PERIVENTRICULAR NODULAR HETEROTOPIA - EPILEPTOGENIC FINDINGS

Purpose: We studied 17 patients with periventricular nodular heterotop ia (PNH) to further investigate the electroclinical pictures and semio logy of the associated seizures. Methods: PNH was diagnosed by means o f magnetic resonance imaging (MRI). The patients' clinical and familia l histories were carefully analyzed, and their electroclinical feature s and course of epilepsy followed for periods ranging from 10 months t o 22 years. The electroclinical data were compared with those of previ ously reported PNH cases. Results: The patients were subdivided into t hose with bilateral (7) and unilateral (10) PNH. The former were mainl y characterized by structural abnormalities in the posterior cerebral fossa and multiple seizure types; the latter were characterized by the paratrigonal location of the malformation and, frequently, by element ary seizures with a visual or auditory onset. Focal seizures were drug resistant in most cases. The interictal EEG abnormalities were always focal and consistent with the location of the PNH. A previously unrep orted photic driving of posterior background activity was observed in all patients and was always consistent with the PNH location. Conclusi ons: Our present findings and previously reported data show that bilat eral and unilateral PNH cases are different in their morphological and electroclinical features and may be determined by different etiologie s. The female predominance, frequent familial occurrence, and positive family history for epilepsy suggest that genetic factors may be invol ved in the genesis of bilateral and symmetrical PNH, whereas the prese nce of prenatal risk factors and its location in the watershed paratri gonal area suggest that vascular mechanisms may determine unilateral P NH.