The Cause

Vertigo is most commonly caused by benign paroxysmal positional vertigo (BPPV), Meniere’s disease, labyrinthitis, and migraines.

BPPV is a disorder of the inner ear. The inner ear is made up of two main functional parts: the cochlea, which is dedicated to hearing; and the labyrinth, which helps regulate balance. Within the labyrinth, there are three canals:

• The lateral, or horizontal, semicircular canal detects motion in the horizontal plane (like shaking your head “no”).
• The anterior, or superior, semicircular canal detects motion forward and backward (like nodding your head “yes”).
• The posterior semicircular canal detects motion at an angle (like touching your ear to your shoulder).

These canals are filled with a viscous fluid (called endolymph), which lags behind as the head turns due to inertia. As the head turns, the fluid stays in place and bends hair cells lining the canals, which in turn cause the vestibular nerve to activate and tell your brain that your head is moving.

In BPPV, crystals from another part of the labyrinth (called “otoliths”) fall out of place into one of these canals (most commonly the posterior), and disrupt the normal flow of endolymph, causing exaggerated responses in the hair cells to only minor movements. The resulting symptoms are severe, often accompanied by nausea and vomiting, but generally very short acting (generally 5-30 seconds, although up to a couple of minutes).

The incidence of BPPV increases with age, and is most common between 50 and 70 years of age. There are several potential risk factors, including head trauma and whiplash, prior inner ear disorders (including those discussed below), and certain post-viral processes. BPPV is the most common cause of vertigo, accounting for about 20 percent to 30 percent of diagnoses in clinics that specialize in the management of dizziness, and occurs in roughly 2 percent to 3 percent of people over their lifetime. The attacks usually occur for up to two weeks, and approximately 50 percent of people will have more than one attack in their lifetime.

Labyrinthitis is an inflammatory or infectious issue arising in the same structures affected in BPPV, leading to a combination of vertigo and often unilateral ringing in the ears or hearing loss. Generally, it is preceded by a cold or flu by one to four weeks, although occasionally no inciting illness can be found in the patient’s history. It can come on suddenly and last for significant amounts of time (usually one to six weeks total), although generally waxes and wanes over its course. There is frequently significant nausea and vomiting early in the course.

The exact mechanism behind the symptoms are unclear, but generally the condition is due to inflammation in the inner ear. In approximately 5 percent of cases, the symptoms do not resolve completely. While there are no specific risk factors, there are associations with high alcohol consumption, smoking, stress, and use of certain medications (especially aspirin and antibiotics).

Ménière’s disease is another disorder of the inner ear that affects balance and hearing. It usually presents as attacks of vertigo associated with ringing in one ear or the other, and/or diminished hearing on the same side. The symptoms usually jump back and forth between the two ears, and over time lead to significant or total hearing loss. It is thought to be caused by a buildup of endolymph from overproduction or blocked drainage.

Excessive salt consumption can exacerbate symptoms or cause a flare. There are reports linking Ménière’s to smoking, caffeine use, alcohol, chocolate, and cheese, but the evidence is very loose. It is difficult to estimate a true prevalence of the disease as it is difficult to diagnose; it is generally rarer than the other causes of vertigo, with some reports suggesting about 43 cases per 100,000 people.

Migraines are probably the most common cause of vertigo, although in most migraines the sensation is less severe. However, vestibular migraine, a less common migraine variant, is generally associated with significant vertigo, nausea, slurred speech and difficulty swallowing. Approximately 18 percent of women and 6 percent of men suffer from migraines, with 50 percent of those having some degree of vertigo. Overall, about 1 percent of the population suffers from vestibular migraines specifically.

Less commonly, vertigo can be caused by strokes to the brainstem, or from masses causing swelling. In most cases, the symptoms of vertigo are clearly due to a benign cause, and further workup is not necessary. However, when vertigo is accompanied by other neurologic deficits (like significant incoordination, trouble speaking or swallowing, numbness of the face or body, etc.), these more serious causes need to be ruled out with imaging.

Lateral Medullary Syndrome (Source: Wikimedia Commons)

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