Original ArticleOptimizations and Nuances in Neurosurgical Technique for the Minimization of Complications in Subdural Electrode Placement for Epilepsy Surgery
Introduction
Epilepsy affects nearly 0.5% of adults (35) leading to an estimated 150,000 new patients in the United States each year (31). Up to 40% of patients have persistent epilepsy despite medical treatment (3). The decision to proceed with surgery must take into consideration the chance of freedom from seizures with additional antiepileptic drug trials and the adverse long-term effects of uncontrolled seizures.
Surgery has the potential to offer patients an improved quality of life as well as the chance of achieving freedom from seizures 9, 14. The identification and localization of the seizure focus is essential to successful outcomes, but this is not always readily determined by clinical presentation, imaging, and electroencephalography (EEG) studies (26). Subdural grid electrodes have been used to record ictal patterns for more than 40 years and have been used as long-term recording devices since 1975 (24). The coverage of large surface areas of the brain for electrographic monitoring purposes necessitates a craniotomy to obtain sufficient sampling of cerebral activity. The combination of strip and grid electrode arrays as well as depth electrodes can be used in patients in whom the epileptogenic focus is ambiguous.
Good surgical and clinical results have been achieved from resective surgery after invasive electrode recording 5, 13, 16, 20, 23, 25, 28, 30, 32, 38, 39. However, patients undergoing these procedures are exposed to inherent risks and complications, such as infection, extraaxial fluid collections, and cerebrospinal fluid (CSF) leaks. Immobility in the postoperative period can lead to a deep vein thrombosis (DVT) and possible pulmonary embolus (PE).
The reported literature contains significant variation in complication rates; however, most published studies tend to support 1) improvement over time or with experience and 2) a dependency on surgical technique and perioperative care. We performed a rigorous study to determine our complication rates, compare them with the reported literature, and identify any aspects of our technique and perioperative regimen that may be beneficial (or detrimental) to our outcomes and to share those of potential significance that may be beneficial to others.
Wyler et al. (38) were the first to study systematically the use of subdural strip electrodes, and in 2000, they reported an overall complication rate of 0.85% (39). However, the literature has reported variable complication rates ranging from 0.85% to 26.3% in one series 2, 16, 39. Hamer et al. (16) reported one of the highest overall complication rates based on cases performed over a 17-year span (1980–1997) at a single institution. This study, which included cases performed more than 30 years ago, demonstrated a dramatic improvement in complication rates over time, beginning with a complication rate of 33% (1980–1991 cases), with complication rate reductions to 19% (for 1992–1997 cases) and further to 13.5% (for 1994–1997). This improvement was attributed to improvements in grid technology, surgical technique, and postoperative care (16). A meta-analysis by Arya et al. (1), in which 21 studies comprising 2542 patients were reviewed, demonstrated significant complication rates for most of a set of specific adverse events that were studied. Although lack of information regarding patient uniqueness in some included studies precluded a determination of overall complication rates, the pooled prevalence rates included pyogenic infections 2.3% (95% confidence interval = 1.5–3.1) and superficial infections 3.0% (95% confidence interval = 1.9–4.1). Operative technique plays an important role in preventing postoperative complications. The purpose of this article is to report on the complication rate of subdural electrode placement and on the importance of specific aspects of operative technique thought to be valuable in limiting its potential morbidity.
Section snippets
Study Group
This institutional review board–approved retrospective analysis used a prospectively maintained institutional epilepsy surgery database at Rush University. During the period 1997–2010, 127 consecutive patients underwent invasive EEG monitoring with subdural electrodes placed by a single surgeon. Reportable complications included symptomatic subdural or epidural hematoma, symptomatic cerebral edema, neurologic deficit, infarction, infection, DVT, PE, or death.
Surgical Evaluation
All surgeries were performed at Rush
Results
There were 127 consecutive patients who underwent invasive EEG monitoring. The sample group consisted of 76 male and 51 female patients. Mean age of patients was 30 years old (range, 3–63 years old). Follow-up ranged from 2–11 years with an average follow-up of 4.6 years.
Table 1 lists and compares the complication rates found in our series with the complication rates reported in the meta-analysis by Arya et al. (1), which included 21 studies comprising 2542 patients. For each category, σ was
Discussion
Epilepsy is a significant disabling condition and persists in 30%–40% of patients despite medical treatment (17). Only 64% of patients with a diagnosis of epilepsy experience freedom from seizures by the time they try a third antiepileptic drug (3). The decision to proceed with surgery must take into consideration both the chance of seizure freedom with additional antiepileptic drug trials and the adverse long-term effects of uncontrolled seizures (10).
Surgical intervention is an important
Conclusions
Attention to surgical technique and postoperative care may lead to a low complication risk with invasive EEG monitoring. We have accumulated consistent experience in a single institution and using a particular surgical technique, admittedly in the absence of a control group, that supports but does not prove the importance of a subgaleal drain throughout the monitoring period to provide the dual functionality of ICP control and reduction in CSF leakage through the skin, which may facilitate
Acknowledgments
We thank Timothy J. Harris, Jr., B.S., of the Epilepsy Center, Department of Neurological Sciences, Rush University Medical Center, for his valuable assistance in taking and editing intraoperative photographs for this manuscript.
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