Nerve biopsy
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6472243/
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8359441/
https://practicalneurology.com/articles/2024-apr/diagnosis-and-treatment-of-vasculitic-neuropathy
https://jnnp.bmj.com/content/79/12/1376
https://academic.oup.com/rheumatology/article/59/Supplement_3/iii55/5826896
https://onlinelibrary.wiley.com/doi/full/10.1002/mus.27201
https://jamanetwork.com/journals/jamaneurology/fullarticle/782848
https://www.mdpi.com/2075-4418/14/11/1169