Salivary gland immunohistochemistry vs substantia nigra sonography: comparative analysis of diagnostic significance

Abstract

Introduction. Parkinson's disease (PD) urges for new instrumental methods of diagnosis. Transcranial sonography of the substantia nigra (SN TCS) is an established method for early PD diagnosis but its application is limited. Recently, biopsies (primarily that of salivary gland) and test for abnormal α-synuclein are suggested to verify PD. Materials and methods. We assessed 12 individuals with PD, Hoehn–Yahr 2.3 ± 0.4. The assessments included: UPDRS, NMSQ, NMSS, RBDSQ, PDQ-8, MoCA, and HADS scoring; SN TCS; and sublingual gland immunohistochemistry for phosphorylated α-synuclein (PS-129) with automated morphometric analysis. Results. Substantia nigra hyperechogenicity was shown in 75% of patients whereas biopsy revealed PS-129 in 100% of patients. Echogenic area of the substantia nigra was 0.24 [0.21; 0.3] cm2. PS-129 inclusion area varied from 28.47 [27.55; 96.26] to 238.77 [234.13; 272.49] μm2, and PS-129 proportion varied from 13.4% to 93.4% of the nervous fiber area across the patients. We found relations between PS-129 and NMSQ (r = 0.8; p 0.001), NMSS (r = 0.9; p 0.001), PDQ-8 (r = 0.7; p = 0.003), UPDRS-I (r = 0.7; p = 0.009), UPDRS-II (r = 0.6; p = 0.03), and HADS (anxiety r = 0.8; p = 0.002; depression r = 0.6; p = 0.04) scores. Conclusion. The results demonstrate a higher biopsy sensitivity as compared to SN TCS. Automated morphometric analysis has been newly applied to assess PS-129 occurrence. Immunohistochemistry results are directly related to non-motor symptom severity, which may indicate high probability of PS-129 presence and diagnosis confirmation in early disease.