Abstracts

Rationale: A persistent fetal posterior cerebral artery (fPCA) is considered a normal variant of cerebral vasculature in about 10-20% of the population. At our institution, we observed a high prevalence of fPCAs in people with medically refractory epilepsy (MRE) undergoing an intracarotid amobarbital procedure (IAP) for language and memory evaluation. Our primary hypothesis is that fPCAs are more common in MRE patients than in people undergoing cerebral angiograms for other indications. Secondly, we postulate that the presence of a fPCA may reflect a developmental etiology and therefore aid with the lateralization of the epileptogenic zone (EZ).Methods: We conducted a retrospective chart review of consecutive patients undergoing cerebral angiograms at University Hospital in San Antonio, Texas, from 2000-2008. We compared the rate of fPCAs in this group to that in MRE patients who underwent IAPs from 2000-2011 at the same institution. The prevalence of fPCAs in both groups was compared using Chi Square analysis, while the concordance of fPCAs with the EZ and their association with a seizure free outcome was assessed using Fischer-Exact Tests. The cerebral angiograms in the MRE group were reviewed by one neurointerventialist (LB) to assure consistency of interpretation. Those patients without clear visualization of the posterior circulation on IAP or other imaging studies were excluded.Results: Cerebral angiograms were performed in 188 people for reasons other than epilepsy (CTL), and 144 MRE patients underwent IAP (Table 1). Based on a two-tailed Chi Square analysis, the fPCAs were significantly more prevalent in the MRE (N=42, 29.2%) than the CTL (N=19, 10.1%) group (p<0.001). Among the 42 MRE patients with unilateral EZs, fPCAs were ipsilateral in 24 (63%), while the remaining 14 patients (33.3%) had discordant lateralization of the fPCA (Table 2). Surgical outcomes, based on the ILAE 2001 classification, were compared between MRE patients with and without fPCA. Seventy-nine patients (77.5%) without fPCA, and 25 (59.5%) with fPCAs, had resective surgery. Seizure-free outcomes were not different between people with or without fPCAs, although in patients with pathologically proven hippocampal sclerosis, the presence of an fPCA was associated with a greater chance for seizure freedom, especially if the fPCA was ipsilateral to the EZ. Conclusions: Persistent fetal PCAs are more common in the MRE patients compared to people undergoing cerebral angiograms for other reasons. The fPCAs are more likely to be lateralized to the EZ, particularly in patients with hippocampal sclerosis. These findings suggest that fPCAs may be markers for developmental abnormalities underlying localization-related MRE.