Clinical Studies and Results
Non-Invasive Techniques:
a) Transcranial Magnetic Stimulation (TMS)
Several clinical studies have explored the efficacy of TMS in PD treatment. A recent meta-analysis by [31] investigated the impact of repetitive TMS (rTMS) on motor symptoms in PD patients. The analysis included 34 randomized controlled trials with a total of 1,092 participants. The results indicated that high-frequency rTMS applied to the primary motor cortex or supplementary motor area significantly improved motor symptoms, as assessed by the Unified Parkinson’s Disease Rating Scale (UPDRS) motor scores. Moreover, some studies have reported positive effects of TMS on non-motor symptoms, such as cognitive function and mood [35].
Despite these promising results, the optimal stimulation parameters and treatment duration for TMS in PD patients remain to be established. Furthermore, TMS may cause mild discomfort or pain at the stimulation site and is contraindicated in patients with a history of seizures or implanted metal devices [32].
b) Transcranial Direct Current Stimulation (tDCS)
tDCS has also been the subject of several clinical studies in PD treatment. A systematic review and meta-analysis by [34] evaluated the effects of tDCS on motor and non-motor symptoms in PD patients. The analysis included 20 studies involving 536 participants. The results suggested that anodal tDCS applied to the primary motor cortex led to significant improvements in gait, balance, and cognitive function. However, the authors noted that the heterogeneity of stimulation parameters and treatment duration across studies warrants further investigation to determine the optimal tDCS protocol for PD patients.
Potential side effects of tDCS include skin irritation and discomfort at the stimulation site. In addition, the long-term effects of tDCS in PD treatment need to be further explored [36].
Minimally Invasive Techniques:
a) Vagus Nerve Stimulation (VNS)
Preliminary clinical studies have investigated the potential benefits of VNS in PD treatment. A pilot study by [37] assessed the safety and efficacy of VNS in 17 PD patients with motor fluctuations. After six months of treatment, participants experienced significant improvements in their UPDRS motor scores, as well as in non-motor symptoms, such as sleep and mood. The authors concluded that VNS could be a promising adjunctive therapy for PD patients who do not respond adequately to pharmacological treatments. However, larger-scale, randomized controlled trials are needed to confirm these findings and determine the optimal stimulation parameters for VNS in PD treatment [38].
b) Trigeminal Nerve Stimulation (TNS)
Clinical research on TNS for PD treatment is still in its early stages. A pilot study by [39] evaluated the safety and efficacy of external TNS (eTNS) in 12 PD patients with motor and non-motor symptoms. After 12 weeks of treatment, participants showed significant improvements in their UPDRS motor scores, as well as in sleep quality and cognitive function. The authors suggested that eTNS could be a promising non-pharmacological treatment for PD, but larger and longer-term studies are required to confirm its efficacy and safety.
In conclusion, next-generation cranial nerve stimulation and neuromodulation techniques have shown promising results in clinical studies, suggesting potential advantages over traditional pharmacological and surgical treatments for PD. However, further research is needed to establish the optimal stimulation parameters, treatment duration, and long-term effects of these innovative approaches, as well as to identify the patient populations that may benefit the most from these therapies.