What is the role of the HINTS (Head Impulse Test, Nystagmus, Test of Skew) exam in evaluating patients with vertigo?

Role of HINTS Exam in Evaluating Patients with Vertigo

The HINTS (Head Impulse, Nystagmus, Test of Skew) examination is a highly sensitive and specific bedside test that distinguishes between peripheral and central causes of vertigo, with its primary value being the early detection of potentially life-threatening stroke in patients with acute vestibular syndrome (AVS), even outperforming early MRI in sensitivity when performed by specially trained clinicians. 1

What is the HINTS Exam?

The HINTS exam consists of three components:

• Head Impulse Test: Assesses the vestibulo-ocular reflex
• Nystagmus evaluation: Observes the direction and characteristics of nystagmus
• Test of Skew: Checks for vertical misalignment of the eyes

When to Use HINTS

HINTS should be used specifically for patients presenting with:

• Continuous vertigo/dizziness (not episodic)
• Presence of nystagmus
• Associated symptoms like nausea/vomiting
• Head motion intolerance
• New gait unsteadiness 1, 2

Using HINTS in patients who don't meet these criteria significantly reduces its diagnostic value 2.

Diagnostic Value

When properly performed by trained clinicians, HINTS offers:

• Higher sensitivity for stroke detection than early MRI (100% versus 46%) 3
• Excellent ability to differentiate peripheral from central causes of vertigo
• Potential to reduce unnecessary neuroimaging in patients with peripheral vertigo 1

A peripheral pattern on HINTS (positive head impulse test, unidirectional nystagmus, and negative test of skew) strongly suggests a peripheral cause like vestibular neuritis, while a central pattern indicates possible stroke or other central pathology 1.

Implementation Challenges

Despite its value, several challenges exist with HINTS implementation:

• Training requirements: Accuracy depends heavily on examiner experience and training 3, 4
• Inconsistent terminology: Many providers use ambiguous terms like "HINTS negative" instead of the recommended "HINTS central" or "HINTS peripheral" 5
• Underutilization: Studies show HINTS is significantly underutilized compared to neuroimaging (7.1% vs 36.6% in one study) 5
• Inappropriate application: Many patients receive HINTS despite not meeting criteria for the test 2

Clinical Implications

The high prevalence of cerebrovascular disease in AVS patients (approximately 25% and up to 75% in high vascular risk cohorts) makes proper diagnostic evaluation critical 3. Notably, 75-80% of patients with AVS due to stroke have no associated focal neurologic deficits, making HINTS particularly valuable 3, 1.

A properly performed HINTS exam showing a peripheral pattern may eliminate the need for neuroimaging in appropriate patients 1. However, if HINTS is performed by providers without specialized training, its sensitivity may be insufficient to exclude stroke 3.

Pitfalls to Avoid

1. Using HINTS in inappropriate patients: Only use for continuous vertigo with nystagmus, not episodic vertigo 2
2. Mixing diagnostic approaches: Avoid using both HINTS and Dix-Hallpike in the same patient, as they're intended for different conditions 2
3. Overreliance on HINTS by untrained providers: Recent guidelines note that most emergency physicians haven't received specialized training in HINTS and shouldn't use it as a first-line test before MRI 3
4. Unclear documentation: Always specify "HINTS central" or "HINTS peripheral" rather than ambiguous terms like "HINTS negative" 5

Practical Application

For a patient presenting with vertigo:

1. Determine if they have acute vestibular syndrome (continuous vertigo, nystagmus, etc.)
2. If AVS is present, perform HINTS if properly trained
3. A peripheral HINTS pattern supports peripheral vertigo diagnosis
4. A central HINTS pattern or uncertain findings should prompt neuroimaging
5. Consider patient's vascular risk factors when interpreting results 6

The HINTS exam represents a valuable clinical tool that, when properly applied by trained clinicians, can significantly improve the early detection of central causes of vertigo and potentially reduce unnecessary neuroimaging in patients with peripheral vertigo.