When do you obtain nerve biopsy to evaluate for vasculitic neuropathy in patients with distal symmetric polyneuropathies?

Excellent question. Vasculitic neuropathies can occur as part of systemic or isolated peripheral nerve vasculitis (PNSV). While the majority of PNSV presents as mononeuropathy multiplex (>50%), it is well known that the rest of the patients present either with confluent mononeuropathies (which began...