For transient ischemic attacks both overdiagnosis and underdiagnosis can be perilous

Nov 10 2008

Overdiagnosis neglects the real underlying illness. Underdiagnosis leaves a patient at risk of a full-fledged stroke. Both expose patients to erroneous therapies with potential side effects.

And yet, TIAs are difficult to assess because, by definition, the neurological dysfunction that results is so brief. By the time the patient arrives at a doctor's office or an emergency room, the symptoms are often gone.

Now, researchers at Rush University Medical Center have identified three bedside clinical features that can help more accurately distinguish TIAs from disorders that might mimic their symptoms.

The study has just been published online and will appear in the December issue of Cerebrovascular Diseases .

Two neurologists at Rush University Medical Center, Dr. Shyam Prabhakaran, lead author of the study and head of the stroke service, and Dr. Vivien Lee examined the records of 100 emergency room patients who had an initial diagnosis of TIA and were admitted for further evaluation. Only 40, or 40 percent, of these cases turned out to be true TIAs.

The researchers were able to identify three clinical features that, together, correctly classified 79 percent of the cases.

"Speed of onset, we found, was the strongest indicator of a TIA. I typically ask my patients if their symptoms came on like lightning, within seconds," Prabhakaran said. "With other neurological problems that can mimic a TIA – migraines or seizures, for example – symptoms take more than a minute to manifest themselves."

The researchers found that a TIA was unlikely if a patient reported nonspecific symptoms, such as lightheadedness, tightness in the chest or stomach upset, along with the neurological dysfunction.

A TIA was also unlikely if the patient had a history of similar episodes where a TIA was ruled out.

"It's important not to miss a diagnosis of TIA, as these attacks can be harbingers of stroke and patients need to be treated," Prabhakaran said. "But at the same time, we don't want to overdiagnose TIAs. Overdiagnosis subjects patients to the risks of unnecessary and potentially dangerous medications and tests, and leaves their actual condition untreated or inadequately managed."

Approximately 240,000 TIAs are diagnosed in the United States each year. TIAs carry a particularly high short-term risk of stroke, and about 15 percent of diagnosed strokes are preceded by TIAs. Symptoms vary widely from person to person, depending on the area of the brain affected. The most frequent symptoms include temporary loss of vision, difficulty speaking and weakness, numbness or tingling on one side of the body.