STN-DBS implanted patient frequently develop axial symptoms, such as gait and speech disorders, after this surgical procedure, which dampens long-term quality of life of Parkinson's disease patients. The pathogenesis is not completely understood, as it could be either due to a long-term stimulation side effect or a symptom with later onset in disease progression which is not well controlled with actual stimulation program. In case of freezing of gait onset in STN-DBS, literature suggest reducing stimulation frequency. Although, low pulse width is a promising option to tackle speech disorders after STN implant, it is not known its potential therapeutic potential on freezing of gait.~The aim of this investigation is to compare the effect of low frequency and short pulse width stimulation in patients, who develop axial symptoms during long-term follow-up in chronic conventional STN DBS.~As per protocol, participants will be assessed at baseline with chronic standard stimulation parameters (60 us and 130 Hz) then they will be randomly allocated either to a low-frequency (80Hz) or a low-pulse arm (30 us). The study is designed such that after scheduled re-assessment the participant will be switched from low frequency arm to short pulse width and vice versa according to the crossover nature of protocol design. Both the rating investigator and the participant are blinded to the allocation, whereas an unblinded investigator will modify the parameters according to allocation arm.
The aim is to compare the effect of reducing the conventional pulse width or frequency of stimulation for axial symptoms occurring after Subthalamic nucleus Deep Brain Stimulation (STN DBS) treatment. The participants will be assessed with chronic stimulation with conventional stimulation parameters, namely 60 us and 130 Hz, and after random allocation to short pulse width (30 us) or low frequency (80 Hz).