What are the components of the HINTS (Head Impulse Test, Nystagmus, and Test of Skew) test?

Components of the HINTS Test

The HINTS (Head Impulse, Nystagmus, Test of Skew) examination consists of three specific components designed to distinguish between peripheral and central causes of vertigo, particularly to identify potentially life-threatening stroke in patients with acute vestibular syndrome. 1

Head Impulse Test

• Technique: The examiner rapidly turns the patient's head horizontally while the patient fixates on a target, assessing the vestibulo-ocular reflex (VOR)
• Normal response (negative test): Eyes remain fixed on target during head movement
• Abnormal response (positive test): Eyes move with head, requiring a catch-up saccade to refixate on target
• Interpretation:
  • Abnormal (positive) test suggests peripheral vestibular lesion
  • Normal (negative) test in a patient with acute vertigo suggests central pathology

Nystagmus Assessment

• Technique: Observe eye movements in primary position and with gaze in different directions
• Components to assess:
  • Direction of nystagmus (horizontal, vertical, torsional)
  • Effect of gaze direction on nystagmus
  • Whether nystagmus changes direction with different gaze positions
• Interpretation:
  • Direction-changing nystagmus (changes direction with gaze) suggests central pathology
  • Unidirectional, horizontal nystagmus that increases when looking in the direction of the fast phase suggests peripheral pathology

Test of Skew

• Technique: Alternate cover test to detect vertical misalignment of the eyes
• Procedure: Cover one eye, then quickly uncover it while covering the other eye, watching for vertical refixation movement
• Interpretation:
  • Presence of skew deviation (vertical misalignment) suggests central pathology
  • Absence of skew deviation is consistent with peripheral pathology

Clinical Significance

The HINTS examination is particularly valuable for early stroke detection in patients with acute vestibular syndrome, with studies showing it has higher sensitivity for stroke detection than early MRI (100% versus 46%) when properly performed 1. When performed by trained clinicians, particularly neurologists, HINTS offers remarkable diagnostic power with a sensitivity of 96.7% and specificity of 94.8% 1, 2.

Common Pitfalls

1. Timing of examination: HINTS is most valuable in acute vestibular syndrome (continuous vertigo >24 hours with nausea/vomiting and nystagmus)
2. Examiner expertise: Accuracy varies significantly based on examiner training; neurologists achieve higher accuracy than emergency physicians 2
3. False positives: Up to 54% of peripheral vestibulopathy cases may show positive HINTS signs, requiring careful interpretation 3
4. Nystagmus assessment challenges: Evaluation of nystagmus direction is the most difficult part of HINTS with only fair agreement between clinical and video assessment 4

Enhanced Accuracy

• Video-oculography (VOG) can improve HINTS accuracy to 94.2% with 100% sensitivity and 88.9% specificity compared to expert clinical assessment (88.3% accuracy) 4
• HINTS Plus examination includes an additional assessment of auditory function, with studies showing 95.3% sensitivity and 72.9% specificity 5

The HINTS examination is a powerful bedside tool for distinguishing between peripheral and central causes of vertigo, but requires proper training and careful interpretation to maximize its diagnostic value.