Diagnostics: The HINTS Exam
/You finish taking sign out and look at the tracking board to notice that your next three patients are all presenting with a chief complaint of “dizziness.” At first, you’re surprised by the unlikely coincidence that all of them have the same complaint but then you remember that it’s actually pretty common in the emergency department. Approximately 2-4% of all ED visits in the United States are for “dizziness.” [1,2]
You move past the coincidence and start generating your differential diagnosis. But what do they mean by dizzy?! Are they experiencing vertigo? Pre-syncope? Disequilibrium? Each of these characteristics of dizziness has its own list of differential diagnoses. You can try to narrow down exactly what the patient means by their complaint of dizziness but this approach is often unreliable. Approximately half of patients change how they characterize dizziness when asked the same question 10 minutes apart and more than half of them endorse multiple types of dizziness.3 While it is important and encouraged to ask a patient to characterize the dizziness, their description alone should not guide your differential diagnosis and work-up.[4]
Given the difficulty in consistently characterizing dizziness, it is often challenging to decide how extensive a work-up one should pursue in these patients. As a result, dizzy patients often undergo more lab testing, imaging, have a longer ED length of stay, and are more likely to be admitted than their non-dizzy counterparts.[1,2] Vertigo is one description of a patient’s dizziness. Most commonly, it is the sensation of self-motion when no actual self-motion is occurring. The difficulty in working up this type of dizziness is that the patients can have a benign cause and be safe for discharge, while others can have a dangerous cause and require admission. This is where the HINTS exam can potentially help.
What is the HINTS exam:
It is a series of quick, bedside, physical exam maneuvers used to help distinguish between central and peripheral causes of vertigo in patients experiencing an acute vestibular syndrome (AVS) which is best defined as: rapid-onset vertigo, nausea and/or vomiting, gait unsteadiness, head motion intolerance, and nystagmus.[5]
Head Impulse Test
Have the patient look and maintain their gaze midline. Then ask them to try to maintain their gaze on you while quickly rotating the patient’s head approximately 15-20 degrees to left/right. An intact vestibulo-ocular reflex (VOR) allows the patient to maintain their gaze throughout the rapid rotations.
An abnormal response is one in which the patient is unable to maintain their gaze and their eyes have a corrective saccade back to midline upon rotation. an “abnormal” response is reassuring in that it usually indicates peripheral vertigo.
“normal,” or eyes maintaining central position, is concerning for central vertigo
Nystagmus
This is best tested by primary or lateral gaze.
Unidirectional, horizontal nystagmus is reassuring for peripheral vertigo while
bidirectional, vertical, or torsional nystagmus is concerning for central vertigo.
Test of Skew
Cover the patient’s eye with your hand while asking them to maintain their gaze on you. Uncover the eye as you move to covering the other and note if there is any vertical misalignment upon uncovering. Repeat this maneuver multiple times on each eye. At no point should both eyes be uncovered at the same time during this portion of the exam.
If there is vertical or slanted misalignment it is highly concerning for central vertigo
If there is no misalignment, this is consistent with peripheral vertigo
When to perform the HINTS exam:
The HINTS exam should only be performed in acutely vertiginous patients who are experiencing an AVS. The most important qualifier for this exam is that the patient must be experiencing continuous vertigo for the results to be reliably interpreted.
Discussion
The HINTS exam can be a useful tool when trying to rule out a central cause of vertigo. While any one component of the exam is not sensitive enough to rule out central vertigo, the presence of all three “reassuring” exam findings suggests it can be ruled out. In the original study, a HINTS exam indicating peripheral etiology had a 100% sensitivity for ischemic stroke in AVS while an initial MRI with diffusion-weighted imaging (DWI) had a 88% sensitivity.[5] There are some findings such as skew deviation and vertical or torsional nystagmus that are highly specific but not sensitive for central vertigo.[5]
Furthermore, the HINTS exam does not replace the clinician’s gestalt for serious etiologies of vertigo, such as posterior circulation strokes. If the pre-test probability for a posterior circulation stroke is high (truncal ataxia, high risk patient), one should not forego additional testing just because the HINTS exam indicates a peripheral vestibulopathy. This is evidenced by one of the limitations of the original trial in which approximately 35% of the patients were already admitted to the stroke team. The HINTS exam likely has higher utility in the patient population in whom the clinician suspects a peripheral cause of their vertigo. In this circumstance, the HINTS exam provides an additional piece of supporting evidence for clinical decision making when discharging the patient with a diagnosis of peripheral vertigo.
Another limitation of the HINTS exam is that the original study was conducted by neuro-ophthalmologists who were trained extensively in performing this exam. There have not been any validated studies for emergency physicians performing this exam. Given the lack of familiarity and general skepticism regarding the utility of the head impulse test in the ED, emergency providers rarely utilize the HINTS exam.[6] Another study concluded that approximately half of their emergency physicians incorrectly documented the HINTS exam as positive/negative instead of correctly documenting it as HINTS-central/peripheral. Furthermore, based on their documentation, only 35% of patients with a HINTS exam consistent with a central etiology of vertigo underwent neuroimaging.[7]
While the HINTS exam hasn’t been validated for use by emergency physicians, the STANDING algorithm, which includes some parts of the HINTS exam, has been validated.[8] In this study, trained emergency physicians performed and interpreted the algorithm for ruling out central vertigo with a very high negative predictive value. One of the limitations of the study was that the emergency physicians received an extensive amount of training which might not be as feasible across different institutions. However, it does show that emergency physicians can develop the skill set to utilize these physical exam maneuvers to rule out central vertigo.
As emergency physicians, we have long been taught to evaluate the acutely “dizzy” patient by focusing on how a patient characterizes their dizziness by asking them “what do you mean by dizzy?” This approach is limited by both the patient ability to articulate their sensation and our understanding of pattern recognition. There is a need for a change in the culture for how we evaluate these patients, moving to more objective and reproducible tools to become more diagnostic in our approach, and the HINTS exam is one example of such a change.[7] In conclusion, the HINTS exam can be beneficial in ruling out central vertigo in patients with AVS provided it is performed by an experienced clinician who can also reliably interpret the results.
Post by Hamza Ijaz, MD
Dr. Ijaz is a PGY-1 at the University of Cincinnati in Emergency Medicine
Peer Review by Andrew Golden, MD and Ryan LaFollette, MD
Dr. Golden is a PGY-4 and Chief Resident at the University of Cincinnati in Emergency Medicine. Dr. LaFollette is an Assistant Program Director at the University of Cincinnati in Emergency Medicine
References:
Newman-Toker DE, Hsieh YH, Camargo CA Jr, … Edlow JA. Spectrum of dizziness visits to US emergency departments: cross-sectional analysis from a nationally representative sample. Mayo Clin Proc 2008;83:765–775.
Cheung CS, Mak PS, Manley KV, et al. Predictors of important neurological causes of dizziness among patients presenting to the emergency department. Emerg Med J 2010;27:517–521.
Newman-Toker DE, Cannon LM, Stofferahn ME, Rothman RE, Hsieh YH, Zee DS. Imprecision in patient reports of dizziness symptom quality: a cross-sectional study conducted in an acute care setting. Mayo Clin Proc 2007;82:1329–40.
Edlow JA. Diagnosing dizziness: We are teaching the wrong paradigm! Acad Emerg Med 2013;20:1064-66.
Kattah JC, Talkad AV, Wang DZ, … Newman-Toker DE. HINTS to diagnose stroke in the acute vestibular syndrome. Stroke 2009;40:3504-10.
Walther LE, Lohler J, Agrawal Y, … Schmucker C. Evaluating the diagnostic accuracy of the head-impulse test: A scoping review. JAMA Otolaryngology 2019;145:550-60.
McDowell T, Moore F. The under-utilization of the head impulse test in the emergency department. Can J Neurol Sci 2016;43:398-401.
Quimby AE, Kwok ESH, Lelli D, … Tse D. Usage of the HINTS exam and neuroimaging in the assessment of peripheral vertigo in the emergency department. J of Otolaryngology – Head & Neck Surgery 2018;47-54.
