Spinal cord and optic nerve MRI patterns in neuromyelitis optica spectrum disorders

Spinal cord imaging in the context of acute myelitis in NMOSD usually reveals a LETM lesion extending over three or more vertebral segments. Sagittal T2-weighted MRI of the thoracic spinal cord (A) demonstrates a typical LETM lesion involving most of the thoracic spinal cord (arrows). LETM lesions have a predilection for the central cord, as shown by axial T2-weighted (B, arrowhead) and T1-weighted MRI with gadolinium (C, arrowhead). Cervical LETM may extend into the medulla, a characteristic NMOSD pattern demonstrated in D (arrows; sagittal T2-weighted MRI) and E (arrows; sagittal T1-weighted MRI with gadolinium). Acute LETM lesions can be associated with intralesional hypointensity as shown by sagittal T1-weighted MRI (F, arrow); in this example, a rim of gadolinium enhancement surrounds the hypointense region. Chronic sequelae of LETM may include longitudinally extensive segments of spinal cord atrophy as shown by T2-weighted MRI using sagittal (G, the two arrowheads indicate the atrophic segment and the top arrow indicates the normal diameter of unaffected cervical spinal cord) and axial planes (H, arrowhead shows an atrophic spinal cord). Fast spin echo fat-suppressed T2-weighted MRI in the axial (I) and coronal (J) planes shows increased signal throughout most the length of the left optic nerve, especially its posterior portion (arrows). Axial T1-weighted MRI with gadolinium shows enhancement of the optic chiasm (K, arrows). These images are from two different patients experiencing acute optic neuritis in the setting of NMOSD.