Quantification of autonomic regulation in patients with sudden sensorineural hearing loss

Previous studies have proposed varying causes for idiopathic sudden sensorineural hearing loss (SSNHL), including vascular occlusion, ruptured inner ear membrane, acoustic tumours and circulatory disturbances in the inner ear. The objective of this study was to characterise the autonomic regulation in 19 SSNHL patients in comparison to 19 healthy age-gender matched normal-hearing control subjects (CON) in order to improve the diagnostics of vascular caused hearing loss in SSNHL patients. A high-resolution short-term electrocardiogram (ECG) and the continuous noninvasive blood pressure signal were simultaneously recorded under resting conditions (30min). Linear and nonlinear indices of heart rate- and blood pressure variability (HRV, BPV) were calculated to characterise autonomic regulation. The results showed that HRV analysis did not produce significantly different results between SSNHL and CON, whereas linear and nonlinear BPV indices showed significant differences between both groups (p<0.01). This study was the first to show an altered cardiovascular regulation in SSNHL patients when compared to CON subjects, based on continuous blood pressure analysis. This was characterised by reduced variability, complexity and dynamics of blood pressure time series in SSNHL. These findings may contribute to an improved classification of the controversially discussed causes of SSNHL and, in addition, may lead to improved diagnostic strategies for a subgroup of SSNHL patients whose hearing loss is caused by cardiovascular factors.