Inflammatory pseudotumor of nerve: clinicopathological characteristics and a potential therapy

We sought to determine the clinical, electrophysiological, neuroimaging, and pathological features of inflammatory pseudotumor of nerve. Five patients were identified. All cases presented with a gradually progressive mononeuropathy with symptoms of weakness, sensory loss, and prominent neuropathic pain. The median duration of symptoms was 7 months (range 3-36 months). Electrophysiological results were in keeping with chronic axonal mononeuropathies with variable findings of active denervation and reinnervation. MRI demonstrated irregular, large masses involving and surrounding nerve with heterogenous signal characteristics on T1- and T2-weighted and post-contrast sequences. Histopathological features of the nerve slightly varied but shared commonalities including chronic inflammatory infiltrates, increased collagen, and increased numbers of microvessels. Axonal degeneration and decreased density of myelinated fibers were also noted. Three patients were treated with weekly courses of intravenous steroids for 3 months. All reported improvement in pain and weakness. Inflammatory pseudotumor of nerve is not a neoplasm and has reactive features of inflammation, increased vascularity, and marked fibrosis. It presents as a progressive axonal mononeuropathy with weakness, sensory loss, and pain that may be episodic. The primary pathophysiology is unknown but the inflammation and response to treatment suggests that there may be an immune component.