Adverse events related to extraoperative invasive EEG monitoring with subdural grid electrodes: A systematic review and meta-analysis

Purpose Implantation of subdural grids and invasive electroencephalography (EEG) monitoring is important to define the ictal-onset zone and eloquent cortex in selected patients with medically refractory epilepsy. The objective of this systematic review is to summarize data about adverse events related to this procedure. Methods English-language studies published up to July 2012, reporting such adverse events were reviewed. Outcome measures included demographic variables; surgical protocol including number of subdural electrodes implanted per patient, duration of monitoring, antibiotic, and steroid prophylaxis; and adverse events. Key Findings Twenty-one studies were identified including a total of 2,542 patients. The reported mean number of electrodes per patient and duration of monitoring varied from 52 to 95 and 5 to 17days, respectively. There is a trend toward more uniform use of antibiotics and steroids in the perioperative period. Neurologic infections (pooled prevalence2.3%, 95% confidence interval 1.53.1), superficial infections (3.0%, 1.94.1), intracranial hemorrhage (4.0%, 3.24.8), and elevated intracranial pressure (2.4%, 1.53.3) were found to be the most common adverse events. Up to 3.5% of patients required additional surgical procedure(s) for management of these adverse events. Increased number of electrodes (67) was found to be independently associated with increased incidence of adverse events. Significance Although providing critical information for patients with medically refractory epilepsy, subdural grids implantation and invasive EEG monitoring entails risks of infection, hemorrhage, and elevated intracranial pressure. The prevalence estimates, likely to be conservative due to selective reporting, are expected to be helpful in counseling patients.