Vestibular Test Findings in Auditory Neuropathy Spectrum Disorders: A Systematic Review

Abstract

Introduction: Auditory neuropathy (ANSD) is a hearing condition defined by an absence of Auditory Brainstem Response (ABR), presence of Otoacoustic Emissions (OAE) and cochlear microphonics (CM). cVEMP, oVEMP, vHIT and Caloric tests can be used to diagnose the neuropathy of the vestibular branch of the eighth cranial nerves in patients with ANSD. It is rare to have isolated auditory neuropathy or vestibular neuropathy; instead, the most frequent condition is "audio-vestibular neuropathy" which affects both branches of the eighth cranial nerve. Aim: To conduct a systematic review of articles on vestibular test findings in people with ANSD. Method: The articles were searched in various databases. For the purpose of this systematic review, 17 papers in total fulfilled the inclusion and exclusion criteria. The QUADAS-2 risk of bias assessment tool was used to ensure the quality and possible risk of bias for each article in this study. Results: Most studies indicate that more than 90 percent of people with ANSD do not exhibit cVEMP and oVEMP responses. A few studies have also shown that people with ANSD may have higher VEMP thresholds, prolonged peak and interpeak latencies, and lower amplitudes. The vHIT test showed reduced VOR gain in all semicircular canals as well as the occurrence of both covert and overt saccades in ANSD individuals. Furthermore, Caloric test revealed hypoactive responses among individuals with ANSD. Conclusion: The majority of these findings pointed to a vestibular impairment in people with auditory neuropathy spectrum disorders. These articles also found that individuals with ANSD have no vestibular signs or symptoms. The results of these many tests assist to understand the vestibular pathways affected in ANSD individuals, from which a treatment plan may be developed to rehabilitate these patients and enhance their quality of life.