Seizures following posterior fossa surgery.

A retrospective analysis of seizure incidence in 511 patients who underwent posterior possa operations via a suboccipital craniectomy with prophylactic anticonvulsant agents, was performed. Thirty patients (5.9%) experienced seizures within 2 weeks postoperatively. Their mean age was 15 years. Twenty patients had seizures within 3 h of operation; 24 patients had generalized tonic clonic seizures. Focal motor seizures with secondary generalization and simple focal motor seizures were recorded in three patients each. The incidence of postoperative seizures was highest in patients with acoustic schwanommas (9.09%) followed by those with medulloblastomas (8.54%) and astrocytomas (8.33%). The sitting position, associated with venous air embolism (VAE) and or pneumocephalus, was related to the occurrence (p = 0.001) of postoperative seizures. Seizures occurred in 24 patients out of 250 cases operated on in the sitting position compared with 3/170 and 3/91 in the prone and lateral positions, respectively. Intraoperatively significant VAE occurred in 10 out of 30 patients and postoperative computed tomography revealed pneunocephalus in 20 out of 30 patients. A higher percentage was found in patients with a preoperative ventriculoperitoneal shunt or intraoperative ventriculostomy (6.5%) than in those without (5.1%), but the difference was not statistically significant. In conclusion, seizures after posterior fossa surgery are a significant problem which is not reflected in the published literature. Our study highlights the significance of the sitting position in the causation of seizures after posterior fossa surgery.