Acute respiratory failure caused by brainstem demyelinating lesions in an older patient with an atypical relapsing autoimmune disorder

An 84‐year‐old man presented with somnolence, dysphagia, and right hemiplegia, all occurring within a month, approximately one year after initial admission due to subacute, transient cognitive decline suggestive of acute disseminated encephalomyelitis involving the cerebral white matter. Serial magnetic resonance imaging (MRI) studies over that period revealed three high‐intensity signal lesions on fluid‐attenuated inversion recovery images, appearing in chronological order in the left upper and left lower medulla oblongata and left pontine base. Despite some clinical improvement following methylprednisolone pulse therapy, the patient died of respiratory failure. Autopsy revealed four fresh, well‐defined lesions in the brainstem, three of which corresponded to the lesions detected radiologically. The remaining lesion was located in the dorsal medulla oblongata and involved the right solitary nucleus. This might have appeared at a later disease stage, eventually causing respiratory failure. Histologically, all four lesions showed loss of myelin, preservation of axons, and infiltration of lymphocytes, predominantly CD8‐positive T cells, consistent with the histological features of autoimmune demyelinating diseases, particularly the confluent demyelination observed in the early and acute phases of multiple sclerosis (MS). In the cerebral white matter, autoimmune demyelination appeared superimposed on ischemic changes, consistent with the cerebrospinal fluid (CSF) and MRI findings on initial admission. No anti‐AQP4 or MOG antibodies or those potentially causing autoimmune encephalitis/demyelination were detected in either the serum or CSF. Despite several similarities to MS, such as the relapsing–remitting disease course and lesion histology, the entire clinicopathological picture in the present patient, especially the advanced age at onset and development of brainstem lesions in close proximity within a short time frame, did not fit those of MS or other autoimmune diseases that are currently established. The present results suggest that exceptionally older individuals can be affected by an as yet unknown inflammatory demyelinating disease of the CNS.