Abstracts

The Wada test is a neurological test used for epileptic patients who are scheduled for epilepsy surgery to evaluate memory function and language dominance by injecting a short acting anesthetic, sodium amobarbital, in each internal carotid artery separately, anesthetizing the part of the brain perfused by that circulation. We have observed shivering in a portion of patients undergoing the Wada test. The relationship of shivers in the context of this test has not been delineated. Therefore, in this study, we attempt to attain a further understanding regarding this clinical phenomenon. We studied a total of 14 patients (9.5-50.25 years) prospectively who have undergone the Wada test since 2003. Multiple variables including age, race, sex, site of injection, dose of amobarbital, duration of shivering, duration of slowing on the EEG (as a surrogate for continued effects of amobarbital on the brain), and hemispheric dominance were analyzed. Of the fourteen patients, six (43%) experienced shivering during the Wada test. The duration of shivering was similar to the duration of amobarbital[apos]s effect as monitored by the presence of slowing on EEG. No significant difference in the two groups was noted in terms of age, race, sex, dose of amobarbital, and hemispheric dominance. Of these six patients, four patients shivered after injection to the left ICA and two patients shivered after injection to the right ICA. There is no difference among patient characteristics in those who shivered vs. those who did not, suggesting an anatomical cause for this clinical observation. The anterior cerebral artery and the anterior communicating artery, branches of the ICA, perfuse the anterior hypothalamus. Thus, sodium amobarbital injected into the ICA likely causes a temporary functional lesion of the anterior hypothalamic-preoptic area (heat center). This area normally inhibits the primary motor center for shivering. This [ldquo]lesion[rdquo] likely causes a release of the primary motor center for shivering from the inhibitory effects from the [ldquo]heat center[rdquo] resulting in the clinical manifestation of shivering.