Correlation of Temporal Lobe Glucose Metabolism With the Wada Memory Test

Abstract

Summary: Purpose:The goal of the present study was to examine the relationship of 18 F-fluorodeoxyglucose positron emission tomography (FDG-PET) and the Wada memory test in lateralizing memory dominance and epileptic focus.Methods: FDG-PET and the Wada test were performed in 18 patients with temporal lobe epilepsy (TLE). The asymmetry indices of FDG-PET (PET-AI) were calculated in mesial, polar, anterolateral, midlateral, and posterolateral regions of the temporal lobe, and those of Wada memory test (Wada-AI) were obtained as well.Results: The Wada-AI was significantly correlated with PET-AI in mesial (r ‫ס‬ 0.67, p ‫ס‬ 0.003), polar (r ‫ס‬ 0.55, p ‫ס‬ 0.019), anterolateral (r ‫ס‬ 0.55, p ‫ס‬ 0.019), and midlateral (r ‫ס‬ 0.51, p ‫ס‬ 0.031) regions of the temporal lobe. However, after a linear regression analysis, PET-AI of only the mesial temporal region was significantly correlated with Wada-AI (p ‫ס‬ 0.008). Wada-AI could correctly lateralize the seizure focus in 90% of the left TLE and 75% of the right TLE patients. The PET-AI of the mesial temporal region showed the highest sensitivity of seizure lateralization (80% of left TLE and 87.5% of right TLE). PET-AI of other temporal regions had lower sensitivities (50-80% of left TLE, 20-75% of right TLE). One or two patients showed false seizure lateralization by PET-AI on each temporal region.Conclusions: Although FDG-PET hypometabolism is observed at both mesial and lateral regions of the temporal lobe in mesial TLE, mesial temporal region appeared to be a dominant and leading area for lateralizing Wada memory dominance and epileptic focus.

Hypometabolism and Interictal Spikes during Positron Emission Tomography Scanning in Temporal Lobe Epilepsy

“…1) [21]. The ROI of the whole temporal lobe was the sum of mesial, polar, anterior-lateral, mid-lateral and posterior-lateral ROIs.…”

Non‐invasive alternatives to the Wada test in the presurgical evaluation of language and memory functions in epilepsy patients

“…Both, false positives (patients who failed the Wada without suffering postoperative amnesia) (Novelly and Williamson 1989) and false negatives (patients who passed the Wada but presented post‐operative amnesia) (Jones‐Gotman 1993, Loring et al 1990) have been reported. This may be attributable to the fact that the IAT preferentially perfuses lateral temporal regions and less frequently mesial temporal areas which include the hippocampus (Jeffrey et al 1991, Hong et al 2000). Similarly, the IAT may yield false results in patients with varying degrees of bihemispheric language representation (Oxbury and Oxbury 1984, Loring et al 1990).…”

“…Furthermore, studies comparing PET with other procedures have yielded divergent results. On the one hand, Hong et al (2000), comparing FDG‐PET and Wada asymmetry indices in the same patients, found significant correlations between hypoperfusion in mesial temporal lobe regions and Wada memory lateralization. Similary, Hunter et al (1999) found that compared to IAT, the predictive value of PET for language lateralization ranged from 88 to 91 percent, based on visual inspection of the images by experienced neuroradiologists.…”

The role of PET in presurgical assessment of partial epilepsies

“…The practical consequence of this finding for TLE surgery is that 18 FDG PET may have some predictive value regarding postoperative language and memory deficits [149], which are expected to be less severe when the temporal lobe was hypometabolic before operation. In fact, recent studies could correlate FDG-PET findings with the result of the intra-carotid amobarbital test [150,151].…”

“…No relation between lateral temporal hypometabolism and hippocampal atrophy or neuronal loss as measured with MRI volumetry and histological studies, respectively Sackellares [128], Theodore [71], Radtke [139], Henry [154], Semah [155], Debets [14], O'Brien [156], Ryvlin [15], Salanova [141], Dlugos [157], Foldvary [158], Choi [159], Lamusuo [160], Theodore [161] Mesial temporal hypometabolism correlates with reduced hippocampal volume in TLE Knowlton [162] Temporo-polar hypometabolism correlates with reduced hippocampal volume in TLE Semah [155] Thalamus & putamen metabolism correlate with dentate granule cell density Dlugos [157] Lateral temporal hypometabolism correlates with white matter change on MRI in TL as well as microscopic cortical dysplasia in the lateral temporal cortex Latack [163], Stefan [72], Theodore [71], Ryvlin [80], Choi [159], Diehl [164], Chassoux [165] Relation with neuropsychological testing Correlated in the left temporal lobe with decreased verbal IQ and memory scores in TLE Raush [166] Correlated in prefrontal region with decreased verbal and performance intelligence Jokeit [167] Correlated with ipsilateral memory impairment on intracarotid amobarbital test Salanova [168], Hong [150], Salanova [151] Predictive of less severe verbal memory decline after lobectomy in left TLE Griffith [149] Reversibility after surgery Bilateral metabolic increase after surgey in mesial TLE Hajek [169] Decrease in the contralateral mesial TL after surgey in mesial TLE Hajek [169] Reversible in temporal neocortex after surgery in mesial TLE Hajek [169] Reversible in lateral TL cortex a...…”