Increased body sway at 3.5-8 Hz in patients with phobic postural vertigo

Postural sway during upright stance was analyzed in 12 patients with phobic postural vertigo (PPV) and in 12 age-matched healthy volunteers. Recording s were made under different conditions (with the eyes open or closed): when standing on a foam rubber pad with the head upright, turned 30 degrees to the right or left, or during 1 Hz horizontal head oscillations. Sway analys is included calculation of sway path, of root mean square values of sway an d of the power spectrum of sway in fore/aft and lateral directions. There w as a significant increase in sway activity in the 3.53-8 Hz frequency band in patients with PPV. This did not impair objective postural stability. Inc rease in higher frequency sway activity may simply reflect a change in post ural strategy rather than a sensorimotor dysfunction. The patients' conscio us control of stance may augment co-activation of anti-gravity muscles, a s trategy applied by normal subjects when performing demanding balancing task s. (C) 1999 Elsevier Science ireland Ltd. All rights reserved.