ABSTRACT
A persistent polymorphic delta activity, localized initially to one region, followed by slowing of the posterior dominant rhythm in the affected hemisphere, has been described early in the course of the disease.4 Gradually the slow wave activity spreads to involve multiple lobes of the brain. When the disease is established, disturbance of background activity and focal delta activity occur in nearly all patients. These abnormalities may be bilateral, but there is a clear asymmetry in 90 per cent.5 Multiple independent interictal epileptiform discharges are usually seen, occurring over the affected hemisphere in half of the patients and independently over both hemispheres in one third. Bilateral synchronous spike or sharp and slow wave complexes are observed in half of the patients, often with bifrontal predominance.
