Last month, I came across a clinical review published in the Annals of Emergency Medicine1 that got me really excited!
It got me excited (in a geeky professional sense of course…) as it covered a topic that causes significant diagnostic difficulties in the ED for emergency practitioners, senior and junior alike.
This topic is that of distinguishing between peripheral and central causes of vertigo (dizziness) in patients presenting to EDs with acute onset of symptoms. This distinction causes great anxiety amongst practitioners as it is notoriously difficult to differentiate between the two causes and the prospect of discharging a patient home with a posterior circulation stroke is quite frankly a scary one.
I would suggest however that the bedside diagnosis is actually relatively easy. I have come across many papers/reviews/YouTube videos and attended multiple conferences where this was covered but this is probably the best review I have read in recent years. I therefore propose to summarise it in this short blog post.
As always, I would also suggest you read the original paper which can be accessed here for sake of completeness.
THE SCARY BITS
- three percent of ED patients present with dizziness, lightheadedness or imbalance
- for patients presenting in the ED with acute dizziness, the crucial differential diagnosis for the emergency physician is vestibular neuritis versus posterior circulation stroke
- misdiagnosis of posterior circulation stroke is a needle in haystack phenomenon (haystack = dizziness as presenting complaint, needle = posterior circulation stroke as a diagnosis)
- 28 – 59% (!) of cerebellar strokes are misdiagnosed in the ED
- posterior circulation strokes are missed more than twice as often as anterior circulation strokes
- the personal, economic and public health burdens of misdiagnosis are huge
THE CONFUSING BITS
- the words dizziness, lightheadedness or imbalance are not diagnostically meaningful
- these words are used interchangeably by both patients and clinicians adding to the confusion and diagnostic difficulties
- not all patients with acute onset of dizziness have nystagmus (regardless of the cause for dizziness)
- various medical and neurologic conditions can cause an isolated vestibular syndrome (Wernicke encephalopathy without confusion, anticonvulsant toxicity, multiple sclerosis etc.)
Do you see yet how potentially complex this could be? At the same time, the author suggests in his review that physical examination outperforms MRI scan for diagnosis in the first 48 hours!
And now do you see why I got so excited coming across this review? 🙂
SO HOW DO I DIFFERENTIATE BETWEEN THE TWO CAUSES IN THE ACUTELY DIZZY PATIENT?
The author simply suggests to use the below screening tool which consists of five questions to which you can get a dichotomous answer only:
- is there a central pattern of nystagmus?
- is skew deviation present?
- is the head impulse test negative (in patients with nystagmus)?
- are there any CNS signs on focused neurological exam?
- can the patient sit and walk unaided?
This is reproduced in a very good flowchart in the original article I strongly suggest you consult.
Do not get too worried if you do not understand it fully yet. Just keep reading…
As explained earlier in this post, it is worth mentioning that no single element of the history distinguishes reliably neuritis from stroke so you can probably forget all the traditional teaching given to you on how to do this based on history, risk factors, severity of symptoms etc. It is simply too unreliable.
The author however suggests that physical examination can accurately distinguish between the two entities and this is largely based on the HINTS test (Head Impulse Test, Nystagmus and Test of Skew). FOAMCast has a great summary here which links to other FOAm resources too.
The presence or absence of nystagmus is key as the HINTS test can only be only performed in patients WITH nystagmus. The author suggests to have additional tests at the bottom of the flowchart for those patients WITHOUT nystagmus.
Again, keep reading (I hope you’re still following me)…
The author mentions here (and I agree with him) that the elements of the HINTS test are not traditionally taught to EPs and (so far) only stroke neurologists could accurately distinguish the two entities using this test. I have myself experienced a huge knowledge gap in juniors and seniors alike when it comes to using this test in the ED. Just like the author, I would however argue that it is a fixable knowledge gap and we can learn to understand, perform and interpret the results of this mystical test.
After all, it is NOT the stroke neurologist who will seeing the acutely dizzy patient in the ED but indeed the emergency physician. It is therefore your duty to become acquainted with the below-described diagnostic technique if you do not want to misdiagnose your patients.
Breaking down for you the flowchart into simple questions/steps:
Step 1: is there a central pattern of nystagmus?
Despite the HINTS acronym, the author suggests you start with this assessment and this has been my clinical practice too. The reason behind this is this is probably the easiest and less intrusive test to carry out. The other reason is (as mentioned above) that you can carry out a HINTS test in patient with nystagmus only. So if there is no nystagmus, then you should straight skip to step 4 and 5.
If the answer however is yes to step 1, the cause is presumed to be central and the patient must be assumed to have a posterior circulation stroke.
The next question I hear you ask is: how can I differentiate between central and peripheral causes of nystagmus?
Very broadly speaking, the unidirectional gaze-evoked horizontal one is the only one that should re-assure you (as it points to a peripheral cause). All the others (direction changing, rotational, vertical etc) should start worrying you.
This is how I remember this but it is a very crude representation of something a bit more complex: I strongly suggest you consult and refer to the table found in the original article.
|no nystagmus||normal finding||rules out a vestibular neuritis but consistent with cerebellar stroke|
|spontaneous horizontal nystagmus in primary gaze||does not distinguish||more commonly observed with peripheral causes but is not diagnostic|
|gaze-evoked horizontal nystagmus that beats in only one direction||does not distinguish||suggest a peripheral cause but is not diagnostic|
|direction-changing gaze evoked horizontal nystagmus||central||this is always central but can be benign in cases of intoxication (ethanol, anticonvulsant)|
|pure vertical nystagmus||central||central cause always|
|torsional (also called rotatory) nystagmus||central||expected finding in BPPV but these patients do NOT present but acute vestibular syndrome but a triggered episodic vestibular syndrome|
|skew deviation||normally absent; its presence means a central cause||not very sensitive but if present then means a central cause|
Step 2: the skew deviation test
Again, this does not follow the order of the letters in the acronym but I do suggest you do this one next (this is the S so the last one in the HINTS). This is simple to do: it is an alternate cover test, looking for small vertical corrections of the target by the uncovered eye. This is is highly specific for a central cause (although not very sensitive) so if this is positive, you should continue to be worried about a central cause.
This YouTube video gives a nice demonstration of how to perform this test.
Step 3: the head impulse test
This is probably the most difficult to carry out (though you should be able to get better with practice) and this is the one that causes the most confusion as it is counterintuitive. It is a real headache to understand and remember for those who do not perform this test regularly (Ed – I always look this up for a refresher when assessing a patient with dizziness).
If I didn’t get your attention so far, I need you to focus now!
This is why it is counterintuitive:
- a positive (abnormal test) suggests a peripheral cause. You should worry less as it is likely to be a vestibular neuritis.
- a negative (normal) test should worry you as it suggests a central cause. This is because the reflex does not loop through the cerebellum and is therefore intact in a posterior circulation stroke.
This is how you carry out the test:
- have the patient fix their gaze on your nose
- hold their head and rapidly but minimally (this is important as your patient with dizziness will resist you) turn their head side-to-side by 10 – 15 degrees so they cannot predict the changing directions. I usually sit the patient on the edge of the examination couch (if they can) and warn them I have to get very close to them for this strange test (you need to be able to see their eyes).
The normal/negative is when the patient’s eyes stay locked on target (which is your big nose) and the positive/peripheral is when the eyes move with the head and there is a correctional saccade to bring the gaze back to your nose.
I have highlighted some letters on the above paragraph as it is how I used to remember what the results meant when I started doing this. Please ignore if you have your own way to remember this rather counter-intuitive test.
Stick to abnormal test is good, normal test is bad (even writing this down does not feel right!) 🙂
The saccade should be easily observable but there are suggestions from our FOAMed friends online that you could use the Slo-Mo function of your iPhone camera if you struggle with this. Scott Weingart made a great video of how to use the iPhone to record this (you will need a second pair of hands to perform the test or do the recording)
You really do need to understand, practice and master this test (probably in this order). It is important to explain what you are going to do to the patient as they will naturally resist you because of the very nature of their symptoms and most of your patients will be elderly with limited neck movements – be gentle!
Step 4: the focused neurological exam for patients without nystagmus
We mentioned above that the HINTS test can only be accurately carried out in patients with nystagmus. In those patients who present to you without nystagmus, you should skip step 1-3 and do a focused exam. Here you will specially test the cranial nerves for hearing changes, anisocoria, altered phonation and facial loss of pain or temperature sensation, plus cerebellar ataxia.
Step 5: test for ataxia and gait
Is the patient able to sit up unaided or walk unassisted? I usually simply ask the patient to sit up on the examination couch after reassurance and if this works, I test their gait. These can be challenging as they can be extremely dizzy in presentation and not very keen to cooperate with you. Patients with acute neuritis can usually walk though.
Regardless of this, however, a severe ataxia and/or gait inability would be a good reason to admit not only for safety reasons but further investigations too as you would not able to completely rule out a stroke.
I hope that I have managed to summarise a topic that covers an area of emergency medicine that still causes great difficulty to understand for EPs of all grades. It is important that you familiarise yourselves with the above diagnostic techniques as you will be seeing these patients presenting to your ED.
This is something you cannot just read and assume you will be able to perform at the bedside (even if you understand it). You will need to practice, practice and practice again… And refer to this post whenever you need to.
@baombejp on Twitter
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- Find out more about the St.Emlyn’s team
- A Simplified Approach to the Patient with Dizziness by emDocs
- Differentiating ‘benign’ from ‘dangerous’ vertigo/dizziness by Andy Neill
- EMCrit Podcast 33 – Diagnosis of Posterior Stroke by EMCrit
- Ataxia, incoordination and dysequilibrium Guidemap on LITFL