Concomitant MOG-related optic neuritis and conus medullaris involvement: a case report

Case presentation: A 39 years old man presented with right eye blurred vision along with painful eye movements. After 3 days, he began to experience lower back pain with irradiation down the legs and tingling sensation in both soles of the feet. He denied fever, recent infections or vaccination. A month earlier, he had a similar visual condition with complete recovery after intravenous corticosteroid therapy, which was still under investigation. At examination, visual acuities were 20/25 OD and 20/20 OS, with red desaturation and central scotoma at OD. There was no RAPD and fundoscopy examination showed bilateral normal optic disc. The rest of his neurological examination was normal. Orbits and spine MRI captured a high T2 signal involving the intraorbital segment of the right optic nerve and the conus medullaris, with no contrast enhancement on fat-suppressed T1 images. Lumbar puncture revealed an elevated white cell blood count (15 cells/µL, lymphocytes 90%), with normal protein and glucose level. AQP4-IgG was tested seronegative, while the MOG-IgG was positive. He was treated with 5 days of 1g intravenous methylprednisolone followed by intravenous immunoglobulin 0,4 g/kg once daily for 5 days and oral prednisone, with total improvement of visual acuity and pain complaints. Then, we decided to start maintenance therapy with tocilizumab in order to prevent relapses.

Discussion: In adults, Myelin-oligodendrocyte glycoprotein (MOG) antibody-associated disease (MOGAD) commonly presents as optic neuritis and myelitis, with the conus medullaris frequently affected when compared to other demyelinating disorders of CNS, like NMOSD and MS. This is the first report of concomitant optic neuritis and conus medullaris involvement MOG-related.

Final comments: Differentiation of the demyelinating disorders of the CNS can be challenging in practice and the involvement of conus medullaris, especially if associated with optic neuritis, should raise the suspicion of MOGAD.