Comparative diagnostic sensitivity of the substantia nigra transcranial sonography and salivary gland biopsy in patients with Parkinson’s disease

Parkinson’s disease is a chronic neurodegenerative disease, the diagnosis of which remains challenging at the early stages, although clinical diagnostic criteria are developed. The diagnostic accuracy is only 58% for patients at early Parkinson’s disease stages. The sensitivity and specificity of transcranial sonography of the substantia nigra used for Parkinson’s disease verification is about 85% and 71%, respectively. It has been shown that the aggregates of α-synuclein in the nerve fibers in major salivary glands may be seen in Parkinson’s disease patients. The availability of the salivary glands for morphological study made it possible to investigate the approaches of the in vivo histological diagnosis of Parkinson’s disease based on the detection of α-synuclein aggregates in the nerve fibers innervating the glands.

Aim: To evaluate and compare the sensitivity of transcranial sonography of the substantia nigra and sublingual salivary gland biopsy.

Materials and methods: Six patients with clinically verified Parkinson’s disease were enrolled. Evaluation of the neurological state using special scales, transcranial sonography of the substantia nigra and sublingual salivary gland biopsy was performed.

Results: Mean age of patients was 59 [58; 60.7] years, mean disease duration period was 5 [3; 7.75] years and the mean Hoehn–Yahr stage was 2.25 [2; 2.5]. Hyperechogenicity of the substantia nigra was found in 3 of 6 patients and the substantia nigra sensitivity was shown to be 50%. Sublingual salivary gland biopsy was positive for α-synuclein in 6 of 6 patients and the sensitivity of method was shown to be 100%. No adverse events after biopsy were registered.

Conclusion: The sensitivity of sublingual salivary gland biopsy was higher than those of transcranial sonography of the substantia nigra, which indicates the prospect of using the biopsy method as a more sensitive diagnostic tool in Parkinson’s disease (1 table, bibliography: 19 refs)