Eye test betters MRI in stroke

US researchers have demonstrated in a proof of principle that a short and simple assessment of eye movements in suspected stroke patients can distinguish new strokes from other less serious disorders better than magnetic resonance imaging. The technique demonstrated only in a small-scale study could help screen patients complaining of dizziness, nausea, and spinning sensations.

In a small "proof of principle" study, a team of stroke researchers led by David Newman-Toker, assistant professor of neurology at the Johns Hopkins University School of Medicine and the University of Illinois in Peoria described success using a one-minute eye movement test to examine more than one hundred high-risk patients. The patients, seen at OSF St. Francis Medical Center, were considered to be at higher than normal risk because of pre-existing factors, such as high blood pressure or high cholesterol.

Newman-Toker explains that dizziness is a common medical condition but most outpatients are sent home with a diagnosis of an inner-ear or balance problem. One in twenty, however, turns out too have suffered a stroke or transient ischaemic attack, without presenting other classic stroke symptoms, such as one-sided weakness, numbness, or speech problems. Research suggests that emergency room physicians misdiagnose at least a third of these dizziness cases, which leads to potentially debilitating or fatal outcomes for many patients.

"We know that time is brain, so when patients having a stroke are sent home erroneously, the consequences can be really serious, including death or permanent disability," says neurologist Jorge Kattah, of OSF St. Francis Medical Center, who co-led the study.

Newman-Toker and his colleagues at the University of Illinois College of Medicine in Peoria wondered whether testing eye movements in patients suffering from dizziness might help them discern which patients were in the throes of a stroke and which had other less urgent problems, such as an inner ear infection or some other condition that affects balance.

Previous studies had suggested that during a stroke in the balance part of the brain that eye movements can be seriously affected. Such eye movement changes are distinct from the kinds of eye movements someone with a benign inner ear balance problem (known as vestibular neuritis or labyrinthitis) might reveal, although the tests of three eye movements may look similar to the untrained observer. Unlike most patients with vestibular neuritis, most stroke patients can quickly adjust their eye position if an examiner turns their head quickly to the side. Unlike most patients with vestibular neuritis, stroke victims? eyes may move jerkily in one direction as they try to focus on the doctor's finger when looking to one side, then jerk in the other direction when the patient tries to focus on a finger looking to the other side. Some stroke victims also have vertical misalignment of their eyes, not generally seen with inner ear problems.

Patients recruited into the Peoria trial were seen after complaining of severe dizziness that had lasted for several hours continuously, although none had a history of dizziness prior to admission to the hospital. They did, however, all have at least one medical risk factor for stroke, which made the task of find actual stroke cases in this cohort easier.

The team gave each patient an eye-movement examination that looked for the inability to keep the eyes stable as a patient's head was rotated rapidly side to side, jerkiness as a patient tracked the doctor's finger left and right, and checking eye position to see if one eye was higher than the other. They then performed an early MRI scan on each patient to confirm stroke or another diagnosis in the dizzy patients. Those patients whose eye test results suggested they had had a stroke but the first MRI scan failed to pick this up were given a repeat scan.

Of the 101 patients, 69 were diagnosed with stroke and 25 with inner-ear conditions. The remainder had other neurologicalem problems, the researchers report. Crucially, the three eye-movement tests alone allowed the team to correctly diagnose all of the stroke patients and 24 of the 25 with inner-ear problems. In contrast, the first MRI scan gave false negatives in 8 of the 69 stroke patients, who were later correctly diagnosed with stroke in the follow-up scan.

The researchers emphasize that their preliminary results must now be verified against a much bigger patient cohort selected from the general emergency room population with dizziness. Nevertheless, Newman-Toker says, these initial findings are "incredibly promising." If they ring true, he suggests, then a simple eye movement test could offer a basically free diagnostic and displace preliminary MRI scans for the majority of such patients. This has the important advantage of potentially reducing the time taken to diagnose a stroke diagnosis from several hours to possibly minutes.

"In an era where cost containment is butting up against issues of quality in health care delivery, there's tremendous potential for bedside approaches like ours that could reduce costs while improving quality at the same time," says Newman-Toker.
"We are working now on designing a large clinical trial to study whether either teaching frontline physicians to perform these assessments or providing them a device to measure these movements would be more cost effective than current practice or early MRI scans in all patients," Newman-Toker told SpectroscopyNOW. "The key here is that in the current study we've outlined a way we can use scarce MRI resources for those who need it, as determined by this bedside exam." He suggests that with strong evidence all physicians will adopt this approach. "As for the fate of MRI," he adds, "I'm sure the technology will improve as time goes along, but, for now and the immediate foreseeable future, eye movement assessment in these patients is likely to be more accurate in the early stages after a stroke."

The views represented in this article are solely those of the author and do not necessarily represent those of John Wiley and Sons, Ltd.