Abstract
Degeneration of several brainstem nuclei has been long related to motor and non-motor symptoms (NMSs) of Parkinson’s disease (PD). Nevertheless, due to technical issues, there are only a few studies that correlate that association. Brainstem auditory-evoked potential (BAEP) and vestibular-evoked myogenic potential (VEMP) responses represent a valuable tool for brainstem assessment. Here, we investigated the abnormalities of BAEPs, ocular VEMPs (oVEMPs), and cervical VEMPs (cVEMPs) in patients with PD and its correlation to the motor and NMSs. Fifteen patients diagnosed as idiopathic PD were evaluated by Unified Parkinson’s Disease Rating Scale and its subscores, Hoehn and Yahr scale, Schwab and England scale, and Non-Motor Symptoms Scale. PD patients underwent pure-tone, speech audiometry, tympanometry, BAEP, oVEMPs, and cVEMPs, and compared to 15 age-matched control subjects. PD subjects showed abnormal BAEP wave morphology, prolonged absolute latencies of wave V and I–V interpeak latencies. Absent responses were the marked abnormality seen in oVEMP. Prolonged latencies with reduced amplitudes were seen in cVEMP responses. Rigidity and bradykinesia were correlated to the BAEP and cVEMP responses contralateral to the clinically more affected side. Contralateral and ipsilateral cVEMPs were significantly correlated to sleep (p = 0.03 and 0.001), perception (p = 0.03), memory/cognition (p = 0.025), and urinary scores (p = 0.03). The oVEMP responses showed significant correlations to cardiovascular (p = 0.01) and sexual dysfunctions (p = 0.013). PD is associated with BAEP and VEMP abnormalities that are correlated to the motor and some non-motor clinical characteristics. These abnormalities could be considered as potential electrophysiological biomarkers for brainstem dysfunction and its associated motor and non-motor features.
Highlights
Parkinson’s disease (PD) is a common neurodegenerative disorder caused by degeneration of midbrain dopaminergic neurons of substantia nigra (SN) producing its primary motor cardinal features [1]
Brainstem auditory-evoked potential (BAEP) and vestibularevoked myogenic potential (VEMP) responses represent a valuable tool for brainstem assessment as the neural pathways of both ocular vestibular-evoked myogenic potential (VEMP) and cervical VEMPs pass through the brainstem [12]
Detailed motor and non-motor scores of the PD patients are presented in Tables 1 and 2
Summary
Parkinson’s disease (PD) is a common neurodegenerative disorder caused by degeneration of midbrain dopaminergic neurons of substantia nigra (SN) producing its primary motor cardinal features [1]. The NMSs consist of autonomic dysfunction, sensory symptoms, neuropsychiatric disturbances, sleep disorders, fatigue, and gastrointestinal disorders [2]. Those NMSs are associated with dopaminergic and non-dopaminergic dysfunctions including serotoninergic, noradrenergic, and cholinergic systems [3, 4]. Alpha-synuclein pathology related to NMS was described in brain hemispheres, brainstem, spinal cord, and peripheral nervous system [5]. Some NMS-related pathological changes might have specific distribution and anatomical localization in various levels of the brainstem. Depression and REM sleep behavior disorder are related to degeneration of pontine nuclei [5]
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