To evaluate the prevalence of neuropathic symptoms in Parkinson's disease (PD).

Peripheral neuropathy is seen in 4.8%-55% of Parkinson's patients presenting predominantly as small fiber neuropathy with pain, paresthesia, and dysautonomia, and shares some overlapping features with PD. Use of levodopa and other comorbidities are common associated causes. Recent studies have found alpha synuclein deposition in skin biopsies of PD patients with autonomic dysfunction, but its association with peripheral neuropathy is uncertain. The co-occurence of both diseases leads to increased disability.

We conducted a retrospective study of 84 patients with PD followed at the UConn Health Neurology Clinic during 2020. Demographics, presence and duration of neuropathic symptoms since PD diagnosis, and other common causes of neuropathy were analyzed.

Neuropathic symptoms were detected in 41% (n=35) of PD cases, including tingling of lower extremities (15%), numbness of lower extremities (26%), dry eyes/mouth (25%), diaphoresis (8%), constipation (77%), and pre-syncope/syncope (29%). On average, patients reported neuropathic symptoms 25.5 months following PD diagnosis and 28% (n=10) had preceding symptoms, an average of 19 months prior to PD diagnosis. 46% (n=16) had a documented history of neuropathy but only 23% (n=8) underwent formal work up with EMG. None had skin biopsy. Alcohol use (p=0.194), thyroid disease (p= 0.236), use of levodopa (p=0.469), and diabetes (p=0.570) showed no significant correlation with the presence of neuropathic symptoms.

Our cohort showed similar prevalence of neuropathic symptoms as in prior studies, and confirms that routine neuropathic evaluation may be warranted. Additionally, inspection for alpha synuclein deposits in association with fiber density analysis in skin biopsies might elucidate the association of both diseases and improve patient care.