Peripheral Neuropathy in Parkinson's Disease: A Systematic Review

Background: Parkinson’s disease is a neurodegenerative disease that primarily affects the part of patients‘brain that is responsible for movement according to the Parkinson’s foundation.
Objective: This review aimed to assess the frequency of Peripheral Neuropathy (PN) in Parkinson's disease (PD) cases and assess its functional impact on objective measures of balance and gait.
Methods: A systematic study was conducted to identify relevant literature, utilizing various databases like PubMed, Scopus, Web of Science, Cochrane, and EMBASE for Peripheral neuropathy, Parkinson’s disease, wearable health-technology and functional impact. Primary research papers published in English involving patients diagnosed with PD who underwent comprehensive clinical, neurophysiological, and/or neuropathological assessment for PN were included. Information extracted included patient numbers, PN prevalence rates (LFN/SFN), metabolic risk factors, objective functional gait parameters (speed & stride length), and fall history. A structured systematic review was performed, and the results regarding PN prevalence, etiology, and functional consequences in PD were collated and analyzed.
Conclusion: PN prevalence in PD ranges from 4.8% to 55%. The pooled estimated occurrence of biopsy-proven small fiber neuropathy (SFN) is 56.9% and large fiber neuropathy (LFN) is 16.3%. PN is significantly associated with a higher frequency of falls (50% vs. 14% in controls, p=0.043). PN causes quantifiable deficits, including shorter stride length (P-value equal to 0.029) and slower gait speed (P-value equal to 0.005). Risk factors include Levodopa exposure and vitamin B12 deficiency (OR: 2.667). PN is a prevalent and independent risk factor for falls and gait impairment in PD, often operating independently of conventional PD motor severity (MDS-UPDRS III). Targeted assessment and intervention for PN are warranted to reduce patient disability.