Abstracts

RATIONALE: Neuronal heterotopia encompass disorders of neuronal migration and are commonly associated with epilepsy. The advent of high resolution MRI has resulted in the better identification of the variable morphology and topography of these malformations of cortical development. We reviewed the clinical spectrum of epilepsy in neuronal heterotopia in relation to the neuroanatomical location (periventricular or PV, subcortical or SC) and involvement of the overlying grey matter (heterotopia with cortical dysplasia or CD). METHODS: 56 patients with epilepsy and heterotopic grey matter on MRI were reviewed. They were classified into 3 groups: PV (n=23), SC (n=10), and CD (n=23). We studied these clinical features: age of seizure onset, seizure frequency, semiology, risk factors, gender, family history, neurological abnormalities, and developmental milestones. Statistical analysis was applied using Fisher exact probability test. RESULTS: Seizures in CD tend to occur at a younger age than PV and SC and are more likely to be intractable. 5 out of 23 patients (22%) with CD started having seizures during the neonatal period. None of the patients in the PV and SC groups had neonatal seizures. The presence of CD results in a higher proportion of focal neurological deficits and developmental delay. There is a higher proportion of females affected in the PV and SC groups. Using statistical analysis, the variation in clinical features were significant in seizure frequency (p=0.015) and developmental delay (p=0.001). CONCLUSIONS: In patients with neuronal heterotopia and epilepsy, cortical involvement (CD group) and proximity to the grey matter (SC group) tend to result in more intractable seizures with earlier age of onset. These patients are more likely to be developmentally delayed. Although our data clearly shows that the clinical spectrum varies with the location of the heterotopia and the involvement of the overlying cortex, statistical significance was seen only in 2 parameters (seizure frequency and developmental delay). This is largely due to the small number of patients studied. We expect to overcome this limitation as more patients undergo high resolution MRI.