Objective: To understand to what extent an early cochlear dysfunction may represent an additional non-motor signature of Parkinson’s disease (PD) patients. Further, whether it may correlate with disease progression rate and prognosis.

Background: In line with recent contributions, we have been extensively documenting the impairment of cochlear functions in PD patients. Further, we found a significant asymmetry in the auditory functions when challenged by otoacoustic emissions and audiometric hearing levels (1,2). Actually, both parameters were worse on the body side more affected by motor symptoms. Which mechanisms underlie this finding is still under review.

Method: Pure tone audiometry and distortion product otoacoustic emissions are used as outcome variables in an ample cohort of PD patients. The original series included 80 patients (1), attributable to any PD stage. Of note, an advanced customized acquisition and analysis system was developed and used for otoacoustic testing, which guarantees response stability independent of probe insertion depth, and has the sensitivity necessary to accurately assess the low levels of otoacoustic response typical of elderly subjects. At present, the analysis is extended to a rather large cohort, well characterized in terms of clinical follow-up (phenotype, disease rate, therapy-response) and putative correlation with other NMS, namely cognitive traits and sleep architecture.

Results: So far, the degree of cochlear impairment, in denovo subjects, does not appear to correlate with PD phenotype (tremor-dominant versus akinetic-rigid or early gait impairment). In addition, when considering 2-3 Hoehn & Yahr stages, LEDD and/or levodopa sparing does not play any role. Preliminary results pose ground for a putative correlation with cognitive, subtle, dysfunctions. Yet, only the future completion of two years follow-up, together with the likely increase of inpatients visits in light of better control of COVID-19 pandemic, will allow to validate any significance.

Conclusion: The current enrollment of larger PD populations will ease the understanding of the pathophysiological mechanisms that may underlie asymmetric cochlear damage found in PD. Likely, mechanisms other than modulatory dopaminergic pathways in the lateral olivocochlear bundle (LOC) play a relevant role, among which the Brainstem cholinergic circuitry.

References: 1. Brain Commun 2020 Sep 18;2(2):fcaa144. doi: 10.1093/braincomms/fcaa144. eCollection 2020. Lateralization of cochlear dysfunction as a specific biomarker of Parkinson’s disease Renata Sisto 1, Andrea Viziano 2, Alessandro Stefani 3, Arturo Moleti 2, Rocco Cerroni 3, Claudio Liguori 3, Elena Garasto 3, Mariangela Pierantozzi 3 2. Laterality of Auditory Dysfunction in Parkinson’s Disease.Cerroni R, Pierantozzi M, Moleti A, Stefani A, Sisto R, Mercuri NB, Liguori C, Garasto E, Viziano A.Mov Disord. 2020 Jul;35(7):1283-1284. doi: 10.1002/mds.28131.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/lateralization-of-cochlear-dysfunction-as-a-specific-biomarker-of-parkinsons-disease-role-for-cholinergic-transmission/