Widespread functional deficits in perception-related networks demonstrated by PET in a case with simple visual seizures.

OBJECTIVE

To study benzodiazepine receptor (BZR) density and functional deficits in occipital lobe epilepsy.

METHODS

A 39-year-old man who had simple partial visual seizures after neurosurgical transtentorial extirpation of a pinealoma was studied by EEG, magnetic resonance imaging (MRI), and positron emission tomography (PET) of [18F]2-fluoro-2-deoxy-D-glucose (FDG) at rest and during visual activation task and[11C]flumazenil (FMZ).

RESULTS

Electroencephalographic recordings were nonspecific, and MRI did not reveal any morphologic anomaly in the occipital lobe. Flumazenil-PET demonstrated a small epileptogenic region in the right visual association cortex and FDG-PET showed hypometabolism in a corresponding location and thalamic diaschisis. Stimulation of occipital metabolism by a continuous visual recognition task improved significantly the contrast between the dysfunctional zone and its surround.

CONCLUSIONS

As BZR deficits are restricted to a small region, widespread hypometabolism in networks involved in visual information processing indicates an extensive functional deactivation by the epileptogenic focus.