Electrophysiological Evaluation of Audiovestibular Pathway Dysfunction in Parkinson's Disease and Its Correlates: A Case Control Study

BACKGROUND: Parkinson's disease (PD) is associated with brainstem dysfunction causing non-motor symptoms. Vestibular evoked myogenic potential (VEMP) and brainstem auditory evoked potential (BAEP) are electrophysiological tests to assess the vestibular and auditory pathways in the brainstem. OBJECTIVES: To study the abnormalities of cervical VEMP (cVEMP) and BAEP in PD and to correlate the findings with the symptoms related to brainstem involvement. PATIENTS AND METHODS: cVEMP and BAEP were recorded in 25 PD patients and compared 25 age matched controls. The PD patients were assessed with the following clinical scales: REM Sleep Disorder Screening Questionnaire (RBD-SQ), Epworth Sleepiness Scale (ESS), mini-BESTest, Geriatric Depression Scale (GDS-15) and MMSE (Mini-mental state examination). The P13 and N23 peak latencies and the P13/N23 amplitude of cVEMP, the latencies of waves I, III and V, and the inter-peak latencies (IPL) of waves I-III, III-V and I-V of BAEP were measured. RESULTS: The PD patients showed prolonged latencies and reduced amplitude in cVEMP responses. They had abnormal BAEP in the form of prolonged absolute latencies of wave V, followed by wave III and I–V IPL with no significant difference in waves I and I–III IPL. The cVEMP abnormality was correlated directly with RBD-SQ and inversely with mini-BESTest scores. There were no correlations between cVEMP/BAEP abnormality and disease severity, GDS-15, ESS and MMSE. CONCLUSION: PD is associated with cVEMP and BAEP abnormalities that suggest auditory and vestibular pathway dysfunction in the brainstem and cVEMP correlates with the symptoms of brainstem degeneration like RBD and postural instability.