Objective: To investigate clinical and transcranial B-mode sonography (TCS) characteristics of benign phenotype of Parkinson’s disease (bPD).

Background: Parkinson’s disease (PD) progression is heterogeneous. A bPD has been associated with younger age at onset and tremor-dominant presentation. Data on TCS among bPD is scarce.

Method: We retrospectively collected data of PD patients with at least 5-year from diagnosis (from 2010 to January 2021). We defined bPD by the combination of a Hoehn & Yahr stage (HY)≤ 2.5, Schwab and England scale (SE)≥70, absence of dementia and stable antidopaminergic treatment with levodopa equivalent daily dose (LEDD)≤400mg after ≥ 5 years from the diagnosis.  Patients who did not meet these criteria were included as a control group. Demographic data on the diagnosis, and UPDRS III, HY, SE, motor complications, non-motor symptoms, antiparkinsonian medication, concomitant medication (benzodiazepines, selective serotonin-reuptake inhibitors (SSRI), antipsychotics) and TCS characteristics at the last follow-up visit, were collected and compared between groups.

Results: From a total of 268 PD patients, 59 (22%) met criteria for bPD. The two groups had similar age at onset (71.47 vs 69.34 years; p=0.117) and disease duration (8.25 vs 9.11 years, p=0.233). bPD had lower UPDRS-III scores (6.14 vs 15.94, p<0.01), lower LEDD (247.95 vs 820.95, p<0,001) and lower prevalence of dyskinesias and motor fluctuations (p<0,001). Except for hyposmia (p=0.12), bPD had lower prevalence of non-motor symptoms (constipation, REM sleep behavior disorder, visual hallucinations p≤0.001). In addition, bPD was associated with lower prevalence of exposure to benzodiazepines (p=0.003), SSRI (p=0.002), and antipsychotics (p=0.010).  TCS was performed in 54 patients and showed substantia nigra hyperechogenicity (SN+) in 24 PD patients (61.5%). bPD had significantly lower prevalence of SN+ compared to the control PD group (8.3% vs 91.7%, p=0.006). There were no differences in the width of the third ventricle and the frontal horns of the lateral ventricle.

Conclusion: Despite similar age of onset and time of evolution between bPD and control PD, bPD has fewer motor and non-motor symptoms, less concomitant medication as well as less SN+. These results suggest that bPD may be a distinct clinical entity from PD or the end of clinical spectrum of PD.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/clinical-and-transcranial-sonography-characteristics-in-benign-phenotype-of-parkinsons-disease/