Dynamic assessment of imbalance in acoustic neuroma patients by sway magnetometry

INTRODUCTION: Imbalance may be a significant problem for patients with acoustic neuromas. Prospective data on patients with acoustic neuromas to establish how the vestibular system performs dynamically, in the perioperative phases, is not available. Posturography is an established method of measuring balance and sway magnetometry has been developed as a reliable technique in this field. AIMS: Prospectively to assess pre- and postoperative dynamic vestibular function in patients with acoustic neuromas using sway magnetometry. METHODS: Sway patterns were recorded on 12 patients with acoustic neuromas tested under two sets of conditions: first, a baseline test for 120 s, repeated after 120 s of vestibular stimulation. After each test a validated questionnaire to assess balance subjectively was compeleted: before operation and 1, 3 and 6 months after operation. RESULTS: (1) Patients with acoustic neuromas demonstrate 'overswing' on baseline testing: most exaggerated 1 month postoperatively. After vestibular stimulation the 'recovery' time was prolonged to 50 s postoperatively, 62 s postoperatively (1/12), 43 s (3/12), and 47 s (6/12) postoperatively. (2) Mean path length (normal range, 163-287 mm) was increased in all groups: preoperative = 332 mm, 1 month postoperatively = 358 mm, 3 months postoperatively = 308 and 6 months postoperatively = 343 mm (3) The Dizziness Handicap Inventory scores were elevated at all times of testing and significantly correlated with baseline path length (rs = 0.6, P = 0. 03) and vestibular stimulation path length (rs = 0.7, P = 0.01) preoperatively. CONCLUSIONS: This is the first dynamic, prospective study of balance in patients with acoustic neuromas. Abnormal sway patterns and prolonged recovery times pre- and postoperatively, most marked at 1 month, were demonstrated. A subjective assessment of balance disturbance reflected these abnormal sway measurements confirming its clinical usefulness.