Comment

Good to know that computed tomography (CT) scans are worthless in these cases. I will be sure to send a copy of this article to the patient I recently saw with dizziness and an acute brainstem infarct on CT scan. He had just been sent home from a stroke center with no CT scan.

How does this balance with the malpractice payout for missed stroke diagnosis? How about factoring in the time spent responding to patient complaints and to peer review?

Take-home point: CT is not worthless in the evaluation of dizziness. It is what the patient expects; it is what the peer-review panel (in retrospect) will expect. A normal CT makes for a happy patient and protects the doctor, very worthwhile in my opinion.

—Alan J. Sorkey, MD
Shreveport, Louisiana

Response

Alan, I sense some tension in your voice. You are wise to recognize that many patients do not fit our anticipated paradigm(s) for stroke presentation and do not have to conform to our diagnostic expectations either. Having said that, I think the question at hand is whether to image or not as opposed to the use of CT or magnetic resonance imaging (MRI). The data are clear. Compared to CT, diffusion-weighted MRI is better suited for the evaluation of acute cerebral ischemic events in general and, in particular, posterior fossa ischemia. I would speculate that this patient presented with enough clinical findings (ie, not isolated dizziness) that appropriately prompted the need for imaging, and if MRI were selected, the referenced patient’s brainstem infarct would have been identified. Thus, the identification of the infarct on CT, to me, speaks more to the severity of the infarct than it does to the superiority of CT to diffusion-weighted MRI.

I couldn’t agree with you more that if MRI is not available, CT may be the only alternative. However, providers should be well aware of its limitations and consider informing patients of the same. I would also suggest that whenever possible, we begin to change our ordering patterns to move from CT to MRI for evaluation of posterior fossa ischemia, which may eventually improve availability of this important diagnostic modality.

As risk managers, we have to part ways in our thinking. First, as outlined in my original article, appropriate patient selection is key. If the patient is very low risk for posterior fossa ischemia, imaging may not be indicated (ie, isolated dizziness odds ratio 0.20 for serious neurological cause). Although reducing utilization, meeting patient expectations, and reducing one’s professional liability risk is a challenging and fine balance, I would suggest that overutilization of CT, which is known to be inferior for the disease being looked for, shouldn’t be the answer. I do agree that patients have expectations. However, until we ask each individual patient, we cannot presume to know what those expectations are; communication is key. I do agree that many may expect imaging. However, most patients will not possess the sophistication to fully understand if imaging is indicated or not and which imaging modality is best for their presentation. It is our job to shape expectations, educate our patients, and employ shared decision making to meet the patient’s needs. I believe that this approach substantially reduces risk to the patient and the providers. Again, if CT is utilized, the provider should include an explanation of its limitations. Otherwise, patients may be left with the impression that normal CT means no stroke or serious neurological disease, and that is a path toward medical-legal disaster.

Thank you, Alan, for submitting this very important perspective.

—Kevin M. Klauer, DO, EJD, FACEP
Medical Editor-in-Chief, ACEP Now

Comment

Since a large percentage of posterior fossa strokes are from vertebral artery dissections, what is the value of CT angiograms?

—Chuck Pilcher, MD, FACEP
Kirkland, Washington

Response

Thank you for your question. To provide some additional background for the readership, in general, dissections are responsible for 2 percent of all ischemic strokes but are more of a concern in those under 45 years, representing 20 percent of ischemic strokes in this age group. The annual incidence of spontaneous carotid dissection has been estimated to be 2.5 to 3 per 100,000 while that of vertebral arteries is 1 to 1.5 per 100,000.^1,2 The most common symptoms associated with vertebral artery dissection are vertigo (58 percent), headache (51 percent), and neck pain (46 percent).² Although CT angiography may demonstrate a vertebral artery dissection, MRI/MRA is the preferred diagnostic modality for vertebral artery dissection.²

—Kevin M. Klauer, DO, EJD, FACEP
Medical Editor-in-Chief, ACEP Now

Comment

Although it is good to see an emphasis on the diagnosis of the dizzy patient, Dr. Klauer is perpetuating another myth—that “nystagmus is unreliable.” He is right that the mere presence of any kind of nystagmus does not help to differentiate peripheral from central causes of the acute vestibular syndrome. However, that is akin to saying that “the presence of ECG changes is unreliable” for diagnosing an acute coronary syndrome (ACS). All abnormalities are not created equal; a flat T wave does not have the same significance as ST segment elevation.

It’s the same with nystagmus. Its mere presence does not always help—but the kind of nystagmus is very helpful to the diagnostician in sorting out the cause of dizziness. Some of the source for this comes from the Chase article, but this article (I was an author) only described presence or absence of nystagmus (unfortunately, this is the way more emergency physicians chart it), but it’s not meaningful.³

In a patient with ongoing dizziness, one should be hesitant to diagnose vestibular neuritis or labyrinthitis if there is no nystagmus. The nystagmus is “direction-fixed”—ie, the fast component always beats to the same side no matter what direction the patient is looking in.

On the other hand, direction-changing nystagmus in this setting means that there is a central process (probably stroke). So does torsional or vertical nystagmus. Patients with peripheral causes will have direction-fixed horizontal nystagmus.

In positional (episodic) dizziness, these rules shift. Emergency physicians must learn some of the details about nystagmus as it can really help us to make a confident diagnosis.

The presence/absence of nystagmus, but more important, its quality, is very helpful in making a specific diagnosis in dizzy patients.

—Jonathan Edlow, MD
Boston

Response

Jonathan, thank you for submitting your thoughts. I will certainly defer to your expertise on this topic and appreciate the work you have done to improve our understanding of headache and other serious neurological diseases.

Honestly, I don’t think, fortunately for me, we are that far apart on our thinking.

My statement, “Nystagmus is an unreliable sign and does not differentiate serious neurological disease from other causes of dizziness,” was made in reference to the article by Chase et al, which stated, “Nystagmus was only present in one-third of those with stroke and in one-fifth without stroke.”3 Thus, nystagmus is an unreliable sign with respect to ruling in or ruling out stroke, particularly when, as you noted, many emergency physicians only document its presence or absence.

This is much akin to the ECG analogy you provided: “‘the presence of ECG changes is unreliable’ for diagnosing an acute coronary syndrome.” Although I agree completely that all ECG changes are not created equal, I do think that ECGs are unreliable for diagnosing ACS. ECGs alone, their specific abnormalities, and the presence or absence of those abnormalities are unreliable in exclusively ruling in or ruling out ACS. Thus, they are an important part of the evaluation but could never be used in isolation for risk stratification.

My intent was to draw a bright line between reliability and usefulness. It appears we agree on two things for certain: “the mere presence of any kind of nystagmus does not help to differentiate peripheral from central causes of the acute vestibular syndrome,” and that, when present, the quality of nystagmus does have utility, particularly when a detailed assessment can be performed, as you have adeptly outlined in your letter.

Thank you for the instruction and valuable input.

—Kevin M. Klauer, DO, EJD, FACEP

Medical Editor-in-Chief, ACEP Now

References

1. Redekop GJ. Extracranial carotid and vertebral artery dissection: a review. Can J Neurol Sci. 2008;35:146-152.
2. Merwick Á, Werring D. Posterior circulation ischaemic stroke. BMJ. 2014;348:g3175
3. Chase M, Joyce NR, Carney E, et al. ED patients with vertigo: can we identify clinical factors associated with acute stroke? Am J Emerg Med. 2012;30:587.