Interpretation of Wada Memory Test for Lateralization of Seizure Focus by Use of ^99mTechnetium‐HMPAO SPECT

Abstract

Summary:Purpose: Although the intracarotid amobarbital procedure (IAP) or Wada test is useful in lateralizing seizure focus in patients with temporal lobe epilepsy (TLE), the results of the IAP memory test are frequently nonlateralizing. An insufficient suppression of the medial temporal region contralatera1 to the seizure focus may contribute to the failure of lateralization. We tried to correlate IAP memory results with the functional changes in the contralateral medial temporal region as measured by single photon emission computed tomography (SPECT) during IAP.Methods: We performed a """technetium-(Tc) hexamethylene-propylene-amine-oxime (HMPAO) brain SPECT in 19 medial TLE patients during a contralateral IAP (sodium amobarbital injected contralateral to the seizure focus). Regional cerebral blood flow (rCBF) was measured in the contralateral medial temporal region. The amount of decrease in the rCBF was calculated by subtracting the previous measurement from the one obtained with the interictal SPECT.Results: Ten (53%) patients passed and nine (47%) failed the contralateral IAP. The mean percentage decrease in rCBF was 5.3 5 5.3%. There was a significant negative correlation between a decrease in the rCBF and the IAP memory-retention score by Spearman correlation (p = -0.53; p <0.021). Patients with smaller decreases in rCBF (<5%) more frequently passed the contralateral IAP memory test than did those with larger decreases (80 vs. 22%; p < 0.023). Conclusions:We suggest that an insufficient suppression of the contralateral medial temporal function is partly responsible for nonlateralizing IAP memory tests. An IAP-SPECT may be useful in interpreting IAP memory tests for the lateralization of seizure focus in TLE patients. Key Words: Intracarotid amobarbital procedure-SPECT-TLE-Lateralimtion-Medial temporal region.Since the Wada test or intracarotid amobarbital procedure (IAP) was introduced to determine the hemispheric dominance for language (1 ), its clinical application has widely expanded. It was soon modified by Milner et al. ( 2 ) to determine the hemispheric dominance for memory as well. In most epilepsy centers, the IAP memory test has been used as a predictor of postoperative memory deficits in patients with temporal lobe epilepsy (TLE) (3-6). It has been known to be useful in predicting patients' surgical outcome after a unilateral temporal lobectomy (7-9) and to provide a lateralizing value in the evaluation of seizure focus (9-1 1).Because chronic and repetitive seizures produce dysAccepted June 8, 1999. Address correspondence and reprint requests to Dr. S. K. Lee at Department of Neurology, College of Medicine, Seoul National University Hospital, 28, Yunkeun-Dong, Chongno-Ku, Seoul, 110-744, Korea. E-mail: sangunlee@medicine.snu.ac.kr function in the epileptic temporal lobe, a better memory performance is anticipated when the temporal lobe ipsilateral to the seizure focus is anesthetized than when the opposite side is. Thus we can theoretically assume that the temporal lobe showing a poorer IAP ...

Analysis of Functional Brain Images Using Population-Based Probabilistic Atlas

“…Brain SPECT images acquired after injection of Tc-99m-HMPAO into the internal carotid artery (ICA) during the intracarotid amobarbital procedure in epilepsy patients (IAP SPECT) provided superior anatomical information on the blood flow distribution from the ICA. This procedure used to be performed preoperatively to predict postoperative memory and language deficit after unilateral temporal lobectomy, and yielded very fine data regarding internal carotid arterial supply in population [27,28]. IAP SPECT during Wada test in epilepsy patients enabled the development of probabilistic maps of the distribution of blood supply from the ICA while SPECT images were transformed into the MNI stereotaxic coordinate [26] (Fig.…”