Are focal cortical dysplasias being overlooked as a source of drug resistant epilepsy?

Focal cortical dysplasia first described by Taylor et al in 1971, is a subtype of malformations of cortical development in which developmental abnormality is strictly or mostly intracranial and thus should be referred more or less focalized malformations primarily involving the gray matter of the cortex.

Focal cortical dysplasia is the most common cause of medically refractory epilepsy in the pediatric population particularly in children under the age of two years of life and the second/third most common etiology of medically intractable seizures in adults. The diagnosis is usually considered in disabled patients particularly those with refractory epilepsy. However, in some patients the diagnosis is overlooked as in at least 1/3 of the patients, the cognitive function is within normal range with no seizures and about 1/5 have normal EEG and/or negative MRI in about 30–40%, particularly for type-I focal cortical dysplasia where in the majority of cases MRI is normal.

The correct and accurate localization of the lesion is mandatory. A percentage of up to 80% of post-surgically seizures free following a complete resection, drops down to 20% after an incomplete resection. For this additional diagnostic imaging techniques such as FDG PET, MEG, DTI, 3T-MRI and intra-cranial EEG are widely used to improve diagnostic accuracy and decide on management.

Surgery in focal cortical dysplasia is a curative option except for those cases where abnormalities involve vital for life brain areas. A better understanding is needed of drug resistant epilepsies and advances in genetic and neuroimaging to help provide more successful pharmacological and/or surgical options.