The relationship between MRI cortical lesion sites and the topographic distribution of EEG spike-and-wave foci was studied in 34 children with tuberous sclerosis at the Service de Neuropediatrie, Hopital Saint Vincent de Paul, Paris, France and the Instituto di Neuropsichiatria Infantile, Roma, Italy. Seizures had appeared in the first year of life in 30 patients, they were partial in ten and infantile spasms in 11, or both in nine. MRI revealed localized cortical areas of high intensity signal, or tubers, in all but two patients. EEG performed at the same age as MRI showed focal spikes and slow waves in all but three patients. Of 34 patients 26 had both MRI cortical large or intermediate tubers and EEG foci (76%). There was a significant correlation between the number of large tubers and the number of EEG foci. Patients with frontal lobe involvement on MRI showed frontal EEG foci after age two. Secondary bilateral synchrony in the EEG was associated with frontal tubers. 
COMMENT. The MRI is more efficient than CT in detecting and localizing tubers of tuberous sclerosis which appear as high intensity signal areas in T2-weighted sequence. The cortical tubers shown on MRI are epileptogenic whereas subependymal calcifications as detected by CT are non-epileptogenic. Frontal lesions present from the first year of life often have a delayed EEG expression, in keeping with the posteroanterior migration of epileptic foci in childhood, the result of maturational changes.