Implant Site Infection and Bone Flap Osteomyelitis Associated with the NeuroPace Responsive Neurostimulation System

The NeuroPace RNS System is a method recently approved by the U.S. Food and Drug Administration for closed-loop direct brain stimulation in selected patients with drug-resistant partial seizures. The long-term risks of implant site infection and accompanying bone flap osteomyelitis associated with responsive neurostimulation (RNS) devices have not been fully appreciated.

We report 3 cases of refractory partial epilepsy that were treated with RNS therapy in conjunction with antiepileptic drugs. Patients underwent invasive epilepsy monitoring and resection of seizure foci. All patients continued to have debilitating partial seizures and underwent implantation of the RNS device, which resulted in various degrees of symptomatic relief. On average, the battery of the implantable pulse generator was replaced every 2 years. All 3 patients developed implant site infection and bone flap osteomyelitis with multiple implantable pulse generator replacements, and the RNS devices were removed. Bone flaps were removed in 2 patients because of significant osteomyelitis and were reconstructed in a delayed fashion with customized cranial implants. No patient had evidence of meningitis or cerebritis. The patients were treated via a multidisciplinary approach, and all patients recovered well with satisfactory wound healing and seizure control.

Implant site infection and bone flap osteomyelitis are significant adverse events associated with the RNS device. The incidence of infection in this series (10%) is comparable to the incidence reported in the long-term trial. The infection risk is mainly associated with reoperations and increases with multiple implantable pulse generator replacements. The RNS device may benefit from reducing technical risk factors that are associated with postoperative bone and soft tissue infections.