Chapter 5
Inner Ear Causes of Dizziness and Vertigo
Lloyd B. Minor, M.D.

John E. Bordley Professor
Department of Otolaryngology—Head and Neck Surgery
The Johns Hopkins University School of Medicine

Disorders of the inner ear can cause symptoms and signs that are indicative of vestibular dysfunction. This chapter will review these symptoms and signs that can occur when there’s a disturbance in the normal functional mechanisms of the inner ear. Specific disorders that can affect the inner ear will then be described. . .

Why is it important for the brain to receive exquisitely accurate information about head movement from the vestibular receptors? Many of the reflexes that are responsible for normal posture and balance and for maintaining steady visual fixation on objects during head movements depend upon information about the motion of the head coming from the labyrinth. While other sensory information (such as vision and the sense of touch) provides some information on motion, the signals from these other sensory systems are relatively slow and less accurate when compared to the information that comes from normal functioning vestibular receptors. Thus, symptoms and signs of vestibular dysfunction reflect abnormalities in motion perception (and in the information about motion received by the brain).

You’ll recall that earlier in this book the Vestibulo-Ocular Reflex (VOR) was discussed. This is one of the most important reflexes controlled by the vestibular system. Remember that when it functions properly, this reflex enables us to maintain steady fixation on a stationary object while our head is moving.

Visual acuity during head movements is dependent upon the precisely calibrated function of the VOR. Deficits in vestibular function lead to impairments in the way the VOR attempts to compensate. Symptoms include oscillopsia, the apparent motion of objects that are known to be stationary during head movements. Acute changes in the level of neural activity arising from the labyrinth can result in vertigo, an illusion of motion. The symptom of vertigo is often accompanied by nystagmus, a rapid to-and-fro beating of the eyes caused by unequal activity between the two labyrinths.

Let’s now explore inner ear causes of dizziness and vertigo. . .