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.

 

 

 

In my relatively new position running a Balance Disorders program at a large teaching hospital, I am exposed to a very different patient population than what I encountered in my private practice. One example of this is being exposed to patients that have recently undergone cochlear implantation.

 One recent case triggered my curiosity about how often a patient might experience a vestibular injury, or some temporary vestibular symptoms, following implant surgery. This nice lady was doing well with her implant. She was in her sixties and hearing for the first time in years. About two weeks after the surgery, she woke to vertigo, nausea and disequilibrium.  The surgeon asked me to see her that same day.

On arrival, she had spontaneous nystagmus following Alexander’s law, beating away from the implant side.  This pattern would be interpreted as a likely recent reduction in function of the labyrinth in the implant ear. This pattern is most often the result of a viral inflammation of a branch of the vestibular nerve that connects the inner ear to the brain (a condition known a vestibular neuritis) . The patient had no prior viral symptoms, and it would have been awfully coincidental to occur two weeks after surgery. Her rotary chair on that day also suggested a recent reduction in labyrinthine function on the implant side. A recheck one week later showed improvements in all of the above, including her symptoms.

I decided to review the literature regarding vestibular symptoms or measurable dysfunction after cochlear implantation. Here is summary of what I found:

Several studies measured caloric responses on the implant side, both pre and post surgery. Reports indicate that there is a measurable reduction in caloric response in about 30% when averaging these several studies. One study also looked at changes in rotational chair results and saw reduction in VOR response in about 30%.  In a small study, cVEMP responses were reduced in 40%.

 Subjectively, these changes don’t always translate into significant or prolonged symptoms. Some studies showed a significant increase in complaints of dizziness shortly after surgery, while one large study showed no change at 4 months post-surgery.

 It seems that patients undergoing cochlear implant surgery might benefit from counseling that changes in vestibular function are not unusual, may cause some temporary symptoms, but are unlikely to have lasting effect.

Photo courtesy of National Institute of Health