Extremes of stroke symptoms attract misdiagnoses

Jul 24 2015

By Eleanor McDermid, Senior medwireNews Reporter

Patients with very mild or very severe stroke symptoms are at the greatest risk of being misdiagnosed in the emergency department, research suggests.

These “stroke chameleons” were mostly missed by emergency physicians, who failed to consider a stroke diagnosis in 91.5% of the 47 patients studied. However, neurologists also did not consider stroke in 57.6% of the 33 patients about whom they were consulted.

“Based on our data, some stroke chameleons may be preventable in part by educating physicians about unusual presentations of stroke”, say Benjamin Richoz (Centre Hospitalier Universitaire Vaudois and University of Lausanne, Switzerland) and co-researchers. They also suggest lowering the threshold for consulting a neurologist.

Another problem was coexisting neurological and psychiatric conditions, which “often masked correct stroke diagnosis”, leading to misattribution of symptoms in 19.1% of patients.

The stroke chameleon patients were identified from among 2200 acute ischaemic stroke patients admitted to a single centre over 8.25 years. Richoz et al stress that, had they been correctly diagnosed, 23.4% of the stroke chameleon patients would have been eligible for thrombolysis.

Misdiagnosis had consequences for patient outcomes. Significantly fewer stroke chameleon patients achieved a favourable 12-month outcome, at 50.0% versus 61.6% of correctly diagnosed patients, and they were more likely to die, at 30.4% versus 19.4%, and to have a recurrence, at 13.3% versus 9.9%.

Most independent predictors of misdiagnosis were indicative of mild stroke in younger patients with a low-risk profile. Pre-existing use of lipid-lowering drugs and the presence of eye deviation reduced the risk by 70% to 80%, and the risk of misdiagnosis also declined with older age and higher diastolic blood pressure.

The researchers call the tendency to misdiagnose patients with a low-risk profile “understandable”, but say “it shows the importance of educating medical personnel of the possibility of stroke in young patients with acute, unexplained neurologic symptoms.”

Cerebellar stroke was 3.78-fold more likely to be misdiagnosed than other strokes, in line with previous studies.

Many stroke chameleon patients had low National Institutes of Health Stroke Scale scores, but a group had very high scores, of around 25 to 35, and unexplained decreased level of consciousness was a frequent misdiagnosis, given to 21.3% of patients. Eleven patients presented in a stupor or coma, mostly because of basilar artery occlusion.

“This presentation may mislead physicians to suspect a metabolic, toxic, or anoxic encephalopathy rather than stroke”, writes the team in Neurology.

Even brain imaging did not always prevent misdiagnosis; indeed, it contributed to the wrong diagnosis in 40.4% of the patients. In nine patients, noncontrast computed tomography (CT) findings were misinterpreted, with subtle, early ischaemic changes often overlooked, and 10 patients had no changes, leading to the exclusion of stroke as a diagnosis.

The team therefore advises “the more systematic use” of more sensitive imagining techniques such as multimodal CT and magnetic resonance imaging.

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