Altered cerebellar-cerebral functional connectivity in benign adult familial myoclonic epilepsy

Altered dynamic functional connectivity of motor cerebellum with sensorimotor network and default mode network in juvenile myoclonic epilepsy

Objective

To investigate whether changes occur in the dynamic functional connectivity (dFC) of motor cerebellum with cerebral cortex in juvenile myoclonic epilepsy (JME).

Methods

We adopted resting-state electroencephalography-functional magnetic resonance imaging (EEG-fMRI) and a sliding-window approach to explore the dFC of motor cerebellum with cortex in 36 JME patients compared with 30 and age-matched health controls (HCs). The motor cerebellum was divided into five lobules (I-V, VI, VIIb, VIIIa, and VIIIb). Additionally, correlation analyses were conducted between the variability of dFC and clinical variables in the Juvenile Myoclonic Epilepsy (JME) group, such as disease duration, age at disease onset, and frequency score of myoclonic seizures.

Results

Compared to HCs, the JME group presented increased dFC between the motor cerebellum with SMN and DMN. Specifically, connectivity between lobule VIIb and left precentral gyrus and right inferior parietal lobule (IPL); between lobule VIIIa and right inferior frontal gyrus (IFG) and left IPL; and between lobule VIIIb and left middle frontal gyrus (MFG), bilateral superior parietal gyrus (SPG), and left precuneus. In addition, within the JME group, the strength of dFC between lobule VIIIb and left precuneus was negatively (r = -0.424, p = 0.025, Bonferroni correction) related with the frequency score of myoclonic seizures.

Conclusion

In patients with JME, there is a functional dysregulation between the motor cerebellum with DMN and SMN, and the variability of dynamic functional connectivity may be closely associated with the occurrence of motor symptoms in JME.

Familial Adult Myoclonus Epilepsy: A Non-Coding Repeat Expansion Disorder of Cerebellar-Thalamic-Cortical Loop

Familial adult myoclonus Epilepsy (FAME) is a non-coding repeat expansion disorder that has been reported under different acronyms and initially linked to four main loci: FAME1 (8q23.3-q24.1), FAME 2 (2p11.1-q12.1), FAME3 (5p15.31-p15.1), and FAME4 (3q26.32-3q28). To date, it is known that the genetic mechanism underlying FAME consists of the expansion of similar non-coding pentanucleotide repeats, TTTCA and TTTTA, in different genes. FAME is characterized by cortical tremor and myoclonus usually manifesting within the second decade of life, and infrequent seizures by the third or fourth decade. Cortical tremor is the core feature of FAME and is considered part of a spectrum of cortical myoclonus. Neurophysiological investigations as jerk-locked back averaging (JLBA) and corticomuscular coherence analysis, giant somatosensory evoked potentials (SEPs), and the presence of long-latency reflex I (or C reflex) at rest support cortical tremor as the result of the sensorimotor cortex hyperexcitability. Furthermore, the application of transcranial magnetic stimulation (TMS) protocols in FAME patients has recently shown that inhibitory circuits are also altered within the primary somatosensory cortex and the concomitant involvement of subcortical networks. Moreover, neuroimaging studies and postmortem autoptic studies indicate cerebellar alterations and abnormal functional connectivity between the cerebellum and cerebrum in FAME. Accordingly, the pathophysiological mechanism underlying FAME has been hypothesized to reside in decreased sensorimotor cortical inhibition through dysfunction of the cerebellar-thalamic-cortical loop, secondary to primary cerebellar pathology. In this context, the non-coding pentameric expansions have been proposed to cause cerebellar damage through an RNA-mediated toxicity mechanism. The elucidation of the underlying pathological mechanisms of FAME paves the way to novel therapeutic possibilities, such as RNA-targeting treatments, possibly applicable to other neurodegenerative non-coding disorders.

Altered brain connectivity in hyperkinetic movement disorders: A review of resting-state fMRI

BACKGROUND

Hyperkinetic movement disorders (HMD) manifest as abnormal and uncontrollable movements. Despite reported involvement of several neural circuits, exact connectivity profiles remain elusive.

OBJECTIVES

Providing a comprehensive literature review of resting-state brain connectivity alterations using resting-state fMRI (rs-fMRI). We additionally discuss alterations from the perspective of brain networks, as well as correlations between connectivity and clinical measures.

METHODS

A systematic review was performed according to PRISMA guidelines and searching PubMed until October 2022. Rs-fMRI studies addressing ataxia, chorea, dystonia, myoclonus, tics, tremor, and functional movement disorders (FMD) were included. The standardized mean difference was used to summarize findings per region in the Automated Anatomical Labeling atlas for each phenotype. Furthermore, the activation likelihood estimation meta-analytic method was used to analyze convergence of significant between-group differences per phenotype. Finally, we conducted hierarchical cluster analysis to provide additional insights into commonalities and differences across HMD phenotypes.

RESULTS

Most articles concerned tremor (51), followed by dystonia (46), tics (19), chorea (12), myoclonus (11), FMD (11), and ataxia (8). Altered resting-state connectivity was found in several brain regions: in ataxia mainly cerebellar areas; for chorea, the caudate nucleus; for dystonia, sensorimotor and basal ganglia regions; for myoclonus, the thalamus and cingulate cortex; in tics, the basal ganglia, cerebellum, insula, and frontal cortex; for tremor, the cerebello-thalamo-cortical circuit; finally, in FMD, frontal, parietal, and cerebellar regions. Both decreased and increased connectivity were found for all HMD. Significant spatial convergence was found for dystonia, FMD, myoclonus, and tremor. Correlations between clinical measures and resting-state connectivity were frequently described.

CONCLUSION

Key brain regions contributing to functional connectivity changes across HMD often overlap. Possible increases and decreases of functional connections of a specific region emphasize that HMD should be viewed as a network disorder. Despite the complex interplay of physiological and methodological factors, this review serves to gain insight in brain connectivity profiles across HMD phenotypes.

Altered Cerebro-Cerebellar Effective Connectivity in New-Onset Juvenile Myoclonic Epilepsy

(1) Objective: Resting-state fMRI studies have indicated that juvenile myoclonic epilepsy (JME) could cause widespread functional connectivity disruptions between the cerebrum and cerebellum. However, the directed influences or effective connectivities (ECs) between these brain regions are poorly understood. In the current study, we aimed to evaluate the ECs between the cerebrum and cerebellum in patients with new-onset JME. (2) Methods: Thirty-four new-onset JME patients and thirty-four age-, sex-, and education-matched healthy controls (HCs) were included in this study. We compared the degree centrality (DC) between the two groups to identify intergroup differences in whole-brain functional connectivity. Then, we used a Granger causality analysis (GCA) to explore JME-caused changes in EC between cerebrum regions and cerebellum regions. Furthermore, we applied a correlation analysis to identify associations between aberrant EC and disease severity in patients with JME. (3) Results: Compared to HCs, patients with JME showed significantly increased DC in the left cerebellum posterior lobe (CePL.L), the right inferior temporal gyrus (ITG.R) and the right superior frontal gyrus (SFG.R), and decreased DC in the left inferior frontal gyrus (IFG.L) and the left superior temporal gyrus (STG.L). The patients also showed unidirectionally increased ECs from cerebellum regions to the cerebrum regions, including from the CePL.L to the right precuneus (PreCU.R), from the left cerebellum anterior lobe (CeAL.L) to the ITG.R, from the right cerebellum posterior lobe (CePL.R) to the IFG.L, and from the left inferior semi-lunar lobule of the cerebellum (CeISL.L) to the SFG.R. Additionally, the EC from the CeISL.L to the SFG.R was negatively correlated with the disease severity. (4) Conclusions: JME patients showed unidirectional EC disruptions from the cerebellum to the cerebrum, and the negative correlation between EC and disease severity provides a new perspective for understanding the cerebro-cerebellar neural circuit mechanisms in JME.

Altered cerebellar-motor loop in benign adult familial myoclonic epilepsy type 1: The structural basis of cortical tremor

OBJECTIVE

Cortical tremor/myoclonus is the hallmark feature of benign adult familial myoclonic epilepsy (BAFME), the mechanism of which remains elusive. A hypothesis is that a defective control in the preexisting cerebellar-motor loop drives cortical tremor. Meanwhile, the basal ganglia system might also participate in BAFME. This study aimed to discover the structural basis of cortical tremor/myoclonus in BAFME.

METHODS

Nineteen patients with BAFME type 1 (BAFME1) and 30 matched healthy controls underwent T1-weighted and diffusion tensor imaging scans. FreeSurfer and spatially unbiased infratentorial template (SUIT) toolboxes were utilized to assess the motor cortex and the cerebellum. Probabilistic tractography was generated for two fibers to test the hypothesis: the dentato-thalamo-(M1) (primary motor cortex) and globus pallidus internus (GPi)-thalamic projections. Average fractional anisotropy (FA), axial diffusivity (AD), mean diffusivity (MD), and radial diffusivity (RD) of each tract were extracted.

RESULTS

Cerebellar atrophy and dentate nucleus alteration were observed in the patients. In addition, patients with BAFME1 exhibited reduced AD and FA in the left and right dentato-thalamo-M1 nondecussating fibers, respectively false discovery rate (FDR) correction q < .05. Cerebellar projections showed negative correlations with somatosensory-evoked potential P25-N33 amplitude and were independent of disease duration and medication. BAFME1 patients also had increased FA and decreased MD in the left GPi-thalamic projection. Higher FA and lower RD in the right GPi-thalamic projection were also observed (FDR q < .05).

SIGNIFICANCE

The present findings support the hypothesis that the cerebello-thalamo-M1 loop might be the structural basis of cortical tremor in BAFME1. The basal ganglia system also participates in BAFME1 and probably serves a regulatory role.

Hyperperfusion in the cerebellum lobule VIIb in patients with epileptic seizures

Background

The cerebellum plays an important role in motor control, however, its involvement in epilepsy has not been fully understood. Arterial spin labelling perfusion magnetic resonance image (ASL) is a noninvasive method to evaluate cerebral and cerebellar blood flow. We investigated cerebellar perfusion in patients with epileptic seizures using ASL.

Methods

Adult patients with epileptic seizures who underwent ASL in three post labeling delay (PLD) conditions (1525, 1800, and 2500 msec) and conventional electroencephalography (EEG) on the same day were investigated. Clinical and EEG characteristics of them were retrospectively analyzed.

Results

Six patients (6 women, age; 36.2 ± 17.9 years (mean ± SD)) showed hyperperfusion in selective areas in the cerebellar paravermis of lobule VIIb. One patient with generalized epilepsy (tentative diagnosis of juvenile myoclonic epilepsy or epilepsy with myoclonic absences) showed unilateral hypoperfusion in PLD 1525 msec and hyperperfusion in PLD 1800 and 2500 msec at the area while EEG showed generalized spike-wave complexes. After successful treatment, these perfusion abnormalities disappeared. In two patients with focal epilepsy manifesting with asymmetrical motor symptoms, cerebellar hyperperfusion was found on the opposite side to the seizure focus estimated by seizure semiology. Besides hyperperfusion of the VIIb lobule, hypoperfusion at the same area was detected in shorter PLD condition in four patients and in longer PLD condition in one patient.

Conclusion

The cerebellar paravermis of lobule VIIb can be a component of motor circuit and participate in epileptic network in humans. Cerebellar perfusion abnormalities can be associated with neurovascular coupling via capillary bed.

Aberrant visual-related networks in familial cortical myoclonic tremor with epilepsy

INTRODUCTION

In familial cortical myoclonic tremor with epilepsy, photic stimulation can trigger visual symptoms and induce a photoparoxysmal response, or photosensitivity, on electroencephalography. However, the mechanism is poorly understood. In this study, we aimed to explore the neuroimaging changes related to visual symptoms and photosensitivity in genetically confirmed familial cortical myoclonic tremor with epilepsy type 1.

METHODS

Resting-state functional magnetic resonance imaging and electroencephalography data were collected from 31 patients carrying the heterozygous pathogenic intronic pentanucleotide (TTTCA)n insertion in the sterile alpha motif domain-containing 12 gene and from 52 age- and sex-matched healthy controls.

RESULTS

(1) Both regional homogeneity and degree centrality values in the bilateral calcarine sulcus were significantly increased in patients compared with healthy controls. (2) When the calcarine sulcus area with increased regional homogeneity was taken as a seed, increased functional connectivity values were observed in the right precentral gyrus, while decreased functional connectivity values were observed in the right superior frontal gyrus and right inferior parietal lobule. (3) Independent component analysis showed increased connectivity in the left calcarine sulcus inside the medial visual network. (4) Correlation analysis revealed a significant positive correlation between regional homogeneity values and frequency of seizure, and photoparoxysmal response grades were positively correlated with the severity of cortical tremor and duration of epilepsy.

CONCLUSION

These findings provide strong evidence for the interpretation of visual symptoms and photosensitivity in familial cortical myoclonic tremor with epilepsy. We speculate that functional changes in the primary visual cortex may be an imaging biomarker for the disease.

Imaging Genetics in Epilepsy: Current Knowledge and New Perspectives

Epilepsy is a neurological network disease with genetics playing a much greater role than was previously appreciated. Unfortunately, the relationship between genetic basis and imaging phenotype is by no means simple. Imaging genetics integrates multidimensional datasets within a unified framework, providing a unique opportunity to pursue a global vision for epilepsy. This review delineates the current knowledge of underlying genetic mechanisms for brain networks in different epilepsy syndromes, particularly from a neural developmental perspective. Further, endophenotypes and their potential value are discussed. Finally, we highlight current challenges and provide perspectives for the future development of imaging genetics in epilepsy.

White matter alterations in familial cortical myoclonic tremor with epilepsy type 1

OBJECTIVE

Although previous imaging studies have reported cerebellar gray matter loss in patients with familial cortical myoclonic tremor with epilepsy (FCMTE), the corresponding white matter alterations remain unknown. We investigated white matter structural changes in FCMTE1 and compared them with clinical and electrophysiological features.

METHODS

We enrolled 36 patients carrying heterozygous pathogenic intronic pentanucleotide insertions in the SAMD12 gene and 52 age- and sex-matched healthy controls. Diffusion tensor imaging-derived metrics, including fractional anisotropy, mean diffusivity (MD), axial diffusivity (AD), and radial diffusivity (RD) were calculated along with white matter voxel-based morphometry (VBM) analysis. We also examined correlations between MR metrics and clinical and electrophysiological features.

RESULTS

We detected widespread white matter reductions in MD, RD, and AD values in FCMTE patients, including in the commissural, projection, and association fibers. VBM analysis revealed that increases in white matter volume predominantly occurred in the right cerebellum and sagittal stratum. MD, RD, AD, and VBM analysis clearly indicated changes in the sagittal stratum. We found a positive correlation between VBM values in the right cerebellum and SEP P25-N33 amplitude. Decreased MD and AD values in the right sagittal stratum were detected in patients with versus without photophobia.

SIGNIFICANCE

FCMTE is a network disorder involving a wide range of cortical and subcortical structures, including the cerebellum, thalamus, thalamo-cortical connections, and cortico-cortical connections. The right sagittal stratum is closely related with visual symptoms, especially photophobia. Our findings indicate that cerebellum and cortical hyperexcitability are closely linked, and emphasize the important role of the cerebellum in the pathophysiological mechanisms of cortical tremor.

Altered Spontaneous Neural Activity and Functional Connectivity in Parkinson's Disease With Subthalamic Microlesion

Background

Transient improvement in motor symptoms are immediately observed in patients with Parkinson's disease (PD) after an electrode has been implanted into the subthalamic nucleus (STN) for deep brain stimulation (DBS). This phenomenon is known as the microlesion effect (MLE). However, the underlying mechanisms of MLE is poorly understood.

Purpose

We utilized resting state functional MRI (rs-fMRI) to evaluate changes in spontaneous brain activity and networks in PD patients during the microlesion period after DBS.

Method

Overall, 37 PD patients and 13 gender- and age-matched healthy controls (HCs) were recruited for this study. Rs-MRI information was collected from PD patients three days before DBS and one day after DBS, whereas the HCs group was scanned once. We utilized the amplitude of low-frequency fluctuation (ALFF) method in order to analyze differences in spontaneous whole-brain activity among all subjects. Furthermore, functional connectivity (FC) was applied to investigate connections between other brain regions and brain areas with significantly different ALFF before and after surgery in PD patients.

Result

Relative to the PD-Pre-DBS group, the PD-Post-DBS group had higher ALFF in the right putamen, right inferior frontal gyrus, right precentral gyrus and lower ALFF in right angular gyrus, right precuneus, right posterior cingulate gyrus (PCC), left insula, left middle temporal gyrus (MTG), bilateral middle frontal gyrus and bilateral superior frontal gyrus (dorsolateral). Functional connectivity analysis revealed that these brain regions with significantly different ALFF scores demonstrated abnormal FC, largely in the temporal, prefrontal cortices and default mode network (DMN).

Conclusion

The subthalamic microlesion caused by DBS in PD was found to not only improve the activity of the basal ganglia-thalamocortical circuit, but also reduce the activity of the DMN and executive control network (ECN) related brain regions. Results from this study provide new insights into the mechanism of MLE.

A Biomarker for Benign Adult Familial Myoclonus Epilepsy: High-Frequency Activities in Giant Somatosensory Evoked Potentials

BACKGROUND

Benign adult familial myoclonus epilepsy (BAFME) is one of the diseases that cause cortical myoclonus (CM) with giant somatosensory evoked potentials (SEPs). There are no useful diagnostic biomarkers differentiating BAFME from other CM diseases.

OBJECTIVE

To establish reliable biomarkers including high-frequency oscillations (HFOs) with giant SEPs for the diagnosis of BAFME.

METHODS

This retrospective case study included 49 consecutive CM patients (16 BAFME and 33 other CM patients) who exhibited giant P25 or N35 SEPs. SEPs were processed by a band-pass filter of 400-1000 Hz to analyze HFOs. Clinical and SEP findings were compared between (1) BAFME and other CM groups and (2) patients with presence and absence of P25-HFOs (HFOs superimposed on giant P25). The diagnostic power of each factor for BAFME was calculated.

RESULTS

All 16 BAFME patients showed SEP P25-HFOs with significantly higher occurrence (P < 0.0001) compared with that of other CM groups. The presence of P25-HFOs significantly correlated with a BAFME diagnosis (P < 0.0001) and high SEP P25 and N35 amplitudes (P = 0.01 and P < 0.0001, respectively). BAFME was reliably diagnosed using P25-HFOs with high sensitivity (100%), specificity (87.9%), positive predictive value (80%), and negative predictive value (100%), demonstrating its superiority as a diagnostic factor compared to other factors.

CONCLUSIONS

P25-HFOs with giant SEPs is a potential biomarker for BAFME diagnosis. P25-HFOs may reflect cortical hyperexcitability partly due to paroxysmal depolarizing shifts in epileptic neuronal activities and higher degrees of rhythmic tremulousness than those in ordinary CM. © 2021 International Parkinson and Movement Disorder Society.

Epilepsy in China: major progress in the past two decades

China has approximately 10 million people with epilepsy. There is a vast epilepsy treatment gap in China, mainly driven by deficiencies in health-care delivery and social discrimination resulting from cultural beliefs about epilepsy. WHO's Global Campaign Against Epilepsy project in China showed that it was possible to treat epilepsy in primary care settings, which was a notable milestone. The China Association Against Epilepsy has been a necessary force to stimulate interest in epilepsy care and research by the medical and scientific community. Nearly 20 different anti-seizure medications are now available in China. Non-pharmacological options are also available, but there are still unmet needs for epilepsy management. The Chinese epilepsy research portfolio is varied, but the areas in which there are the most concentrated focus and expertise are epidemiology and clinical research. The challenges for further improvement in delivering care for people with epilepsy in China are primarily related to public health and reducing inequalities within this vast country.

Unravelling the enigma of cortical tremor and other forms of cortical myoclonus

Cortical tremor is a fine rhythmic oscillation involving distal upper limbs, linked to increased sensorimotor cortex excitability, as seen in cortical myoclonus. Cortical tremor is the hallmark feature of autosomal dominant familial cortical myoclonic tremor and epilepsy (FCMTE), a syndrome not yet officially recognized and characterized by clinical and genetic heterogeneity. Non-coding repeat expansions in different genes have been recently recognized to play an essential role in its pathogenesis. Cortical tremor is considered a rhythmic variant of cortical myoclonus and is part of the 'spectrum of cortical myoclonus', i.e. a wide range of clinical motor phenomena, from reflex myoclonus to myoclonic epilepsy, caused by abnormal sensorimotor cortical discharges. The aim of this update is to provide a detailed analysis of the mechanisms defining cortical tremor, as seen in FCMTE. After reviewing the clinical and genetic features of FCMTE, we discuss the possible mechanisms generating the distinct elements of the cortical myoclonus spectrum, and how cortical tremor fits into it. We propose that the spectrum is due to the evolution from a spatially limited focus of excitability to recruitment of more complex mechanisms capable of sustaining repetitive activity, overcoming inhibitory mechanisms that restrict excitatory bursts, and engaging wide areas of cortex. Finally, we provide evidence for a possible common denominator of the elements of the spectrum, i.e. the cerebellum, and discuss its role in FCMTE, according to recent genetic findings.

Familial cortical myoclonic tremor with epilepsy: TTTCA/TTTTA repeat expansions and expanding phenotype in two Chinese families

Recently, expanded intronic TTTCA and TTTTA repeat in SAMD12 were identified in families with familial cortical myoclonic tremor with epilepsy (FCMTE). We conducted to this study to clarify the genetic etiology and to describe the clinical, neurophysiologic, and imaging features in two unrelated Chinese families with FCMTE. In this study, we performed the RP-PCR and long-range PCR analysis to examine and verifyTTTCA and TTTTA expansions in five affected members whose severities of cortical tremor, neuropsychology and MRI were also evaluated. Reliable clinical information was collected from another two affected members. Our results revealed that expansions of intronic TTTCA and TTTTA repeats in SAMD12 were both identified in all five affected subjects. All seven affected living patients had cortical tremor with a median age at onset of 16.4 years (range, 10-22 years). Convulsions occurred in 5 of 7 with a median age at onset of 32.4 years (range, 10-42 years). Among five patients evaluated for cortical tremor severity and psychiatric comorbidity, two patients had severe cortical tremor, anxiety and depression. Abnormal brain MRI findings including the possible existence of demyelination, severe atrophy of the cerebral hemisphere and abnormal bilateral symmetrical signals in the globus pallidus were observed in three patients, respectively. These results further expanded the known genotype in two Chinese families affected with FCMTE. Border clinical spectrum needs to be confirmed in future studies from additional FCMTE families genetically diagnosed.

TTTCA Repeat Expansion of SAMD12 in a New Benign Adult Familial Myoclonic Epilepsy Pedigree

Benign adult familial myoclonic epilepsy (BAFME) is an autosomal dominant disorder characterized by adult-onset cortical myoclonus with or without seizures. Recently, it was reported to be associated with intronic TTTTA/TTTCA expansions. To investigate whether these abnormal expansions are involved in our new pedigree from China, whole exome sequencing (WES) and repeat-primed polymerase chain reaction (RP-PCR) analysis were performed to detect potential mutation in pedigree members. Neither causal mutations cosegregated with the disease in the family nor any novel mutation was identified through WES, while an abnormal TTTCA expansion in SAMD12 was identified by RP-PCR and then proved to be cosegregated in the pedigree. All the 12 alive affected individuals (M/F = 4/8; average age = 46.7 years old, range from 27 to 66) showed typical characteristics of BAFME. In addition, maternal clinical anticipation was observed in six mother/child pairs. In conclusion, our study offered the evidence of intronic pentanucleotide expansions in SAMD12 from a new Chinese BAFME pedigree, which further confirmed the association between this expansion and the pathogenesis of BAFME.

fMRI functional connectivity as an indicator of interictal epileptic discharges

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Functional connectivity to successful EEG/fMRI response indicates higher IED rates.

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The results hold when correcting for distance to maximum EEG-fMRI and laterality.

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Intracranial IED rates correlate with functional connectivity to EEG/fMRI maxima.

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Results suggest it is feasible to non-invasively infer the brain regions with IEDs.

Objective

To explore the relationship between functional connectivity and presence of interictal epileptic discharges (IEDs) in different brain regions in intracranial EEG (iEEG).

Methods

We studied 38 focal epilepsy patients who underwent simultaneous EEG/fMRI scanning and subsequent intracerebral stereo-EEG investigation. In EEG/fMRI analysis, IEDs with different spatial distributions were considered independent studies and IED-related maximal BOLD responses were evaluated. Studies with iEEG electrodes inside the maximal responses were selected and divided into three groups: Studies with 1. distinct maximal BOLD highly concordant with seizure-onset-zone (SOZ); 2. Moderate maximal BOLD concordant with SOZ; 3. maximal BOLD discordant with SOZ. Using maximal BOLD as seed, its functionally connected zone (FCZ) was determined. IED rates in iEEG channels inside and outside the FCZ were compared in the three groups. The effect of laterality and distance between channels and maximal BOLD, and correlation between functional connectivity values and IED rates were analyzed.

Results

Thirty-six studies in 25 patients were included. IED rates of intracranial EEG channels inside the FCZ were significantly higher than outside in Group 1 (p = 2.6×10−6) and Group 2 (p = 1.2×10−3) and the inside-outside difference remained after regressing distance and laterality factors. In Group 1, connectivity values were significantly correlated with IED rates in channels inside the FCZ (p < 0.05).

Significance

Our results indicate a higher probability of finding intracranial IEDs in the FCZ of SOZ-concordant maximal BOLD responses than in other regions, regardless of distance and laterality. In studies with distinct maximal BOLD, connectivity values can partially predict IED rates in intracranial EEG. It is thus feasible to non-invasively delineate brain regions that are likely to have high IED rates.

Radiation-induced cerebellar-cerebral functional connectivity alterations in nasopharyngeal carcinoma patients

The current study aimed to investigate the altered cerebellar-cerebral functional connectivity (FC) induced by radiotherapy to nasopharyngeal carcinoma (NPC) patients. Twenty-four NPC patients without treatment, and 35 NPC patients receiving radiotherapy underwent functional MRI scanning. Montreal cognitive assessment (MoCA) was performed to evaluate the cognitive status of all participants. FC between 10 predefined cerebellar seeds, which were demonstrated to be involved in different brain functional networks, and all brain voxels was obtained for each participant. Using a second-level two-sample t-test, three significantly different FCs between the two patient groups were found, including the connections between the left lobule VIII and the right medial frontal gyrus, the left lobule VIII and the right crus I, and the right lobule VIIb and the right fusiform gyrus. The altered cerebellar-cerebral FCs were also significantly correlated to the MoCA score, as well as the attention score, one of the seven subscores in MoCA. We suggested that the altered cerebellar-cerebral FCs may underlie the radiation-induced cognitive deficits in NPC patients, especially in the domain of attention. Furthermore, considering the functional networks in which the altered connections involved, the anticorrelation between the default network and dorsal attention network may be impaired, and the mediating function of the frontoparietal network to dorsal attention network may be disrupted. The significantly altered cerebellar-cerebral FC may serve as the potential biomarker in revealing the radiation-induced functional abnormalities and may help in the early intervention to the cognitive impairment.

Familial Cortical Myoclonic Tremor and Epilepsy, an Enigmatic Disorder: From Phenotypes to Pathophysiology and Genetics. A Systematic Review

Background

Autosomal dominant familial cortical myoclonic tremor and epilepsy (FCMTE) is characterized by distal tremulous myoclonus, generalized seizures, and signs of cortical reflex myoclonus. FCMTE has been described in over 100 pedigrees worldwide, under several different names and acronyms. Pathological changes have been located in the cerebellum. This systematic review discusses the clinical spectrum, treatment, pathophysiology, and genetic findings.

Methods

We carried out a PubMed search, using a combination of the following search terms: cortical tremor, myoclonus, epilepsy, benign course, adult onset, familial, and autosomal dominant; this resulted in a total of 77 studies (761 patients; 126 pedigrees) fulfilling the inclusion and exclusion criteria.

Results

Phenotypic differences across pedigrees exist, possibly related to underlying genetic differences. A "benign" phenotype has been described in several Japanese families and pedigrees linked to 8q (FCMTE1). French patients (5p linkage; FCMTE3) exhibit more severe progression, and in Japanese/Chinese pedigrees (with unknown linkage) anticipation has been suggested. Preferred treatment is with valproate (mind teratogenicity), levetiracetam, and/or clonazepam. Several genes have been identified, which differ in potential pathogenicity.

Discussion

Based on the core features (above), the syndrome can be considered a distinct clinical entity. Clinical features may also include proximal myoclonus and mild progression with aging. Valproate or levetiracetam, with or without clonazepam, reduces symptoms. FCMTE is a heterogeneous disorder, and likely to include a variety of different conditions with mutations of different genes. Distinct phenotypic traits might reflect different genetic mutations. Genes involved in Purkinje cell outgrowth or those encoding for ion channels or neurotransmitters seem good candidate genes.