Auditory brainstem evoked responses and vestibular evoked myogenic potentials: potential biomarkers in Parkinson\u2019s disease

Abstract

ObjectiveThe aim of this study was to investigate brainstem functions in Parkinson’s disease (PD) through studying auditory brainstem evoked responses (ABRs), and ocular and cervical vestibular evoked myogenic potentials (oVEMP and cVEMP) and to explore their relation with motor symptoms, if any.Study designFifteen individuals diagnosed as having idiopathic PD and 15 age-matched controls were included. The PD patients were evaluated using the Unified Parkinson’s Disease Rating Scale, the Hoehn and Yahr Scale, and the Schwab and England Scale. The subscores of major symptom were calculated, such as tremor, rigidity, bradykinesia, and axial signs. During medication ‘on’ states, PD patients and controls underwent pure-tone audiometry, speech audiometry, tympanometry, ABR, oVEMP, and cVEMP. The test findings in PD patients were grouped into ipsilateral and contralateral results in relation to the clinically more affected motor side and were compared with the age-matched controls.ResultsPD patients showed abnormal ABR wave morphology, prolonged absolute latencies of ABR wave V, and I–V interpeak latencies. Absent responses were the evident abnormality seen in oVEMP. Prolonged latencies with reduced amplitudes were seen in cVEMP responses. The main motor features of PD (rigidity and bradykinesia) were correlated to the ABR and cVEMP responses contralateral to the clinically more affected side.ConclusionDysfunction at different levels of the brainstem was confirmed in patients with PD. The impairment of ABRs and VEMP responses is related to characteristic clinical asymmetry of PD and its cardinal motor features. ABRs and VEMPs could be used as potential electrophysiological biomarkers for PD.