Head-Shaking (2-3 Hz)

Head-shaking: instruct the patient to close their eyes and perform active rapid head-shaking at 2-3 Hz for ~15 secs. If a unilateral vestibulopathy is present, head-shaking-induced (contralesional) nystagmus is often provoked, with the slow phase toward the affected ear. With central lesions, the nystagmus may be vertical (see example - https://collections.lib.utah.edu/details?id=1550674&q=hyperventilation&fd=title_t%2Cdescription_t%2Csubject_t&facet_setname_s=ehsl_novel_gold) or may change direction from the baseline spontaneous nystagmus. If there's strong HSN without clear unilateral vestibular loss (https://collections.lib.utah.edu/details?id=1295175), think about a central process