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NEUROSURGICAL ANESTHESIA

A Retrospective Analysis of the Effect of General Anesthetics on the Successful Detection of Interictal Epileptiform Activity in Magnetoencephalography

Guruswamy Balakrishnan, MD^*, Kavita M. Grover, MD, Karen Mason, BS T, Brien Smith, MD, Gregory L. Barkley, MD, Norman Tepley, PhD, and Susan M. Bowyer, PhD

From the Departments of *Anesthesiology, and Neurology, Henry Ford Medical Group, Detroit, Michigan; Department of Neurology, Wayne State University, Detroit, Michigan; and Department of Physics, Oakland University, Rochester, Michigan.

Address correspondence and reprint requests to S. M. Bowyer, PhD, Henry Ford Hospital, Neuromagnetism Lab CFP 78/79, 2799 West Grand Boulevard, Detroit, MI 48202. Address e-mail to sbowyer1{at}hfhs.org.

BACKGROUND: A magnetoencephalography (MEG) study requires the patient to lie still for a prolonged period of time. In children and uncooperative adults with epilepsy, general anesthesia or sedation may be required to insure a good quality study. As general anesthetics have anticonvulsant and proconvulsant properties, we investigated whether the use of anesthesia reduced the successful detection of interictal epilepsy activity.

METHODS: MEG testing was performed on 41 epilepsy patients (10 women, 31 men; 1–48 yr) while anesthetized. To determine the impact of anesthesia on the identification of epileptiform activity, the anesthesia group of patients was compared with all other patients with epilepsy who were recorded in our laboratory without anesthesia, as well as with a subgroup of children with epilepsy who were able to be recorded without the need for anesthesia.

RESULTS: Propofol was used in 38 patients, etomidate in two, and one received sevoflurane. Twenty-nine (71%) were found to have interictal epileptiform activity in their MEG results. The percentage of MEG studies with a positive yield for interictal epileptiform activity is comparable with the percentage (63%) found in the patients with epilepsy undergoing MEG without anesthesia. In the 38 children younger than 18 yr, 28 (74%) had interictal epileptiform activity compared with 80% done without anesthesia.

CONCLUSION: We conclude that levels of anesthesia needed to provide unconsciousness and immobility during MEG studies do not significantly alter the likelihood of recording interictal epileptiform spike activity with MEG.

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