Benign paroxysmal positional vertigo (BPPV) is a mechanical disorder of the semicircular canals of the inner ear. There are three of these ring-shaped canals in each ear, along with two other sensors that are able to sense gravity because they are capped by a bed of relatively heavy crystals. It is the shifting of these crystals on the gravity sensor that give you the sensation of going up and down in an elevator, or let you know when your head is tilted. The problem is that all of the canals and the gravity sensors are interconnected by fluid pathways, so if these gravity-sensor crystals become dislodged, they can migrate into other parts of the ear.
BPPV arises when some of these crystals enter a semicircular canal. The openings to the semicircular canals lie just above the gravity sensors when a person is upright, so particles can’t easily enter. However, when you lie down flat on your back, the openings are located just below the sensors, allowing gravity and side-to-side rolling movements of your body to accidentally shift the particles into a canal. The semicircular canals are only capable of sensing rotation or turning and do not detect gravity, so the presence of particles moved by gravity causes normal tilting motions of the head to be incorrectly sensed as violent spinning.
Symptoms usually first come on while in bed. Rolling over in bed to one side can cause a very sudden, strong sensation of head-over-heels whirling that lasts for several seconds and then dies away. If your eyes are open, the room can appear to spin violently. Attempting to sit up from lying down, to lie back down, or to roll over in bed can set off a spell. After you get out of bed, another spell can be brought on by tipping the head upward (while shampooing or reaching up toward a high shelf, for example), looking up and back over one shoulder, or by bending over forward and then lifting your head quickly. In people who are sensitive to motion sickness, there can be vomiting and prolonged, less severe dizziness even when upright. Older people may notice their balance is affected in between spells.
The dizzy spells end when the displaced crystals leave the semicircular canal, which can happen spontaneously within a couple of hours, or can be delayed for many years. Certain movements can help to roll the particles back out of the semicircular canals. These therapeutic maneuvers can be performed by a trained health care worker like a physician, nurse practitioner, audiologist or physical therapist, but they can often be done easily as a home exercise. All maneuvers cause the dizziness to recur, so some people are not able to do them without assistance. The video and book on our home page show how to treat this at home. If symptoms don’t improve, a health care provider should evaluate you.