Peripheral Nervous System Involvement

Vasculitis is an uncommon but treatable and thus important cause of neuropathy. Vasculitic neuropathy can occur as an isolated entity (nonsystemic vasculitic neuropathy) but more frequently evolves in the setting of a systemic vasculitis. Polyarteritis nodosa, anti-neutrophil antibody-associated vasculitides (especially microscopic polyangiitis and eosinophilic granulomatosis with polyangiitis), rheumatoid vasculitis, and cryoglobulinemic vasculitis are the systemic disorders most commonly associated with neuropathy. Both systemic vasculitic and nonsystemic vasculitic neuropathy usually present with a subacutely progressive, asymmetric/multifocal, painful, distal-predominant, axonal, sensory-motor phenotype. Available evidence suggests that nonsystemic and most systemic vasculitic neuropathies are mediated primarily by T-cell mechanisms, but immune complexes probably contribute. Evaluation of patients with suspected vasculitic neuropathy usually includes EMG, laboratory studies, and nerve/muscle biopsy. In patients lacking definite vasculitis in nerve biopsy, clinically probable vasculitic neuropathy can be diagnosed by recourse to supportive clinicopathologic findings. Vasculitic neuropathies occurring in the ANCA-associated vasculitides are treated in accordance with the underlying systemic vasculitis. About 50% of neuropathy-predominant primary systemic vasculitides are not controlled by initial corticosteroid monotherapy. IVIg or rituximab can induce remission in refractory or relapsing patients. Long-term outcome is reasonably good.