What is the utility, sensitivity, and specificity of the HINTS (Head Impulse, Nystagmus, and Test of Skew) exam in diagnosing stroke in patients with suspected vertebrobasilar insufficiency or acute dizziness/vertigo?

HINTS Exam Utility, Sensitivity, and Specificity

Direct Answer

The HINTS exam demonstrates excellent diagnostic accuracy when performed by trained specialists (sensitivity 95.3%, specificity 92.6%), but most emergency physicians lack adequate training to perform it with sufficient accuracy as a first-line test before MRI, and should not rely on it alone to exclude stroke in patients with acute vestibular syndrome. 1, 2, 3

Diagnostic Performance by Examiner Expertise

Specialist-Performed HINTS

• Sensitivity: 95.3% (95% CI: 92.5-98.1%) for detecting stroke in acute vestibular syndrome 3
• Specificity: 92.6% (95% CI: 88.6-96.5%) overall, with subspecialists achieving significantly higher specificity of 97.6% versus 89.1% for non-subspecialists 3
• HINTS outperforms early MRI-DWI obtained within 24-48 hours (sensitivity 95.3% vs 85.1%), as early MRI has a false-negative rate of approximately 15% for posterior fossa strokes 2, 3, 4

Emergency Physician-Performed HINTS

• Sensitivity drops to 83% (95% CI: 63-95%) when performed by emergency physicians 5
• Specificity falls dramatically to 44% (95% CI: 36-51%) in emergency department settings 5
• The Society for Academic Emergency Medicine and American College of Emergency Physicians explicitly 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 confirms that when HINTS is used in isolation by emergency physicians (not neurologists), it is not adequately sensitive to exclude stroke 1

Clinical Utility and Appropriate Patient Selection

When HINTS is Indicated

• HINTS is specifically designed for Acute Vestibular Syndrome (AVS): acute, persistent (not intermittent) vertigo with nystagmus, head motion intolerance, nausea/vomiting, and gait unsteadiness 2, 6
• HINTS is more sensitive than ABCD2 score for differentiating stroke from mimics in this specific population 1
• Approximately 25% of AVS cases are caused by stroke, with 75-80% of posterior circulation stroke patients lacking focal neurologic deficits on standard examination 1, 2

Critical Limitations by Stroke Location

• Sensitivity is lower for AICA strokes (84.0%) compared to PICA strokes (97.7%), but adding bedside hearing tests (HINTS+) increases sensitivity to 99.2% 2, 3
• Classic Wallenberg syndrome is seen in only a small proportion of posterior circulation stroke patients 1

Mandatory Imaging Regardless of HINTS Results

High-Risk Features Requiring MRI

• Age over 50 years with vascular risk factors (hypertension, diabetes, smoking, atrial fibrillation) 2
• Any focal neurologic deficits (diplopia, dysarthria, dysphagia, limb weakness) 2
• New severe headache or neck pain 2
• Severe (grade 3) gait/truncal instability disproportionate to vertigo 2

When HINTS Suggests Central Cause

• Any one central finding mandates urgent MRI: normal head impulse test, direction-changing or vertical nystagmus, or skew deviation 2
• MRI with diffusion-weighted imaging is superior to CT for detecting posterior circulation stroke (CT sensitivity only ~10%) 1

Common Pitfalls and How to Avoid Them

Examiner Training Issues

• Physician uptake was high (19.5%) but diagnostic value was limited in one ED study where 96.9% of patients did not meet criteria for HINTS (lacked nystagmus or had intermittent symptoms) 7
• Emergency physicians frequently performed both HINTS and Dix-Hallpike exams, which are intended for mutually exclusive patient populations 7
• Do not use HINTS for intermittent vertigo or patients without documented nystagmus 7

False Reassurance Risk

• A negative HINTS does not exclude stroke when performed by non-experts in the emergency department 1, 5
• Even with expert performance, early MRI has a 15% false-negative rate within 48 hours, emphasizing the need for clinical judgment 2, 3

Practical Algorithm for Emergency Department Use

For patients presenting with acute, persistent vertigo:

1. Confirm AVS criteria: persistent (not intermittent) vertigo, documented nystagmus, head motion intolerance, and gait unsteadiness 2, 6

2. Check for mandatory imaging criteria (age >50 with vascular risk factors, focal deficits, severe headache/neck pain) → if present, proceed directly to MRI 2

3. If HINTS-trained specialist available: perform HINTS exam; if any central features present, obtain urgent MRI 2, 3

4. If only emergency physicians available without specialized training: do not rely on HINTS alone—proceed with MRI for high-risk patients 1, 2, 5

5. For suspected AICA stroke: add bedside hearing testing to increase sensitivity 2, 3