Through selective tests of the function of the canal and otolith sense organs, it is possible to assert that patient conditions are purely otolithic and that the canals are not involved. The video head impulse test selectively tests each semicircular canal; the ocular vestibular-evoked myogenic potential to 500 Hz Fz (Fz is the location on the forehead in the midline at the hairline) bone-conducted vibration (BCV) selectively tests the utricular macula and the cervical vestibular-evoked myogenic potential to 500 Hz Fz BCV selectively tests the saccular macula. The development of new specific tests of otolith function has shown that some patients may have specific deficits of just otolithic function. In the authors' experience, patients who complain strongly of postural unsteadiness should be suspected to have otolithic deficits. They may also have vertigo and in some cases have spontaneous nystagmus of peripheral origin, even though their semicircular canal function is normal. The prognosis for such patients is good. They usually appear to regain their postural stability spontaneously over weeks (or longer), even though they still have an otolithic deficit as shown by objective tests when they are free of symptoms. It is not known what procedures may accelerate the recovery of otolith function.
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