Perform the HINTS Examination to Differentiate Peripheral from Central Causes
In a patient with dizziness and left-beating nystagmus whose orthostatic vital signs are normal, the next step is to perform the HINTS (Head-Impulse, Nystagmus, Test of Skew) examination to distinguish between benign peripheral vestibular causes and potentially life-threatening posterior circulation stroke. 1
Why HINTS Examination is Critical
This patient presents with acute vestibular syndrome (AVS) - characterized by persistent vertigo with nystagmus. The critical decision point is determining whether this represents:
- Peripheral cause (vestibular neuritis/labyrinthitis) - benign, self-limiting
- Central cause (posterior circulation stroke) - requires urgent neuroimaging and treatment
The Diagnostic Challenge
Even with normal orthostatic vital signs and a normal general neurologic examination, up to 25% of patients with AVS have posterior circulation infarcts, and 75-80% of these patients have NO focal neurologic deficits 1. This makes the standard neurologic examination inadequate for ruling out stroke.
The HINTS Examination Protocol
When performed by trained practitioners, HINTS has 100% sensitivity for detecting stroke versus only 46% for early MRI 1. The examination consists of:
- Head-Impulse test: Abnormal (corrective saccade) suggests peripheral; normal suggests central
- Nystagmus direction: Unidirectional (same direction in all gaze positions) suggests peripheral; direction-changing or purely vertical suggests central
- Test of Skew: Vertical misalignment suggests central cause
Critical Caveat
If the complete HINTS triad is consistent with peripheral vertigo, imaging is not required - in one study of 610 emergency department patients, not a single patient with a complete peripheral HINTS pattern had abnormalities on CT/MRI 1.
When to Proceed to Imaging
If HINTS examination suggests a central cause or if you are not trained in performing HINTS reliably (non-expert performance shows mixed results 1):
- MRI brain without and with IV contrast is the preferred imaging modality - detects acute brain lesions in 11% of patients with AVS versus only 6% with CT 1
- CT imaging has very low yield (<1%) in patients with normal neurologic examination 1
Key Pitfalls to Avoid
- Do not rely solely on symptom quality (vertigo vs. lightheadedness) - this outdated approach does not distinguish benign from dangerous causes 2, 3
- Do not assume normal neurologic exam excludes stroke - one-third to two-thirds of posterior circulation strokes present without focal deficits 1
- Do not order imaging reflexively - if HINTS is clearly peripheral and performed by trained examiner, imaging adds no value and increases costs 1
The left-beating nystagmus in this patient is unidirectional, which could be consistent with either peripheral or central pathology, making the complete HINTS examination essential for safe disposition.