[Wada test. An investigation of language and memory functions in epileptic patients evaluated for temporal...

Intracarotid sodium amytal injection was introduced as a clinical investigation of epileptic patients by Juhn Wada around 1950. The Wada test causes a brief inhibition of cerebral functions of the anaesthetized hemisphere, thus allowing tests to be performed on the contralateral hemisphere. The test is widely used to lateralize language functions and to assess the risk of postoperative amnesia in epileptic patients evaluated for temporal lobectomy Subjects and methods: Five epileptic patients were investigated. Three patients had hippocampal sclerosis and two had a benign tumour in the amygdala region. The sodium amytal was first injected to the hemisphere with seizure onset. After the development of paralysis of the contralateral side of the body, language and memory functions of the non-anaestetized hemisphere were assessed. The test was then repeated for the other hemisphere.

The left hemisphere was dominant for language in three patients. In one patient the right hemisphere was dominant for language and in another patient language was bilaterally represented. In the three patients with hippocampal sclerosis, verbal and nonverbal memory was worse on the side of the lesion. This difference was not as marked for the two patients with lesion in the amygdala region. Total memory score was worse on the side of the lesion in all five patients.

In both right and left handed individuals language is usually located in the left hemisphere. When epileptic seizures, with onset in the left hemisphere, start early in life, the language function can be transferred to the right hemisphere. This is a likely explanation for the right hemisphere language dominance in one patient. In all patients total memory score was lower for the hemisphere with seizure onset. This is in agreement with the suggestion of a lateralizing value of the Wada test.