Abstracts

Rationale: Deep brain stimulation (DBS) is an approved therapy for Parkinson disease, essential tremor, and dystonia. According to the Medtronic database, more than 80,000 patients have had implantation of DBS electrodes thus far. In addition to approved uses, DBS is being investigated for other movement disorders, pain conditions, psychiatric conditions, and epilepsy. It is anticipated, therefore, that use of DBS will increase in the future. Seizure is one complication associated with placement of DBS electrodes. The incidence of seizures in the immediate post-operative period has ranged from 0 to 10% in different case series. A recent meta-analysis estimated a risk of 2.4%, but noted flaws in available data, including inconsistent and duplicate reporting (Coley et al, 2009, Brit J Neurosurg 23:179-83). The subsequent clinical course of patients who suffer perioperative seizures is not known, nor is the risk of developing seizures or epilepsy in the late-postoperative period.Methods: We present a retrospective case series based on chart review of all patients who underwent DBS surgery for any indication at Mayo Clinic Arizona between 2002 and 2010. Data gathered included: age, sex, indication for surgery, DBS target, number of surgeries, pre-operative seizure risk factors, post-operative imaging abnormalities, post-operative time to seizure, semiology of seizure, EEG findings, treatment initiated and duration of treatment. Results are presented as percentages of total (n=116) or percentage of those with seizure (n=5). Due to the small incidence of post-operative seizures, the data were not appropriate for parametric statistical analysis, but results are presented as percentages of total and of patients with seizures.Results: Of 116 patients who underwent DBS surgery, 5 had documented seizures at some point after surgery, representing 4.3% of patients, and 2.3% of surgeries performed. No subjects had a preexisting seizure disorder. 1/5 had a seizure only four years after surgery, which was likely related to a later stroke rather than the DBS surgery. The other seizures occurred at 7 hours, 17 hours, 24 hours, and 48 days after surgery. 2/3 who seized within 24 hours after surgery had hemorrhage on their post-op imaging (66%), compared to 16% of total patients. Those 2 also had focal seizures with secondary generalization, while the remaining 3 had apparently generalized seizures without lateralizing findings on EEG. No patients developed epilepsy or required treatment beyond one year. While 14% of patients undergoing DBS had risk factors for seizures prior to surgery, none who did seize had any prior risk factors.Conclusions: Our data support an incidence of post-operative seizures with DBS implantation at 2.3% of surgeries, consistent with prior studies. The number of pre-operative seizure risk factors was unrelated to occurrence of post-operative seizures, but bleeding complications did increase risk. This information is especially useful given investigations into using DBS as a treatment for epilepsy.