What is the HINTS (Head-Impulse Nystagmus Test of Skew) examination?

The HINTS Examination: A Critical Bedside Test for Differentiating Central from Peripheral 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). 1

Components of the HINTS Examination

The HINTS examination consists of three specific components:

1. Head Impulse Test (HIT):

   • Examiner rapidly turns the patient's head to one side while patient fixates on a target
   • Normal response (positive test): Eyes remain fixed on target (intact VOR)
   • Abnormal response (negative test): Eyes move with head, requiring catch-up saccade to refixate
   • Interpretation: Abnormal HIT suggests peripheral cause; normal HIT with AVS suggests central cause

2. Nystagmus Assessment:

   • Examiner observes for direction-changing nystagmus in different gaze positions
   • Peripheral pattern: Unidirectional nystagmus that increases when looking in direction of fast phase
   • Central pattern: Direction-changing nystagmus or vertical nystagmus
   • Interpretation: Direction-changing nystagmus suggests central cause

3. Test of Skew:

   • Examiner performs alternate cover test to detect vertical misalignment
   • Normal: No vertical movement when covering/uncovering eyes
   • Abnormal: Vertical refixation movement (skew deviation)
   • Interpretation: Presence of skew deviation suggests central cause

Diagnostic Value

When properly performed by trained clinicians, HINTS offers remarkable diagnostic power:

• Higher sensitivity for stroke detection than early MRI (100% versus 46%) 1
• For peripheral vertigo diagnosis: Sensitivity 94.0% and specificity 86.9% 2
• For central vertigo diagnosis: Positive likelihood ratio 5.61 and negative likelihood ratio 0.06 3

Clinical Application

The HINTS examination is particularly valuable because:

• Up to 75-80% of patients with AVS related to stroke have no associated focal neurologic deficits 4
• The prevalence of cerebrovascular disease in AVS patients is approximately 25% and up to 75% in high vascular risk cohorts 4

Interpretation Pattern

A central cause of vertigo is suggested by any one of the following ("INFARCT" pattern):

• Impulse normal (no corrective saccade)
• Nystagmus that changes direction with gaze
• Fast-phase Alternating Refixation on Cover Test (skew deviation)

Important Caveats

1. Examiner expertise matters significantly:

   • When performed by neurologists: Sensitivity 96.7%, specificity 94.8% 5
   • When performed by mixed physician groups including emergency physicians: Sensitivity 83%, specificity 44% 5
   • Most emergency physicians haven't received specialized training in HINTS 1

2. False positives in peripheral disorders:

   • Up to 54% of patients with confirmed peripheral vestibulopathy may show positive HINTS signs 6
   • Careful interpretation is required in clinical context

3. HINTS Plus:

   • Adds assessment of hearing (finger rub at ear)
   • Sudden hearing loss suggests central cause
   • Improves sensitivity to 95.3% and specificity to 72.9% 2

Clinical Decision Making

1. When to use HINTS:

   • Only in patients with true acute vestibular syndrome (continuous vertigo >24h with nausea/vomiting, nystagmus)
   • Not appropriate for episodic vertigo, positional vertigo, or non-vestibular dizziness

2. When to trust HINTS results:

   • When performed by specially trained providers 4
   • When all three components are assessed properly
   • When results show a consistent pattern

3. When to proceed to neuroimaging despite HINTS:

   • Inconsistent HINTS findings
   • Examination performed by untrained providers
   • High clinical suspicion despite reassuring HINTS
   • Presence of other neurological signs or symptoms

Implementation Recommendations

• Specialized training is essential for accurate HINTS performance
• Consider video-assisted HINTS for improved accuracy and documentation
• Integrate HINTS into stroke protocols in emergency departments
• Use HINTS as part of a comprehensive evaluation, not in isolation

The HINTS examination represents a powerful clinical tool that, when properly performed and interpreted, can significantly improve early detection of central causes of vertigo and potentially reduce unnecessary neuroimaging in patients with peripheral vertigo.