The Wada Test Has Non-Selective Effects in the Brain: A Power Spectral Study.
Abstract number :
3.075
Submission category :
Year :
2001
Submission ID :
178
Source :
www.aesnet.org
Presentation date :
12/1/2001 12:00:00 AM
Published date :
Dec 1, 2001, 06:00 AM
Authors :
M.M. Thompson, BS, Flint Hills Scientific, LLC, Lawrence, KS; J.E. Dubin, BS, Tulane University, New Orleans, LA; D. Eckard, MD, Radiology, Kansas University Medical Center, Kansas City, KS; A.I. Troster, PhD, Psychiatry, University of Washington, Seattle
RATIONALE: The risk of amnesia after temporal lobectomy is assessed through intracarotid injection of sodium amytal (ICSA), even though the hippocampus (H) is not in this vessel[scquote]s territory. It is therefore relevant that the effect of ICSA and posterior cerebral sodium amytal injection (PCSA) on the H and other regions be characterized and compared, using power spectral analysis.
METHODS: Power spectral analysis was performed on signals recorded before, during and after ICSA (13 injections, 100 mg) and PCSA (8 injections, 30 mg) on 7 subjects undergoing epilepsy surgery evaluation. Recordings were made directly from the H, and the frontal (F) and temporal (T) neocortex. Power changes in any band were deemed significant if they were above the 95th percentile or below the 5th percentile of baseline for at least 25% of the time between the onset and resolution of clinical deficits.
RESULTS: Hemiparesis occurred in 12/13 ICSA tests and visual field cuts occurred in 8/8 PCSA tests. Power changes in F paralleled hemiparesis in all ICSA tests, but power changes in H paralleled visual field cuts in only 5/8 PCSA tests. ICSA induced significant power changes in F in 12/13, T in 8/12, H in 7/13 and contralateral F in 8/11 tests. PCSA induced significant power changes in H in 5/8, F in 2/7, T in 1/7 and contralateral H in 1/7 tests. In H, power increases were similar in all bands.
CONCLUSIONS: ICSA and PCSA caused widespread anatomical and non-selective spectral changes in power that did not consistently involve the hippocampus, the structure of interest. The implications of these findings, for the validity of this test as a predictor of risk for post-operative amnesia, will be discussed in detail.