Diagnosing Stroke in Acute Dizziness

Pauline Anderson

November 17, 2015

In patients presenting with acute dizziness and nystagmus or imbalance, a combination of readily available clinical information can help risk-stratify acute stroke, a new study suggests.

Patients with dizziness from stroke are challenging because they often lack typical stroke warning signs or symptoms, the researchers say.

"In acute dizziness presentations, the combination of ABCD2 [age, blood pressure, clinical features, duration, and diabetes] score, general neurologic examination, and a specialized OM [ocular motor] examination has the capacity to risk-stratify acute stroke on MRI," Kevin A. Kerber, MD, University of Michigan Health System, Ann Arbor, and colleagues conclude in their report.

The findings were published online October 28 in Neurology.

The prospective, single-center, observational study included patients presenting with acute dizziness without an obvious cause, as well as nystagmus or imbalance.

The study was unique in that researchers used active and passive surveillance methods to prospectively capture acute dizziness cases.

In addition to physical examinations, participants underwent MRI and received a general neurologic examination that included assessment of visual fields, cranial nerves, strength, sensation, coordination, and balance.

Investigators also collected bedside information, including history of stroke, the ABCD2 score, and HINTS (assessment of head impulse, nystagmus pattern, test of skew), which is based on a specialty bedside OM examination.

"These methods enable a more generalizable estimate of stroke prevalence" than any prior study of patients with acute dizziness and nystagmus or imbalance, the authors noted.

Researchers defined stroke as acute infarction or intracerebral hemorrhage (ICH) on a clinical or research MRI performed within 14 days of dizziness onset.

They determined low (<5%), intermediate (5% to <10%), and high (≥10%) predicted probability risk categories.

The study excluded patients with benign paroxysmal positional vertigo, medical causes, or moderate to severe neurologic deficits.

Of the 320 patients enrolled in the study, 272 (85%) underwent MRI within 14 days of symptom onset. In this population, investigators identified acute stroke in 29 of 272 patients (10.7%), including 26 infarctions and three ICHs.

The false-negative frequency (ie, frequency of stroke in the lowest-risk categories) was 5.1% for ABCD2 less than 4; 5.9% for OM assessment (4.9% for HINTS peripheral findings), 7.8% for other central nervous system features, and 10.8% for prior stroke.

In comparing stroke and nonstroke patients, the study showed several associations. In a model that included all HINTS components, for the ABCD2 score (continuous), the odds ratio (OR) was 1.74 (95% confidence interval [CI], 1.20 - 2.51), and for any other central nervous system feature, the OR was 2.54 (95% CI, 1.06 - 6.08).

For the OM assessment, the OR was 2.82 (95% CI, 0.96 - 8.30), and for prior stroke the OR was 0.48 (95% CI, 0.05 - 4.57).

There were no stroke cases in the low-risk probability category vs nine in the moderate-risk category (9.6%) and 20 in the high-risk category (21.7%).

"Our findings indicate that the ABCD2 score and the specialized OM evaluation both meaningfully influence the probability of stroke at the individual patient level in this acute dizziness cohort, even adjusting for all model predictors," the authors write.

No single examination can identify a sufficiently low-risk group to rule out stroke in acute vestibular syndrome (AVS), they said. They suggest using a mathematical modelling approach that combines all factors to identify a very low-risk population without stroke.

The new results don't support conclusions of prior studies that the ABCD2 or OM assessment alone can identify a sufficiently low-risk group because it found that the stroke frequency in the low-risk group of each of the variables was 0.5% (more than 1 in 20).

The difference between the current findings and those of the prior ABCD2-based research likely relates to the study populations, said the authors. The earlier study included all dizziness symptom presentations, even patients with dizziness from obvious medical causes, transient or chronic symptoms, and a normal examination. The new study required new-onset and constant symptoms in addition to examination.

Future work should be performed to define acceptable risk tolerance (ie, frequency of false-negative results) for stroke diagnosis, say the authors. "This information is necessary for designating decision cutpoints that are based on the probability of stroke."

Acceptance of higher risk (for example, 5%) is likely to enable a decision tool with fewer components than if lower risk is required (eg, 1%).

"The Eyes Have It"

In an accompanying commentary, David Newman-Toker, MD, PhD, Department of Neurology, Otolaryngology and Emergency Medicine, The Johns Hopkins University School of Medicine, Baltimore, Maryland, pointed out some analytic disadvantages to eye movement examinations in the study. These included low-quality eye movement examinations with mixed-skill raters and only fair inter-rater agreement.

"There were no quantitative recordings used to validate clinical examinations," Dr Newman-Toker writes.

Another example was using eye movements in the wrong patients, he said. "HINTS should only be applied in AVS with nystagmus. The authors include AVS without nystagmus and count cases due to stroke against the eye movement approach."

Despite this, the authors found HINTS to be the strongest predictor of stroke in their model, he noted.

"In fact, they found that HINTS identified 20 of 22 (90%) of causal (nonincidental) strokes when applied to the correct patients, despite inconsistent eye examinations from nonexpert raters. Obviously these findings suggest 'the eyes still have it.'"

This project was supported by a grant from the Agency for Healthcare Research and Quality. Dr Kerber has received research support from the National Institutes of Health (NIH)/National Center for Research Resources and NIH/ational Institute on Deafness and Other Communication Disorders, received speaker or author honoraria from the American Academy of Neurology, was an expert witness for National Medical Consultants, and received publishing royalties from Oxford University Press. Disclosures for coauthors appear in the paper. Dr Newman-Toker has received NIH research grants and has been loaned research equipment (GM Otometrics, Interacoustics) related to diagnosis of dizziness using eye movement analysis.

Neurology. Published online October 28, 2015. Abstract Editorial

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