Hello greentilesouffle,
The WADA test protocol and interpretation varies depending on the
center where the procedure is performed. Online you can read a
thorough explanation of the test procedures and results of the WADA
test on the The Medical College of Georgia, Departments of Neurology
and Surgery (Neurosurgery). I've provided a brief snippet of the
article below, but a detailed explanation goes on for many pages.
Since I am not a medical professional, I would not venture to be more
specific in my answer to you, but the information seemed clear, even
for a layman like me.
"There are three main goals of Wada testing in the context of epilepsy
surgery evaluation, although these goals are emphasized to varying
degrees among the different epilepsy surgery centers. These include:
1) establishing cerebral representation of language function(s), 2)
predicting patients who are at risk for developing a post-surgical
amnestic syndrome, 3) identifying lateralized dysfunction to help
confirm seizure onset laterality. Variants of this procedure are also
used in other elective neurosurgical procedures (e.g., AVM
embolization), although the identification of functional tissue may
simply depend on subtle EEG changes observed following injection.
The standard carotid amobarbital procedure varies from center to
center including differences in drug administration (e.g., dosage,
concentration and injection rate) and method of behavioral assessment
(e.g., type and timing of stimuli). Thus, comparisons among centers
are sometimes difficult due to procedural differences. In this
monograph, the review clinical and research issues of Wada testing
related to the assessment of language, memory, attention, and other
behavioral functions will be reviewed."
Here is the page:
http://www.neuro.mcg.edu/np/INS%20Wada%20Syllabus.htm
It goes on to explain numerical results. They also have description
of how the test is administered and how the numbers are compiled, the
rating scale, on the following page:
http://www.neuro.mcg.edu/np/wada.html
Additional information on WADA testing can be found in these research
papers, which cannot be viewed online without subscription. However,
you may be able to find the hard copy publications at a local medical
library.
"Memory performance on the intracarotid amobarbital procedure as a
predicator of seizure focus," 243 -- 248, D.D. Roman, T.E. Beniak, S.
Nugent, Epilepsy Research, Volume (issue): 25 (3) 1996
"Lateralizing value of the Wada memory test in non-Western patients
with temporal lobe epilepsy," 125 -- 131, H. Kim, S. Yi, J. Kim, E.I.
Son, Epilepsy Research, Volume (issue): 33 (2-3) 1999
"Wada memory and timing of stimulus presentation 461 -- 464," D.W.
Loring, K.J. Meador, G.P. Lee, M.E. Nichols, D.W. King, A.M. Murro,
Y.D. Park, J.R. Smith, Epilepsy Research, Volume (issue): 26 (3) 1997
I hope that answers your question specifically.
Regards,
historybuff |
Clarification of Answer by
historybuff-ga
on
02 Aug 2002 14:42 PDT
Here is another quote from an article by Dr. Allen R. Wyler, MD
appearing on the emedicine web site. I include it because it
reiterates the approximate nature of results interpretation of the
WADA test. A recurring theme in the literature was questioning of the
effectiveness of the test in predicting surgical outcomes. Much
research also appears on alternatives that may replace or be used in
conjunction with the WADA test. Here is the quote and the link:
"Intracarotid amobarbital (Wada) test
The intracarotid amobarbital test (ICAT) was developed by Wada to
preoperatively determine which hemisphere contains language function.
This remains its primary use. It also has been used to test memory
function within each hemisphere when considering temporal lobectomy.
The major problem with this test is that it never has been
standardized and neuropsychologists within various epilepsy centers
perform and interpret results using proprietary protocols, leaving
precise interpretation subject to controversy.
The test is accomplished by individually cannulating each carotid
artery. After contrast arteriography verifies that blood flows to the
corresponding hemisphere and not to the brainstem or contralateral
side, a dose of sodium amobarbital (sufficient to impede hemispheric
function) is injected into one carotid artery. If the drug produces a
contralateral hemiparesis, function of that hemisphere is assumed to
be minimized. If speech persists in the face of this hemiparesis,
speech function is assumed not to be contained within that hemisphere.
The deficiencies of this test for evaluating memory function directly
relate to the multiple problems of targeting a drug effect to specific
brain structures via cerebral blood flow. Injection of a drug into the
internal carotid artery does not assure drug effect in the basal
temporal area in general or the hippocampal region specifically, which
are areas thought to be involved in memory retrieval. This is because
of variations in the direct blood supply to the hippocampus and to
inequalities in drug delivery when injected into the blood stream."
http://www.emedicine.com/med/topic3177.htm
A couple more abstracts that may prove useful from the European
Journal of Epilepsy that:
"Functional MRI and the Wada test provide complementary information
for predicting post-operative seizure control", William D. S.
Killgore, Guila Glosser, Daniel J. Casasanto, Jacqueline A. French,
David C. Alsop, John A. Detre,p 450-455, Volume 8, Number 8, December
1999.
"Comparison of localizing values of various diagnostic tests in
non-lesional medial temporal lobe epilepsy," Young-Je Son, Chun-Kee
Chung, Sang-Kun Lee, Kee Hyun Chang, Dong Soo Lee, Yung Nahn Yi, Hyun
Jib Kim,p 465-470, Volume 8, Number 8, December 1999.
The last two articles discuss the predictive value and usefulness of
the WADA test results.
Search terms used:
epilepsy WADA
amobarbital epilepsy
WADA test results
|
Request for Answer Clarification by
greentilesouffle-ga
on
03 Aug 2002 19:09 PDT
well you have a great start only I still have no way to rate the test.
None of the info you gave was anymore enlightning.
I have a copy of the test here. It lists heading 1 TIMES AFTER
INJECTION 3 subheads: Response, Motor & EEG Normal. under the Response
heading are "Nonverbal" with a numeric score of lets say 00.38, next
under Response is "Verbal" with a numeric score of oh say 05.24.....
Under Motor catagory there is Grade III & Grade V, under EEG Normal
catagory their are subs of Ipsilateral and Ccontralat. both having
numeric scores for both left & right areas of the brain.
This example is from Cleveland Clinic
What I want to know is what those numbers mean how are they evaluated.
how is 5.24 evaluated...I know this is a tough one...good luck
|
Clarification of Answer by
historybuff-ga
on
03 Aug 2002 21:33 PDT
Greentilesouffle,
I cannot practice medicine without a license. If I were to discuss
your specific test results, and explain their meaning, which I am not
qualified to do, I would be overstepping my bounds as a layperson.
I suggest you discuss these results with your physician. As I
indicated in my answer, each center has it's own unique rating scale.
A physician at the Cleveland Clinic is uniquely qualified to interpret
your test results.
I am sorry I could not provide the answer you were after.
Regards,
historybuff
|
Clarification of Answer by
historybuff-ga
on
04 Aug 2002 09:11 PDT
Here are number calculations, what the numbers represent and how they
are calculated. Please note again the caution that significant
variations exist between medical centers.
MCG Wada Protocol: Clinical Core
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.
Here is the page in its entirety:
http://www.asif37.com/brainlanguage.htm
To derive any meaning from the numbers, even if we understand the
calculations, requires extensive medical training. This is why there
is so much research on interpretation of the numbers, because it is by
no means a straighforward, "cut and dried results" test.
Regrads,
historybuff
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