Four patients aged 9 to 19 years with focal myoclonus and intractable focal motor seizures beginning at age 4 to 6 years were treated surgically at the Montreal Neurological Hospital and Institute, McGill University, Montreal, Quebec, Canada. All 4 had a mild progressive hemiparesis, cognitive deficits, focal EEG seizure discharges in the contralateral rolandic areas, 3 showed cortical architectonic abnormalities on MRI, and evidence of focal cortical dysplasia with abnormally wide gyri at operation. All improved following surgery. The authors stress the value of the MRI in visualization and diagnosis of neuronal migration cortical dysplasias whereas other imaging techniques had been unrevealing. 
COMMENT. The authors consider the clinical, MRI and pathological features of these 4 patients sufficiently similar to suggest a clinical entity not previously described. The focal seizure pattern, hemiparesis, focal epileptiform EEG discharges and focal cortical dysplasia all indicated a localized lesion, yet a generalized abnormality of EEG background activity and widespread cognitive defects pointed to a more diffuse cerebral dysfunction as well. The differential diagnosis included tumor, post-traumatic or ischemic lesions, metabolic disorder, and chronic localized encephalitis of . The report of macrogyria in 3 of the patients and giant astrocytes in both patients with histological studies is suggestive of a forme fruste tuberous sclerosis that might be entertained in the differential diagnosis.