Morning Report: 6/18/2013

A set of 3 tests used to specifically differentiate central from peripheral etiology in setting of acute vestibular syndrome/ AVS (rapid onset (seconds to hours) of vertigo, nausea/vomiting and gait unsteadiness with head-motion intolerance and nystagmus lasting days to weeks.  BPPV is not in the differential of AVS, because, according to the authors, BPPV should last less than 24hrs).

Hi = Head impulse testing

N = Nystagmus

TS = Test of skew

Head impulse testing looks specifically at the vestibulo-occular reflex (VOR).  The patient is asked to maintain gaze fixation as the head is turned side-to-side (about 20˚).  The test is positive if patient looses gaze fixation during head turning.  A positive test = peripheral pathology.  If negative (normal), and pt has vertigo, this strongly suggests central pathology.

Nystagmus testing:  In peripheral vertigo, nystagmus should be in same direction whether the gaze is to right or left.  Test is positive (= central pathology) if direction-changing nystagmus is present on eccentric gaze.

Test of skew:  Tests processing of vestibular information in brainstem nuclei.  The test is performed by having patient maintain gaze fixation, while tester alternates covering one eye.  The is positive (= central pathology) if vertical refixation eye movements are present.

These test have a reported sensitivity and specificity of 85%/ 95%, 38%/92%, and 30%/ 98% respectively, but as a set, sensitivity and specificity is 100%/ 96%.   The set is positive (indicating central pathology), if any one of the tests suggests central pathology.

A mnemonic to remember the test results that equal central pathology: INFARCT (Impulse Normal, Fast-phase Alternating, Refixation on Cover Test).

According to authors, the exam takes about 1 min to perform and can be taught to non-specialists.

It out performs MRI during the initial 24-48 hrs of presentation (MRI in first 24-48 hrs Sensitivity 80%, specificity 97%)

Of course, CTH performs poorly, with a sensitivity of 26% for posterior circulation strokes.

1. Data is from 2 studies looking at 184 patients- not yet validated.

2. Might not be generalizable- Populations tested was highly selected, having clinically consistent peripheral vertigo, and at least 1 of defined risk factors (age, htn, dm, prior stroke)

3. Requires skill of tester

4. Severely vertiginous patient may not be able to tolerate.

1. Multiple prodromal episodes of dizziness

2. Neck pain or headache

3. Focal neurologic Sx

4. Age >50y

5. Other Vascular risk factors (DM, HTN, HCHoles, smoking, etc.)

6. History of trauma

The exam is probably most useful for patients who have intermediate pre-test probability for central vertigo.

Check out the links below for videos of the exam, and a great PV card from Dr. Lin at ALIEM.

Benign Paroxysmal positional vertigo.  BMJ Best Practice.  Updated 9/7/12.  Retrieved online 5/10/13

Denninghoff, K.  The Clinical Differentiation of Cerebellar Infarction from Common Vertigo Syndromes.  Western Journal of Emergency Medicine.  Nov 2009, Vol. 10, No. 4.

Halker, R.  Establishing a Diagnosis of Benign Paroxysmal Positional Vertigo Through the Dix-Hallpike and Side-Lying Maneuvers; A critically Appraised Topic. The Neurologist. May 2008. Vol 14, No 3.

Mattu, A. et al.  Avoiding Common Errors in the Emergency Department.  Ch 188, 440-441 Wolters Kluwer, May 24 2010. 1st ed.

Newman-Toker, D. et al.  Normal Head impulse test differentiates acute cerebellar strokes from vestibular neuritis.  Neurology.  June 10, 2008.

Strayer, R. Benign Paroxysmal Positional Vertigo and Acute Otitis Externa in the ED: Current Guidelines.  Guidelines Update.  EMpractice November 2009, Vol1 No 2.

Olshaker, J.  Dizziness and Vertigo.  Rosen’s Emergency Medicine, 7th Ed., Ch 12.  Mosby 2010.