Polyarteritis nodosa and other vasculitides often involve peripheral nerves causing single or multiple mononeuropathies (due to nerve ischemia), asymmetric polyneuropathy, and distal symmetric polyneuropathy.
A sural nerve biopsy along with a muscle biopsy are the best tissues for establishing the diagnosis of vasculitis. The nerve biopsy is diagnostic in over half of patients with systemic vasculitis and clinical neuropathy, and the diagnostic yield increases with the addition of a muscle biopsy.
Such biopsies show necrotizing arteritis, perivascular inflammatory infiltrates, hemorrhage and hemosiderin deposition, neovascularization in epineurial arteries, and variable changes in nerve fascicles, depending on the severity and stage of neuropathy. The muscle shows vasculitis and denervation atrophy.