Thalamic hypometabolism on 18FDG-positron emission tomography in medial temporal lobe epilepsy.
OBJECTIVE
Degree of hypometabolism in the thalamus on (18)Fluorodeoxyglucose-positron emission tomography (FDG-PET) was compared with those of medial and lateral temporal lobes in patients with medial temporal lobe epilepsy (mTLE), and its relationship with post-operative seizure outcomes was investigated.


METHODS
Twenty-six patients with mTLE who underwent anterior temporal lobectomy were included. Post-operatively, 13 patients became completely seizure-free and 13 showed residual seizure, regardless of frequency (five patients became almost seizure-free, six had rare seizures and two showed significant improvements). Degrees of hypometabolism in bilateral thalamus, ipsilateral medial and lateral temporal lobes were evaluated visually and semi-quantitatively by determining the asymmetry index (AI), a value indicating 100 x (ipsilateral - contralateral)/[1/2 x (ipsilateral + contralateral)] and the region-to-cerebral hemisphere ratio (R/C ratio) being the ratio between averaged counts in each area and those in the cerebral hemisphere of the same side.


RESULTS
Hypometabolism in the medial temporal lobe was visually observed in all patients. Hypometabolism in the lateral temporal lobe was observed in 20 patients and was semi-quantitatively more prominent than that of the medial temporal lobe. Pathologically, hippocampal sclerosis and prominent astrogliosis of the lateral temporal lobe were present in all cases. However, while thalamic hypometabolism was visually observed in nine patients (in the ipsilateral side of four cases, contralateral side of three and on both sides of two), no significant thalamic hypometabolism was semi-quantitatively observed. No significant differences in metabolic rate in any area except for the lateral temporal lobe between seizure-free patients and residual seizure patients were seen semi-quantitatively.


CONCLUSIONS
Data indicated that metabolism in the lateral temporal lobe of patients with mTLE significantly decreased and revealed pathologic glial changes. Thalamic hypometabolism was quite mild and did not correlate with post-operative seizure outcome.
Hashiguchi
Kimiaki
K
Department of Neurosurgery, Graduate School of Medical Science, Kyushu University, Fukuoka, Japan.
Morioka
Takato
T
Yoshida
Fumiaki
F
Kawamura
Tadao
T
Miyagi
Yasushi
Y
Kuwabara
Yasuo
Y
Sasaki
Masayuki
M
Koga
Hirofumi
H
Nagata
Shinji
S
Sasaki
Tomio
T
D000293:Adolescent; D000328:Adult; D002648:Child; D004734:Energy Metabolism / Q000502:physiology; D004833:Epilepsy, Temporal Lobe / Q000000981:diagnostic imaging* / Q000378:metabolism* / Q000503:physiopathology; D005260:Female; D019788:Fluorodeoxyglucose F18; D005911:Gliosis / Q000209:etiology / Q000473:pathology; D005947:Glucose / Q000378:metabolism; D006624:Hippocampus / Q000000981:diagnostic imaging / Q000378:metabolism / Q000503:physiopathology; D006801:Humans; D008297:Male; D008875:Middle Aged; D019635:Neurosurgical Procedures; D049268:Positron-Emission Tomography / Q000379:methods; D011183:Postoperative Complications / Q000000981:diagnostic imaging / Q000209:etiology / Q000503:physiopathology; D012640:Seizures / Q000209:etiology / Q000503:physiopathology; D013702:Temporal Lobe / Q000000981:diagnostic imaging* / Q000378:metabolism* / Q000503:physiopathology; D013788:Thalamus / Q000000981:diagnostic imaging* / Q000378:metabolism* / Q000503:physiopathology; D016896:Treatment Outcome
D019788:Fluorodeoxyglucose F18; D005947:Glucose