THE CLINICAL SPECTRUM OF FOCAL CORTICAL DYSPLASIA AND EPILEPSY

Focal cortical dysplasia is an important pathologic substrate in patie nts with epilepsy, but its clinical spectrum has not yet been complete ly defined. We retrospectively studied 30 epilepsy surgery patients wi th focal abnormalities of neuronal migration as the only histopatholog ic finding in resected tissue. Patients comprised two clinical groups. Seventeen patients with extratemporal epilepsy had early (median age, 7.0 years) extratemporal resection or hemispherectomy for severe epil epsy (47% of patients with > 10 partial seizures a day) that began in infancy or early childhood (median age, 1.0 year), usually in the sett ing of mental retardation or developmental delay (59% of patients), an d often with magnetic resonance imaging (MRI) evidence of focal neuron al migration abnormality (44% of patients). In contrast, 13 patients w ith temporal lobe epilepsy were significantly older at age of seizure onset (median, 8.0 years; p = 0.001) and surgery (median, 22.0 years; p = 0.001), with less severe epilepsy (no patients with an average of > 10 seizures a day; p = 0.004), and without mental retardation or MRI evidence of neuronal migration abnormality (p = 0.001). In both group s, positron emission tomography (PET) was more sensitive than MRI and showed focal hypometabolism in seven patients with normal MRI. Seizure -free outcome tended to be more common after temporal lobectomy (77%) than after extratemporal resection or hemispherectomy (53%). Pathologi c abnormalities were more severe in patients with extratemporal epilep sy than in patients with temporal lobe epilepsy. The clinical spectrum of focal cortical dysplasia included not only infants and children wi th severe extratemporal epilepsy and mental retardation, but also olde r patients with temporal lobe epilepsy and at least boderline IQ. Preo perative diagnosis may be difficult in cases with less severe patholog ic abnormality, but high-resolution MRI and PET can increase the yield .