Aim: to assess the possible incremental value of a functional perfusion/metabolism (P/M) image in epilepsy patients, as the uncoupling of perfusion and metabolism has been suggested to be useful in localising the seizure focus. (Eur J Med Mol Imaging 2008;35:579-588)

Methods: Forty patients with intractable epilepsy being considered for neurosurgery had EEG telemetry, MRI, ictal and interictal ECD SPECT and FDG PET. Nuclear Medicine evaluation included ictal-interictal subtraction and 3D-SSP functional images. Final diagnosis for the purpose of this study was based on surgical outcome or a combination of seizure semiology, EEG and the results of all investigations.

The P/M image was produced by spatially registering interictal ECD SPECT and resolution corrected FDG PET images to the patient’s MRI. Each study was normalized using whole brain counts and then the corrected ECD count was divided by the corrected FDG count in each voxel. The functional image was scaled for viewing and P/M measured to assess its accuracy in comparison with routine assessment.

Results: Eighteen patients had suspected temporal and 22 extratemporal epilepsy. The forty patients were divided into 3 groups: 8 had previous brain surgery (lobectomy in 6), 18 had lesions on MRI and 14 had non lesional epilepsy. Review of the functional P/M images in all 3 groups showed no patient with a perfusion metabolism mismatch at a site that was normal or equivocal on routine SPECT and PET assessment.

Conclusion: P/M ratio functional images do not add additional information for localising the epileptic focus.