Peri-ictal SPECT in temporal lobe epilepsy: post-surgical evaluation

Background: our aim was to evaluate the usefulness of peri-ictal SPECT in localising the epileptogenic region (ER) in candidates for temporal lobectomy to treat medically refractory complex partial seizures (CPS). Interictal and ictal SPECT, MRI and video-EEG results were compared and the positive predictive value (PPV) was calculated in those patients with good surgical outcome.

Methods: 37 patients who had a minimum of 3 years follow-up after surgery were studied retrospectively. Pre-surgical evaluation had included video-EEG monitoring, MRI and interictal and ictal SPECT. These results were compared to the surgically treated ER and successful outcome confirmed by post-surgical clinical follow-up. 29/37 patients remained seizure-free in the post-surgical follow-up. Interictal and peri-ictal SPECT were performed using 740 MBq of 99mTc-HMPAO. Peri-ictal SPECT was ictal in 25 patients and postictal in 12.

Results: ER concordance with video-EEG and peri-ictal SPECT was 86% (32/37 patients). It was 84% (31/37) for MRI and 54% (20/37 patients) for interictal SPECT. Peri-ictal SPECT localised the ER in 8/11 patients with discordant MRI and video-EEG results. Ictal SPECT localised the ER in the correct temporal lobe in 23/25 patients (92% concordance). In the 29 patients with a good surgical outcome, the PPV of video-EEG was 95% (27/29) and it was 90% (26/29) for both MRI and peri-ictal SPECT.

Conclusions: peri-ictal brain SPECT is well able to localize ER in patients with temporal lobe epilepsy. Periictal SPECT concordance with ER was as good as video-EEG and MRI and its PPV was as good as that of MRI. We strongly recommend its use in the pre-surgical evaluation of temporal lobe epilepsy, especially when MRI and EEG are discordant.