Risk of Seizures in EEA

Introduction: The onset of seizures following craniotomy has been estimated at 15–20%. This has prompted the routine use of anti-epileptic drug (AED) prophylaxis among many surgeons. Endoscopic endonasal approaches (EEA) have increased in popularity for treatment of a variety of intracranial pathologies. One of the benefits of the expanded endonasal approach is that it allows access to the skull base with minimal cortical manipulation, theoretically reducing the incidence of post-operative seizures. However, the incidence of post-operative seizures in this population is unknown.

Methods: This is a retrospective chart review of all adult patients undergoing EEA that developed post-operative seizures from July, 2007 through June, 2014. A list of patients was generated by an electronic search using the billing codes for EEG and endoscopy. Patients were excluded if they had a history of seizures or presented with a seizure pre-operatively, history of craniotomy, combined EEA and craniotomy, or if the EEG and clinical impression was not consistent with a seizure. Patients were included if they had EEG findings consistent with seizure, or a witnessed clinical event consistent with seizure activity. The same search method was used to determine the number of patients who had new onset seizures following craniotomies for tumor resection.

Results: 9 patients met inclusions criteria for seizures following EEA, 2 meningiomas, 1 esthesioneuroblastoma, 1 pituitary adenoma, 1 chondrosarcoma, 1 squamous cell carcinoma, 1 spontaneous CSF leak, 1 epidermoid, and one Rathke’s cleft cyst (RCC).

Clinical and radiographic characteristics were quite diverse in these patients. Although 4 patients had seizures within one week of their surgery, the mean number of days in the remaining patients was 241 (range 61–540, median 185). The average size of the tumor was 2.95 cm (range 1.3–5.2, median 3.75). Seven patients had intra-operative CSF leaks. Except for two patients with meningiomas and one patient with RCC, all patients had at least one complication including hematoma (1), meningitis (3), post-op CSF leak (2), marked pneumocephalus (1), or abscess (1). All patients were managed with anti-epileptic drugs, and there were no deaths during the study period.

During the study period, 9 (0.84%) out of 1518 patients experienced in the EEA group and 28 (1.6%) out of 1704 patients in the open craniotomy for tumor group experienced seizures post-operatively (p = 0.00614). 827 procedures from the EEA group were intracranial, excluding patients without intra-operative CSF leaks. In the open craniotomy group, 792 of these patients had extra-axial tumors. In this cohort, 24 (3.0%) had post-operative seizures, 15 (1.8%) of which were meningiomas.

Conclusion: Seizures are a rare occurrence following uncomplicated EEA. This rate is significantly lower than the risk associated with craniotomy for the same diagnosis, despite the fact that patients undergoing craniotomies are routinely administered AED’s. Further studies must be done to elucidate the risk factors associated with post-operative seizures in both populations.