F.E. Jansen

Cognitive impairment in tuberous sclerosis complex is a multifactorial condition

Objective: In patients with tuberous sclerosis complex (TSC), associations between tuber number, infantile spasms, and cognitive impairment have been proposed. We hypothesized that the tuber/brain proportion (TBP), the proportion of the total brain volume occupied by tubers, would be a better determinant of seizures and cognitive function than the number of tubers. We investigated tuber load, seizures, and cognitive function and their relationships. Methods: Tuber number and TBP were characterized on three-dimensional fluid-attenuated inversion recovery MRI with an automated tuber segmentation program. Seizure histories and EEG recordings were obtained. Intelligence equivalents were determined and an individual cognition index (a marker of cognition that incorporated multiple cognitive domains) was calculated. Results: In our sample of 61 patients with TSC, TBP was inversely related to the age at seizure onset and to the intelligence equivalent and tended to be inversely related to the cognition index. Further, a younger age at seizure onset or a history of infantile spasms was related to lower intelligence and lower cognition index. In a multivariable analysis, only age at seizure onset and cognition index were related. Conclusions: Our systematic analysis confirms proposed relationships between tuber load, epilepsy and cognitive function in tuberous sclerosis complex (TSC), but also indicates that tuber/brain proportion is a better predictor of cognitive function than tuber number and that age at seizure onset is the only independent determinant of cognitive function. Seizure control should be the principal neurointervention in patients with TSC.

Overlapping neurologic and cognitive phenotypes in patients with TSC1 or TSC2 mutations

Objective: The purpose of this study was to systematically analyze the associations between different TSC1 and TSC2 mutations and the neurologic and cognitive phenotype in patients with tuberous sclerosis complex (TSC). Methods: Mutation analysis was performed in 58 patients with TSC. Epilepsy variables, including EEG, were classified. A cognition index was determined based on a comprehensive neuropsychological assessment. On three-dimensional fluid-attenuated inversion recovery MR images, an automated tuber segmentation program detected and calculated the number of tubers and the proportion of total brain volume occupied by tubers (tuber/brain proportion [TBP]). Results: As a group, patients with a TSC2 mutation had earlier age at seizure onset, lower cognition index, more tubers, and a greater TBP than those with a TSC1 mutation, but the ranges overlapped considerably. Familial cases were older at seizure onset and had a higher cognition index than nonfamilial cases. Patients with a mutation deleting or directly inactivating the tuberin GTPase activating protein (GAP) domain had more tubers and a greater TBP than those with an intact GAP domain. Patients with a truncating TSC1 or TSC2 mutation differed from those with nontruncating mutations in seizure types only. Conclusions: Although patients with a TSC1 mutation are more likely to have a less severe neurologic and cognitive phenotype than those with a TSC2 mutation, the considerable overlap between both aspects of the phenotype implies that prediction of the neurologic and cognitive phenotypes in individuals with tuberous sclerosis complex should not be based on their particular TSC1 or TSC2 mutation.

Epilepsy surgery in tuberous sclerosis: The Dutch experience

INTRODUCTION Epilepsy associated with tuberous sclerosis complex (TSC) is drug resistant in more than half of the patients. Epilepsy surgery may be an alternative treatment option, if the epileptogenic tuber can be identified reliably and if seizure reduction is not at the expense of cognitive or other functions. We report the pre-surgical identification of the epileptogenic tuber and post-surgical outcome of patients with TSC in The Netherlands. METHODS Twenty-five patients underwent the pre-surgical evaluation of the Dutch Comprehensive Epilepsy Surgery Programme, including a detailed seizure history, interictal and ictal video EEG registrations, 3D FLAIR MRI scans and neuropsychological testing. Suitability of the candidates was decided in consensus. Seizure outcome, scored with the Engel classification, and cognition were reassessed at fixed post-surgery intervals. RESULTS Epilepsy surgery was performed in six patients. At follow-up, four patients had Engel classification 1, two had classification 4. Improved development and behaviour was perceived by the parents of two patients. Epilepsy surgery was not performed in 19 patients because seizures were not captured, ictal onset zones could not be localised or were multiple, interictal EEG, video EEG and MEG results were not concordant, or seizure burden had diminished during decision making. A higher cognition index was found in the surgical patients compared to the non-surgical candidates. CONCLUSIONS Epilepsy surgery can be performed safely and successfully in patients in whom semiology, interictal EEG, ictal EEG, MEG and the location of tubers are concordant. In other cases the risk of surgery should be weighed against the chance of seizure relief and in case of children subsequent impact on neurodevelopment.

Differential localization of hamartin and tuberin and increased S6 phosphorylation in a tuber

In a tuberous sclerosis patient with a mutation in the TSC1 tumor suppressor gene, no second-hit mutation was found in a resected cortical tuber. Tuber giant cells showed predominantly nuclear hamartin, cytosolic tuberin, and hyperphosphorylation of S6. Differential accumulation of hamartin and tuberin in separate cellular compartments of giant cells may prevent formation of the hamartin–tuberin complex, resulting in increased S6 phosphorylation. These data provide an alternative mechanism for tuberogenesis.

Diazepam-enhanced β activity in Sturge Weber syndrome: its diagnostic significance in comparison with MRI

OBJECTIVES This study was performed to assess the extent of functional involvement of the affected hemisphere in Sturge Weber syndrome in comparison with the uninvolved hemisphere. To this end beta activity in the electroencephalogram (EEG) was measured, both before and after administration of diazepam intravenously (i.v.). METHODS In 9 patients asymmetry in beta band activity was studied before and after diazepam administration. Several beta bands and asymmetry parameters were calculated. beta band asymmetries were compared with structural abnormalities (magnetic resonance imaging, MRI). RESULTS Total beta activity was reduced in the involved hemisphere in all patients after diazepam administration. In 3 patients functional abnormalities were found in brain regions that were structurally intact. CONCLUSIONS Decreased diazepam-enhanced beta activity in the EEG is a sensitive criterion of functional abnormality. In patients with subtle structural abnormalities diazepam-enhanced EEG may have added value in diagnosing functional involvement and in monitoring disease progression in patients.