in the frontal and parietal lobes. Within these areas, FC in patients correlated inversely with clinical impairment. Finally, FC correlated inversely with lesion load and microstructural brain damage.

CONCLUSION

Our findings indicate that dentate FC at rest is altered in MS patients. Whether these functional changes are induced by the disease and play a compensatory role remains to be established.

Hyperintensity in the Dentate Nucleus on Nonenhanced T1-Weighted Magnetic Resonance Imaging Suggests Dechelation of Contrast Agents

With the exception of renal failure patients, gadolinium-based contrast agents (GBCAs) for magnetic resonance imaging (MRI) have a high tolerance and acceptability in patients needing to undergo an enhanced MRI. Now that enhanced MRIs are becoming increasingly popular and nephrogenic systemic fibrosis cases are becoming a rarity, a common belief is that these GBCAs are essentially "biologically inert" materials. However, recent reports have emerged querying the link between these GBCAs and hyperintensity in the dentate nucleus on unenhanced T1-weighted MRI in some patients. This review article outlines the basic chemistry and characteristics of currently approved GBCAs, summarizes the described research findings of gadolinium deposition in the dentate nucleus, and identifies areas for future research.

Effects of developmental hyperserotonemia on the morphology of rat dentate nuclear neurons

Autism Spectrum Disorder (ASD) is a neurodevelopmental disorder characterized by deficits in social cognition, disordered communication, restricted interests and repetitive behaviors. Furthermore, abnormalities in basic motor control, skilled motor gestures, and motor learning, are common in ASD. These characteristics have been attributed to a possible defect in the pre- and postnatal development of specific neural networks including the dentate-thalamo-cortical pathway, which is involved in motor learning, automaticity of movements, and higher cognitive functions. The current study utilized custom diolistic labeling and unbiased stereology to characterize morphological alterations in neurons of the dentate nucleus of the cerebellum in developing rat pups exposed to abnormally high levels of the serotonergic agonist 5-methyloxytryptamine (5-MT) pre-and postnatally. Occurring in as many as 30% of autistic subjects, developmental hyperserotonemia (DHS) is the most consistent neurochemical finding reported in autism and has been implicated in the pathophysiology of ASD. This exposure produced dramatic changes in dendritic architecture and synaptic features. We observed changes in the dendritic branching morphology which did not lead to significant differences (p>0.5) in total dendritic length. Instead, DHS groups presented with dendritic trees that display changes in arborescence, that appear to be short reaching with elaborately branched segments, presenting with significantly fewer (p>0.001) dendritic spines and a decrease in numeric density when compared to age-matched controls. These negative changes may be implicated in the neuropathological and functional/behavioral changes observed in ASD, such as delays in motor learning, difficulties in automaticity of movements, and deficits in higher cognitive functions.

Linear Gadolinium-Based Contrast Agents Are Associated With Brain Gadolinium Retention in Healthy Rats

OBJECTIVES

The aim of this study was to evaluate Gd retention in the deep cerebellar nuclei (DCN) of linear gadolinium-based contrast agents (GBCAs) compared with a macrocyclic contrast agent.

MATERIALS AND METHODS

The brain tissue retention of Gd of 3 linear GBCAs (gadobenate dimeglumine, gadopentetate dimeglumine, and gadodiamide) and a macrocyclic GBCA (gadoterate meglumine) was compared in healthy rats (n = 8 per group) that received 20 intravenous injections of 0.6 mmol Gd/kg (4 injections per week for 5 weeks). An additional control group with saline was included. T1-weighted magnetic resonance imaging was performed before injection and once a week during the 5 weeks of injections and for another 4 additional weeks after contrast period. Total gadolinium concentration was measured with inductively coupled plasma mass spectrometry. Blinded qualitative and quantitative evaluations of the T1 signal intensity in DCN were performed, as well as a statistical analysis on quantitative data.

RESULTS

At completion of the injection period, all the linear contrast agents (gadobenate dimeglumine, gadopentetate dimeglumine, and gadodiamide) induced a significant increase in signal intensity in DCN, unlike the macrocyclic GBCA (gadoterate meglumine) or saline. The T1 hypersignal enhancement kinetic was fast for gadodiamide. Total Gd concentrations for the 3 linear GBCAs groups at week 10 were significantly higher in the cerebellum (1.21 ± 0.48, 1.67 ± 0.17, and 3.75 ± 0.18 nmol/g for gadobenate dimeglumine, gadopentetate dimeglumine, and gadodiamide, respectively) than with the gadoterate meglumine (0.27 ± 0.16 nmol/g, P < 0.05) and saline (0.09 ± 0.12 nmol/g, P < 0.05). No significant difference was observed between the macrocyclic agent and saline.

CONCLUSIONS

Repeated administrations of the linear GBCAs gadodiamide, gadobenate dimeglumine, and gadopentetate dimeglumine to healthy rats were associated with progressive and significant T1 signal hyperintensity in the DCN, along with Gd deposition in the cerebellum. This is in contrast with the macrocyclic GBCA gadoterate meglumine for which no effect was observed.

High signal intensity in dentate nucleus and globus pallidus on unenhanced T1-weighted MR images in three patients with impaired renal function and vascular calcification

Gadolinium‐based contrast agents (primarily those with linear chelates) are associated with a dose‐dependent signal hyperintensity in the dentate nucleus and the globus pallidus on unenhanced T1‐weighted MRI following administration to selected patients with normal renal function. The accumulation of gadolinium has also been reported in the skin, heart, liver, lung, and kidney of patients with impaired renal function suffering from nephrogenic systemic fibrosis (NSF). Here we report on three patients with impaired renal function and vascular calcification (two with confirmed NSF) whose unenhanced T1‐weighted MRIs showed conspicuous high signal intensity in the dentate nucleus and the globus pallidus after they had been exposed to relatively low doses of linear gadolinium‐based contrast agents (0.27, 0.45, and 0.68 mmol/kg). Signal ratios between dentate nucleus and pons and between globus pallidus and thalamus were comparable with previously reported measurements in subjects without renal impairment. Of note, all three analysed patients suffered from transient signs of neurological disorders of undetermined cause. In conclusion, the exposure to 0.27‐0.68 mmol/kg of linear gadolinium‐based contrast agent was associated with probable gadolinium accumulation in the brain of three patients suffering from impaired renal function and vascular calcification. © 2016 The Authors. Contrast Media & Molecular Imaging published by John Wiley & Sons Ltd.

Signal Change in the Dentate Nucleus on T1-Weighted MR Images After Multiple Administrations of Gadopentetate Dimeglumine Versus Gadobutrol

OBJECTIVE

The objective of this study was to evaluate signal changes in the dentate nucleus on unenhanced T1-weighted MR images after multiple administrations of gadopentetate dimeglumine versus gadobutrol.

MATERIALS AND METHODS

Two study groups were identified, each of which included 25 consecutive patients. Each group received six or more administrations of either gadobutrol only or gadopentetate dimeglumine only, without having had exposure to any other gadolinium-based contrast agent (GBCA). The mean signal intensity (SI) in the dentate nucleus on unenhanced T1-weighted MR images was measured, with the use of the pons and the cerebellar peduncle as references to calculate the DNP SI ratio (i.e., the ratio of the SI in the dentate nucleus to the SI in the pons) and the DCP SI ratio (i.e., the ratio of the SI in the dentate nucleus to the SI in the cerebellar peduncle).

RESULTS

After six administrations of gadopentetate dimeglumine, the SI in the dentate nucleus on unenhanced T1-weighted MR images increased from a DCP SI ratio of 0.997 before administration to 1.034 after the last of six administrations (p = 0.0007) and then to 1.063 after all administrations (p = 0.0004). No statistically significant increase was noted in association with administration of gadobutrol, for which the DCP SI ratio was 0.995 before administration, 1.009 after the last of six administrations (p = 0.1172), and 0.992 after all administrations (p = 0.7592). The change in the DCP SI ratio after administration of gadopentetate dimeglumine correlated with the number of administrations the patient received (p < 0.0001).

CONCLUSION

Unenhanced T1 signal hyperintensity was observed in the dentate nucleus after multiple administrations of gadopentetate dimeglumine, a linear ionic agent, but not after multiple administrations of gadobutrol, a macrocyclic GBCA.

Neurohistiocytosis of the Cerebellum: A Rare Cause of Ataxia

Erdheim-Chester disease (ECD) is a non-Langerhans cell histiocytosis that affects multiple body organs, notably the skeletal system. We examined a 58-year-old man who presented with ataxia and T2 hyperintensity of the middle cerebellar peduncles and dentate nuclei without contrast enhancement on MRI brain. Workup for malignancy revealed "hairy kidneys" on CT scan of the abdomen, and excisional biopsy of the retroperitoneal mass for concerns of lymphoma revealed foamy histiocytes that tested positive for CD68 and negative for CD1a, confirming the diagnosis of ECD. Further genetic testing on excised tissue revealed BRAF (V600E) gene mutation that is present in 50% of ECD patients. Treatment was initiated with targeted therapy using the BRAF inhibitor Dabrafenib. X-ray of the lower extremities did not reveal sclerosis of the long bones, and bone scan with technetium 99 was negative except for a nonspecific tracer uptake in left calvarial bone with no corresponding CT changes or T1/T2 signal changes on MRI. His MRI brain revealed classic cerebellar involvement in ECD without other central nervous system (CNS) involvement. It has been postulated that bone involvement is almost universal in ECD; however, our patient with ECD had ataxia and cerebellar involvement without significant bone involvement, as evidenced by bone scan. This is a rare presentation of ECD affecting the CNS and sparing the skeletal system. It confirms the wide spectrum of presentation this multisystem disease can have.

The nondecussating pathway of the dentatorubrothalamic tract in humans: human connectome-based tractographic study and microdissection validation

OBJECT The dentatorubrothalamic tract (DRTT) is the major efferent cerebellar pathway arising from the dentate nucleus (DN) and decussating to the contralateral red nucleus (RN) and thalamus. Surprisingly, hemispheric cerebellar output influences bilateral limb movements. In animals, uncrossed projections from the DN to the ipsilateral RN and thalamus may explain this phenomenon. The aim of this study was to clarify the anatomy of the dentatorubrothalamic connections in humans. METHODS The authors applied advanced deterministic fiber tractography to a template of 488 subjects from the Human Connectome Project (Q1-Q3 release, WU-Minn HCP consortium) and validated the results with microsurgical dissection of cadaveric brains prepared according to Klingler's method. RESULTS The authors identified the "classic" decussating DRTT and a corresponding nondecussating path (the nondecussating DRTT, nd-DRTT). Within each of these 2 tracts some fibers stop at the level of the RN, forming the dentatorubro tract and the nondecussating dentatorubro tract. The left nd-DRTT encompasses 21.7% of the tracts and 24.9% of the volume of the left superior cerebellar peduncle, and the right nd-DRTT encompasses 20.2% of the tracts and 28.4% of the volume of the right superior cerebellar peduncle. CONCLUSIONS The connections of the DN with the RN and thalamus are bilateral, not ipsilateral only. This affords a potential anatomical substrate for bilateral limb motor effects originating in a single cerebellar hemisphere under physiological conditions, and for bilateral limb motor impairment in hemispheric cerebellar lesions such as ischemic stroke and hemorrhage, and after resection of hemispheric tumors and arteriovenous malformations. Furthermore, when a lesion is located on the course of the dentatorubrothalamic system, a careful preoperative tractographic analysis of the relationship of the DRTT, nd-DRTT, and the lesion should be performed in order to tailor the surgical approach properly and spare all bundles.

T1-Weighted Hypersignal in the Deep Cerebellar Nuclei After Repeated Administrations of Gadolinium-Based Contrast Agents in Healthy Rats: Difference Between Linear and Macrocyclic Agents

OBJECTIVES

To prospectively compare in healthy rats the effect of multiple injections of macrocyclic (gadoterate meglumine) and linear (gadodiamide) gadolinium-based contrast agents (GBCAs) on T1-weighted signal intensity in the deep cerebellar nuclei (DCN), including the dentate nucleus.

MATERIALS AND METHODS

Healthy rats (n = 7/group) received 20 intravenous injections of 0.6 mmol of gadolinium (Gd) per kilogram (4 injections per week during 5 weeks) of gadodiamide, gadoterate meglumine, or hyperosmolar saline (control group). Brain T1-weighted magnetic resonance imaging was performed before and once a week during the 5 weeks of injections and during 5 additional weeks (treatment-free period). Gadolinium concentrations were measured with inductively coupled plasma mass spectrometry in plasma and brain. Blinded qualitative and quantitative evaluations of the T1 signal intensity in DCN were performed, as well as a statistical analysis on quantitative data.

RESULTS

A significant and persistent T1 signal hyperintensity in DCN was observed only in gadodiamide-treated rats. The DCN-to-cerebellar cortex signal ratio was significantly increased from the 12th injection of gadodiamide (1.070 ± 0.024) compared to the gadoterate meglumine group (1.000 ± 0.033; P < 0.001) and control group (1.019 ± 0.022; P < 0.001) and did not significantly decrease during the treatment-free period. Total Gd concentrations in the gadodiamide group were significantly higher in the cerebellum (3.66 ± 0.91 nmol/g) compared with the gadoterate meglumine (0.26 ± 0.12 nmol/g; P < 0.05) and control (0.06 ± 0.10 nmol/g; P < 0.05) groups.

CONCLUSIONS

Repeated administrations of the linear GBCA gadodiamide to healthy rats are associated with progressive and persistent T1 signal hyperintensity in the DCN, with Gd deposition in the cerebellum in contrast with the macrocyclic GBCA gadoterate meglumine for which no effect was observed.

Friedreich ataxia: failure of GABA-ergic and glycinergic synaptic transmission in the dentate nucleus

Atrophy of large neurons in the dentate nucleus (DN) is an important pathologic correlate of neurologic disability in patients with Friedreich ataxia (FA). Thinning of the DN was quantified in 29 autopsy cases of FA and 2 carriers by measuring the thickness of the gray matter ribbon on stains with anti-glutamic acid decarboxylase, the rate-limiting enzyme in the biosynthesis of γ-amino-butyric acid (GABA). The DN was thinner than normal in all cases of FA, and atrophy correlated inversely with disease duration but not with age at onset or length of the homozygous guanine-adenine-adenine trinucleotide expansions. In 13 of the FA cases, frozen DN tissue was available for assay of frataxin. Dentate nucleus atrophy was more severe when frataxin was very low. Immunohistochemical staining for glutamic acid decarboxylase revealed grumose reaction and preservation of small GABA-ergic neurons in the DN of FA patients. Residual small DN neurons and varicose axons also contained the glycine transporter 2, identifying them as glycinergic. Immunohistochemistry also confirmed severe loss of GABA-A and glycine receptors in the DN with comparable depletion of the receptor-anchoring protein gephyrin. Thus, loss of gephyrin and failure to position GABA-A and glycine receptors correctly may reduce trophic support of large DN neurons and contribute to their atrophy. By contrast, Purkinje cells may escape retrograde atrophy in FA by issuing new axonal sprouts to small surviving DN neurons where they form reparative grumose clusters.

Cerebellar mutism in acute disseminating encephalomyelitis

BACKGROUND

Cerebellar mutism in children occurs after posterior fossa tumor resection and can have lasting effects on cognition, language, and behavior. Cerebellar mutism in acute disseminated encephalomyelitis is rare.

PATIENT

A 7-year-old boy with a 3-day history of fever, vomiting, and diarrhea presented with altered mental status and expressive aphasia. Magnetic resonance imaging showed new diffusion restriction in the bilateral dentate nuclei and right cerebellum. With treatment, he began to verbalize again but had long-term cognitive and language difficulties.

CONCLUSION

Acute disseminated encephalomyelitis is commonly a benign process, but its effect on the cerebellum can be long-lasting.