SGEM#376: I Wonder Why She Ran Away from the HINTS Exam

Date: September 16th, 2022 Reference: Gerlier C, et al.  Differentiating central from peripheral causes of acute vertigo in an emergency setting with the HINTS, STANDING and ABCD2 tests: A diagnostic cohort study. AEM 2021 Guest Skeptic: Dr. Peter Johns has been practicing emergency medicine since 1985 and has been passionate about vertigo education for the last two decades.  He co-authored the Vertigo chapter in the current edition of Tintinalli’s emergency medicine textbook and has a YouTube channel about vertigo with over 16,000 subscribers and five million views. Case: This is a real case seen by Peter and you can see the actual exam findings in a video on his YouTube channel. A 70-year-old woman wakes up with dizziness and presents to the emergency department (ED) later that day.  She’s vomited twice, and describes her dizziness as a constant spinning sensation, which gets worse when she moves her head.  She has some unsteadiness but can walk unaided.  She has no other neurologic symptoms.  In particular, she denies any new significant headache or neck pain, or focal weakness or paresthesia, dysarthria, diplopia, dysmetria, dysphagia or dysphonia, (the so-called Dangerous D’s).  When you examine her, and she is looking straight ahead, you observe that she has horizontal and slight torsional nystagmus beating towards her left ear. That means that the fast component of the nystagmus is horizontal, to the left, and there is a slight rotation with the upper pole of the eyes beating towards the left as well. Background: We have looked at acute vestibular syndrome (AVS) on the SGEM with Dr. Mary McLean who was the guest skeptic on SGEM #310. The bottom line from that episode was that: Dr. Mary McLean "the available evidence does not support the use of the HINTS examination alone by emergency physicians in patients with isolated vertigo or AVS to rule out a posterior stroke." In that episode, the case patient was told they would be admitted to the hospital to have a neurologist do the HINTS exam and decide if an MRI was necessary. But the question remains: can emergency physicians be taught how to use the HINTS exam to make clinical decisions? This is a difficult task, in part because vertigo education for emergency physicians has historically contained lots of  misinformation.  If there’s one thing we learned from the current pandemic, it is that misinformation is easier to spread than to correct. The tsunami of misinformation around COVID-19 has been coined the “infodemic”. We talked about this with Simon Carley on an SGEM Xtra and he emphasized “principles EBM are even more important now than in any time in our career”. There is a great quote by Thomas Francklin in 1787 about misinformation that rings true over two-hundred years later in the age of social media. He said: “Falsehoods will fly, as it were, on the wings of the wind, and carry its tale to every corner of the earth; whilst truth lags behind; her steps, though sure, are slow and solemn.” There is quote from another famous Franklin, Ben, which is apropos to the HINTS exam. "You will observe with concern how long a useful truth may be known, and exist, before it is generally received and practiced on." Myths & Misinformation about Dizziness: Myth: Asking what they mean by dizzy is the most important question to ask a dizzy patient. In fact, the patient's description of the sensation of their dizziness cannot be used to generate a reliable differential diagnosis. Myth: Tables of central vs peripheral characteristics of vertigo are helpful. Let us just say they are not.  You can watch my YouTube video about this for more info. Myth: If it gets worse when you move your head, that means it’s a peripheral cause. All vertigo gets worse when you move your head. If it does not, it probably is not vertigo. Myth: A CT or CTA will prevent you from sending home a stroke presenting with dizziness. Nope. CT has very poor sensitivity for stroke. Myth: Hearing loss only happens in peripheral causes. In fact, an AICA stroke, (anterior, inferior cerebellar artery) can cause hearing loss. Myth: If you see any vertical nystagmus, it must be a central cause. In fact, the most common cause of nystagmus is BPPV, and vertical upward nystagmus is an expected finding. Spontaneous vertical nystagmus, (nystagmus you see when the patient is just sitting or lying there) is central. There are a lot of dogmas and myths in medicine. We have discussed some of them on the SGEM including SGEM#9, SGEM#63, and SGEM Xtra: Dogmalysis 2021.  It is no wonder emergency physicians struggle with dizzy patients when what we were taught for decades is often not very helpful. Added to these myths is the fact that some cerebellar strokes appear very similar to vestibular neuritis.  Poor understanding of vertigo leads to fear and avoidance of seeing these kinds of patients, which leads to continued poor knowledge, more avoidance and so on.  I call this the Vertigo Vicious Cycle of Vexation.  And most emergency physicians are caught in that cycle. The problem, as illustrated by the case, is that most of the patients with AVS (constant vertigo, which is worse with head movement, nausea/vomiting, difficulty walking, AND nystagmus) have vestibular neuritis (VN).  But some will be have a posterior circulation stroke (PCS). There are other rarer causes of AVS but, functionally, the differential diagnosis in AVS is VN vs stroke.  Many, but not all, patients with PCS will have other central features. It would be unusual for a patient with VN to have a new significant headache or neck pain, which are red flags for a cerebellar hemorrhage or vertebral artery dissection. Other concerning features would include focal weakness or paresthesia, or diplopia, dysarthria, dysmetria, dysphagia, dysphonia, or spontaneous vertical nystagmus or the inability to walk unaided. Any of those features in a patient with vertigo and nystagmus at rest should make you very concerned that your patient is having a stroke.  The first line of defence against missing a PCS should therefore be screening for thee central features, and NOT the HINTS exam.  If you find any of those central features, work them up for stroke. What do we do with the majority of patients who have AVS but, none of those central features, like in the case scenario? Do we just say: “no neuro findings, must be VN, and send them home” or do we get an MRI in them all? Since most patient with AVS (again with nystagmus) have VN, the cost and availability of MRI for this indication becomes a real practical issue.   In addition, MRIs done within the first 24 hours of onset can miss approximately 20% of PCS. (Shah et al AEM 2022). Should we admit all of these dizzy patients for two or three days and get an MRI? Some well-funded systems do that, but most systems are simply unable to afford such practices. Therefore, there is a great need for a clinical test with excellent negative predictive value to rule out stroke in these low risk AVS patients with no central features. The HINTS plus exam has been shown in expert hands to have a -LR of 0.01, that’s pretty darn low. (Newman-Toker et al AEM 2013) The key phrase is in “expert hands”. David Newman-Toker is an MD, PhD and Professor of Neurology, Ophthalmology, & Otolaryngology. This leads back to the question of can the HINTS exam be correctly applied and interpreted in the hands of an emergency physician? The SRMA by Ohle et al AEM 2020 suggested they cannot. In the one study that included a specially trained emergency physician, the diagnostic accuracy of the HINTS exam was not impressive: sensitivity was 83% and specificity was 44%. In Kerber’s 2015 study, there was only one emergency physician amongst the three physicians using the HINTS exam.  The HINTS should be seen as an extra safety measure to ensure we aren’t missing a stroke in patients suffering with what is most likely vestibular neuritis. It is very important to stress that the HINTS exam should not be viewed as a stand-alone test on all patients presenting with vertigo. The HINTS exam must also be applied in the correct clinical situation. In a retrospective chart review of 2,309 patients presenting with dizziness, the HINTS exam was misapplied 97% of the time. (Dmitriew et al AEM 2021). This study showed the drawbacks of applying a new, somewhat sophisticated bedside examination technique without training.  If you just handed out ultrasound machines in the 1990’s without training, you'd be getting similar bad results. Again, HINTS should only be used in patients with significant, constant vertigo AND spontaneous nystagmus who don’t have the central features we already described. The HINTS exam consists of three bedside tests: assessment of nystagmus, test of skew, and the head impulse test. The HINTS “plus” exam is HINTS with the addition of a bedside test of hearing (the finger rub test) to help pick up an AICA stroke. An anterior inferior cerebellar artery stroke can present with the other HINTS exam findings identical to vestibular neuritis, as the AICA stroke produces an infarct of the organs of balance and hearing as well as part of the cerebellum.  So, a new hearing loss in a patient who presents with vertigo and findings consistent with a vestibular neuritis in that same ear signals a potential AICA stroke.  The bedside test of hearing can pick up these AICA strokes and make the negative predictive value for HINTS even higher. The questions remain: how much training is required to use the HINTS exam in clinical decisions, and how should it be taught? And, if you decide to not use the HINTS exam, what are you using to evaluate these patients in its place? The paper we will discuss compares the HINTS exam to the STANDING protocol.  STANDING is an algorithm by Dr. Vanni et al.