RADIOPHARMACEUTICAL: 3.4 mCi F-18 Fluorodeoxyglucose i.v.
In this 6 years old male with chronic seizures and diffuse atrophy of one of the hemispheres, the most likely diagnosis is Rasmussen’s encephalitis. Encephalitis from prior TORCH infections would be unusual given the unilateral presentation. In addition, one would expect changes of encephalomalacia if this was a consequence of an old ischemic event.
Rasmussen’s encephalitis is a chronic inflammatory disease that involves a single hemisphere of the brain. The patient may present with frequent seizures, hemiparesis, and cognitive deficits. Throughout the disease’s course of about 8-12 months, further deficits can occur. However, in most cases, brain damage stabilizes. During the active phase of the disease, corticosteroids and intravenous immunoglobulin may be helpful. Hemispherectomy and hemispherotomy can be performed to reduce the frequency of seizures after the neurolgic deficits stabilize given that most anti-epileptic medications are ineffective.
It was also noted the patient also has volume loss and gliosis of the hippocampal formations, compatible with bilateral mesial temporal sclerosis.