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Neuroradiology Case of the Week
Case 426
July 2009
Balasubramanya Kolar, MD and P-L Westesson, MD, PhD, DDS
Clinical
Presentation: A 37-year-old female presented with right temporal lobe epilepsy and underwent PET imaging as part of her presurgical assessment.
Imaging Findings: PET imaging showed reduced uptake and hypometabolism within the right temporal lobe. The rest of the brain including the left temporal lobe showed a normal uptake and metabolism.
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Figures 1A-C: PET (color maps) show reduced metabolism/uptake within the right temporal lobe and normal metabolism in left temporal lobe. |
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| Figures 2A-C: Corresponding PET images (gray maps) show the same findings. |
Diagnosis: Temporal lobe hypometabolism in interictal period in mesial temporal sclerosis
Discussion: Mesial temporal sclerosis is a very common etiological entity for temporal lobe epilepsy especially in adult patients [1]. The possibility that this entity could be the cause of seizures or a result of seizures is much debated upon. MRI is the imaging modality of choice which confirms the findings which include signal abnormalities, alteration of the architecture of medial temporal lobes or hippocampal atrophy [2].
PET imaging with FDG in the interictal period has shown hypometabolism in approximately 80% of patients. This finding has also been considered a favorable prognostic indicator post-surgery [3].
Certain studies have shown that the hypometabolism is more in the temporolimbic network with temporal pole and hippocampal region showing more hypometabolism than other areas of temporal lobe [4]. However, correlation of severity of hypometabolism with neuronal density has not been adequately reflected in other studies. Neuronal density in areas of hippocampus such as the subiculum, CA1, CA4, and DG did not correlate with severity of hypometabolism [5].
References:
- Gates JR, Cruz-Rodriguez R. Mesial temporal sclerosis: pathogenesis, diagnosis, and management. Epilepsia. 1990;31 Suppl 3:S55-66. PMID: 2226372 [PubMed]
- Connor SE, Jarosz JM. Magnetic resonance imaging of patients with epilepsy. Clin Radiol. 2001 Oct;56(10):787-801. PMID: 11895296 [PubMed]
- Lee SK, Lee DS, Yeo JS, et al. FDG-PET images quantified by probabilistic atlas of brain and surgical prognosis of temporal lobe epilepsy. Epilepsia. 2002 Sep;43(9):1032-8. PMID: 12199728 [PubMed]
- Semah F, Baulac M, Hasboun D, et al. Is interictal temporal hypometabolism related to mesial temporal sclerosis? A positron emission tomography/magnetic resonance imaging confrontation. Epilepsia. 1995 May;36(5):447-56. PMID: 7614921 [PubMed]
- Foldvary N, Lee N, Hanson MW, et al. Correlation of hippocampal neuronal density and FDG-PET in mesial temporal lobe epilepsy. Epilepsia. 1999 Jan;40(1):26-9. PMID: 9924898 [PubMed]
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