Dizzy Dean, the great baseball pitcher of the 1930s-1940s, once quipped, "The doctors x-rayed my head and found nothing."

That is as good an analogy as any in describing what often happens to patients with the symptom of dizziness. They see a doctor, get an MRI scan (the x-ray of the 21st century) and nothing is found.

To extend the baseball theme, patients sometimes complete a triple-play-going from family doctor to ear specialist to neurologist. And when all is said and done, none of the doctors is willing to own the symptom. Each says it's the other doctors' problem!

So where does that leave the patient? Probably out of a lot of bucks and getting more frustrated by the minute!

But, upon close analysis of the symptom, a case of dizziness can give up its secrets. It turns out that the word "dizziness" gets used to describe a variety of experiences, and those different experiences can themselves result from a number of underlying causes.

So the way one gets to first base is to sort through the patterns and narrow down the list of possibilities. In analyzing the symptom of dizziness, sometimes a multiple-choice approach works best. Most people can select one of the following three descriptions as most resembling their symptom:

#1. A sense of motion, perhaps spinning, rotating or even just drifting in space. It doesn't matter if the person feels they are spinning or that the room around them is spinning: both mis-perceptions have the same significance. These perceptions are known as "vertigo."

#2. A feeling of unsteadiness or imbalance in the body more than in the head.

#3. A feeling of light-headedness, wooziness, giddiness, or even verging on losing consciousness.

That the term "dizzy" can sometimes have still other connotations is illustrated by Mr. Dean's own nickname. He probably didn't get it because of attacks of imbalance. In fact, the pitcher supplied his own explanation with another of his famous quips: "The good Lord was good to me. He gave me a strong body, a good right arm, and a weak mind."

Let's focus on the more usual three patterns.

Distinguishing among these patterns helps separate the cases involving the head's balance (vestibular) system from those that don't. In short, pattern #1 (vertigo) is most likely to involve a disturbance in the balance system, while pattern #3 (light-headedness) is least likely. Instead, light-headedness or wooziness can be due to a momentary drop in blood pressure (for example, when standing up too quickly) or due to the same factors that produce outright fainting. Pattern #2 (bodily imbalance) is somewhere in-between-sometimes caused by a disturbed balance system and sometimes due to something else.

The vestibular system consists of the left and right inner ears, certain pathways within the brainstem (junction between the upper brain and the spinal cord) and the nerves that connect the inner ears to the brainstem. A problem in any of these components can lead to the symptom of vertigo. But the kinds of problems that can disturb the brainstem-like stroke, tumor or multiple sclerosis-are quite different and usually more serious than most the conditions that disturb the inner ears or their associated nerves.

So once the pattern of vertigo (mis-perception of movement) has been distinguished from the other kinds of dizziness, there is still more figuring to do-is the problem in the brain (central pattern) or in the inner ears and their connecting nerves (peripheral pattern)?

Luckily, central and peripheral vertigos can usually be distinguished from each other based on the clinical history and physical exam. The key is in looking for any symptom or physical abnormality that can't be blamed on the vestibular system.

How about nausea, vomiting, unsteadiness, walking into walls, blurred vision or even jumping vision? A malfunctioning vestibular system could easily account for them all. But double vision, slurred speech, weakness or numbness on one side of the body? No way. These symptoms would have to be generated outside of the balance system, and imply that other pathways in the brainstem are damaged.

Where does the MRI scan fit in? The MRI is good at seeing areas of abnormal growth or damage within the brainstem, as from tumors, strokes or multiple sclerosis. It can also see tumors that arise from the nerves connecting the brainstem to the inner ears. But that's about all it can see that is at all related to the symptom of vertigo.

However, there are far more cases of peripheral vestibular disease than of central (brain-based) disease causing vertigo, so that's why most MRI scans turn out negative. In short, the MRI is normal, but the patient isn't.

So what can cause peripheral vestibular disease? The causes are varied, but are more usually annoying than life-threatening. The most explosive form of peripheral vestibular disease is vestibular neuronitis or "inner ear attack." The typical story for this condition is that the person awakes with violent spinning, nausea and inability to walk a straight line. This condition is at its worst on the first day, gradually improving over subsequent days and weeks.

Another peripheral vestibular condition is Meniere's disease in which recurrent bouts of vertigo occur in conjunction with deafness and "roaring" tinnitus, or ringing in the ear. This is due to high fluid pressure within the inner ear which is also wired for hearing.

Yet another peripheral vestibular disease involves a stone (otolith) rattling around within the canals of an inner ear. This variety can sometimes be fixed by "vestibular repositioning" in which the patient's head is put through a series of abrupt position-changes designed to make the otolith stick in one place.

Medications can also be useful in diminishing the symptom of vertigo. The most widely used drug is meclizine (brand name Antivert) which is related to the antihistamines and helps simmer down an overactive inner ear. A second drug used in the same way is scopolamine, usually delivered via a patch on the skin (Transderm Scop). Finally, diazepam (Valium) can also be used a "vestibular suppressant" though is usually the last choice owing to its possibility of becoming habit-forming.

And how about those other forms of dizziness that involve lightheadedness, wooziness or giddiness? As a baseball player might say, "That's a whole other ball game."

© 2006by Gary Cordingley

Gary Cordingley, MD, PhD, is a clinical neurologist, teacher and researcher. For more health-related articles, see his website at: http://www.cordingleyneurology.com