A 21-year-old woman was admitted due to altered mental status and hypothermia. The patient had a diagnosis of neuromyelitis optica (NMO) for 12 years and she was positive for serum anti-aquaporin 4 antibody. On admission, physical examination revealed coma with decerebration rigidity and poikilothermia. Magnetic resonance images of the brain revealed widespread, gadolinium enhancing lesions in the periventricular areas and the diencephalic structures. Laboratory investigations revealed hyponatremia and hypothyroidism. The patient was treated with high dose steroids. Both symptomatic and asymptomatic brain lesions may develop in patients with NMO. However, poikilothermia has not been reported in patients with NMO before.