[AQP4 positive neuromyelitis optica spectrum disorder: an atypical pathology with nerve root enlargement and peripheral nervous system damage in demyelination].

A 72-year-old woman with limb weakness was admitted to our hospital. Her symptoms began just one month prior to presentation and showed gradual progression, leading to difficulties in physical movement. She had undergone breast cancer surgery at the age of 70 years. Neoadjuvant chemotherapy with epirubicin, cyclophosphamide, and docetaxel was administered, and the patient subsequently underwent a simple mastectomy and axillary lymphadenectomy. Neurological examination revealed bilateral relative afferent pupillary defects, severe muscle weakness in the limbs, hyporeflexia of the lower extremities, sensory disturbances below Th1 level, dysuria, and constipation. MRI revealed a left internal capsule lesion, extensive longitudinal transverse myelitis at C4-Th10 level, nerve root enlargement in the extraspinal canal, and high bilateral cervical/lumbar cord intensity. Nerve conduction studies revealed bilateral demyelinating polyneuropathy of the median nerves. Positive anti-AQP4 antibodies in both serum and cerebrospinal fluid ‍led to the diagnosis of neuromyelitis optica spectrum disorder (NMOSD). The patient's symptoms improved after immunosuppressive treatment. Here, we describe the case of a patient with AQP4 autoantibody-positive NMOSD who demonstrated nerve root enlargement in the extraspinal canal and peripheral nervous system damage during demyelination.