Abstracts

RATIONALE: With the advent of sophisticated new imaging techniques, in particular high resolution MRI, there is an increasing number of patients with newly diagnosed epilepsy in whom even subtle causes for their seizure disorder are detected. Heterotopias are a typical example of this progress. The current classification distinguishes between 1. subependymal heterotopia (SEH), 2. subcortical heterotopia (SCH) and 3. band heterotopia or double cortex syndrome (DCS). Seizure manifestation may be the only clinical symptom in patients with SEH and SCH.
METHODS: We report on the course of two 17-year old identical twin sisters. We came to know the index patient (IP) at age 15 years when she presented with partial motor seizures of her right side for the first time. The clinical examination was normal and there was no family history of epilepsy. The mother though reported several spontaneous abortions. The identical twin sister (ITS) had no seizures at that time and was without any clinical pathology.
RESULTS: Interictal EEG-monitoring in the IP showed no focal abnormality. High resolution MRI detected significant, widespread, symmetrical distributed SEH and right fronto-parietal tissue density suspicious for cortical dysplasia. A very similar pattern was then found in both the patient[ssquote]s mother and her ITS. The IP remained seizure free under lamotrigine monotherapy. Within one year, the ITS also presented in our clinic with her first generalized tonic-clonic seizure. She was also started on AED treatment and has been seizure-free since.
CONCLUSIONS: The heterogeneity of neuroradiologically proven cases of heterotopia was recently emphasized (Gleeson et al., Neurology 2000, 47 (2): 265-9). The most probable genetic mutation underlying the SEH in both these patients and their mother would be a mutation of the filamin gene. However, on-going molecular genetic analyses have not yet uncovered any abnormalities in the first 8 exons studied. Our observation suggests that genetic factors in epilepsy may direct not only very similar epileptogenic tissue changes in first degree relatives but may also play a significant role in the timing of first seizure manifestation.
Objective: At the end of this activity the participants should be able to discuss the relationsship between genetics, structural abnormalities and timing of seizure manifestation in identical twins.