Case of the Month—March 2004

FDG PET for Seizure Focus

History
A 27-year-old female presented with intractable complex partial seizure disorder for a period of three years. An MRI study of the brain was unremarkable and EEG was inconclusive. A PET FDG scan was requested for further evaluation and was performed as an interictal study.

Finding of the PET Study
The PET scan demonstrated focal areas of hypometabolism involving the right medial and the anterior aspect of the right temporal lobe, which is suggestive of seizure focus of interictal status.

Follow-up
The patient underwent depth electrode placement for seizure monitoring. This confirmed that the seizure was from the right temporal lobe. The patient then underwent right anterior temporal lobectomy and amygdaohippocampectomy and was seizure-free after the surgery. The patient was still seizure free at a follow-up exam three months after surgery.

How Did PET Help?
PET helped to identify seizure focus and guided depth electrode placement. PET proved beneficial in pre-surgical evaluation and planning.

Discussion
FDG PET imaging can play an important role in localization of seizure focus and pre-surgical evaluation in patients with partial seizure disorders. PET imaging with FDG will demonstrate focus of decreased glucose utilization at the site of interictal seizure focus in 60 to 70% of patients with normal MRIs (1). In the ictal state, PET FDG imaging will reveal focus of increased glucose uptake.

(1) Henry, T.R., et al, Journal of Nuclear Medicine, “Clinical Evaluation of Interictal Fluorine-18-Fluorodeoxyglucose PET In Partial Epilepsy,” 34, 1993, pp. 1892-1898.

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