A 52 year old woman presented with pain in the back and upper limbs and progressive weakness and sensory impairment of the upper and lower limbs. She developed frequent episodes of severe generalised muscle spasms associated with piloerection and hyperventilation. Nerve conduction studies and electromyography were normal. MRI demonstrated a lesion of the cervical spinal cord and lower brainstem. A biopsy of the cord revealed perivascular cuffing with mononuclear cells and inflammatory changes in the parenchyma, with increased numbers of microglia, reactive astrocytes and plasma cells. Following treatment with corticosteroids she showed substantial improvement.