Diagnostic Approach to Vertigo or Suspected Stroke

Introduction to HINTS Exam

• The American College of Radiology recommends the HINTS (Head Impulse, Nystagmus, Test of Skew) examination as a powerful bedside diagnostic tool to differentiate between central and peripheral causes of vertigo, with greater sensitivity than early MRI for detecting stroke when performed by properly trained clinicians 1, 2

Components and Interpretation of HINTS Exam

• The Head Impulse Test assesses the vestibulo-ocular reflex, and an abnormal response suggests peripheral vestibular dysfunction, while a normal response in a dizzy patient raises concern for a central cause 3
• Nystagmus Assessment evaluates the direction and characteristics of nystagmus, with direction-changing nystagmus suggesting a central cause, and unidirectional horizontal nystagmus suggesting a peripheral cause 1, 4
• The Test of Skew detects vertical misalignment of the eyes, suggesting a central lesion, and is performed by covering and uncovering each eye while the patient fixates on a target, looking for vertical correction movements 1, 2

Clinical Application and Patient Selection

• The HINTS exam is specifically designed for patients with Acute Vestibular Syndrome (AVS), characterized by acute, persistent vertigo with nausea/vomiting, head motion intolerance, nystagmus, and gait unsteadiness 2, 3
• When properly performed in appropriate patients, HINTS has shown remarkable diagnostic accuracy, and is more sensitive than early MRI when performed by specialists 1

Diagnostic Accuracy and Clinical Decision Making

• The American College of Radiology suggests that HINTS can identify patients with vertigo due to stroke even when traditional neurological examination is normal, with a high sensitivity and specificity when performed by properly trained clinicians 1
• The exam's accuracy depends heavily on examiner expertise and proper patient selection, with subspecialists achieving higher specificity compared to non-subspecialists 1, 3

Diagnostic Approach to Acute Vestibular Syndrome

Introduction to HINTS Examination

• The American College of Emergency Physicians and Society for Academic Emergency Medicine state that most emergency physicians have not received adequate training to perform HINTS with sufficient accuracy as a first-line test before MRI, highlighting the importance of examiner expertise in achieving higher accuracy 5

Diagnostic Accuracy and Patient Selection

• Up to 25% of Acute Vestibular Syndrome cases are caused by stroke, and approximately 75-80% of posterior circulation stroke patients lack focal neurologic deficits on standard examination, emphasizing the need for careful patient selection and accurate diagnostic tools 5
• A meta-analysis suggests that when HINTS is performed by emergency physicians in isolation, it is not adequately sensitive to exclude stroke, particularly in patients over 50 years with vascular risk factors 5

Diagnostic Recommendations

• If HINTS suggests a central cause, urgent MRI is indicated, as it is superior to CT for detecting posterior circulation stroke 5
• Consider MRI with diffusion-weighted imaging for patients with vascular risk factors or when severe imbalance is disproportionate to vertigo 5

Diagnostic Approach to Acute Vestibular Syndrome

Patient Selection and Diagnostic Criteria

• The American College of Emergency Physicians and Society for Academic Emergency Medicine state that HINTS should be performed by trained specialists to achieve sufficient accuracy as a first-line test before MRI, with sensitivity of 96.7% and specificity of 94.8% for detecting stroke 6
• Patients with suspected anterior inferior cerebellar artery (AICA) stroke should undergo bedside hearing testing in addition to HINTS, increasing sensitivity to 99.2% 6
• Age over 50 years with vascular risk factors, such as hypertension, diabetes, smoking, or atrial fibrillation, requires imaging regardless of HINTS results 6
• Focal neurologic deficits, such as diplopia, dysarthria, dysphagia, or limb weakness, require imaging regardless of HINTS results 6
• New severe headache or neck pain requires imaging regardless of HINTS results 6

Diagnostic Accuracy and Clinical Performance

• HINTS has a sensitivity of 96.7% and specificity of 94.8% for detecting stroke when performed by trained specialists 6
• HINTS is more sensitive than MRI-DWI obtained within 24-48 hours of symptom onset, with a sensitivity of 95.3% vs. 85.1% 6
• Subspecialists achieve significantly higher specificity (97.6%) compared to non-subspecialists (89.1%) when performing HINTS 6

Imaging Recommendations

• If HINTS suggests a central cause, urgent MRI with diffusion-weighted imaging is indicated 6
• MRI is superior to CT for detecting posterior circulation stroke 6
• If performed by non-expert examiners in the emergency department, do not rely on HINTS alone to exclude stroke - proceed with MRI for high-risk patients 6

HINTS Examination for Acute Vestibular Syndrome

Interpretation of Test Results

• The presence of skew deviation, as indicated by any vertical corrective movement when uncovering either eye during the Test of Skew, suggests brainstem or cerebellar pathology, according to the American Academy of Ophthalmology 7, 8
• The American Academy of Ophthalmology recommends that the presence of any one central finding, including normal head impulse test, direction-changing or vertical nystagmus, or skew deviation, should prompt urgent MRI with diffusion-weighted imaging to rule out stroke 7

Mandatory Imaging Guidelines

• The American Heart Association suggests that patients with focal neurologic deficits, such as diplopia, dysarthria, dysphagia, or limb weakness, should proceed directly to MRI, as recommended by the American Academy of Ophthalmology 7

Diagnostic Accuracy of HINTS Exam in Acute Vestibular Syndrome

Introduction to HINTS Exam

• The American College of Emergency Physicians and Society for Academic Emergency Medicine state that most emergency physicians have not received adequate training to perform HINTS with sufficient accuracy as a first-line test before MRI, highlighting the need for specialized training for accurate interpretation 9

Limitations of HINTS Exam Based on Examiner Training

• A normal neurologic examination does NOT exclude stroke—up to 75-80% of posterior circulation stroke patients lack focal deficits on standard examination, emphasizing the importance of considering HINTS results in the context of clinical presentation and risk factors 9

Diagnostic Yield of Early MRI

• Early MRI has a false-negative rate of approximately 15% within the first 48 hours, particularly for small posterior fossa strokes, underscoring the potential limitations of early imaging in diagnosing stroke 10

Evidence‑Based Guidance on the HINT S Examination for Acute Vestibular Syndrome

Diagnostic Performance and Evidence of the HINT S Test

• The HINT S bedside oculomotor assessment can differentiate central (stroke) from peripheral vestibular causes in acute vestibular syndrome, but its diagnostic accuracy is highly dependent on examiner expertise; emergency physicians without specialized training should not rely on HINT S alone to exclude stroke. 11

• The Society for Academic Emergency Medicine and the American College of Emergency Physicians state that most emergency physicians have not received adequate training to perform HINT S with sufficient accuracy as a first‑line test before MRI. 12, 11

• A meta‑analysis of studies in which emergency physicians performed HINT S in isolation found that the test is not adequately sensitive to rule out stroke in this setting. 11

• In acute vestibular syndrome, approximately 25 % of cases are caused by stroke, and 75‑80 % of posterior‑circulation strokes lack focal neurolog‑ic deficits on standard examination, highlighting the risk of false‑negative clinical assessment. 11

Clinical Implications for Practice

• Because of the limited sensitivity of HINT S when performed by non‑specialists, guideline‑issued societies recommend maintaining a low threshold for urgent MRI with diffusion‑weighted imaging in patients over 50 years of age or those with vascular risk factors, even if a peripheral HINT S pattern is observed. 11

• When HINT S is performed by a trained neurologist, neuro‑ophthalmologist, or neuro‑otologist, the test achieves high diagnostic performance (sensitivity ≈ 95 %, specificity ≈ 90 % in published series), but these figures should not be extrapolated to emergency physicians without comparable expertise. 11

• The high prevalence of stroke in acute vestibular syndrome and the frequent absence of focal deficits necessitate that a peripheral HINT S pattern be interpreted in the broader clinical context and does not guarantee safety in high‑risk patients. 11

All facts are derived from the cited literature and reflect the current evidence base; evidence strength is indicated where explicitly stated in the source (e.g., meta‑analysis, expert consensus).