The eyes are the window to the brain: HINTS exam in acute vestibular syndrome
Resident Clinical Pearl
Jacqueline MacKay, PGY2 iFMEM, Dalhousie University, Saint John, New Brunswick
Reviewed by: Dr Joanna Middleton and Dr David Lewis
Acute vestibular syndrome (AVS) is the rapid onset of vertigo, nausea/vomiting, and gait unsteadiness combined with head-motion intolerance and nystagmus that lasts days-weeks. Often these dizzy patients have a benign, self-limiting cause for their symptoms, however it is estimated that up to 25% of AVS presentations to emergency departments are due to posterior circulation infarcts.
CT scan has low sensitivity for identifying acute infarct, especially in the posterior fossa. MRI is not always available, and will often have false-negative results in acute posterior circulation strokes. Are bedside predictors able to identify central causes of acute vestibular syndrome?
The HINTS exam is a bedside test that carefully assesses eye movements. HINTS stands for Head Impulse-Nystagmus-Test of Skew.
Head Impulse: test of vestibulo-ocular reflex function. A normal Head Impulse test (HIT) strongly indicates a central localization for the AVS. An abnormal HIT usually indicates a peripheral lesion.
Nystagmus: bilateral nystagmus which changes direction on eccentric gaze or primarily vertical nystagmus is predictive of central pathology.
Skew Deviation: a vertical ocular misalignment that is assessed by alternate cover testing
Watch the video! A short and excellent description of the exam with good examples of normal and abnormal:
https://vimeo.com/133033089 (Courtesy of EMCrit)
Interpretation
A benign HINTS exam is defined as abnormal HIT + direction-fixed horizontal nystagmus + absent skew.
A dangerous HINTS exam is defined as any one of:
- Normal/untestable HIT
- or direction-changing horizontal nystagmus present/untestable
- or skew deviation present/untestable
(Untestable refers to those patients with obvious oculomotor pathology or lethargy in whom the tests were unable to be completed).
The acronym INFARCT can be used to remember what constitutes a dangerous HINTS exam:
Impulse Normal
Fast-phase Alternating
Refixation on Cover Test.
A dangerous HINTS result was found to be 100% sensitive and 96% specific for the presence of a central lesion when applied to patients with acute vestibular syndrome (continuous vertigo and nystagmus) with at least one stroke risk factor. In fact, the HINTS exam is more accurate than MRI to diagnose stroke in patients with AVS in the first 48 hours!
Bottom Line:
In the acutely dizzy patient with at least one stroke risk factor, remember the HINTS to an INFARCT
References:
- Kattah, J. C., Talkad, A. V., Wang, D. Z., Hsieh, Y. H., & Newman-Toker, D. E. (2009). HINTS to diagnose stroke in the acute vestibular syndrome three-step bedside oculomotor examination more sensitive than early MRI diffusion-weighted imaging. Stroke, 40(11), 3504-3510. DOI: 10.1161/STROKEAHA.109.551234
- EMCrit http://emcrit.org/misc/posterior-stroke-video/ – original source of the videos is http://novel.utah.edu/Newman-Toker/collection.php
Update:
GRACE 3 (March 2023) –Guidelines for reasonable and appropriate care in the emergency department 3 (GRACE-3): Acute dizziness and vertigo in the emergency department.
Excellent GRACE 3 Summary from Skeptics – SGME:
