Focal, continuous spikes suggest cortical developmental abnormalities - Clinical, MRI and neuropathological correlates

Objectives - Widespread use of MRI now gives us increased insights into the different expressions of malformations of cortical development (MCD). The heterogeneity of these disorders are reflected by their varied clinical and neuroimaging features. Characteristic and intense scalp EEG abnormalities have been described in some patients. Material and methods - We report the MRI and clinical findings of 3 adult patients (age 32-36) with a peculiar EEG pattern of distinct, localized, fast, continuous spiking. These patients represent all patients with such EEG findings that have been recognized by the first author during 9 years. Results - MRI showed MCDs in all, respectively hemimegalencephaly, a subcortical heterotopion, and a focal cortical dysgenesis. The EEG findings had been stable since childhood and were posteriorly located. Two patients had fairly well controlled epilepsy in adult age. The third patient was incapacitated by persistent seizures and was treated with surgery. Histologically cortical dysplasia with neuronal clusters was found in this patient. Variable degrees of cognitive dysfunction were present in all. Conclusion - Focal, continuous, fast spiking is an unusual scalp EEG pattern. It is not an inevitable sign of severe epilepsy. It may suggest an MCD. It is not yet clear to what extent such findings are predictive of a dysgenetic etiology of epilepsy.