Regional Ictal Hyperperfusion in the Contralateral Occipital Area May Be a Poor Prognostic Marker of Anterior Temporal Lobectomy: A SISCOM Analysis of MTLE Cases

BACKGROUND AND OBJECTIVE: Subtraction of ictal SPECT coregistered to MRI (SISCOM) provides complementary information for detecting the ictal onset zone, especially in patients with MRI-negative focal epilepsy, and provides additional useful information for predicting long-term postresection outcomes. This study sought to investigate the relationship between surgical failure and increased cerebral blood flow (CBF) pattern using SPECT in patients with mesial temporal lobe epilepsy with unilateral hippocampal sclerosis (MTLE-HS). METHODS: Among 42 subjects who underwent anterior temporal lobectomy with amygdalohippocampectomy (ATL-AH) for MTLE-HS, 29 (69.0%) were seizure-free (SF group). Hyperperfusion was compared in 14 ipsilateral and contralateral brain regions in SISCOM images between the two groups. RESULTS: The pattern of ictal hyperperfusion in temporal regions did not vary significantly between the SF and non-seizure-free (NSF) groups. However, CBF increases in the contralateral occipital area was more frequent in the NSF group than in the SF group. Furthermore, ictal hyperperfusion of the ipsilateral occipital and contralateral parietal areas tended to be more frequent in the NSF group. CONCLUSION: The results indicate that poor ATL-AH surgical outcome is associated with a tendency of ictal hyperperfusion of the contralateral occipital cortex based on SISCOM analysis. The pattern of early ictal CBF changes implicating the propagation from temporal to occipital cortices can be considered a marker of poor surgical outcomes of ATL-AH in MTLE-HS patients.