Exploration of sleep spindles from surgically induced unilaterally deaf adult humans with and without tinnitus

Objective: In the neural noise-cancellation mechanism, reduced auditory thalamic reticular nucleus (TRN) activity is thought to result in tinnitus. As a biomarker of TRN activity is sleep spindles, we performed an exploratory study to ask whether individuals with tinnitus would exhibit altered sleep spindles compared with controls. Methods: Unilaterally deaf adults with tinnitus (UD+T; n = 13), without tinnitus (UD-T; n = 8), and controls without tinnitus or UD (CO; n = 13) were recruited. 2-hour polysomnography nap data were obtained from 64-channels. Spindles were characterised in both frequency and time domains. Results: We observed no statistically significant differences between our groups in any parameter. However, a dual trend towards lower spindle density (1.8 ± 2.1 spindles/min) and higher spindle amplitude (24.6 ± 9.1 µV) amongst the UD+T group was noted. Conclusions: A tentative interpretation of the dual trends is the possible altered auditory TRN function associated with tinnitus. Albeit not statistically significant, these exploratory data at least provide a valuable foundation for future studies to probe the effect further. This includes a higher sample size and longer overnight sleep data. Significance: This is the first study which investigated sleep spindles in UD patients with and without tinnitus.