Understanding vertigo.
Vertigo. To some the word conjures up images of the 1958 Alfred Hitchcock film of the same name in which Jimmy Stewart suffers from height vertigo. To others however vertigo has a more immediate meaning. It is the distressing and recurrent symptom of the room spinning or at least being unsteady.
Vertigo (the word comes from the Latin verb “vertere” to turn) may be defined as “an illusion of movement.” It may be a sensation of the surroundings spinning or moving, but it may be only a sense of disorientation or loss of equilibrium. It is often associated with nausea or even vomiting and sometimes hearing loss. Vertigo is a symptom, not a disorder in itself and it has many causes. It is frequently (but not always) caused by an inner ear disorder. It needs to be distinguished from dizziness or light-headedness in which there is no sensation of the surroundings moving and this would not suggest an inner ear disorder.
Why does it occur? How does the balance mechanism ( “vestibular system” ) of our inner ears work? The inner ear consists of three tiny fluid-filled semi-circular canals, all at right angles to one another. These canals are connected to other sacs and to the cochlea - the hearing mechanism. When our head turns the fluid in the semi-circular canals that are in the plane of the movement of the head lags behind the head movement momentarily, stimulating nerve endings, resulting in impulses (electrical potentials) being rapidly transmitted along the vestibular nerve to relay stations in the brain stem called vestibular nuclei. These nuclei receive about 1.5 million impulses or “action potentials” per second from the inner ears alone and they also receive input from neural connections with other parts of the brain, from the eyes and from touch and position sensors in the neck, spine and limbs. The processed output goes to the conscious brain, giving us a sense of our position in space and to the muscles that move the eyes, helping to stabilize vision despite our head movements, and to our neck, spine and limbs to assist in the control of posture and movement. It is like a computer, with input, processing of the data and output. Like a computer, if there is a conflict in the input, then there will be a problem with the output.
Click here to see a diagram of the ear (courtesy of the American Medical Association)
Information received by the brain from one ear is normally consistent with that received from the other and with that received from the eyes and other senses. When the information from the two sides, or the other senses, does not match up due to a disease or disorder then there is conflict or a “mismatch” and vertigo may result (until the condition resolves or the brain adapts to the new situation). Vertigo may also occur in healthy people from unusual (unadapted) stimulation such as motion sickness or a ride at the fairground. In motion sickness nausea and vomiting are the predominant symptoms. However a sense of imbalance (a form of vertigo) can persist on disembarking from a ship and returning to dry land which can occasionally persist for weeks or even longer (a condition called "mal d' debarquement").
The commonest cause of vertigo that we see in the clinic is benign paroxysmal positional vertigo, BPPV for short, (covered in more detail on another page) in which change in position, especially turning over in bed or looking up, precipitates episodes. It is caused by tiny crystals breaking loose from gravity sensing areas (in a sac adjoining the semi-circular canals) called otoliths. These crystals can fall into one of the fluid-filled canals and movement of the head into certain positions will cause them to drift in the canal, following gravity, with a plunger-like effect, stimulating the nerve endings resuting in vertigo. Some patients have these symptoms for years without a correct diagnosis being made. The diagnosis can be made by a positioning test (the Dix-Hallpike test). Treatment by the Epley (after an Oregon physician) and other re-positioning maneuvers is frequently successful.
Of course there are many other causes of vertigo, and some will be covered in other parts of this web-site.
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