HINTS for Stroke in Acute Vestibular Syndrome

HINTS Exam Calculator

Head Impulse Test

Nystagmus

Test of Skew

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Identifies potential stroke in patients with acute vestibular syndrome (AVS).

Why Use

AVS is a common presentation to EDs, outpatient clinics, and inpatient services. Differentiation between central and peripheral etiologies is important in narrowing the differential diagnosis and facilitate emergent therapies. Acute MRI (<24-48 hours) may initially be falsely negative due to lower resolution in the posterior fossa in this time window, and so a “normal” MRI in this population cannot be relied upon to provide complete reassurance.

When to Use

Only use in patients with continuous vertigo. Do not use in patients with episodic vertigo (e.g. benign paroxysmal positional vertigo) or whose dizziness has resolved by the time of assessment.

Formula

See video with instructions from the authors here . Test Result Horizontal head impulse test (h-HIT) Abnormal Normal/untestable Observation of nystagmus Direction-fixed horizontal nystagmus Direction-changing horizontal/untestable nystagmus Test of skew Absent skew deviation Present/untestable skew deviation HINTS = Head Impulse, Nystagmus, Test of Skew

Pearls / Pitfalls

Requires some specialized experience to perform, and sensitivity is reduced in non-neuro-ophthalmologists ( Kerber 2015 ). Ruling out stroke in patients with a moderate or high pre-test probability may not be possible by non-specialists. Acute (<24-48 hours) MRI has lower sensitivity for posterior fossa ischemia than HINTS, assuming scoring by a specialist ( Kattah 2009 ). In non-expert hands, consideration of the patient’s overall vascular risk (e.g. ABCD² Score ) improves the sensitivity of the assessment. Delayed or repeat MRI (>48 hours) may be useful in ambiguous cases. Ischemia in the territory of the anterior inferior cerebellar artery can mimic a peripheral etiology and should be kept in the differential when the HINTS localizes to the periphery but the patient has vascular risk factors, experiences sudden onset of symptoms, and/or has associated ipsilateral hearing loss.

Management

Consider neurologist, neuro-ophthalmologist, or neuro-otologist consultation in the disposition of AVS patients, as even if the HINTS examination is “benign,” many peripheral lesions are amenable to time-sensitive therapy (eg. vestibular neuronitis). Vestibular suppressants, such as prochlorperazine, can impede recovery and compensation of a peripheral vestibular lesion, and thus should be very rarely and sparingly used (if at all). Patients with a “dangerous” HINTS examination are generally admitted for neuroimaging and appropriate directed therapies (e.g. stroke).

Critical Actions

HINTS does not replace a detailed history and general neurological examination, and care must be taken not to ignore other non-vestibular diagnoses (e.g. the vertiginous aura of superior temporal lobe seizures).

Advice

A “benign” HINTS examination, in the absence of other neurological deficits, suggests a peripheral localization, and investigation and management can be directed at this possibility. A “dangerous” HINTs examination strongly supports a central lesion, and appropriate workup is required. An important exception is that acute ischemia of the anterior inferior cerebellar artery territory can produce a “benign” HINTS examination. This possibility should be considered in patients with vascular risk factors, sudden-onset symptoms, or concurrent ipsilateral hearing loss.

More Information

HINTS exam is benign: Abnormal h-HIT plus direction-fixed horizontal nystagmus plus absent skew deviation HINTS exam is dangerous: Normal/untestable h-HIT or direction-changing horizontal/untestable nystagmus or present/untestable skew deviation