Eye-Motion Analysis Aids Diagnosis of Posterior Stroke

March 07, 2013

A new device that analyzes head and eye movements could revolutionize the diagnosis of vertebrobasilar strokes, a new study suggests.

Lead author David E. Newman-Toker, MD, PhD, from Johns Hopkins University School of Medicine, Baltimore, Maryland, explained to Medscape Medical News that unlike classic stroke in the anterior part of the brain, vertebrobasilar strokes in the posterior part of the brain (the brainstem or cerebellum) present with dizziness as the main symptom. As a result, they are commonly misdiagnosed as inner-ear issues, such as vertigo or other vestibular conditions, leading to many patients being wrongly sent home only to experience larger strokes or adverse outcomes.

This new device, which resembles a pair of swimming goggles with added technology, appears able to accurately distinguish patients who are having a stroke from those who have the relatively benign inner-ear issues.

A "proof-of-concept" study looking at the utility of the device was published online March 5 in Stroke.

"ECG for the Eyes"

In this study, 12 patients presenting to the emergency department with acute vestibular syndrome, defined as new, persistent vertigo/dizziness, nystagmus, nausea/vomiting, head motion intolerance, or new gait unsteadiness, underwent testing with the new device. The device recorded eye movements, including quantitative horizontal head impulse testing of vestibulo-ocular-reflex function.

Dr. David Newman-Toker uses the device, which analyzes head and eye movements to diagnose verterbrobasilar stroke

All patients also underwent confirmatory MRI for stroke diagnosis. Results showed that the new device was 100% accurate in correctly diagnosing strokes (6 patients) and peripheral vestibular conditions (6 patients).

Dr. Newman-Toker noted that his group has previously described a way of diagnosing stroke in this patient group by personally analyzing different eye movements.

"But this is a very difficult thing to do," he said. "It takes years of experience and at present only highly trained neuro-ophthalmologists or neuro-otologists can do it. But these highly trained specialists are not available in most ERs [emergency rooms], and it is unrealistic to expect the regular ER doctors to be able to analyze highly complex eye movements. But now we have a device that can do it automatically."

"The sensitivity accuracy is very high — about 99% — and specificity is also very high at around 97%," he added. "This way outperforms even MRI scans, which have a sensitivity of about 80%."

Use of the device, known as ICS Impulse (GN Otometrics), involves the patient wearing a pair of goggles that are fitted with an infrared camera. The camera records 10- to 15-minute video of the eye and head movements; these are then interpreted by a computer program. Dr. Newman-Toker likens it to electrocardiography (ECG) for the eyes. "In the same way as the ECG tells us that a patient is having a heart attack, this device will tell us that a patient is having a stroke."

Dr. Newman-Toker explained that around 75% of strokes occur in the anterior part of the brain and have the classic stroke presentation of weakness on one side of the body and speech disturbances, making them relatively straightforward to diagnose. The other 25% of strokes occur in the posterior part of the brain and present as dizziness and balance problems.

"There may not be any weakness on one side of the body, and these strokes are very often misdiagnosed as inner-ear problems." He estimates that about one third of these types of strokes are missed at present; if there is no weakness on one side of the body and people just present with dizziness, then about half are missed.

Of about 200,000 strokes that occur in the brain stem or cerebellum each year in the United States, he estimates that 20,000 to 30,000 people suffer permanent harm "because we are not intervening promptly."

He adds that there are about 4 million visits to the emergency department each year for dizziness, but only about 5% of these patients are actually having a stroke. "Of these 4 million cases of dizziness, about 40% may get a CT [computed tomography] scan. But these cerebellum strokes don't often show up on a CT scan; only about 20% are detected that way. So we are wasting hundreds of millions of dollars on CT scans. An MRI is better, but only 1-2% of patients will get an MRI because they are prohibitively expensive."

Dr. Newman-Toker pointed out that while the classic symptoms of stroke are now quite well recognized, most people would not recognize dizziness as a stroke symptom. "We need much more education on this. When this device becomes more generally available, I think this will encourage education programs to alert the public to this of stroke."

Affordable Technology

Another positive about the device, he says, is that it will be affordable. He estimates each device will cost about $15,000 to $20,000, and each recording will cost around $30 to $70. In contrast, an MRI scanner costs around $1 million to $2 million and each scan costs about $1200 to $1600.

The device used in the current study is made by GN Otometrics. It is already approved by the US Food and Drug Administration for safety and for vestibular measurement for inner-ear problems. However, Dr. Newman-Toker noted, "While the device is out there already I'm not advocating that every ER buy one right away for the diagnosis of stroke. We are not there yet. But I expect in 5 years' time we will be."

In the meantime, he says, a larger study should look more closely at costs and quality of care associated with the device, and he is now looking for funding for such a trial. "We will look at how many stroke patients are missed with and without the device."

This study work was supported by grants from the Swiss National Science Foundation, Agency for Healthcare Research and Quality, and National Institutes of Health. GN Otometrics loaned the equipment. Dr. Newman-Toker has disclosed no relevant financial relationships or interest in the company.

Stroke. Published online before print March 5, 2013. Abstract