The case of a patient who presented with a necrotic myelopathy and bilateral optic neuritis in association with a thymoma and circulating anti-CV2/CRMP5 antibodies is reported. This case shows that in some rare instances, a clinical presentation suggestive of a neuromyelitis optica can be of paraneoplastic origin.

A 45-year-old woman with a history of Hashimoto thyroiditis presented with a 4-month history of asthenia and a weight loss of 10 kg. A computed tomography of the chest showed an anterior mediastinal mass suspicious for a thymoma. The mediastinal mass was completely removed by surgery. Histological examination showed a B2-type thymoma with pleural, pericardial and left phrenic local extension. There was no evidence of mediastinal adenopathy or metastasis on computed tomography of the abdomen and pelvis. Treatment with radiation therapy was planned, but 1 month later the patient developed difficulties in walking for over 2 weeks, paraesthesia of the four limbs and bladder dysfunction.

Neurological examination showed a left spastic motor paresis, brisk reflexes and a left Babinski response; proprioceptive sensation was predominantly affected on the left limbs, whereas pain and thermal sensation were affected on the right limbs, suggesting a left cervical Brown–Sequard syndrome. Visual acuity was initially normal. There was no sign of polyneuropathy, and electromyography was normal. The patient did not have fever, and had no signs of systemic disease and …