Low-Tech Eye Test Delivers Accurate Stroke Diagnosis
It presents a diagnostic challenge for doctors when patients arrive at the ER complaining of dizziness and other symptoms, all of which began suddenly. Often this ends up diagnosed as “acute vestibular syndrome” (AVS), characterized by the rapid onset of vertigo, nausea and/or vomiting, unsteady gait and intolerance of head motion. The most frequent cause is a benign inner-ear condition called vestibular neuritis — but, the big “however” is that dizziness is also the most common symptom of ischemic stroke, caused by a blood clot affecting the brain stem or cerebellum.
Stroke, of course, is a medical emergency, so it’s a diagnosis that no doctor wants to miss. It is excellent news, therefore, that researchers have found that a new low-tech test that can be easily performed by a doctor at a patient’s bedside is quite an accurate diagnostic tool — and also happens to be faster and far less expensive than MRI.
The Eyes Tell All
Johns Hopkins and University of Illinois researchers studied 101 patients who complained of dizziness and found that a three-part eye test, which takes less than one minute to administer, outperformed the costlier imaging tests that are typically used to diagnose stroke. All patients in the study had AVS symptoms that had lasted at least several hours and were considered to be at heightened risk for stroke, due to such factors as high blood pressure or high cholesterol.
It turned out that 69 of these patients had indeed had a stroke… 25 had the inner-ear condition… and the rest had other neurologic problems. The eye tests correctly identified all 69 stroke cases — compared with the 61 correctly identified by the initial MRI. (The diagnosis was confirmed by a later repeat MRI scan, obtained because the eye tests had suggested a stroke.)
The three tests, collectively called H.I.N.T.S., are…
Head-impulse. The examiner rapidly rotates the patient’s head, instructing him/her to look at the examiner’s nose. Stroke patients usually can do this, while AVS patients cannot.
Nystagmus. This test assesses jerking movements in the eye. Instructed to follow movement of a finger, those whose eyes jerk in only one direction have AVS, while the eyes of many stroke patients jerk both to the right and the left.
Test-of-skew. Examiners check eye position to see if one eye appears higher than the other. Vertical misalignment is a sign of stroke.
Time Is Brain
“Speed is of the essence when diagnosing and treating stroke,” says David E. Newman-Toker, MD, PhD, assistant professor of neurology at Johns Hopkins University School of Medicine and coauthor of the study. “These three eye tests tell, with a high degree of certainty, whether or not the patient has had a stroke.” In a patient with AVS symptoms, the authors found that having at least one of the three findings pointed to stroke with 96% certainty.
Stroke diagnosis can be tricky — imaging technologies differ in their reliability for detecting various types of strokes, depending on the location within the brain. However, ischemic (blockage) strokes in certain parts of the brain can be virtually undetectable by CT scan during the first 24 hours, and false negatives occurred in 12% of the initial MRIs in this study. Studies suggest there is at least a 35% chance of misdiagnosing stroke when the main complaint is dizziness. The H.I.N.T.S. eye tests, if applied correctly by physicians, might reduce that risk to near zero.
Dr. Newman-Toker advises seeking attention for any dizziness that comes on unexpectedly and has no obvious explanation, particularly if it lasts more than a few seconds. In situations where you still feel dizzy when you arrive at the ER, request the eye tests, he says, but be aware that not every doctor has the training and experience to perform them. If your doctor doesn’t know how to perform these tests, request that he/she consider an MRI to look for stroke. Fast — because speed is of the essence when treating stroke.