SGEM-HOP Ultrasound in High Fidelity Simulation

The most recent SGEM-HOP podcast took a look at ultrasound in high fidelity simulation.  Ken and I got a chance to speak with Dr. Paul Olszynski from the University of Saskatchewan.  He recently authored the following article in which two novel ultrasound interventions were introduced for emergency medicine resident simulation training.  The CJEM article is […]

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SGEM-HOP Update

Hey all,  If you haven’t been listening to the Skeptics Guide to Emergency Medicine – Hot off the Press (SGEM-HOP) series, why not?  This series of podcasts is the ultimate in early knowledge translation, with articles from Academic Emergency Medicine (AEM) and the Canadian Journal of Emergency Medicine (CJEM) being reviewed with the authors of the […]

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SGEM-HOP and CAEPCAST

Hey all, Over the past few months I’ve been working on two podcasts, SGEM-HOP and CAEPCAST. The first Canadian edition of the SGEM-HOP podcast (Skeptics Guide to Emergency Medicine-Hot off the Press) was recently released. Working with Ken Milne of The SGEM, Hot off the Press critically appraises an article from the Canadian Journal of Emergency […]

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HINTS Exam for Vertigo: Caveat Emptor

 

Hey all,

The March edition of Journal Club reviewed the HINTS exam for acute vestibular syndrome.  Much has been written/podcasted in the FOAM world about this controversial article, with the HINTS exam being touted as a godsend by some, while others recommend cautious use.  In addition to the usual critical appraisal of the article, journal club leaders Anthony Seto, Vanessa Potok and Andrew McRae also had us review the recommendations of 4 FOAM resources based on the HINTS article.  The FOAM recommendations were highly variable, to say the least. This post should be enlightening to many of us, and highlights the importance of actually reading articles yourself and critically appraising them, rather than implicitly taking advice based on the recommendations of a blog.

Article: HINTS to Diagnose Stroke in the Acute Vestibular Syndrome: Three-Step Bedside Oculomotor Examination More Sensitive Than Early MRI Diffusion-Weighted Imaging 

Jorge C. Kattah, Arun V. Talkad, David Z. Wang, Yu-Hsiang Hsieh, and David E. Newman-Toker. Stroke. 2009;40:3504-3510.

HINTSVertigo

Image courtesy emjclub.com

Before getting into the nitty gritty, these are a few major reasons we should be cautious with use of the HINTS exam.

1)The definition of the acute vestibular syndrome (AVS) is continuous vertigo for > 24 hours. Ie: Not intermittent vertigo.  There is a very small subset of patients who actually have AVS, and in general we would likely have a higher index of suspicion for ominous causes in patients with continuous vertigo.  At journal club we agreed that many of us were applying this to patients with intermittent vertigo.  These patients were not included in the study.

2)This was done by a single neuro-ophthamologist using specialized equipment (Frenzl goggles) on a small number of patients (n=101) who were referred to a tertiary care stroke center from 25 community centres.  Most of us are not likely using Frenzl goggles in the ED, nor have we had specific training in this exam.  The study needs to be validated by EPs performing the exam in a typical group of patients presenting primarily to the ED.

caveat-emptor

 

Image courtesy takenotenigeria.com

Here are the FOAM blog views on this article.

Blogs: ALiEM, BoringEM, EM Nerd, EP Monthly

BlogKey MessagesLimitations and InaccuraciesIf you had a “blog-based” practice, how would reading this SINGLE blog affect how you practice?
ALiEM“HINTS seems just as good as diffusion weighted MRI to diagnose posterior stroke”. INFARCT is acronym to use to remember central features on HINTS exam (Impulse Normal, Fast-phase Alternating, Refixation on Cover Test) The paper’s key message is that HINTS is better than MRI for ruling out stroke, rather than “just as good” to “diagnose” Since HINTS is as good as MRI, I would just use HINTS.
BoringEM Notes evidence for HINTS “very strong”. ONLY use for persistent and continuous vertigo.Proceed with HINTS exam with caution, since we don’t expect the same high sensitivity and specificity when used by non-expert clinicians.Okay to use HINTS < 24h, since the study enrolled patients >1h. Does not go into critically appraising the paper to support the statement that evidence is “very strong” I would only use HINTS for persistent/continuous vertigo, but only with caution, since I am not an expert in the technique
EM Nerd Head impulse hard to do and may produce vertebral artery dissection. 2013 HINTS versus ABCD2 acts as validation set. However, ABCD2 was not designed to differentiate between central versus peripheral, so of course HINTS would perform better. Specialist does HINTS. Small sample size. Very select population.In high risk patient, HINTS would be used to rule out central cause and symptoms.

HINTS could aid decision making process for low risk patients to help identify a subtle presentation of central vertigo.

Until HINTS is examined in ED, performed by ED docs, and on our patients, cannot know if any benefit and if it will contribute to clinical decision making.
Inaccuracy: “Sensitivity of 96%” is not acceptable to safety r/o central cause. It was the specificity that was 96%. Sensitivity was 100%. I will be cautious about performing HINTS until it is studied as performed by emergency docs on a less high risk population.
EP Monthly The people performing HINTS in the study were well trained (neuroophthalmologist, neurologist).

HINTS only if continuous vertigo.
Overall, pro-HINTS I need to make sure the residents in my program get trained in HINTS. Only trained people should use HINTS, but if trained, we should all be using it

 

Criticalappraisal

Now let’s critically appraise the article.

METHODS/SETTING/DESIGN/NUMBER OF PATIENTS INCLUDED

  • Prospective, cross-sectional study performed at single urban, academic hospital serving as regional stroke referral centre for 25 community hospitals

Patients were recruited from the emergency department (n=59), other institutions (n=37), admitted patients with cerebellar infarctions (n=4), and one outpatient (n=1). A total of 101 patients studied, collected over 9 years. 65% were men with mean age 62 (range 26 – 92 years old).

  • Single neuroophthalmologist did HINTS exam on patients
  • HINTS exam was performed between 1 hour to 9 days from symptom onset (mean 26 hours). 75% were examined within 24h of symptom onset.
  • All patients underwent neuroimaging generally after bedside HINTS. If they had imaging prior to HINTS, examiner was blinded to these results at time of assessment. 70% were imaged within 6h of symptom onset. 97% were imaged within 72h of symptom onset.
  • All patients (including those with suspected acute peripheral vestibulopathy) were admitted for observation and serial daily examinations
  • Stroke diagnosis: MRI with DWI (97%) or CT
  • Acute peripheral vestibulopathy diagnosis: absence of stroke in brainstem/cerebellum on MRI with DWI, lack of neurological signs on serial exam, and characteristic clinical course, +/- caloric testing
  • Eight patients with initial negative MRI later underwent repeat MRI for unexplained neurological signs suggesting brainstem localization

INTERVENTION/CONTROL

  • One neuroophthalmologist conducted HINTS exam
    • HI = Head Impulse
    • N = Nystagmus
    • TS = Test of Skew
  • “Benign” HINTS = abnormal “HI”, direction-fixed “N”, and absent “TS”
  • “Dangerous” HINTS = normal/untestable “HI” or direction-changing “N”, or present/untestable “TS”


INCLUSION CRITERIA

  • Core features of acute vestibular syndrome (rapid onset of vertigo, N/V, and unsteady gait +/- nystagmus). Note that duration of symptoms was not important to be included in the study, some patients had ~ 1 hr of symptoms prior to HINTS exam.
  • At least 1 stroke risk factor
    • Smoking
    • Hypertension
    • Diabetes
    • Hyperlipidemia
    • Atrial fibrillation
    • Eclampsia
    • Hypercoagulable state
    • Recent cervical trauma
    • Prior stroke
    • Prior MI

 

EXCLUSION CRITERIA

  • History of recurrent vertigo +/- auditory symptoms

OUTCOMES

  1. Determine diagnostic accuracy of skew deviation for identifying stroke in acute vestibular syndrome: compare proportions with skew deviation in peripheral versus central cases
  2. Determine added value of skew deviation beyond h-HIT: stratify results by horizontal head impulse test findings
  3. Compare HINTS exam’s sensitivity and specificity for presence of stroke

RESULTS

  1. Skew present in 17% of the 101 studied subjects and was associated mainly with brainstem lesions
    1. Skew in 4% (n=1 of 25) with acute peripheral vestibulopathy, 4% (n=1 of 24) with pure cerebellar lesions and 30% (n=15 of 50) with brainstem lesion (chi-squared, P=0.003)
  2. Skew correctly predicted lateral pontine stroke in 2 out of the only 3 cases in which an abnormal horizontal head impulse test erroneously suggested peripheral localization (Table 3, below)
  3. Dangerous HINTS = 100% sensitive and 96% specific for central lesion (Table 4, below)

STUDY CONCLUSIONS

  1. Skew deviation is insensitive for central pathology but fairly specific for brainstem involvement for patients with acute vestibular syndrome
  2. Skew may help identify stroke when a positive head impulse test falsely suggests a peripheral lesion
  3. HINTS appears more sensitive (100% for HINTS) and specific (96% for HINTS) than MRI with DWI in detecting stroke in first 24-48 hours after symptom onset

CRITICAL APPRAISAL

  • Internal validity
  • Pros
    • An appropriate reference standard was used initially: neuroimaging
    • Cons:
    • Partially unmasked examiner: although masked to results of imaging, was not masked to patient’s clinical history, general neurological exam, or obvious oculomotor findings
    • Selective MRI follow-up scans: MRI follow-up was only obtained for selected cases based on evolution of new neurological signs or atypical subtle oculomotor signs, potentially leading to the misclassification of strokes and acute peripheral vestibulopathy, increasing apparent sensitivity
    • Observer bias in interpretation of eye findings may inflate HINTS sensitivity
    • Unclear whether radiologist was blinded to HINTS exam results
    • Unclear whether there may have been other eye exam components that would be useful for predicting stroke and a validation study would be required if the current study functions as just derivation data
    • Relatively small sample size (N=101)
  • External validity
    • Pros:
    • HINTS is not very time consuming to do, and it is free
    • HINTS may be useful for the right patient population, i.e. active symptoms to avoid labeling a normal head impulse test as “central” in normal patients
    • Acute vestibular syndrome in the literature is defined as >24 hours. The study enrolled patients between 1 hour to 9 days. It seems to suggest that HINTS can be used for patients presenting as early as 1 hour after symptom onset.
    • Cons:
    • Generalizability of exam technique: HINTS was performed by a neuroophthalmologist and not by emergency physicians
    • Single examiner: unsure if testing style can be replicated by others
    • Restricted enrollment to high-risk patients: unclear whether results can be extrapolated to lower-risk population. However, there were some younger patients in the mix (15 were less than 50 y.o. and 6 were less than 40 y.o.). It was not clear which patients of what age had which risk factors, and if those combinations would make one at “lower” or “higher” risk.

It may have been useful to stratify patients into ataxic versus non-ataxic, since we are more concerned about what to do about patients who have less obvious neurological findings.

UCalgary Journal Club Group

These points were discussed during Journal Club on March 19, 2015:

  • In a patient with acute vestibular syndrome, who had a normal CTA and reassuring HINTS, would you send them home? 43% would consult neurology first. 57% would send the patient home.
  • Would you incorporate HINTS as an additional part of your physical examination? Most people agreed they would consider incorporating the HINTS components as part of their examination and, in particular, examining for high-risk nystagmus and skew deviation. There appeared to be agreement that the head impulse test may be challenging to perform, and we may not have adequate inter-rater reliability with a single, experienced neuro-ophthalmologist.
  • If you do use HINTS, ensure you use it on the right patient population: i.e. someone who has active persistent vertigo (acute vestibular syndrome patient) and not an intermittent vertigo like BPPV.
  • You may consider downloading a slow-motion camera application on your mobile device in order to detect the subtle ocular symptoms. However, the safety and accuracy of this practice has not been rigorously evaluated. Evidence in support of slow-motion applications is anecdotal at best, and its use is not recommended without evidence of its utility.
  • It may be challenging to differentiate between a normal versus abnormal head-impulse test. Moreover, an abnormal head-impulse test, although should imply a peripheral cause, can still mean a central cause. Therefore, direction-changing nystagmus and present skew deviation may be elements of HINTS less challenging to interpret.
  • Although there are many limits to the generalizability of the HINTS exam, if it can be conducted on the right patient population using appropriate technique, it may add to your overall diagnostic evaluation for patients with acute vestibular syndrome. Consider reviewing the HINTS exam: http://empablogsite.com/2014/08/hints-exam/

There are many online resources and blogs that pertain to Emergency Medicine. Views may differ and there may often be limitations and inaccuracies. Remember to keep a critical mind when reading the online blogs and consult other resources as well as the primary source article.

Thanks again to Anthony Seto and Vanessa Potok for compiling this excellent summary.

 

Cheers,

Chris

 

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