Abstracts

Rationale: Obstructive sleep apnea (OSA) is commonly seen with refractory epilepsy.  The use of vagus nerve stimulator (VNS) has been implicated in worsening or precipitating both obstructive and central sleep apneas.  In a past study, 31% of subjects were diagnosed with OSA three months after VNS implantation.  However, data regarding prevalence and risk factors of OSA with long-term VNS use is limited.  The aim of this study is to identify the prevalence of OSA risk and risk factors of OSA in subjects with VNS use, with the use of STOP-BANG (Table 1) questionnaire and sleep apnea sleep disorders questionnaire (SA-SDQ).   Methods: This study was approved by the local institutional review board.  EMR was used to identify subjects with VNS and their VNS parameters and demographics.  After obtaining consent, subjects were asked to complete STOP-BANG and SA-SDQ questionnaires and provide information about their epilepsy via telephone.  A score of more than 3 on STOP-BANG was suggestive of high risk of sleep apnea.  Scores of 29 for men and 26 for women were suggestive of high risk of sleep apnea, based on previous studies. [1] Descriptive statistics were represented by mean, standard deviation (SD) and percentages. Pearson correlations were performed to identify associations between individual VNS parameters (current, stimulation frequency, on time and off time), seizure frequency, age, and STOP-BANG and SA-SDQ scores. Significance was assessed at p < .05. Results: 17 subjects provided consent to participate.  The subject characteristics are represented in Table 2.  The mean (SD) VNS settings were as follows: current 1.2 (0.3) m V, frequency 27.4 (4) Hz, on time 20.4 (7.8) seconds, off time 1.7 (1.7) min, and magnet current: 1.4 (0.3) mV.  The average STOP- BANG score was 3.4 (SD: 1.90) and SA-SDQ was 23.2 (SD: 6.7).  A high risk of sleep apnea was identified in 64.7% of subjects per STOP-BANG data and in 29.4% subjects according to SA-SDQ data.  The correlation analysis did not show any significant associations between questionnaire scores and VNS parameters.   A trend towards association was noted between STOP-BANG and SA-SDQ questionnaire scores and seizure frequency (r=0.48, p=0.058; r=0.48 p=0.054, respectively).   Conclusions: In our cohort, 29-65% of subjects with VNS were at risk of sleep apnea, depending on the questionnaire.  On-going seizure frequency showed association with a higher risk of OSA, however this was not statistically significant.  Overall, this study suggests higher risk of OSA in subjects with VNS.  Treatment of OSA has potential to improve seizure frequency.  Further larger studies evaluating OSA with polysomnography are needed to identify the prevalence and risk factors for OSA in subjects with VNS use. Reference:1. Weatherwax, K.J., et al., Obstructive sleep apnea in epilepsy patients: the Sleep Apnea scale of the Sleep Disorders Questionnaire (SA-SDQ) is a useful screening instrument for obstructive sleep apnea in a disease-specific population. Sleep Med, 2003. 4(6): p. 517-21 Funding: No funding was received