A 57-year-old banker complains of 2 days of severe dizziness. When she sits up or rolls over in bed, she has a spinning sensation that lasts for a few seconds and is followed by nausea. These episodes have occurred many times a day and prevent her from working. She denies fever or upper respiratory symptoms and takes no medications. When moved quickly from a sitting to a lying position with her head turned and hanging below the horizontal plane, she complains of dizziness, and horizontal nystagmus is noted. The most likely diagnosis is
High-Yield Explanation
Dizziness is a nonspecific symptom that may refer to several different sensations, including impending faint, spinning sensation, or impaired balance. A sensation of spinning or rotation is referred to as vertigo and may be due to central or peripheral causes. Peripheral causes of vertigo are usually associated with nystagmus and more troublesome to the patient but are not due to life-threatening disease. The commonest cause of peripheral vertigo is benign paroxysmal positional vertigo (BPPV), which characteristically begins in middle-age persons, occurs with sudden changes of position, and is thought to be due to cellular debris in the semicircular canals. The diagnosis is supported by the Dix-Hallpike maneuver, where the patient is moved quickly from a sitting to a lying position with head turned and hanging below the horizontal plane. The occurrence of dizziness and horizontal nystagmus after a few second latency period constitutes a positive test. This patient's symptoms are not brought on by standing; so orthostatic hypotension is unlikely. Meniere disease is a chronic disease of both the labyrinth and the cochlea; so progressive unilateral hearing loss and tinnitus are usually present. Acoustic neuroma is also a chronic (rather than episodic) condition associated with hearing loss, unsteadiness of gait, and loss of corneal reflex on the affected side. Central causes of vertigo (vertebrobasilar stroke, cerebellar hemorrhage) cause constant (rather than intermittent) symptoms and are associated with ataxia and focal CNS signs. The Dix-Hallpike test in brainstem disorders causes immediate vertigo (i.e., no latent period) and often vertical or rotatory nystagmus.