Free-water metrics in medial temporal lobe white matter tract projections relate to longitudinal cognitive decline

Although hippocampal volume has served as a long-standing predictor of cognitive decline, diffusion magnetic resonance imaging studies of white matter have shown similar relationships. Still, it remains unclear if gray matter and white matter interact to predict cognitive impairment and longitudinal decline. Here, we investigate whether free-water (FW) and FW-corrected fractional anisotropy (FA_T) within medial temporal lobe white matter tracts provides meaningful contribution to cognition and cognitive decline beyond hippocampal volume. Using data from the Vanderbilt Memory & Aging Project (n = 319), we found that FW was associated with baseline memory and executive function beyond that of hippocampal volume and other comorbidities. Longitudinal analyses demonstrated significant interactions of hippocampal volume and inferior longitudinal fasciculus (p = 0.043) and cingulum bundle (p = 0.025) FA_T on memory decline and with fornix FA_T (p = 0.025) on decline in executive function. Results suggest that FW metrics of white matter have a unique role in cognitive decline and should be included in theoretical models of aging, cerebrovascular disease, and Alzheimer's disease.

Verbal Memory Decline following DBS for Parkinson's Disease: Structural Volumetric MRI Relationships

Background

Parkinson’s disease is a chronic degenerative movement disorder. The mainstay of treatment is medical. In certain patients Deep Brain Stimulation (DBS) may be offered. However, DBS has been associated with post-operative neuropsychology changes, especially in verbal memory.

Objectives

Firstly, to determine if pre-surgical thalamic and hippocampal volumes were related to verbal memory changes following DBS. Secondly, to determine if clinical factors such as age, duration of symptoms or motor severity (UPDRS Part III score) were related to verbal memory changes.

Methods

A consecutive group of 40 patients undergoing bilateral Subthalamic Nucleus (STN)-DBS for PD were selected. Brain MRI data was acquired, pre-processed and structural volumetric data was extracted using FSL. Verbal memory test scores for pre- and post-STN-DBS surgery were recorded. Linear regression was used to investigate the relationship between score change and structural volumetric data.

Results

A significant relationship was demonstrated between change in List Learning test score and thalamic (left, p = 0.02) and hippocampal (left, p = 0.02 and right p = 0.03) volumes. Duration of symptoms was also associated with List Learning score change (p = 0.02 to 0.03).

Conclusion

Verbal memory score changes appear to have a relationship to pre-surgical MRI structural volumetric data. The findings of this study provide a basis for further research into the use of pre-surgical MRI to counsel PD patients regarding post-surgical verbal memory changes.

The Arcuate Fasciculus in auditory-verbal hallucinations: a meta-analysis of diffusion-tensor-imaging studies

Auditory-verbal hallucinations (AVHs) are associated with an impaired connectivity of large-scale networks. To examine the relationship between white-matter integrity and AVHs, we conducted a meta-analysis of diffusion-tensor-imaging studies that compared patients with schizophrenia and AVHs with matched healthy controls (HCs). Five studies were retained gathering 256 DTI data points, divided into AVHs (n=106) and HCs (n=150). The meta-analysis demonstrated a reduced fractional anisotropy in the left Arcuate Fasciculus (AF) of hallucinators (hg= -0.42; CI[-0.69,-0.16]; p<10(-3)). The current meta-analysis confirmed disruptions of white matter integrity in the left AF bundle of schizophrenia patients with AVHs.

[Case of wall-eyed bilateral internuclear ophthalmoplegia (WEBINO) syndrome with cerebellar ataxia and facial dysesthesia]

We report an 85-year-old man presenting with wall-eyed bilateral internuclear ophthalmoplegia (WEBINO) syndrome with cerebellar ataxia and facial dysesthesia. He experienced an abrupt onset of double vision and exotropia of the right eye with unsteady gait and dysesthesia around upper lip. He was admitted to our hospital ten days after the onset of the double vision. On admission, he presented with WEBINO, left limb ataxia, and dysesthesia around upper lip on the right side. His exotropia was prominent on the right side. Diffusion weighted images of MRI revealed a high intensity lesion in the paramedian pontine tegmentum involving bilateral medial longitudinal fasciculus (MLF), consistent with acute ischemic lesion. Four months after the onset, the WEBINO persisted, without cerebellar ataxia and facial dysesthesia. Putative lesions of the WEBINO, cerebellar ataxia and facial dysesthesia were bilateral MLF, left superior cerebellar peduncle and trigeminothalamic tract, respectively, which were broader than the MRI lesion. Neurological examination is critical for evaluation of accurate ischemic area.

Reduction in parvalbumin expression in the zona incerta after 6OHDA lesion in rats

In an effort to understand better the neurochemical changes that occur in Parkinson disease, we have examined the expression patterns of the calcium-binding protein parvalbumin in the zona incerta in parkinsonian rats. Sprague-Dawley rats had small volumes of either saline (control) or 6 hydroxydopamine (6OHDA) injected into the medial forebrain bundle, the major tract carrying dopaminergic nigrostriatal axons. After various post-lesion survival periods, ranging from 2 hrs to 84 days, rats were perfused with formaldehyde and their brains processed for routine tyrosine hydroxylase (TH) or parvalbumin immunocytochemistry. In the 3 to 84 days post-lesion cases, there was an overall 50% reduction in the number of parvalbumin(+) cells in the zona incerta on the 6OHDA-lesioned side when compared to control. In the 2 hrs post-lesion cases, there was no substantial loss of parvalbumin(+) cells in the zona incerta after 6OHDA lesion, although in these cases (unlike the longer survival periods), there was limited loss of TH(+) cells in the midbrain on the lesion side. The loss of parvalbumin(+) cells from the zona incerta was due to a loss of antigen expression rather than a loss of the cells themselves, since the number of Nissl-stained cells in the zona incerta was similar on the control and 6OHDA-lesioned sides. In summary, our results indicate that a loss of the midbrain dopaminergic cells induces a major change in parvalbumin expression within the zona incerta. This change may have key functional and clinical implications.

Stimulation of the caudal zona incerta is superior to stimulation of the subthalamic nucleus in improving contralateral parkinsonism

Deep brain stimulation (DBS) has an increasing role in the treatment of idiopathic Parkinson's disease. Although, the subthalamic nucleus (STN) is the commonly chosen target, a number of groups have reported that the most effective contact lies dorsal/dorsomedial to the STN (region of the pallidofugal fibres and the rostral zona incerta) or at the junction between the dorsal border of the STN and the latter. We analysed our outcome data from Parkinson's disease patients treated with DBS between April 2002 and June 2004. During this period we moved our target from the STN to the region dorsomedial/medial to it and subsequently targeted the caudal part of the zona incerta nucleus (cZI). We present a comparison of the motor outcomes between these three groups of patients with optimal contacts within the STN (group 1), dorsomedial/medial to the STN (group 2) and in the cZI nucleus (group 3). Thirty-five patients with Parkinson's disease underwent MRI directed implantation of 64 DBS leads into the STN (17), dorsomedial/medial to STN (20) and cZI (27). The primary outcome measure was the contralateral Unified Parkinson's Disease Rating Scale (UPDRS) motor score (off medication/off stimulation versus off medication/on stimulation) measured at follow-up (median time 6 months). The secondary outcome measures were the UPDRS III subscores of tremor, bradykinesia and rigidity. Dyskinesia score, L-dopa medication reduction and stimulation parameters were also recorded. The mean adjusted contralateral UPDRS III score with cZI stimulation was 3.1 (76% reduction) compared to 4.9 (61% reduction) in group 2 and 5.7 (55% reduction) in the STN (P-value for trend <0.001). There was a 93% improvement in tremor with cZI stimulation versus 86% in group 2 versus 61% in group 1 (P-value = 0.01). Adjusted 'off-on' rigidity scores were 1.0 for the cZI group (76% reduction), 2.0 for group 2 (52% reduction) and 2.1 for group 1 (50% reduction) (P-value for trend = 0.002). Bradykinesia was more markedly improved in the cZI group (65%) compared to group 2 (56%) or STN group (59%) (P-value for trend = 0.17). There were no statistically significant differences in the dyskinesia scores, L-dopa medication reduction and stimulation parameters between the three groups. Stimulation related complications were seen in some group 2 patients. High frequency stimulation of the cZI results in greater improvement in contralateral motor scores in Parkinson's disease patients than stimulation of the STN. We discuss the implications of this finding and the potential role played by the ZI in Parkinson's disease.

Stimulation sous-thalamique dans la maladie de Parkinson sévère

The subthalamic nucleus (STN) is the main target of deep brain stimulation (DBS) treatment for severe idiopathic Parkinson's disease. But there is still no clear information on the location of the effective contacts (used during the chronic phase of stimulation). Our aim was to assess the anatomical structures of the subthalamic area (STA) involved during chronic DBS. Ten patients successfully treated were included. The surgical procedure was based on direct STN targeting (stereotactic MRI based) pondered by the acute effects of intraoperative stimulation. We used a formaldehyde-fixed human specimen to compare by matching MRI images obtained at 1.5 Tesla (performed in clinical stereotactic conditions) and at very high field at 4.7 Tesla. This allowed accurate analysis of the anatomy of the STA and retrospective precision of the location of the center of effective contacts which were located within the STN in 4 patients, at the interface between the STN and the ZI and/or FF in 13, at the interface between ZI and FF in 2 and between the STN and the substantia nigra in one. These results were consistent with the literature, revealing the implication of neighboring structures, especially the zona incerta and Forel's Field, in the clinical benefit.

Conjugate eye deviation due to traumatic striatal-subthalamic lesion

We report the case of a 22-year-old man after severe cranial trauma, who was noted to have conjugate eye deviation (CED) to the left. A magnetic resonance imaging (MRI) scan demonstrated a lesion in the left (ipsilateral) striatal-subthalamic region. The involvement of supranuclear fibres from the left frontal eye field (FEF) traveling to the right parapontine reticular formation (PPRF) could explain this clinical finding. Alternatively, involvement of deep brain nuclei, such as the striatum and the subthalamic nucleus, could be responsible for this phenomenon. This neurological presentation is unusual after severe cranial trauma.

Effects of stimulation of the subthalamic area on oscillatory pallidal activity in Parkinson's disease

The pattern of neuronal discharge within the basal ganglia is disturbed in Parkinson's disease (PD). In particular, there is a tendency for neuronal elements to synchronise at around 20 Hz in the absence of dopaminergic treatment, whereas this activity can be replaced by spontaneous synchronisation at much higher frequencies (>70 Hz) following dopaminergic treatment [J. Neurosci. 21 (2001) 1033; Brain 126 (2003) 2153]. In two PD patients (3 sides), we show that stimulating the subthalamic area at around 20 Hz exacerbates synchronisation at similar frequencies in the globus pallidus interna, the major output structure of the human basal ganglia. In contrast, stimulating the subthalamic area at >70 Hz suppresses pallidal activity at about 20 Hz. Clinically, stimulation of the subthalamic area at similar high frequencies reverses parkinsonism and forms the basis of therapeutic deep brain stimulation in PD. The results point to a possible common mechanism by which both dopaminergic treatment associated synchronisation of subthalamic activity at very high frequency and synchronisation imposed by therapeutic stimulation of the subthalamic area inhibit an abnormal and potentially deleterious synchronisation of basal ganglia output at around 20 Hz. If this activity is unchecked by synchronisation at higher frequency, then pathological 20-Hz oscillations may cascade through the basal ganglia, increasing at subsequent levels of processing.

Functional organization of the circuits connecting the cerebral cortex and the basal ganglia: implications for the role of the basal ganglia in epilepsy

The basal ganglia are composed of a set of forebrain structures implicated in the adaptive control of behaviour. These structures process information originating from the entire cerebral cortex, as well as from nonspecific thalamic nuclei and the amygdala. In turn, they redistribute the integrated signals toward thalamic and brainstem nuclei related to motor, premotor, prefrontal and limbic cortical areas. During the two last decades, there has been increasing experimental evidence that the basal ganglia circuitry may be part of a remote control system influencing the spread of epileptic seizures. In the present article, we review the basic principles of the functional organization of the basal ganglia and provide experimental data on the activity that is transmitted by the cerebral cortex to the input stage of the basal ganglia during absence seizures. The functional organization of the basal ganglia supports the current hypothesis that these structures can dynamically control generalized seizures through their input-output relationships.

Hemiballism after subthalamotomy in patients with Parkinson's disease: report of 2 cases

The occurrence of persistent hemiballism after subthalamotomy for Parkinson's disease (PD) has not been described as frequently as mild or transient dyskinesia. We report on 2 patients with advanced PD who developed hemiballism and/or dyskinesia after subthalamotomy. One patient with a small lesion confined to the subthalamic nucleus (STN) developed persistent hemiballism; the other with a larger lesion involving the STN and also the zona incerta presented with a transient dyskinesia in a single limb. We conclude that a precise STN lesion might bear a potential risk of persistent hemiballism.