Case Author(s): J. Philip Moyers and Farrokh Dehdashti, M.D. , 9/23/95 . Rating: #D3, #Q4

Diagnosis: Epileptogenic focus Left temporal lobe Mesial temporal sclerosis

Brief history:

Intractable partial complex seizures since childhood.


Coronal 18-FDG images of brain

View main image(pb) in a separate image viewer

View second image(mr). Coronal MR image of brain, T2 weighted

View third image(mr). Coronal MR image of brain, T2 weighted

Full history/Diagnosis is available below

Diagnosis: Epileptogenic focus Left temporal lobe Mesial temporal sclerosis

Full history:

This is a 55-year old woman with a history of complex partial seizures since childhood. Her seizures have been intractable with medical management. A recent MRI demonstrated small left hippocampal formation and atrophic cerebellum. PET imaging was requested as part of a presurgical management plan.


F-18 fluorodeoxyglucose


There is an area of hypometabolism in the left temporal lobe and left thalamus. This corresponds well to the findings of mesial temporal sclerosis involving the medial aspect of the left temporal lobe, hippocampal gyrus and amygdala. In addition, generalized hypometabolism of the cerebellum was seen, correlating with atrophic changes seen on MRI. This is likely related to long- term Dilantin therapy.


Complex partial seizures with a temporal lobe focus are common among epileptic patients. Imaging can be performed with CT, MRI, or PET. MRI is superior to CT in identifying morphologic abnormalities in patients with epilepsy. Small areas of gliosis or small AVMs can be overlooked with CT examination. Also, heterotopic gray matter may also be missed by CT examination. A cause of complex partial seizures is mesial temporal sclerosis. In this pathologic entity, there is prominent hippocampal cell loss with atrophy of the medial aspect of the temporal lobe involved. In some patients with partial seizures, MRI may be normal or demonstrate a smaller temporal lobe without increased signal intensity on the side of the lesion. Therefore, interictal PET studies are helpful to evaluate for interictal cerebral metabolism. Studies of cerebral blood flow, metabolism, and neurotransmitter activity are felt to be more promising than structural imaging in the evaluation of patients with epilepsy who have negative or unequivocal MRI. Clearly, measurement of regional cerebral glucose metabolism has proved the most useful in evaluation of patients for seizure surgery. FDG-PET may avoid unnecessary invasive tests. Most studies demonstrate interictal hypometabolism in approximately 60-90% of patients with complex partial seizures. The degree of hypometabolism on the PET study is not related to the percentage of neuronal loss and, the hypometabolic regions are usually larger than the area of pathologic abnormality. For example in the patient with mesial temporal sclerosis where hippocampal cell loss is a prominent feature, hypometabolism involved the entire temporal lobe rather than just the medial aspect in the region of the hippocampal gyrus. Both qualitative and quantitative analysis of PET studies can be used to lateralize the abnormal temporal lobe for surgical resections, although it is unclear which approach should be used. In this patient, atrophy is demonstrated in the medial aspect of the left temporal lobe consistent with the diagnosis of mesial temporal sclerosis. Comparison with the coronal PET images demonstrates hypometabolism and decreased size of the left temporal lobe when compared with the right temporal lobe.

References: 1) Mazziotta JC, Gilman S. Clinical brain imaging: principles and applications. Philadelphia, PA: FA Davis Company, 1992. 2) Fisher RS, Frost JJ. Epilepsy. J Nucl Med 1991;32:651-659.


MRI and monitored EEG suggest a left temporal lobe seizure focus.

ACR Codes and Keywords:

References and General Discussion of PET Brain (Nontumor) Imaging Studies (Anatomic field:Skull and Contents, Category:Organ specific)

Search for similar cases.

Edit this case

Add comments about this case

Read comments about this case

Return to the Teaching File home page.

Case number: pb003

Copyright by Wash U MO