MCG Wada Protocol: Clinical Core

General

Baseline language and memory performance is obtained on a separate day by going 
through the entire protocol in the patient's hospital room. 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. Following demonstration of hemiplegia and evaluation of 
eyegaze deviation, the patient is requested to execute a simple midline command 
(e.g., "touch your nose"). Beginning approximately 30-45 seconds following 
injection, eight common objects are presented for 4-8 seconds each, and the 
object names are repeated twice to the patient. Examples of Wada memory items 
include a combination of ordinary household items (e.g., fork, mousetrap), small 
toys (e.g., troll), and plastic food (e.g., hotdog, pizza). 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. Recognition memory of material presented during the procedure is tested 
after amobarbital effects have worn off as demonstrated by return baseline 
language performance on all tasks described below, return of 5/5 strength, and 
absence of pronator drift, tactile extinction, asterixis and bradykinesia. 

Language

Language rating is based upon performance on five linguistic tasks (viz., 
counting disruption, comprehension, naming, repetition, and reading). Although 
we have developed a formalized approach to calculate a language laterality 
ratio, this is for research purposes and is not routinely used clinically. 

Expressive Language/Counting. The expressive language score (0-4) is based upon 
disruption of counting ability at the initiation of the Wada test (4 = normal, 
slowed, or brief pause < ~20 seconds; 3 = counting perseveration with normal 
sequencing; 2 = sequencing errors; 1 = single number or word perseveration; 0 = 
arrest > ~20 seconds). 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. If speech arrest occurs, patients are 
repeatedly urged to begin counting again starting with "1" since the more 
overlearned portion of the sequence will be less likely disrupted from 
generalized medication effects.

Comprehension. Simple comprehension is assessed after assessment of eyegaze 
deviation by requesting the patient to execute a simple midline command (e.g., 
"stick out your tongue"). 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. Comprehension is 
rated based upon the level of syntactic complexity in the command that is 
correctly executed: 1. "point to the blue circle after the red square," 2. 
"point to the red circle and then point to the blue square," 3. "point to the 
red square." A score of 3 is awarded for completion of a complex two-stage 
command with inverted syntax, a score of 2 reflects successful simple two-stage 
command, 1 is scored for one-stage commands, and 0 if the subject cannot perform 
any commands. 

Confrontation Naming. Two line drawings of common objects (i.e., watch and 
jacket) are presented and the subject is asked to name the objects and parts of 
the objects (e.g., watchband, collar). Performance is qualitatively scored on a 
0-3 point scale. 

Repetition. Following object naming, the patient repeats phases (e.g., "No ifs, 
ands, or buts") and repetition is graded on a 0-3 rating scale. If unable to 
provide any response, the patient is asked to repeat "Mary had a little lamb."

Reading. Patients are asked to read either "The car backed over the curb" or 
"The rabbit hopped down the lane." Performance is rated on a 0-3 point scale.

General Language Considerations. When language impairments are present, language 
stimuli are presented throughout the recovery phase to monitor drug effects. The 
time of complete language recovery is noted. The same or alternative stimuli as 
those employed during the initial assessment are used with the exception of 
repetition. Repetition is a very sensitive measure of mild language impairment, 
and additional repetition items such as "Methodist-Episcopal" and sentences from 
the Boston Diagnostic Aphasia Examination are used to monitor recovery (e.g., 
The spy fled to Greece). Positive paraphasic responses are considered the single 
strongest evidence of language representation in the hemisphere being studied. 

Memory

A minimum of 10 minutes following amobarbital injection is required prior to 
memory testing. Although free recall of object memory stimuli is obtained, 
interpretation of Wada memory performance is based solely on object recognition. 

Ipsilateral Performance. Each of the 8 objects are presented randomly 
interspersed with 16 foils, and forced choice recognition is obtained. One-half 
the number of false positive responses is subtracted from the number of objects 
correctly recognized to correct for possible response bias and guessing. Thus, 
the expected score in the absence of true recognition is 0.

Laterality Scores. Since Wada memory scores are used to assist in seizure onset 
lateralization by demonstrating lateralized dysfunction, the order of injection 
is randomized across subjects and memory results are interpreted in a blind 
fashion. To assess lateralized asymmetries, interhemispheric Wada memory 
difference scores (i.e., [left injection] - [right injection]) derived from 
corrected memory performances are computed; positive scores suggest left 
temporal lobe dysfunction and negative scores suggest right temporal lobe 
impairment. 

General Memory Considerations. Fixed pass/fail criteria are not employed for 
memory performance following injection ipsilateral to the seizure onset. 
However, we generally require a score of at least 2/8 in order to not repeat the 
Wada memory assessment, and are more comfortable with scores of at least 3/8 
correct. Asymmetries of at least 2 are interpreted as evidence of lateralized 
impairment, although greater asymmetries are interpreted with more confidence. 
As with the ipsilateral performance, the asymmetries scores are not considered 
absolute, and memory performance is always considered in the context of other 
clinical factors such as consistency of seizure onset or presence of a 
structural lesion such as tumor or hippocampal atrophy on MRI. Although 
asymmetries in the "wrong" direction are sometimes observed, when they are 
present, they are cause for particular concern and the procedure may be repeated 
bilaterally using a 75 mg dose and beginning on the side ipsilateral to the 
presumed seizure onset.

(c) 1995, Medical College of Georgia