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.