48 CASE 48
The sensation has become progressively worse since it was first noted about 5 months ago. He has stopped social drinking but with no sign of improvement. He also indicates his left ear is problematic, with mild ear pain, a gradual decrease in hearing, and often a constant ringing (tinnitus).
PATHOPHYSIOLOGY OF KEY SYMPTOMS
The patient’s symptoms are generally tied to the function of the vestibulocochlear nerve (cranial nerve VIII), which carries the afferent signals from the cochlea (hearing) and vestibular system (balance). Vestibular system disorders manifest as vertigo, often accompanied by nystagmus. This simultaneous occurrence of both of these deficits indicates a problem tied to the eighth cranial nerve.
The vestibular system is a complex sensory organ that determines both acceleration and position relative to gravity. There are three semicircular canals oriented at right angles to each other so that movement in all three planes in space can be detected. The hair cells of the crista ampullaris detect movement of the fluid within the semicircular canal and transmit this information along the sensory nerves of the vestibular system. The macula of the utricle and saccule contains small calcium carbonate stones that activate hair cells and thus detect the orientation of the head with respect to gravity as well as linear acceleration (Fig. 48-1).
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