Biomechanical assessment of botulinum toxin effects in Pisa syndrome disease

Pisa syndrome is defined as a postural deviation that could occur among patients with Parkinson's disease, and it is described by a lateral flexion of the trunk (greater than 10 degrees respect to the vertical alignment). The pathophysiology of Pisa syndrome is still not clear but different hypothesis, based on the investigation of altered posture, have been proposed involving the hyperactivity of spinal and abdominal muscles and the description of the relationship between postural control and vertical perception deficit. Different clinical solutions have been adopted and tested with experimental studies. Among them, the treatment with botulinum toxin of paraspinal muscles contributed to the reduction of muscles hyperactivity, bending angles and subjective evaluation of pain. The current research deals with the analysis of botulinum toxin effects on 13 Pisa syndrome patients. A standardized botulinum toxin treatment protocol was applied to all subjects. Subjects performed standing posture in natural and self-corrected conditions before and 1 month after the treatment. Spine kinematics, body weight distribution and muscles activations have been considered as objective biomechanical parameters for the analysis. Two healthy subjects participated to the test as control group. Results highlighted significant differences in body weight distribution for both natural (p-value=0.02) and correct (p-value=0.008) posture, with an improved symmetry after the treatment. Moreover, a significant reduction (p-value=0.002) of the modification in the contralateral muscle pattern was pointed out when assuming a correct posture. Despite the differences in kinematic posture do not highlight significant results, the investigation of several biomechanical features indicated a positive effects of botulinum treatment with potential clinical implications.