From the Research
The side lying test should be performed by having the patient sit on an examination table and then quickly lie down on their side with the affected ear facing downward, observing for nystagmus and asking about vertigo symptoms, as this test can help differentiate between peripheral and central vertigo, with the most recent and highest quality study 1 providing evidence on the usefulness of nystagmus patterns in distinguishing peripheral from central acute vestibular syndromes. To perform this test, have the patient sit on an examination table and then quickly lie down on their side with the affected ear (the one they report causes dizziness) facing downward.
- Observe for nystagmus (involuntary eye movements) and ask about vertigo symptoms.
- In peripheral vertigo (like benign paroxysmal positional vertigo), nystagmus typically appears after a brief latency period of 1-5 seconds, is rotatory or horizontal in direction, lasts less than one minute, and fatigues with repeated testing.
- The patient will also report significant vertigo symptoms.
- In central vertigo (caused by brainstem or cerebellar issues), nystagmus appears immediately without latency, may be purely vertical or direction-changing, persists longer than one minute, and doesn't fatigue with repeated testing.
- Symptoms may be milder despite pronounced nystagmus. This test works because peripheral vertigo results from displaced otoconia in the semicircular canals that move with position changes, while central vertigo stems from neural pathway dysfunction that doesn't respond to positional changes in the same characteristic way, as discussed in 2 and 3. Always perform this test with caution in elderly patients or those with neck problems, and be prepared to assist patients who experience severe vertigo during testing, as the side-lying test has been shown to be a useful alternative to the Dix-Hallpike test in certain cases, with a high sensitivity and specificity, as reported in 4 and 5.