Effects of deep brain stimulation on balance and gait in patients with Parkinson's disease: A systematic neurophysiological review.

Deep brain stimulation (DBS) of the subthalamic nucleus (STN) and internal globus pallidus (GPi) deep brain stimulation (DBS) provides an efficient treatment for the alleviation of motor signs in patients with Parkinson's disease. The effects of DBS on gait and balance disorders are less successful and may even lead to an aggravation of freezing of gait and imbalance. The identification of a substantia nigra pars reticulata (SNr)-mesencephalic locomotor region (MLR) network in the control of locomotion and postural control and of its dysfunction/lesion in PD patients with gait and balance disorders led to suggestion that DBS should be targeting the SNr and the pedunculopontine nucleus (part of the MLR) for PD patients with these disabling axial motor signs. However, the clinical results to date have been disappointing. In this review, we discuss the effects of DBS of these basal ganglia and brainstem structures on the neurophysiological parameters of gait and balance control in PD patients. Overall, the data suggest that both STN and GPi-DBS improve gait parameters and quiet standing postural control in PD patients, but have no effect or may even aggravate dynamic postural control, in particular with STN-DBS. Conversely, DBS of the SNr and PPN has no effect on gait parameters but improves anticipatory postural adjustments and gait postural control.