Ictal SPECT analyzed by three-dimensional stereotactic surface projection in frontal lobe epilepsy patients

We analyzed preoperative ictal SPECT results from 18 frontal lobe epilepsy patients who underwent epilepsy surgery (mean age 22.9 years). Seizure onset at implanted subdural electrodes was defined as the epileptic focus in 16 of 18 patients. In two additional patients, the resected area on postoperative magnetic resonance images was defined as the epileptic focus. The radioisotope 99mTc-ECD was injected in all patients within 5 s after seizure onset. SPECT images were analyzed by three-dimensional stereotactic surface projection (3-D SSP). Areas of hyperperfusion identified by ictal SPECT were concordant with the site of epileptic focus in 11 patients (61.1%, concordant group) and were non-concordant in 7 patients (38.9%, non-concordant group). The non-concordant group had a higher number of patients with a history of acquired brain damages, such as encephalitis or brain surgery (p < 0.05). Only 3 of 11 patients in the concordant group showed areas of localized hyperperfusion within epileptic foci, whereas 8 patients showed areas of hyperperfusion extending to other regions. Ictal SPECT analyzed by 3-D SSP is useful as a mode of presurgical evaluation in frontal lobe epilepsy patients without a history of encephalitis or surgical treatment. We caution that rapid seizure spread may result occasionally in areas of hyperperfusion extending to adjacent or remote regions.