Non-fluctuating Unilateral Vestibular Loss

Ablative insults to the vestibular sensory organ and/or the vestibular nerves result in a physiologic deficit of peripheral vestibular input to the brain. Unilateral physiologic change within the dynamic vestibular system results in the development of clinically apparent symptoms such as vertigo, motion-exacerbating dizziness, and visual disturbance. Insults that present either as an isolated event or as a progressive process ending in destruction of remaining ipsilateral vestibular function can be grouped into a category of physiological disorders referred to as a non-fluctuating unilateral vestibular loss. The loss of peripheral input leads to the activation of central vestibular compensatory mechanisms. Patients often present with vestibular symptoms during acute insults, but the intensity of the symptoms lessens during the compensation process. When central compensation is complete, patients with non-fluctuating unilateral vestibular loss are often asymptomatic. Impaired or delayed compensation will result in a chronic vestibulopathy with concomitant symptoms. Crucial aspects of the management of patients with these disorders include assessing the etiology of the vestibular loss, identifying impediments to compensatory mechanisms, and maximizing the central compensation process. This chapter assesses a variety of conditions, ranging from infectious to iatrogenic, that cause a non-fluctuating unilateral vestibular loss with attention given to the underlying pathophysiology, clinical assessment, and treatment options for common conditions within this category.