The clinical utility of MRI in patients with neurodevelopmental disorders of unknown origin.

INTRODUCTION: Neuroimaging of the brain in the diagnostic work-up of patients with neurodevelopmental disorders is a matter of continuing debate. Recommendations range from performing brain imaging in all patients with neurodevelopmental disorders to performing an MRI only in those with indication on clinical examinations. Important indications for neuroimaging are head size abnormalities and focal neurological findings. METHODS: Patients with neurodevelopmental disorders of unknown origin (n = 410), referred to a specialized tertiary diagnostic center for neurodevelopmental disorders were included in a retrospective analysis. A 1-day work-up, including an MRI of the brain was performed. Studied were the: (i) yield of MRI scans of the brain and (ii) associations of specific clinical symptoms/signs with abnormal and diagnostic MRI scans. RESULTS: (i) In 30.7% of the 410 patients with neurodevelopmental disorders (n = 126), abnormal MRI scans were observed, leading to an etiological diagnosis in 5.4% of the patients (n = 22). (ii) Pyramidal disorders (P = 0.001), epilepsy (P = 0.04) and an abnormal head circumference (P = 0.02) were associated with an abnormal MRI scan. The presence of one of the following neurological symptoms/signs: movement disorders, pyramidal disorders, epilepsy, or an abnormal head circumference was associated with a diagnostic MRI scan (P < 0.001) (diagnostic MRI % in neurological versus no neurological symptoms/signs, 13.0% versus 1.9%). CONCLUSION: Neuroimaging of the brain in a tertiary care center for patients with neurodevelopmental disorders of unknown origin is useful, especially in case of neurological symptoms/signs.

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.