Sadegh Jafarzadeh - Department of Audiology, School of Paramedical Sciences, Mashhad University of Medical Sciences, Mashhad, Iran.
Mohammad Reza Golrokhian Sani - Department of Otolaryngology, Sina Hospital, Mashhad, Iran.
Nematollah Mokhtari Amirmajdi - Department of Otolaryngology, Mashhad University of Medical Sciences, Mashhad, Iran.
Masoud Firouzi - Markazi Vestibular Assessment and Rehabilitation Center, Mashhad, Iran.

Introduction: Vestibular abnormalities are common problems in the whole world, which can lead to bilateral vestibular dysfunction (BVD). That results in symptoms, such as vertigo, unsteadiness, falling, oscillopsia, and lower quality of life. The Objective of this study was to determine BVD in adults and elderlies with vertigo and unsteadiness.   Materials and Methods: This study was conducted on 384 patients in two categories of adults (age range of 18-64 years) and elderlies (65 years old and above) through Electronystagmography (ENG), including caloric test and video head impulse test (vHIT). Patients called bilateral vestibular dysfunction when they have an abnormal bilateral weakness (summation of nystagmus response less than 20 for 4 stimulations and less than 12 for each ear) in caloric test and their vHIT has a gain lower than 0.6. The results of caloric tests were categorized into four groups, including normal, unilateral weakness, bilateral weakness, and central abnormalities.   Results: The obtained results revealed that the frequency of BVD is higher than previously reported data in the medical literature. The frequency of BVD was 10.9% for the investigated patients (39.1% abnormal caloric, 12.5% abnormal vHIT, and 10.9% abnormal in both tests). The 38.5% of elderly patients had bilateral abnormal results in both tests.   Conclusion: The results of this study showed BVD in some cases by caloric and vHIT tests.Elderlies showed more cases of BVD compared to adult patients.

Aminoglycoside, Bilateral vestibular dysfunction, Caloric test, Ototoxicity, Video head impulse test