Paired neurophysiological and clinical approach to brainstem assessment in Parkinson’s Disease

Abstract

Background Recent research has highlighted the role of brainstem (BS) structures in the early spread of Parkinson’s Disease (PD) pathological process. Vestibular Evoked Myogenic Potentials (VEMPs) corresponding to the Vestibulo-Ocular (VOR), Vestibulo-Masseteric (VMR) and Vestibulo-Collic (VCR) reflexes can provide information on BS function. Aims: to test the aforesaid set of VEMPs in a cohort of PD patients and healthy controls and to correlate it with presence of symptoms ascribable to BS dysfunction. Methods 19 PD patients (age 66.9 ± 5.4 years; 12 males; mean disease duration 6.16 ± 3.54 years) and 15 age and sex matched controls underwent bilateral recording of VOR, VMR and VCR from inferior oblique, masseter and sternocleidomastoid active muscles, respectively. PD patients were additionally administered a series of clinical scales used for evaluation of brainstem-integrated activities, namely sleep disorders (Epworth Sleepiness Scale, Parkinson’s Disease Sleep Scale and REM Sleep Behavior Disorder-Screening Questionnaire or RBD-SQ), postural instability (MiniBESTest) and depression (Geriatric Depression Scale). Groups’ comparisons were performed with χ 2 test and Mann–Whitney U-test; Sperman’s rho test was used for correlation analysis. Results VEMPs were significantly impaired in patients compared to controls, absence being the main pattern of alteration. When the set of the 3-VEMP battery was analyzed, both number of altered reflexes ( p = 0.017) and severity of alteration ( p = 0.001) were significantly higher in patients than controls. As for each single VEMP, only the VOR and the VMR were significantly altered (VOR: p = 0.022; VMR: p = 0.005; VCR: p = 0.056). Clinical scales revealed the presence of some degree of depression in 36.8% of patients, sleep disturbances in 68.4%, REM sleep disorder in 26.3% and postural instability in 36.8% of PD patients. A significant correlation with VEMP alterations was found only for high scores on RBD-SQ ( ρ = 0.554; p = 0.014). Conclusions Combined assessment of VOR, VMR and VCR was able to detect BS dysfunction in a rostro-caudal extension in PD. This may prove interesting in the perspective of identifying neurophysiological markers of BS dysfunction in early stages of the disease.