Abstracts

Rationale: Magnetoencephalography (MEG) is a non-invasive tool used clinically for the pre-surgical evaluation of patients with medically intractable epilepsy. MEG records the magnetic fields caused by neuronal electrical activity and is used to localize the epileptogenic zone for the planning of epilepsy surgery. These recordings require patients to lie still for prolonged periods of time within a magnetically shielded room (MSR), designed to reduce ambient magnetic noise. Children or uncooperative adults with epilepsy may require sedation to reduce movement artifact and obtain high quality recordings. Potential challenges related to the use of total intravenous anesthesia (TIVA) in the MEG environment include limited access to the patient’s airway, remote location, suppression of cortical activity, and increased patient care expenses. Dexmedetomidine (DEX) causes minimal effects to EEG/MEG, is well tolerated in pediatric patients, and intranasal DEX can be administered by a non-anesthesiologist. We report our experience with intranasal DEX as sedation for intractable epilepsy patients undergoing MEG. Methods: Patients with medically intractable epilepsy were monitored with 275 MEG channels (CTF Systems Inc., VSM MedTech Ltd.) and 21 EEG channels using 10-20 placement as well as one electrocardiogram (ECG) channel. A recording of spontaneous activity was immediately followed by median nerve electrical stimulation. Sleep deprivation occurred the night before MEG testing. Following procedural consent, 2 mcg/kg intranasal DEX was administered via a Mucosal Atomization Device (MAD) and patients were asked to remain recumbent for 1-2 minutes to maximize absorption. Oxygen saturation, blood pressure, and pulse rate were recorded continuously on a monitor outside the MSR with cables passed through a porthole. Nursing staff recorded vital signs every 5 minutes. Results: Seventeen patients (8 females, 9 males) with medically intractable epilepsy (average age 12.6 ± 4.0 yrs, range 6.2-19.7 yrs) were recorded with this sedation procedure. The average weight of the patients was 52.0 ± 27.3 kg (range 19.7-102.7 kg). There were no failures of sedation. The time between dexmedetomidine administration and the first sleep spindle on EEG was 28 ± 15.3 min (range 11-61 min). MEG recordings lasted an average of 92.1 ± 20 min (range 55-134 min) and no patients required an additional dose of dexmedetomidine. Although there were patients who experienced transient bradycardia during the procedure, none required intervention and the recording did not need to be stopped. In all cases, artifact-free MEG recordings were obtained and somatosensory evoked field testing was well tolerated. Conclusions: Our experience suggests that intranasal dexmedetomidine is an advantageous sedation option for children and adults with intractable epilepsy who are undergoing MEG. Further research is needed to determine the best ways to apply these methods to younger children and those with developmental disabilities.       Funding: None