This week, we will review an article by Dr. David Newman-Toker. Dr. Newman-Toker has been a leader in the movement to change the way patients with sudden onset acute vertigo are evaluated. The primary concern of the physician evaluating these patients is to determine, as best possible, “Is this a stroke versus a benign labyrinthine condition?”
Historically, patients presenting to the Emergency Department (ED) with vertigo are primarily assessed through imaging. Imaging should identify stroke, right? Not so fast. In the first 48 hours after symptom onset, a Cranial CT scan is only 16% sensitive for detecting stroke in the brainstem or cerebellum, and MRI, though much better, is only 83% sensitive. So, the old adage, “Let’s get an MRI just to be sure” isn’t such a sure bet after all. Is there a better way?
We have discussed the HINTS protocol in the past, but today I want to review some sensitivity and specificity data that Dr. Newman-Toker has made available. HINTS is a mnemonic for Head Impulse, Nystagmus, and Test of Skew.
According to Dr. Newman-Toker:
Head Impulse- A normal horizontal Head Impulse test is the single best test to separate a stroke from Vestibular Neuritis (VN),a more common peripheral vestibular cause of acute sudden onset vertigo. He reports that an abnormal Head Impulse test is 85% sensitive and 95% specific for VN.
Nystagmus – If nystagmus is present and is direction changing, this is considered only 38% sensitive, but 92% specific for stroke. By direction changing, we are describing nystagmus that is right beating in gaze right, and left beating in gaze left. Nystagmus associated with VN is direction fixed, meaning it won’t change direction as a result of change in gaze.
Test of Skew – This refers specifically to vertical ocular misalignment (one eye is fixed higher than the other, and can be detected by performing the cover test), and is referred to as “Skew Deviation.” When Skew Deviation is present, it is highly specific (98%) for stroke, but is only 30% sensitive for detecting stroke.
Editors Note and Summary:
When a patient arrives with acute sudden onset spontaneous vertigo, the examiner can take a couple of minutes to assess the patient far faster, far cheaper, and far more accurately than CT scan and even MRI. If the patient has direction fixed nystagmus and a positive Head Impulse test, it is almost certainly a peripheral cause. If the patient has direction changing nystagmus, there is a high probability of stroke. If the patient has Skew Deviation, there is an even higher possibility of stroke. If you see none of the above, you are right back where you started.