What is the HINTS (Head‑Impulse, Nystagmus, Test of Skew) exam and how does it differentiate peripheral vestibular neuritis from central posterior‑fossa stroke in acute continuous vertigo?

HINTS Exam: A Bedside Tool for Differentiating Stroke from Peripheral Vertigo

The HINTS (Head Impulse, Nystagmus, Test of Skew) exam is a three-component bedside oculomotor assessment designed to distinguish central (stroke) from peripheral vestibular causes in patients with acute vestibular syndrome, but its accuracy depends critically on examiner expertise—emergency physicians without specialized training should not rely on HINTS alone to exclude stroke. 1, 2

What is the HINTS Exam?

The HINTS examination consists of three sequential bedside tests performed in patients presenting with acute, continuous vertigo, nystagmus, and gait unsteadiness (acute vestibular syndrome): 2

1. Head Impulse Test (HIT)

• Assesses the vestibulo-ocular reflex by rapidly turning the patient's head while they fixate on a target 2, 3
• Abnormal result (corrective saccade) = peripheral vestibular dysfunction 2
• Normal result in a dizzy patient = raises concern for central (stroke) cause 2

2. Nystagmus Assessment

• Evaluates the direction and characteristics of spontaneous nystagmus 2
• Unidirectional horizontal nystagmus = suggests peripheral cause 2
• Direction-changing nystagmus (changes with gaze direction) or pure vertical nystagmus = suggests central cause 2, 4

3. Test of Skew

• Detects vertical misalignment of the eyes by covering and uncovering each eye while the patient fixates on a target 2
• Any vertical corrective movement = suggests brainstem or cerebellar pathology (central cause) 2, 5

Diagnostic Accuracy: The Critical Role of Examiner Training

When Performed by Trained Specialists

HINTS demonstrates excellent diagnostic accuracy when performed by neurologists or neuro-ophthalmology/neuro-otology subspecialists: 2

• Sensitivity: 94.0% to 96.7% for detecting stroke 2, 3
• Specificity: 86.9% to 94.8% 2, 3
• More sensitive than early MRI (within 24-48 hours): HINTS 95.3% vs. MRI-DWI 85.1% 2
• Subspecialists achieve significantly higher specificity (97.6%) compared to non-subspecialists (89.1%) 2

When Performed by Emergency Physicians

The Society for Academic Emergency Medicine and American College of Emergency Physicians state that most emergency physicians have not received adequate training to perform HINTS with sufficient accuracy as a first-line test before MRI. 1, 2

• A meta-analysis found that when HINTS is performed by emergency physicians in isolation, it is not adequately sensitive to exclude stroke 1
• One retrospective study showed that despite widespread use in the ED, HINTS had limited diagnostic value when performed by non-specialists, with the test frequently misapplied to patients who did not meet criteria 6
• In 96.9% of cases, emergency physicians used HINTS in patients lacking documentation of nystagmus or with intermittent (not continuous) symptoms 6

Appropriate Patient Selection: Who Should Receive HINTS?

HINTS is specifically designed ONLY for patients with Acute Vestibular Syndrome (AVS), defined as: 2

• Acute, persistent (continuous, not episodic) vertigo
• Nausea and vomiting
• Head motion intolerance
• Spontaneous nystagmus present
• Gait unsteadiness 2

Common Misapplication Pitfall

Do NOT perform HINTS on patients with episodic or positional vertigo—these patients require Dix-Hallpike testing for BPPV, not HINTS. 6 Many emergency physicians incorrectly perform both HINTS and Dix-Hallpike on the same patient, despite these tests being designed for mutually exclusive populations. 6

Interpreting HINTS Results: Central vs. Peripheral Patterns

Central Pattern (Suggests Stroke) — Any ONE of the following:

• Normal head impulse test (no corrective saccade) 2, 5
• Direction-changing nystagmus or pure vertical nystagmus 2, 5
• Skew deviation present (vertical misalignment) 2, 5

Peripheral Pattern (Suggests Vestibular Neuritis)

• Abnormal head impulse test (corrective saccade present) 2
• Unidirectional horizontal nystagmus 2
• No skew deviation 2

HINTS Plus: Adding Auditory Assessment

HINTS Plus includes bedside hearing testing in addition to the three HINTS components, increasing sensitivity to 99.2% for detecting anterior inferior cerebellar artery (AICA) stroke. 2

• Clinical HINTS Plus: 95.3% sensitive, 72.9% specific 3
• Particularly important because AICA strokes can present with hearing loss mimicking labyrinthitis 2

Critical Limitations and Pitfalls

1. False Reassurance from Peripheral HINTS Pattern

Up to 25% of acute vestibular syndrome cases are caused by stroke, and 75-80% of posterior circulation stroke patients lack focal neurologic deficits on standard examination. 1, 2 A peripheral HINTS pattern does not guarantee safety in high-risk patients.

2. Peripheral Vestibulopathy Can Show "Central" HINTS Findings

One study found that 54% (7/13) of patients with confirmed peripheral vestibulopathy showed positive (central-appearing) HINTS signs, including normal head impulse test or skew deviation. 7 This underscores that HINTS results must be interpreted in clinical context.

3. Early MRI Has False-Negative Rate

Early MRI has a false-negative rate of approximately 15% within the first 48 hours, particularly for small posterior fossa strokes. 2 This is why HINTS, when performed by experts, can be more sensitive than early imaging.

Mandatory Imaging Regardless of HINTS Results

Proceed directly to urgent MRI with diffusion-weighted imaging if ANY of the following are present: 2, 5

• Age over 50 years with vascular risk factors (hypertension, diabetes, smoking, atrial fibrillation) 2
• Focal neurologic deficits (diplopia, dysarthria, dysphagia, limb weakness) 2, 5
• New severe headache or neck pain 2
• Severe imbalance disproportionate to vertigo 2
• Downbeating nystagmus on Dix-Hallpike without torsional component 5
• Baseline nystagmus without provocative maneuvers 5
• Failure to respond to appropriate peripheral vertigo treatment 5

Clinical Algorithm for Emergency Department Use

For patients presenting with acute, continuous vertigo:

1. Confirm Acute Vestibular Syndrome criteria (continuous vertigo, spontaneous nystagmus, gait unsteadiness) 2

   • If episodic or positional → perform Dix-Hallpike for BPPV, NOT HINTS 6

2. Screen for mandatory imaging criteria (see list above) 2

   • If ANY present → proceed directly to MRI, do not rely on HINTS 2

3. If HINTS is performed by non-expert (emergency physician):

   • Do NOT use HINTS alone to exclude stroke 1, 2
   • Maintain low threshold for MRI in patients over 50 or with vascular risk factors 2
   • Consider neurology consultation for high-risk patients 1

4. If HINTS suggests central cause (normal HIT, direction-changing nystagmus, or skew deviation):

   • Urgent MRI with diffusion-weighted imaging 2, 5

5. If HINTS suggests peripheral cause but performed by non-expert:

   • Consider MRI anyway if age >50 or vascular risk factors present 2
   • Close follow-up mandatory 2

Video-Assisted HINTS

Video-oculography (VOG) HINTS shows promise for improving accuracy: 8

• Overall accuracy 94.2% with 100% sensitivity and 88.9% specificity 8
• Better than expert clinical assessment (88.3% accuracy) 8
• Nystagmus direction assessment remains the most difficult component even with video assistance 8

However, video-assisted HINTS data remain limited, with very low to moderate certainty of evidence. 3