Clinical features, EEG findings and outcome in patients with bilateral periventricular nodular heterotopia and epilepsy

Aim: To review the clinical, electrophysiological and neuroimaging data of eight adult patients (4F/4M) with epilepsy and bilateral periventricular nodular heterotopia (PNH) after a long duration of follow-up. Materials and Methods: The clinical charts were reviewed for demographic and clinical features, seizure types and frequency, treatment and prognosis of all eight patients who were under follow-up by one of the authors (SS). The recordings of video-EEG monitoring with scalp electrodes in five patients and routine EEGs in all patients were reviewed. Results: The clinical semiology was in accord with seizures originating from temporal lobe region in four patients, while an extratemporal onset was assumed in the others (in one with additional temporal seizures). Interictal EEGs were normal in one patient, who was diagnosed as having psychogenic nonepileptic seizure. Abnormalities seen in interictal EEGs were bilateral independent temporal focus in three, unilateral epileptiform abnormalities in two, and generalized 3 cyc/sec discharges mimicking idiopathic generalized epilepsies in two patients. Only two patients' MRI revealed bilaterally contiguous heterotopic nodules (symmetric and asymmetric type) and, interestingly, these two patients did not have intractable seizures while the other six patients with bilateral, asymmetric and noncontiguous heterotopic nodules suffered from intractable seizures. Conclusions: Patients with bilateral PNH have different clinical features, EEG findings and extension of the heterotopic nodules. These patients may be misdiagnosed as having idiopathic generalized epilepsy, temporal lobe epilepsy or even psychogenic nonepileptic seizures without high quality MRI because of the misleading seizure semiology and interictal-ictal EEG findings. Seizures are usually drug-resistant but the patients who have diffuse symmetric or asymmetric contiguous heterotopic nodules may have good prognosis.