What is a "mini-stroke?" Doubtlessly, you've heard someone use this term before, and you might have even seen it in print. What does this term mean to you? Probably something less than a full-fledged stroke, which is a permanent brain injury due to a blocked blood vessel or a hemorrhage that produces obvious clinical impairment. But, apart from that, what exactly does it mean?

One might suppose mini-stroke to be a term with a definite meaning that everyone agrees upon. However, this is far from the case. Just as beauty is in the eye of the beholder, so too, the meaning of mini-stroke depends on what is in the mind of its user. Lewis Carroll's Humpty Dumpty said it best: "When I use a word," Humpty Dumpty said, in rather a scornful tone, "it means just what I choose it to mean -- neither more nor less." Clearly, Humpty could have been talking about mini-strokes.

As a community-based neurologist, I have encountered several uses of this term. One is as a substitute for "transient ischemic attack" or TIA. In this case, the term TIA already has a specific meaning. It is an episode of obvious clinical impairment lasting fewer than 24 hours resulting from a temporary interruption of blood-flow to a portion of the brain. Employed in this fashion, mini-stroke is a user-friendly version of a longer, precisely defined term. If this were the only usage of mini-stroke, there would be no problem.

But, of course, mini-stroke can mean much, much more. The most unsettling use is as a pat explanation for any small, otherwise unexplained event. This "diagnosis" emerges from patients themselves, family members and even primary care physicians. A typical example is that a patient had an episode of confusion or unconsciousness followed by full recovery. Explanation: "That was a mini-stroke." Yet the more usual causes of such episodes have nothing whatsoever to do with strokes or TIAs.

Unfortunately, labeling these events as mini-strokes means that the more likely causes are shut off from consideration, and the unlucky patients don't receive appropriate evaluation and treatment for their actual ailments. Moreover, by labeling such episodes as mini-strokes, improper treatments can ensue, for example, a surgical clean-out of a carotid artery, which in this context could cause more harm than good.

Magnetic resonance imaging (MRI) scans have led to another confusing use of the term mini-stroke. MRIs are marvelous tools that sensitively reveal a wide variety of diseases afflicting the brain. It's best at showing "lesions," i.e. discrete, anatomic disturbances affecting limited portions of the brain. Sometimes, MRIs show apparent lesions that are not disturbances at all. Unknown bright objects (UBOs) are small areas of apparent abnormality often scattered deep within the brains of older individuals. Sometimes they do indeed represent damage from plugged blood vessels that may or may not have produced symptoms. But in other cases they represent other diseases entirely or even no disease at all. For example, normal spaces next to blood vessels can appear as UBOs.

To make a long story short, any and all of these apparent disturbances can get labeled as mini-strokes, e.g., "The scan showed that your brain is full of mini-strokes." Thus, a mini-stroke can additionally refer to something seen on a scan which in many cases had nothing to do with circulation or actual symptoms.

When a term like mini-stroke gets used for so many things, it becomes meaningless and confusing. When a meaningless and confusing term is applied to real patients with real problems, the result is bad medicine.

(C) 2006 by Gary Cordingley