Abstracts

Rationale: SPECT provides a snapshot of brain activity at the time of injection. We studied the hyper- and hypoperfused brain regions in mesial temporal lobe epilepsy (MTLE) patients with complex partial seizures (CPS) to understand the functional interaction of brain networks underlying epileptic seizures.Methods: Thirty patients (female = 12; mean age 16 ± 12 years old，mean injection time is 85.6 sec, standard deviation is 63.6, range from 18 to 367 sec) with CPS without secondarily generalized seizures were injected with 99mTc-hexamethylpropylene amine oxime during inpatient Video-EEG monitoring were identified. Patients were divided into 5 groups: early ictal, mid ictal, late ictal (20-40 sec, 40-60 sec and >60 sec after seizure onset respectively) and early postictal and late postictal (0-20 sec and >20 sec after seizure offset respectively). Ictal and interictal SPECT images of right MTLE were flipped to the left to make a uniform data set. Ictal-interictal SPECT analyzed statistical parametric mapping (ISAS) were used to identify significant hyper- and hypoperfused regions (corrected significance p< 0.05). Mean percentage perfusion changes in all brain regions were also determined for the ictal-interictal scan pairs for each time period.Results: ISAS analysis revealed significant ipsilateral mesial temporal lobe (MTL) hyperperfusion during early ictal phase. Ictal hyperperfusion involved lateral temporal lobe (LTL) during mid ictal phase and into supramarginal cortex during late ictal stage (Fig 1). Basal ganglia were increasingly hyperperfused throughout the seizure. Ictal hyperperfusion in bilateral occipital lobes were also noted. Postictally, ipsilateral temporal lobe became hypoperfused during early postictal phase while the contralateral mesial temporal lobe showed hypoperfusion from mid ictal to postictal phase. Hyperperfusion was also seen in contralateral angular gyrus postictally. During CPS, hypoperfusion was identified in default mode network (DMN) circuitries (bilateral mesial prefrontal cortex (MPFC), anterior cingulate cortex (ACC), posterior cingulate cortex (PCC) and ipsilateral angular gyrus). Mean percentage perfusion analysis showed increasing hyperperfusion in the ipsilateral MTL, LTL and basal ganglia during ictal periods. In contrast, bilateral MPFC and ACC remained hypoperfused throughout both ictal and postictal stages and the ipsilateral angular gyrus were hypoperfused during ictal periods. (Fig 2).Conclusions: In this study, we found significant hyperperfusion in the ipsilateral temporal lobe and basal ganglia throughout the ictal period of CPS. This finding suggested reliable seizure onset lateralization in MTLE. In addition, early hypoperfusion in cerebral regions associated as key hubs of the brain’s DMN was noted. This finding could suggest deactivation of DMN nodes and possibly provide some insights into the mechanisms of altered consciousness in CPS.