Perfusion patterns during temporal lobe seizures: relationship to surgical outcome

Abstract

We sought to determine whether patterns of ictal hyperfusion demonstrated using [99mTC]HMPAO (hexamethylpropylene amine oxime) single photon emission computed tomography (SPECT) predict outcome of temporal lobectomy; in particular, whether the more extensive patterns of ictal hyperperfusion are associated with poor outcome. We studied 63 patients who had ictal SPECT studies prior to temporal lobectomy. Hyperperfusion on ictal SPECT scans was lateralized, and classified into: (i) 'typical', (ii) 'typical with posterior extension', (iii) 'bilateral' and (iv) 'atypical' patterns. Outcome (minimum of 2 years follow-up) was classified as either seizure free, or not seizure free. Actuarial analysis was used to test the relationship of SPECT patterns with outcome. There were 35 cases with the typical ictal SPECT pattern, 13 posterior, nine bilateral and six atypical cases. The atypical pattern was associated with lack of pathology in the surgical specimen. Outcome was similar for the typical, posterior and bilateral with 60%, 69% and 67% seizure free, respectively. In contrast, the atypical group had a worse outcome with only 33% seizure free. Actuarial analysis showed a significant difference in outcome between patients with the typical pattern, and patients with the atypical pattern (P = 0.04). We conclude that extended patterns of ictal perfusion in temporal lobe epilepsy do not predict poor outcome, indicating that extended hyperperfusion probably represents seizure propagation pathways rather than intrinsically epileptogenic tissue. Atypical patterns of hyperperfusion are associated with poor outcome and may indicate diffuse or extra-temporal epileptogenicity.