Intractable axonal neuropathy with multifocal peripheral nerve swelling in neuromyelitis optica spectrum disorders: A case report

We report a patient with neuromyelitis optica spectrum disorders (NMOSD) with anti-aquaporin 4 (AQP4) antibodies, who developed intractable axonal neuropathy presenting with multifocal peripheral nerve swelling by magnetic resonance (MR) neurography. A 52-year-old woman with a 12-year history of polymyositis and rheumatoid arthritis had been treated with prednisolone, tacrolimus, and abatacept (CTLA-4-Ig). She developed progressive numbness and tingling sensations in the distal parts of all limbs at the age of 50 years, followed by weakness of both upper limbs 6 months later. Neurological examination revealed severe muscle weakness and atrophy of the right upper limb with proximal dominance, diffuse moderate weakness of the left upper limb, severe sensory impairment of all modalities of four limbs in glove and stocking distribution, wide-based gait with positive Romberg's sign, and absence of all tendon reflexes. She was diagnosed with NMOSD due to positive serum anti-AQP4 antibodies and a longitudinally extensive cervical spinal cord lesion on MR images. Intravenous methylprednisolone pulse therapy, plasma exchange and intravenous immunoglobulin administration were performed, which improved the spinal cord lesion on MRI, but did not ameliorate her symptoms. Notably, she also had axonal neuropathy characterized by asymmetrical, multifocal swelling of peripheral nerves by MR neurography. Histopathological examination of the biopsied sural nerve revealed axonal degeneration and endoneurial edema but no inflammatory cell infiltration. Although she was treated with intravenous methylprednisolone, intravenous immunoglobulin, oral prednisolone, tacrolimus and tocilizumab, her symptoms gradually progressed. Neurologists should be aware of co-existing intractable axonal neuropathy in NMOSD cases presenting as immunotherapy-resistant sensorimotor disturbances.