Vestibular contributions to the Romberg test: Testing semicircular canal and otolith function

Normal stance relies on three sensory inputs: vision, proprioception and vestibular function. The Romberg test, trying to stand with feet together and eyes closed, is familiar to every medical student as a test of distal proprioceptive impairment. It remains the best known of Romberg's many remarkable contributions to clinical neurology. In Romberg's time almost nothing was known about the function of the vestibular system. We now know that standing with the eyes closed on a compliant rather than a firm surface is more a test of vestibular than proprioceptive function. Peripheral vestibular function tests in clinical use today all rely on measurements of oligosynaptic brainstem reflexes. Short‐latency eye rotations in response to rapid, brief head rotations (head impulses) give an accurate, robust and reproducible measure of the function of any and each of the six semicircular canals. Short‐latency evoked potentials from sternomastoid and inferior oblique muscles in response to loud clicks or skull taps (vestibular evoked myogenic potentials) give an accurate and reproducible measure of the function of each and any of the four otolith organs. In the present paper, we briefly review what is now known about the anatomy and physiology of the peripheral receptors and brainstem pathways mediating these reflexes and examine how this knowledge can help interpret the Romberg test. At the time Romberg described his still universally used postural test, proprioceptive impairment, often from neurosyphilis, was the usual reason for a positive result. Since then we have learnt that vestibular impairment can also give a positive result but only when the test is done on a compliant surface (such as a foam mat) but not when done on a firm surface (the floor). Here we review recent advances in vestibular function measurement which are gaining general use.