Biopsy of the submandibular gland could confirm the presence of Parkinson’s disease (PD) in living patients with clinical symptoms, research suggests.
Charles Adler (Mayo Clinic, Scottsdale, Arizona, USA) and colleagues successfully obtained submandibular gland tissue from 12 of 15 patients with clinically diagnosed PD, and nine of these biopsies contained Lewy type α-synucleinopathy (LTS).
The researchers had previously identified the salivary glands as one of the peripheral nervous system sites most likely to harbour LTS and conducted post-mortem submandibular gland biopsies in patients with and without PD.
Currently, there is no way of confirming PD until post-mortem, and clinical diagnosis is reportedly between 46% and 90% accurate, they say. “A tissue biopsy diagnostic test for PD could improve our current ability to treat patients and revolutionize how we perform and validate research studies for PD.”
In the first four patients biopsied, with an 18-gauge needle and parallel insertion, tissue volumes ranged from 7.3 to 8.2 mm3, but the maximum area of submandibular gland tissue obtained was tiny or absent, at 0.0 to 1.6 mm2.
The team then changed the procedure to use a 16-gauge needle and perpendicular insertion, after which overall tissue volume increased to 13.1–34.0 mm3 and maximum submandibular gland tissue area increased to 0.0–9.8 mm2, with gland tissue obtained from all but one patient.
“Submandibular gland biopsies were performed as outpatient procedures, used only local anesthetic, and were well-tolerated,” Adler et al note in Neurology.
Nine of the 12 patients with usable results had gland tissue that was both morphologically consistent with nervous tissue and stained positive for phosphorylated α-synuclein.
Assuming, from rates in published studies, that 85% of the 12 patients with usable biopsies were correctly diagnosed, then it is probable that 10 of them had true PD, say the researchers. In this case, submandibular gland biopsy may be a very accurate means of confirming PD in living patients, they say.
However, they add that in their post-mortem study the biopsies missed affected tissue in two of 19 cases.
In an accompanying commentary, Albert Ludolph (University of Ulm, Germany) calls the findings “exciting”, and raises the possibility that the test might even be used as a preclinical marker, given research by Braak et al suggesting that PD may actually begin in the peripheral nervous system.
He says that “further technical refinement might improve the sensitivity of the procedure to the point of routine clinical utility”, but cautions that it needs further validation.
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