Evaluation of Functional Changes in the Medial Temporal Region During Intracarotid Amobarbital Procedure by Use of SPECT

Abstract

Summary: Purpose: Because the main blood supply to the medial temporal region is through the posterior cerebral artery, the validity of the intracarotid amobarbital procedure (IAP) is still debated. To verify clinical validity of the IAP, we investigated changes in neuronal function in the medial temporal region during IAP.Methods: Brain single photon emission computed tomography (SPECT) was performed during IAP (IAP-SPECT) in 22 patients with temporal lobe epilepsy (TLE), and regional cerebral blood flow (rCBF) in the medial and lateral temporal regions of interest (ROIs) was measured quantitatively. To determine the distribution of sodium amobarbital, in another 20 patients with TLE, SPECT images were obtained after intracarotid injection of 99"Tc-HMPA0 mixed with sodium amobarbital.Results: Mean rCBF was 89.2% in the medial temporal region and 81.6% in the lateral temporal region; in the former region, it was significantly lower than that shown by the results of interictal SPECT (99.1%; p c 0.001). In a few patients, however, rCBF did not decrease in the medial temporal region. In only 25% of patients, the medial temporal region was visualized in SPECT images obtained after intracarotid injection of Conclusions:The results in this study demonstrate that IAP is valid because the medial temporal region is inactivated in spite of infrequent delivery of sodium amobarbital. We assume that intratemporal diaschisis is operating for the inactivation of neuronal function. IAP-SPECT with intratemporal ROIs may be useful for monitoring changes in neuronal function in the medial temporal region during TAP.

Wada Testing Reveals Frontal Lateralization for the Memorization of Words and Faces

“…These data are consistent with findings from previous single photon emission computed tomography (SPECT) studies (Kim, Lee, Nam, Song, & Lee, 1999;Urbach et al, 1999;Jeffrey et al, 1991). These studies strongly suggest that (in the absence of a direct ''fetal'' origin of the PCA from the ICA) an amytal injection into the ICA does not perfuse most of the medial temporal lobe, including most of the hippocampus and its associated cortex, but does anesthetize other cortical regions including the frontal and parietal cortex.…”

“…For example, a SPECT study by Kim et al (1999) revealed decreased regional cerebral blood flow in the posterior portion of the hippocampus following ICA amytal injections. The SPECT study further revealed infrequent delivery of amytal to this region.…”

“…That is, by simply inactivating the anterior tip of the hippocampus, the entire hippocampal formation is rendered functionless. This notion has received some support in the literature (Kim et al, 1999;Urbach et al, 1999;Gotman, Bouwer, & Jones-Gotman, 1992), and it is somewhat difficult to reconcile this possibility with one that implicates other cortical regions. This idea would be particularly appealing if the ipsilateral posterior hippocampus was the only brain region that showed slowing following ICA amytal injections.…”

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.…”

Inferring Function from Structure: Relationship of Magnetic Resonance Imaging-Detected Hippocampal Abnormality and Memory Function in Epilepsy

“…This procedure (the intracarotid amobarbital procedure [IAP], or “Wada” test) provides a more direct assessment of hippocampal function than is possible with traditional assessment of memory. Although a complete review of the controversies regarding the Wada test is beyond the scope of this brief review, numerous lines of evidence have emerged that support the validity of the IAP as a measure of hippocampal function, including a correlation of IAP memory performance with hippocampal EEG changes recorded following injection (9) and reduced metabolism following injection of amobarbital (10,11), as well as neuronal cell loss (12) determined from resected tissue.…”