Stroke

Jonathan Wang, MD

Dawn Lei, MD

Zahir Kanjee, MD, MPH

The ED physician calls you to admit a patient for symptom management related to a presumed diagnosis of peripheral vestibular neuritis. The patient is a 67-year-old man with a history of hypertension and hyperlipidemia who presented after 6 hours of new-onset intense vertigo, nausea, vomiting, and a feeling of postural instability. He reports a viral illness a week ago. You wonder whether this acute vestibular syndrome could in fact be caused by a posterior stroke, an important question given the potentially devastating and rapidly life-threatening nature of such a diagnosis.

What bedside testing can be performed to diagnose a posterior stroke in patients who present with the acute vestibular syndrome?

Head-Impulse-Nystagmus-Test-of-Skew (HINTS) testing can reliably assist in the identification of a posterior fossa stroke in patients presenting with acute vestibular syndrome.

In 2009, a prospective cross-sectional study addressed this question by evaluating 101 ED patients who presented with acute vestibular syndrome.¹ Subjects presented with a complaint of acute onset vertigo, nausea, vomiting, and unsteady gait. To be included, patients were required to have ≥1 stroke risk factor, such as hypertension, hyperlipidemia, atrial fibrillation, or prior stroke. Those with a history of recurrent vertigo or dizziness were
excluded. Patients were clinically examined by a neuro-ophthalmologist and underwent MRI with diffusion-weighted imaging (DWI). Neuro-ophthalmologists were blinded to any MRI results available at the time of their examination. The gold standard of stroke diagnosis was neuroimaging results (in almost every case, MRI); patients with an initially negative MRI whose serial neurologic examination or clinical course were concerning for stroke underwent repeat imaging.

Authors identified a diagnostically useful battery of maneuvers, abbreviated as HINTS, including: normal horizontal Head Impulse test
(Figure 7.1) (which indicates an intact vestibulo-ocular reflex—note: an abnormal reflex suggests a peripheral cause of vertigo); direction-changing Nystagmus with eccentric gaze; or Skew deviation (any vertical ocular misalignment, which may be best appreciated with covering/uncovering the eye).

Figure 7.1 The head impulse test (HIT, sometimes referred to as the head thrust test) is a test of vestibular function that can be easily done during bedside examination. The HIT tests the vestibulo-ocular reflex (VOR) and can help to distinguish a peripheral process (vestibular neuritis) from a central one (cerebellar stroke). With the patient sitting on the stretcher, the physician instructs him to maintain his gaze on the examiner’s nose. The physician holds the patient’s head steady in the midline axis and then rapidly turns the head to about 20° off the midline. Panel 1: The normal response (intact VOR) is for the eyes to stay locked on the examiner’s nose. Panel 2: The abnormal response (impaired VOR) is for the eyes to move with the head, and then to snap back in one corrective saccade to the examiner’s nose. The HIT is usually “positive” (i.e., a corrective saccade is visible) with a peripheral lesion (vestibular neuritis), and the test is normal (no corrective saccade) in cerebellar stroke. This occurs because the VOR pathway does not loop through the cerebellum. Occasionally, patients with small brainstem strokes may have a positive test because the VOR pathway does loop through the brainstem. Because it is the “positive” test that is reassuring with the head impulse test and the “negative” test that is worrisome, it is very important to use the test only in patients with the acute vestibular syndrome (AVS). If one were to use the HIT in patients with pneumonia or with a fractured wrist, the HIT would be “negative” (worrisome for a central nervous system event). Therefore, it is critical that it only be applied to patients presenting with an AVS. (Reprinted from Wolfson AB, Cloutier RL, Hendey GW, Ling L, Rosen CL, Schaider J. Harwood-Nuss Clinical Practice of Emergency Medicine. Philadelphia: Wolters Kluwer; 2015, with permission.)

The study found that the presence of any component of HINTS was 100% sensitive and 96% specific for a central lesion (73/76 of central lesions were posterior ischemic or hemorrhagic stroke), giving +LR (likelihood ratio) 25 (95% CI 3.66-170.59) and −LR 0.00 (95% CI 0.00-0.11). Indeed, the presence of skew deviation correctly identified an infarct in 7/8 cases where the initial MRI was falsely negative. Study authors highlight that the acronym INFARCT can be used to remember the danger signs of Impulse Normal, Fast-phase Alternating (referring to direction-changing nystagmus), Refixation on Cover Test (referring to skew deviation).

Notably, bedside testing in this study was conducted by a neuro-ophthalmologist, and use of these maneuvers by nonspecialists has not been adequately examined. Hospitalists should therefore be aware of the limitations of their nonspecialist HINTS examination in ruling in or out posterior stroke. The study was also limited to patients with acute, new-onset vertigo lasting hours and risk factors for stroke.

On HINTS testing, the patient exhibits a normal head impulse and abnormal cover test, both positive HINTS findings. This raises your concern for a posterior stroke and you order emergent MRI, which reveals a cerebellar infarction. The patient is admitted to the neuro ICU for management.

As you return to the medicine ward, you receive a stat page from a nurse who reports that one of your patients, a 63-year-old man with hypertension who is being treated for cellulitis, has just woken from sleep with acute aphasia and right-sided weakness concerning for a new stroke. He was last seen well when he went to bed about 9 hours ago. You see the patient and confirm the examination, finding him to have a moderate to severe stroke syndrome clinically consistent with ischemia in the left middle cerebral artery (MCA) territory, with National Institutes of Health stroke scale (NIHSS) of 16. His noncontrast head CT is unremarkable but a brain MRI shows a small infarct in the left MCA distribution. Given that he was last seen without deficits >6 hours ago, you know he is out of window for thrombolysis, but wonder if other directed therapies may be helpful.

Are any directed therapies beneficial in patients with acute stroke who were last seen well within 6 to 24 hours?

Mechanical thrombectomy can reduce disability in select stroke patients who were last seen well 6 to 24 hours ago when there is mismatch between deficit and infarct size.

The DAWN randomized clinical trial² assessed the impact of mechanical thrombectomy among 206 patients at 26 locations in North America, Europe, and Australia with a new stroke who were last seen well 6 to 24 hours prior. Adults ≥18 years old with occlusion of the intracranial internal carotid artery and/or the first segment of the MCA on CTA or MRA were included if they demonstrated a more severe neurologic deficit than would be expected based on their radiographic findings on CT perfusion or DWI MRI (suggesting a period when prompt reperfusion could prevent severe infarction). Patients were randomized to mechanical thrombectomy or usual care. Co-primary outcomes were level of disability (measured by utility-weighted modified Rankin scale, in which higher scores indicate decreasing disability) and rate of functional independence (measured by modified Rankin scale) assessed at 90 days. Secondary outcomes included safety and serious adverse events.

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