Abstracts

Tuberous sclerosis complex (TSC) is a multisystem disorder associated with high rates of mental retardation and autism, often attributed to cortical tubers and seizure activity. The number, location, and size of cortical tubers may contribute to the development of mental retardation. A greater number of tubers is usually found in individuals with cognitive impairment. In individuals with seizures, an earlier age of seizure onset and infantile spasms are most strongly linked with cognitive impairment.
The goal of the current study was to investigate the relation between bilateral cortical tubers and seizure variables and mental retardation in individuals with tuberous sclerosis complex (TSC). The records of twenty-seven individuals with tuberous sclerosis undergoing neuropsychological assessment were examined. The sample included 11 males and 16 females. Mean age at the time of neuropsychological assessment was 9 years (SD, 8.4 years; range 6 months to 33 years). Subjects were divided into three groups according to standard scores on the Vineland Adaptive Behavior Scales Interview Edition Expanded Form or the appropriate Wechsler IQ scale. Laterality of cortical tubers (i.e., bilateral versus non-bilateral), the age of seizure onset, and presence of infantile spasms were obtained. Chi-square analyses were performed using level of cognitive status and gender, level of cognitive status and history of infantile spasms, and level of cognitive status and MRI findings (bilateral tubers versus other findings). Point-biserial correlation was computed between level of cognitive status and age at seizure onset (rank ordered). Pearson correlation coefficient was calculated using age and cognitive status as the two variables. Bilateral cortical tubers (p = 0.02) and early age of seizure onset (p = 0.04) were significantly related to impaired cognitive functioning. A similar trend was observed between infantile spasms and cognitive functioning (p = 0.06). Earlier seizure onset and bilateral cortical tubers pose considerable risks for mental retardation in TSC. Similar risks are noted for infantile spasms in other studies although the small sample size in the current report may have limited the power to detect such a relationship.