Gait instability in patients with acoustic neuroma.

OBJECTIVE

To investigate pathological gait in patients with unilateral acoustic neuroma using tactile sensors placed under both feet.

MATERIAL AND METHODS

Forty-three patients were enrolled in the study. They were categorized into two groups: the small tumor group had tumors < 2 cm from the porus acousticus without any brainstem compression and the large tumor group had tumors > 2 cm from the porus acousticus with brainstem compression. Eighteen healthy subjects served as controls. Subjects were asked to walk freely with eyes open or closed for a distance of nearly 8 m. The coefficients of variation (CVs) of stance, swing and double support were calculated. The stability of the trajectories of the center of force and the foot pressure difference were also studied.

RESULTS

The CVs of stance, swing and double support were significantly greater with eyes closed and, with the exception of double support, these differences were greater in the tumor groups. The instability of the trajectories of the center of force was significantly greater in the tumor group, and in the large tumor group the horizontal component of sway movement of the trajectories of the center of force of the foot on the same side as the lesion was greater than that on the intact side with eyes closed. Regarding foot pressure differences between the two feet, the large tumor group had a greater foot pressure for the foot on the same side as the lesion than for the foot on the intact side, especially with eyes closed. No significant difference was found in the small tumor group.

CONCLUSION

The presence of acoustic neuroma may cause unstable gait, and steady gait is considerably dependent on visual input. Larger tumors may produce shifts in the body's center of gravity to the lesioned side during gait, especially under conditions of visual deprivation. These abnormalities may reflect some influences on gait control systems such as phase and muscular tonus control systems.