Complications of invasive monitoring used in intractable pediatric epilepsy

Invasive monitoring for intractable epilepsy is useful when the epileptogenic focus is in question even after an extensive noninvasive presurgical evaluation, or when the epileptogenic focus is located in or near eloquent cortex. From June 1989 to June 2001 at the Children's Hospital of Philadelphia, 64 children with intractable epilepsy underwent 67 invasive monitoring procedures as part of their presurgical evaluation. The average age at implantation was 10 years. In all but two cases, subdural strips and grids were used. Depth electrodes, when used, were placed stereotactically or under direct vision. The average duration of the monitoring period was 5.87 days. Every patient had intradural cultures sent during removal of the electrodes, and lumbar punctures were performed in 15 patients. Twenty-one patients had at least one episode of a CSF leak. Of the 67 patients, 10 had positive intradural cultures, only 1 of whom had a positive lumbar puncture and none of whom developed clinically significant meningitis. No clinically relevant hemorrhages occurred as a result of the invasive monitoring. One patient did have a transient visual field loss after placement of an occipital grid. While CSF leaks are common after invasive monitoring despite precautions, clinically significant CSF infections are uncommon and appear to be unrelated to the duration of monitoring, the occurrence of a CSF leak or the length of time the patient is on perioperative antibiotics. We conclude that invasive monitoring for intractable epilepsy is generally safe.