MRI characteristics of neuromyelitis optica spectrum disorder: an international update

Abstract

Since its initial reports in the 19th century, neuromyelitis optica (NMO) had been thought to involve only the optic nerves and spinal cord. However, the discovery of highly specific anti-aquaporin-4 antibody diagnostic biomarker for NMO enabled recognition of more diverse clinical spectrum of manifestations. Brain MRI abnormalities in patients seropositive for anti-aquaporin-4 antibody are common and some may be relatively unique by virtue of localization and configuration. Some seropositive patients present with brain involvement during their first attack and/or continue to relapse in the same location without optic nerve and spinal cord involvement. Thus, characteristics of brain abnormalities in such patients have become of increased interest. In this regard, MRI has an increasingly important role in the differential diagnosis of NMO and its spectrum disorder (NMOSD), particularly from multiple sclerosis. Differentiating these conditions is of prime importance because early initiation of effective immunosuppressive therapy is the key to preventing attack-related disability in NMOSD, whereas some disease-modifying drugs for multiple sclerosis may exacerbate the disease. Therefore, identifying the MRI features suggestive of NMOSD has diagnostic and prognostic implications. We herein review the brain, optic nerve, and spinal cord MRI findings of NMOSD.

Figure 1. MRI lesions characteristic of neuromyelitis optica spectrum disorder

Diencephalic lesions surrounding (A.a) the third ventricles and cerebral aqueduct, (A.b) which include thalamus, hypothalamus, and (A.c) anterior border of the midbrain. (B.a) Dorsal brainstem lesion adjacent to the fourth ventricle, (B.b) linear medullary lesion that is contiguous with cervical cord lesion, (B.c) edematous and extensive dorsal brainstem lesion involving the cerebellar peduncle. (C.a) Callosal lesion immediately next to the lateral ventricle, following the ependymal lining, (C.b) “marbled pattern” callosal lesion, (C.c) “arch bridge pattern” callosal lesion. (D.a) Tumefactive hemispheric white matter lesions, (D.b) a long spindle-like or radial-shape lesion following white matter tracts, (D.c) extensive and confluent hemispheric lesions show increased diffusivity on apparent diffusion coefficient maps suggesting vasogenic edema, (D.d) hemispheric lesions in the chronic phase showing cystic-like cavitary changes. (E.a) Corticospinal tract lesions involving the posterior limb of the internal capsule and (E.b) cerebral peduncle of the midbrain, (E.c) longitudinally extensive lesion following the pyramidal tract. (F.a) Cloud-like enhancement, (F.b) linear enhancement of the ependymal surface of the lateral ventricles, (F.c) meningeal enhancement.

Figure 2. MRI lesions characteristic of MS

(A) Contrasting MS periventricular and callosal lesions, which are discrete, ovoid, and perpendicular to the ventricles. (B) Contrasting MS enhancing lesions, which are ovoid or open-ring gadolinium-enhanced lesions with well-defined borders. MS = multiple sclerosis.

Figure 3. Optic nerve MRI lesions characteristic of neuromyelitis optica spectrum disorder

(A) Dense gadolinium-enhancing lesion at the posterior part of the right optic nerve. (B) Extensive gadolinium-enhancing lesion at the bilateral posterior part of the optic nerve/chiasm.

Figure 4. Spinal cord MRI lesions characteristic of neuromyelitis optica spectrum disorder

(A) Longitudinally extensive cord lesion involving thoracic cord. (B) Exclusive involvement of gray matter (H-shaped cord lesion).