Abstracts

Rationale: Results of chronic cyclic AN thalamic stimulation thalamus was recently reported in Epilepsia (the SANTE study); overall results were positive. The thalamus is a critical structure in sleep, exploring changes in sleep-related physiological parameters (including breathing) is important in evaluating device safety. Sleep apnea can exacerbate epilepsy. Patients with apnea will likely be candidates for AN-stim. Our study evaluates potential sleep-related ventilatory changes in the SANTE cohort. Our goals were: (1) to determine if those receiving AN-stim had more hypopneas or apneas than matched controls, and (2) to determine if hypopneas or apneas appeared central or obstructive in origin. Methods: 4 patients receiving AN-stim and 4 matched controls with epilepsy were studied with standard PSG (and a full EEG montage) for 2 nights. Although the total number of days of recording was 16, only 8 nights of recording generated reliable data for measurement of ventilatory changes and determination of cause (central v. obstructive). All underwent ambulatory PSG EEG. All wore a nasal thermistor, an SaO2 pulse-ox, and effort sensor belts at the chest and abdomen. PSG scoring was performed using Nihon-Kohden, Polysmith software. Results: Among the AN-stim patients, the longest events for each of the 4 nights, were a 78 s (second) obstructive hypopnea (OH) with a minimum SaO2 of 97%, a 78 s OH with a minimum SaO2 of 96%, a 47 s mixed apnea with a minimum SaO2 of 96%, and a 78 s OH with a minimum SaO2 of 96%. The lowest SaO2 values were a 90% associated with a 78 s OH, an SaO2 of 81% associated with a 10 s OH, an SaO2 of 95% associated with a 12 s central apnea, and an SaO2 of 87% associated with a 77 s mixed hypopnea. For comparison, among the non-stimulated, the longest events for each of the 4 nights of recording were as follows: a 17 s OH with a minimum SaO2 of 90%, a 76 s OH with a minimum SaO2 of 95%, a 77 s OH with a minimum SaO2 of 93%, and a 78 s OH with a minimum SaO2 of 93%. The lowest SaO2 values were a 90% associated with a 17 s OH, an SaO2 of 93% associated with a 71 s OH, an SaO2 of 85% associated with a 57 s obstructive apnea, and an SaO2 of 89% associated with a 35 s OH. Conclusions: Patients receiving AN-stim do not appear to have an increased incidence of sleep-related ventilatory disruption. During the long events, the lowest SaO2s were found in controls. AN-stim patients had a slighter higher incidence of central apnea (1) although the longest central apnea was only 12 sec. (SaO2 fell only to 95%). The small (n) precludes statistical analysis. The events were longer than expected; the event times are likely overestimates due to the detection software which is extremely sensitive to minor ventilatory changes. Nevertheless, the Medtronic SANTE device does not appear to provoke adverse ventilatory changes in sleep. Ongoing studies are in progress that may uncover other changes in sleep behavior related to the device.