Background Longitudinally extensive myelitis (>3 vertebral segments) is considered the sine-qua-non of spinal cord involvement in NMO and short spinal cord lesions typical of MS. Similarly, small callosal lesions and U fibre involvement are thought to be characteristic of MS and uncommon in NMO. We present 2 cases that are exceptions to these.

Results Case 1: A 22 year-old man on azathioprine for aquaporin-4 antibody positive NMO, reported slight worsening of his pre-existing visual symptoms. He was already known to have other brain MRI changes supportive for NMO. Further MRI showed small callosal lesions, juxtacortical lesions in the U-fiber layer, which on their own would appear typical for MS.

Case 2 A 38 year-old Asian woman, on azathioprine for aquaporin-4 antibody positive NMO presented with new onset sensory symptoms in the arms. MRI showed new small enhancing lesions at T4 and T6/7 of one segment length only. She was promptly started on steroids with resolution of symptoms.

Conclusions MS-typical brain and spinal cord lesions can be found in NMO. As our knowledge of the spectrum of NMO expands many more unusual clinical and radiological findings are likely to emerge. Prompt recognition and imaging of relapses may influence such the findings.