Thalamic hypoperfusion on SPECT in epilepsy with bilateral synchronous discharge

Abstract

Various childhood epileptic syndromes have been reported to reveal generalized symmetrical spike-wave patterns preceded by unilateral focal discharges. The thalamic rhythmogenic mechanisms responsible for spike-wave discharges have been intensively investigated leading to a better understanding of their anatomo-physiological substrate. We investigated the role of the thalamus in secondary bilateral synchrony on electroencephalography (EEG) in three patients with intractable localization-related epilepsy by performing synchronous single photon emission computed tomography (SPECT) and EEG analysis. The brain scan examination was carried out after injection 18.5 MBq/kg of Tc99m-hexamethyl-propyleneamine oxime at the same time of revealing bilateral synchronous discharges on EEG. The SPECT revealed thalamic hypoperfusion in all cases. In addition, the SPECT revealed hypoperfusion in the left cortical regions and ipsilateral thalami, corresponding to the EEG abnormalities in the cortical regions. These findings in this study suggested that the thalamus may play a role of secondary bilateral synchronization on EEG. Specific thalamic nuclei fire concurrent with cortical epileptiform discharges and are hypothesized to play a role in seizure propagation. Our findings demonstrated thalamo-cortical coupling by SPECT. In conclusion, the thalamus may play a crucial role as a pacemaker of rhythmic EEG activities such as secondary bilateral synchronous discharges.