We study in detail the influence of Otolith organ dysfunction on head
stability during locomotion. Participants were 20 patients (mean age, 54.0±11.6
years; mean height, 160.9±8cm) with unilateral Acoustic Neuroma (AN), and
9 age- and height-matched controls (mean age, 60.1±8.5 years; mean height,
162.7±8.1cm). All participants underwent measurement of ocular Vestibular
Evoked Myogenic Potential (oVEMP) and cervical VEMP (cVEMP). Subjects
were asked to walk freely with eyes open and closed while head movements
were analyzed using a 3-dimensional motion analysis system. With regard to
VEMP test results, oVEMP only, cVEMP only and both were abnormal in 3, 5 and
9 patients, respectively. Three patients showed normal results for both VEMPs.
Compared with controls, horizontal head movement was greater in patients with
abnormal oVEMP during eyes open and closed conditions and in patients with
abnormal results for both VEMP tests during the eyes closed condition, while
head movement in the pitch plane during walking with eyes open and closed,
and in the roll plane with eyes closed was greater in patients with abnormal
cVEMP or abnormal both VEMP tests. We conclude that, head stability in the
horizontal plane during locomotion is affected by utricular dysfunction, while
stability in the pitch and roll planes is affected by saccular dysfunction.