This week, we delve into the pivotal work of evaluating patients with sudden-onset acute vertigo. Accurately distinguishing between benign labyrinthine conditions and life-threatening strokes is critical, particularly in cases presenting with the acute vestibular syndrome (AVS).
Limitations of Imaging in Acute Vertigo Diagnosis
Traditionally, emergency departments have relied on imaging techniques, such as cranial CT scans and MRI, to assess patients presenting with vertigo. However, these methods have notable limitations:
- Cranial CT Scans: Within the first 48 hours of symptom onset, CT scans demonstrate a sensitivity of only 16% for detecting strokes in the brainstem or cerebellum. This low sensitivity indicates a high likelihood of false negatives, potentially leading to missed diagnoses of serious conditions.
- MRI with Diffusion-Weighted Imaging (DWI): While MRI-DWI is more sensitive than CT, it still falls short in the early detection of posterior circulation strokes. Studies have shown that MRI-DWI can miss up to 20% of these strokes during the initial 24 to 48 hours of symptom onset.
These limitations underscore the necessity for more reliable bedside diagnostic tools to promptly and accurately identify stroke in patients with AVS.
The HINTS Protocol: A Superior Diagnostic Tool
The HINTS protocol—a three-step bedside oculomotor examination—has been developed as a more accurate way to differentiate central (stroke) from peripheral causes of vertigo, often outperforming early MRI-DWI. HINTS stands for:
- Head Impulse Test: Assesses the vestibulo-ocular reflex. An abnormal (positive) head impulse test suggests a peripheral vestibular lesion, such as vestibular neuritis, whereas a normal (negative) test raises suspicion for a central cause like stroke.
- Nystagmus Assessment: Evaluates the type of nystagmus present.
- Direction-fixed horizontal nystagmus typically indicates a peripheral cause.
- Direction-changing (gaze-evoked) or vertical nystagmus suggests a central etiology.
- Test of Skew: Involves alternate eye covering to detect vertical misalignment (skew deviation). The presence of a skew deviation is indicative of a central pathology.
In a seminal study, the HINTS examination demonstrated a sensitivity of 100% and a specificity of 96% for identifying stroke in patients with AVS, outperforming early MRI-DWI.
Summary and Clinical Implications
When a patient arrives with acute, sudden-onset spontaneous vertigo, the examiner can take a couple of minutes to assess the patient far faster, far cheaper, and far more accurately than CT scan and even MRI.
If the patient has direction-fixed nystagmus and a positive head impulse test, it is almost certainly a peripheral cause. If the patient has direction-changing nystagmus, there is a high probability of stroke. If the patient has skew deviation, the probability of stroke is even higher. If none of the above findings are present, further assessment is required to determine the underlying cause.
This approach highlights the importance of bedside clinical expertise in improving patient outcomes and reducing unnecessary imaging.
Reference:
Kattah JC, Talkad AV, Wang DZ, Hsieh YH, Newman-Toker DE. HINTS to diagnose stroke in the acute vestibular syndrome: three-step bedside oculomotor examination more sensitive than early MRI diffusion-weighted imaging. Stroke. 2009 Nov;40(11):3504-10. doi: 10.1161/STROKEAHA.109.551234. Epub 2009 Sep 17. PMID: 19762709; PMCID: PMC4593511.
About the author
Alan Desmond, AuD, is the director of the Balance Disorders Program at Wake Forest Baptist Health Center, and holds an adjunct assistant professor faculty position at the Wake Forest School of Medicine. He has written several books and book chapters on balance disorders and vestibular function. He is the co-author of the Clinical Practice Guideline for Benign Paroxysmal Positional Vertigo (BPPV). In 2015, he was the recipient of the President’s Award from the American Academy of Audiology.
