Periodic electroencephalographic pattern in subacute sclerosing panencephalitis modified by preexisting damaged cerebral hemisphere.

We report a 15 year old girl with a childhood hemiplegia, who developed a recent progressive intellectual decline associated with elevated globulins and measles antibody titres in the cerebrospinal fluid, indicating a diagnosis of subacute sclerosing panencephalitis (SSPE). The magnetic resonance imaging revealed left hemispheric atrophy concordant with a long-standing right hemiplegia, and electroencephalography exhibited lateralized periodic complexes (PCs) over the right hemisphere concordant with left-sided myoclonic jerks. The modification of PCs in our patient due to preexisting damaged cerebral hemisphere illustrate that a fairly functional cortex and subcortical white matter are needed for the expression of the PCs of SSPE.