Interictal brain SPECT is useful for the localization of a seizure focus. Concomitant hypoperfusion of the ipsilateral thalamus on interictal SPECT has been noted for temporal lobe epilepsy. In this study, we aimed to evaluate the prevalence of thalamic hypoperfusion ipsilateral to temporal hypoperfusion (ipsilateral thalamic hypoperfusion) and to assess the usefulness of this finding for the lateralization of epileptic foci on interictal SPECT for temporal lobe epilepsy patients.
Methods: Forty-six patients with refractory temporal lobe epilepsy underwent interictal brain SPECT after intravenous injection of 555-740 MBq of 99mTc-ECD. Perfusion impairments in the brain, especially the temporal lobe and thalamus, were evaluated. The localization of seizure foci was determined in conjunction with scalp, ictal and cortical electroencephalography, MRI and clinical outcomes. Ictal SPECT was performed for 5 of the 12 patients.
Results: Concomitant decreased perfusion in both the temporal lobe and the ipsilateral thalamus was observed for 12 (26%) of 46 temporal lobe epilepsy patients on interictal brain SPECT. Seven patients showed hypoperfusion in the left temporal lobe and ipsilateral thalamus. Five patients showed hypoperfusion in the right temporal lobe and ipsilateral thalamus. In addition, hypoperfusion in the ipsilateral basal ganglia (ten patients) or contralateral cerebellum (four patients) was observed.
Conclusion: Ipsilateral thalamic hypoperfusion is not uncommon in temporal lobe epilepsy. The exact mechanism causing ipsilateral thalamic hypoperfusion is uncertain; however, corticothalamic diaschisis may be an important factor. This finding may aid in the lateralization of seizure foci on interictal brain SPECT.