Abstracts

Rationale: Evidence has been accumulating about the key role of PET scan in epilepsy surgical planning for identification of a metabolic epileptogenic zone. When PET scan was not readily available, the patient was often excluded from further surgical work up if MRI was negative. PET scan has been fully integrated as a routine test during presurgical evaluation in our epilepsy center, with all patients undergoing PET on day one of admission for Phase 1. Surgical planning is typically straightforward if the patient has confirmed focal seizures on an EEG with concordant abnormal PET and MRI. Patients with both negative MRI and PET are considered non-lesional and currently not surgical candidates at our institution unless additional imaging such as MEG or SPECT strongly suggests well-localized seizure focus. We identified patients in which we were able to offer surgical intervention based on positive PET, despite negative MRI.Methods: Retrospective database review was conducted to identify all patients who were admitted to the comprehensive epilepsy center at Children's Hospital of Pittsburgh for phase 1 during Nov 2011 and May 2013. Clinical information, results of relevant tests during phase 1 admission and post-surgical outcomes were collected systematically. Descriptive analysis was done. Results: Forty two patients underwent pre-surgical (Phase 1) evaluation during the time period studied. All but one patient had PET scan as part of the phase 1 evaluation. That patient did not get the PET as it was a repeat phase1. Twelve patients were recommended for surgery. Eight of the patients that had surgery had EEG in concordance with positive findings on either MRI or PET. One patient had both negative PET and MRI and required additional imaging with MEG. 3 patients were identified with negative MRI but positive findings on PET. Two of the three patients with positive PET and negative MRI had resection of epileptogenic foci following monitoring with subdural grid electrodes. A pathologic diagnosis of cortical dysplasia was made and the two patients remain seizure free following surgery. Resection surgery for the third patient is pending.Conclusions: PET is a valuable non invasive tool in presurgical planning and is available early in the process of the epilepsy surgery evaluation. This study can often prevent unnecessary delays in the ability of clinicians to offer further presurgical/surgical interventions even when brain MRI is negative. These cases demonstrate the benefit of PET being a routine part of the epilepsy surgical evaluation in all patients regardless of MRI findings.