Citations

ABSTRACT Background and Aims Nonsystemic vasculitic neuropathy classically presents as a painful asymmetric axonal neuropathy, multiple mononeuropathies or radiculoplexus neuropathy. Demyelinating electrophysiologic features are rare and may lead to misdiagnosis. We describe a patient with biopsy‐proven vasculitic neuropathy presenting as a severe symmetric demyelinating polyradiculoneuropathy. Methods Clinical, electrophysiologic, imaging, laboratory, and histopathologic findings are presented. Results A 57‐year‐old man developed acute ascending weakness, sensory loss, facial weakness, and areflexia following a febrile illness, with initial improvement before developing recurrent neurological decline 6 weeks after initial symptom onset despite treatment with intravenous immunoglobulin and plasma exchange. Cerebrospinal fluid protein was elevated. Nerve conduction studies demonstrated prolonged distal motor latencies, slowed conduction velocities, conduction block, and prolonged blink reflex latencies, fulfilling 2021 European Academy of Neurology/Peripheral Nerve Society electrodiagnostic criteria for chronic inflammatory demyelinating polyradiculoneuropathy (CIDP). MRI demonstrated mild but diffuse lumbosacral plexus enlargement and T2 hyperintensity. Sural nerve biopsy ultimately demonstrated evidence of epineurial inflammation and microvasculitis with ischemic nerve injury, accompanied by both increased rates of axonal degeneration (12%) and segmental demyelination (9%) on teased fiber analysis. Treatment with corticosteroids and rituximab resulted in complete neurological recovery. Interpretation Vasculitic neuropathy may closely mimic CIDP clinically, radiologically, and electrophysiologically. Clues to the vasculitis diagnosis were prominent neuropathic pain, dense denervation on electrophysiology, and poor response to typical CIDP treatment. Peripheral nerve biopsy remains a critical tool in the evaluation of atypical or treatment‐refractory inflammatory neuropathies.

BACKGROUND Perineural spread (PNS) of colorectal carcinoma (CRC) is a rare and challenging diagnosis. Its clinical and radiological presentation is often subtle and can overlap with radiation-induced neuropathy and malignant nerve tumors, complicating timely diagnosis. The role of circulating tumor DNA (ctDNA) in the detection of PNS has not been previously described. OBSERVATIONS A 48-year-old man with a history of rectal cancer and perineural invasion presented with progressive, refractory sciatic neuropathic pain. Conventional surveillance imaging was initially negative despite subtle rising of carcinoembryonic antigen and ctDNA levels. Subsequent MRI revealed abnormalities of the lumbosacral plexus and sciatic nerve, and fascicular biopsy confirmed metastatic CRC involving the sciatic nerve, establishing the diagnosis of PNS. LESSONS This case highlights PNS as a rare but important consideration in patients with focal neuropathic symptoms and prior CRC. Circulating tumor DNA positivity may serve as an early indicator of occult tumor activity even within the nerves when imaging is equivocal. However, currently histopathological confirmation remains the only definitive method to distinguish PNS from alternative diagnoses and is essential to guide appropriate management. https://thejns.org/doi/10.3171/CASE25997