A young patient presents with nausea and spinning vertigo. There are no focal neurologic deficits to suggest stroke, no stroke risk factors, no neck pain or neck trauma to suggest vertebral dissection.
And yet, the patient has severe gait instability, which can be an indicator of a stroke. Is this alone a reason to order an MRI?
This is the exact situation where head impulse testing plays a role in the ED. The head impulse test is a test of peripheral labyrinth function. The labyrinths sense head movement, and send a signal to the eyes to maintain visual gaze despite head movement.
Turn your head side to side while reading this text. No problem right? If you had vestibular neuritis you could not do it. The head impulse test is a way of testing these vestibulo-ocular reflexes.
HOW TO DO IT:
Face your patient, put your hand on each side of the patient’s head, have them look at your nose, and jerk the head 10 degrees to one side, very abruptly. The normal person can maintain fixation on your nose. The vestibular neuritis patient will break gaze, and you will see a catch-up saccade as they look back again at your nose.
An abnormal test is reassuring that this is a peripheral vertigo problem. It is exactly in the SEVERE cases of vestibular neuritis that you are more likely to see a catch-up saccade. It is not 100% specific, as rare patients with strokes will also have catch-up saccades. But this is rare, and in the patient with a low prior probability of stroke, the head impulse test is probably sufficient to effectively rule out stroke.