Conventional and advanced imaging in neuromyelitis optica

Abstract

Myelitis and optic neuritis are prototypic clinical presentations of both multiple sclerosis and neuromyelitis optica. Once considered a subtype of multiple sclerosis, neuromyelitis optica, is now known to have a discrete pathogenesis in which antibodies to the water channel, aquaporin 4, play a critical role. Timely differentiation of neuromyelitis optica from MS is imperative, determining both prognosis and treatment strategy. Early, aggressive immunosuppression is required to prevent the accrual of severe disability in neuromyelitis optica; conversely, MS-specific therapies may exacerbate the disease. The diagnosis of neuromyelitis optica requires the integration of clinical, MR imaging, and laboratory data, but current criteria are insensitive and exclude patients with limited clinical syndromes. Failure to recognize the expanding spectrum of cerebral MR imaging patterns associated with aquaporin 4 antibody seropositivity adds to diagnostic uncertainty in some patients. We present the state of the art in conventional and nonconventional MR imaging in neuromyelitis optica and review the place of neuroimaging in the diagnosis, management, and research of the condition.

Fig 1.

A, T2WI shows extensive patchy pericentral signal change extending from the cervicomedullary junction to the T1 vertebral level in acute symptomatic spinal AQP4-positive NMO. B, Contrast-enhanced T1WI shows that short-segment gadolinium enhancement is present within the cord at the C4 and C7/8 vertebral levels. C, T2WI shows prototypic longitudinally extensive holocord inflammation in acute symptomatic AQP4-positive NMO relapse. D, T2WI shows severe atrophy in a chronic thoracic spinal cord NMO lesion spanning 3 vertebral segments (T2–T4).

Fig 2.

A and B, Contrast-enhanced fat-suppressed T1WI shows acute swelling and enhancement of the right optic nerve during symptomatic AQP4-positive NMO relapse with severe right-eye visual loss. C, Fat-suppressed T2WI. D, Contrast-enhanced fat-suppressed T1WI shows chiasmatic hyperintensity and enhancement during symptomatic AQP4-positive NMO relapse with severe visual impairment affecting the entire field of vision in the left eye and the temporal hemifield of the right eye.

Fig 3.

Typical periependymal lesions following the known distribution of AQP4. A and B, FLAIR MR imaging shows hypothalamic and medullary lesions in symptomatic AQP4-positive NMO spectrum disorder presenting with diplopia, dysarthria, dysphagia, and a right-sided sensorimotor syndrome. C and D, FLAIR MR imaging shows midbrain tegmentum lesions in the same patient during a second symptomatic attack, presenting with diplopia and clinical evidence of bilateral internuclear ophthalmoplegia. (Images courtesy of Prof. Jun-ichi Kira and Dr. Koji Shinoda, Kyushi University, Kyushi, Japan.)

Fig 4.

Periependymal/periventricular lesions in acute AQP4-positive NMO. A, Contrast-enhanced T1WI shows ill-defined periventricular cloudlike enhancement. While relatively specific for NMO, similar patterns can be observed in other inflammatory CNS diseases, such as active neurosarcoidosis (B, Contrast-enhanced T1WI). C and D, T1WI and contrast-enhanced T1WI demonstrate pencil-thin ependymal enhancement involving the anterior horns of the lateral ventricles in AQP4-positive NMO. E, Contrast-enhanced T1WI shows thick periependymal enhancement around the posterior horn of the lateral ventricle in acute symptomatic cerebral AQP4-positive NMO relapse. F, 3T follow-up FLAIR MR imaging shows ventriculomegaly and periventricular encephalomalacia and gliosis. G and H, FLAIR MR imaging and contrast-enhanced T1WI shows extensive periependymal disease involving the right lateral ventricle and a discrete, well-demarcated enhancing lesion abutting the posterior horn of the left lateral ventricle.

Fig 5.

A and C, FLAIR MR imaging shows acute, heterogeneous, “fluffy,” corpus callosum lesions, with prominent splenial hyperintensity and swelling, during symptomatic cerebral AQP4-positive NMO relapse. B, Contrast-enhanced T1WI shows linear enhancement involving the undersurface of the corpus callosum in its anterior third and more focal enhancement within lesions in the body of the corpus callosum. D, 3T follow-up FLAIR MR imaging at 2.5 years shows severe splenial (and global cerebral) atrophy. E, FLAIR MR imaging shows a large, evanescent lesion in the right hemisphere in AQP4-negative NMO spectrum disorder. F, DWI (left) and ADC map (right) confirm facilitated diffusion in the lesion.

Fig 6.

Voxel-based morphometry analysis shows a reduction in the attenuation and volume of gray matter in the motor (A) and visual (B) cortices in patients with NMO compared with the healthy controls. Voxel-based morphometry output is overlaid on the standard CH2 template. Voxelwise DTI analysis shows a significantly lowered fractional anisotropy along the pathway of the optic radiation bilaterally (C) and involvement of both lateral geniculate nuclei (D). Pichiecchio A, Tavazzi E, Poloni G, et al. Advanced magnetic resonance imaging of neuromyelitis optica: a multiparametric approach. Mult Scler 18(6):817–24, copyright © 2012. Reprinted by Permission of SAGE.