The Wada test itself is conducted by a neuropsychologist with the assistance of a neurologist. The testing is performed immediately following cerebral angiography, and both hemispheres are studied on the same day. Patients begin counting repeatedly from 1-20 with their hands held up and their palms turned rostrally and fingers spread. An injection of 100 mg amobarbital sodium is administered by hand over a 4-5 second interval via a percutaneous transfemoral catheter. At times, due to patient confusion, inattention, or non-responsiveness, the patient's eyes are held open.
Language is assessed in detail following presentation of memory items.
Although we have developed a formalized approach to calculate a language laterality ratio, this is for research purposes and is not routinely used clinically. We have adopted a period of speech arrest of this duration to insure that counting interruption is not due to acute generalized disruptive effects of the medication. Following object memory stimulus presentation, comprehension is more systematically assessed with a modified token test. The token test consists of four geometric shapes of different colors which are presented vertically to the subject's ipsilateral visual field. Confrontation Naming .