PERIPHERAL NEUROPATHIES: The nonsystemic vasculitic neuropathies
Nonsystemic vasculitic neuropathy (NSVN) is an under-recognized single-organ vasculitis of peripheral nerves that can only be diagnosed with a nerve biopsy. A Peripheral Nerve Society guideline group published consensus recommendations on the classification, diagnosis and treatment of NSVN in 2010, and new diagnostic criteria for vasculitic neuropathy were developed by the Brighton Collaboration in 2015. In this Review, we provide an update on the classification, diagnosis and treatment of NSVN. NSVN subtypes include Wartenberg migratory sensory neuropathy and postsurgical inflammatory neuropathy. Variants include diabetic radiculoplexus neuropathy and — arguably — neuralgic amyotrophy. NSVN with proximal involvement is sometimes termed nondiabetic lumbosacral radiculoplexus neuropathy. Cutaneous polyarteritis nodosa and other skin-nerve vasculitides overlap with NSVN clinically. Three patterns of involvement in NSVN have been identified: multifocal neuropathy, distal symmetric polyneuropathy, and overlapping multifocal neuropathy (asymmetric polyneuropathy). These patterns lack standard definitions, resulting in inconsistencies between studies. We propose definitions and provide an up-to-date differential diagnosis of multifocal neuropathy. Available evidence suggests that NSVN and neuropathy-predominant systemic vasculitis might be controlled better by treatment with corticosteroids and an immunosuppressive agent than with corticosteroids alone. Treated NSVN rarely spreads to other organs, but 30% of patients experience a relapse. Long-term neurological outcome is favourable, but chronic pain is common.