Magnetic resonance imaging in occipital lobe epilepsy with frequent seizures.

Magnetic resonance imaging and single-photon emission computed tomography provide useful information in the evaluation of the pathophysiology of epileptic foci. Ictal magnetic resonance imaging in a 7-year-old male with occipital lobe epilepsy revealed mild swelling of the left temporo-occipital region, with hyperintensity on T(2)-weighted and fluid attenuated inversion recovery images. This lesion, however, was not detected on diffusion-weighted imaging. An ictal single-photon emission computed tomography study using 99mTc-ECD demonstrated left temporo-occipital hyperperfusion. T(2)-weighted and fluid attenuated inversion recovery images revealed hyperintensity without atrophy 4 months after control of his seizures. The focus in nonconvulsive status epilepticus has been reported as showing hyperintensity on T(2)-weighted, fluid attenuated inversion recovery and diffusion-weighted images. Since hyperintensity on diffusion-weighted imaging reflects cytotoxic intracellular edema due to excitotoxicity, and his ictal diffusion-weighted image exhibited no remarkable change, the lesions in the left temporo-occipital region resulted from vasogenic edema. Cytotoxic edema resulting from excitotoxicity leads to neuronal death, causing cortical atrophy. Thus, diffusion-weighted imaging is a useful tool to predict the prognosis of frequent seizures.