Electroencephalographic findings in patients with circumscribed thalamic lesions.

INTRODUCTION: Thalamo-cortical networks have mainly been studied in the generation of idiopathic (genetic) epilepsies. The purpose of this study was to analyze EEG patterns and the occurrence of focal (symptomatic) epileptic seizures in patients with acquired circumscribed thalamic lesions. PATIENTS AND METHODS: Among 596 patients with thalamic lesions, we identified 47 patients in whom circumscribed thalamic lesions were detected by MRI and who underwent an EEG examination at the same stay at hospital. EEG findings were divided into normal findings, unspecific pathological changes and epileptiform discharges. The EEG findings were correlated to the localisation of the lesion within the thalamus and to the patients symptoms. RESULTS: In 32 patients (68%) pathological EEG findings were observed. They were heterogeneous and comprised regional and generalized slowing, triphasic waves, generalized periodic and regional epileptiform discharges. However, some characteristic findings were seen: Regional slowing was associated with ipsilateral thalamic lesions independent of the thalamic subarea, epileptiform discharges were related to lesions in the ipsilateral medial thalamus and periodic generalized discharges/triphasic waves with lesions in the anterior-ventromedial thalamus. Epileptic seizures were also more common in patients with medial thalamic lesions. Patients with regional epileptiform discharges responded to antiepileptic treatment whereas patients with triphasic waves and generalized periodic patterns did not. In some cases, it remained difficult to decide whether the thalamic lesion was the cause or consequence of epileptic activity. CONCLUSION: Pathological EEG findings are common in patients with acute and chronic thalamic lesions. EEG patterns associated with circumscribed thalamic lesions were influenced by the affected thalamic subregion. As in idiopathic generalized epilepsy, also in symptomatic epilepsy, the medial thalamus revealed to play a role in the generation of epileptiform discharges. In the patients with generalized periodic discharges and acute lesions in the ventral-anterior-medial thalamus, however, EEG changes were more likely caused by a disinhibition of cortico-thalamic networks than by a status epilepticus and thus risks and benefits of an aggressive antiepileptic treatment must be thoroughly balanced.

Intrinsic functional connectivity alterations in progressive supranuclear palsy: Differential effects in frontal cortex, motor, and midbrain networks.

BACKGROUND: The topography of functional network changes in progressive supranuclear palsy can be mapped by intrinsic functional connectivity MRI. The objective of this study was to study functional connectivity and its clinical and behavioral correlates in dedicated networks comprising the cognition-related default mode and the motor and midbrain functional networks in patients with PSP. METHODS: Whole-brain-based "resting-state" functional MRI and high-resolution T1-weighted magnetic resonance imaging data together with neuropsychological and video-oculographic data from 34 PSP patients (22 with Richardson subtype and 12 with parkinsonian subtype) and 35 matched healthy controls were subjected to network-based functional connectivity and voxel-based morphometry analysis. RESULTS: After correction for global patterns of brain atrophy, the group comparison between PSP patients and controls revealed significantly decreased functional connectivity (P < 0.05, corrected) in the prefrontal cortex, which was significantly correlated with cognitive performance (P = 0.006). Of note, midbrain network connectivity in PSP patients showed increased connectivity with the thalamus, on the one hand, whereas, on the other hand, lower functional connectivity within the midbrain was significantly correlated with vertical gaze impairment, as quantified by video-oculography (P = 0.004). PSP Richardson subtype showed significantly increased functional motor network connectivity with the medial prefrontal gyrus. CONCLUSIONS: PSP-associated neurodegeneration was attributed to both decreased and increased functional connectivity. Decreasing functional connectivity was associated with worse behavioral performance (ie, dementia severity and gaze palsy), whereas the pattern of increased functional connectivity may be a potential adaptive mechanism. © 2017 International Parkinson and Movement Disorder Society.

The cerebro-morphological fingerprint of a progeroid syndrome: white matter changes correlate with neurological symptoms in xeroderma pigmentosum.

BACKGROUND: Xeroderma pigmentosum (XP) is a rare autosomal recessive progeroid syndrome. It has recently been shown that the underlying DNA repair defect plays a central role in the aging process. In addition to skin symptoms, various premature neurological abnormalities have been reported. METHODOLOGY/PRINCIPAL FINDINGS: We present the clinical neurological phenotype in 14 XP patients (seven subtypes), in seven of these patients together with conventional and multiparametric advanced MRI data to assess the macrostructural and microstructural cerebral morphology in comparison to controls, including volumetric measurements, MR spectroscopy ((1)H MRS), and diffusion tensor imaging (DTI). Clinical hallmarks were spinocerebellar ataxia, pyramidal tract signs, and mild cognitive deficits. DTI demonstrated significantly reduced WM directionality in all regions investigated, i.e. the thalamus, the corticospinal tracts and the dorsal corpus callosum. Single patients showed a marked relative hippocampal volume reduction, but the patients were not different from controls in the volumetric measurements of hippocampal and whole brain volumes at group level. However, (1)H MRS demonstrated that the hippocampal formation was metabolically altered. CONCLUSIONS: The most prominent feature was the white matter affectation, as assessed by DTI, with volume and directionality reductions of the fiber projections involving both the craniocaudal fibers and the interhemispheric connections. These findings, although heterogeneous among the study sample, could be correlated with the clinico-neurological symptoms. The imaging findings support the position that myelin structures degrade prematurely in the brain of XP patients.