Ultrahigh-Field MR (7 T) Imaging of Brain Lesions in Neuromyelitis Optica

Abstract

Background. Brain lesions are common in neuromyelitis optica spectrum disorder (NMOsd) and may resemble lesions of multiple sclerosis (MS). Objectives. To describe the imaging characteristics of supratentorial lesions in NMOsd on ultrahigh-field (7 T) MRI with special attention to vessel-lesion relationship. Methods. Ten NMOsd patients, all women and all seropositive for NMO IgG, with mean age of 51.3 ± 15.4 years and disease duration of 9.2 ± 6.4 years, were scanned at a 7 T whole-body human MR system with high-resolution 2D gradient echo sequence optimized to best visualize lesions and venous structures, T2- and T1-weighted imaging. Results. In 10 patients with NMOsd, a total of 92 lesions were observed (mean: 9.2 ± 8.8; range: 2-30), but only 8 lesions (9%) were traversed by a central venule. All lesions were <5 mm in diameter, and 83% were located in subcortical white matter. There were no lesions in the cortex or basal ganglia. Two patients exhibited diffuse periependymal abnormalities on FLAIR. Conclusions. Small, subcortical lesions without a central venule are the most consistent finding of NMOsd on 7 T MRI of the brain. Ultrahigh-field imaging may be useful for differentiating between NMOsd and MS.

Figure 1

Examples of typical lesions in NMOsd. Brain lesions on T2*-weighted GRE images with in-plane resolution of 0.2 × 0.2 mm² in six patients with NMO. Most lesions (approximately 85%) (arrows in (a), (b), (c), (d), and (e)) are small, round-shaped, and located in subcortical regions without typical sign of central venule or perivenous migration as seen in MS lesions. Only a few lesions have visible central veins (arrowhead in (d); this particular lesion was seen in enhance with gadolinium on a conventional brain MRI study performed three years previously). Only 3% lesions are juxtacortical (long arrow in (f)).

Figure 2

Examples of “thread-like” lesions in NMOsd. Thread-like lesions in two patients. A thread-like lesion along the corpus callosum white matter tract instead of venous course in one patient on T2-weighted (a) and T2*-weighted GRE (b) images (long arrows). Another lesion in subcortical region on T2*-weighted GRE (c) and T1-MPRAGE (d) images (short arrow) in the second patient.

Figure 3

Examples of diffuse periependymal abnormalities. Abnormal and thickened signal intensities (arrows) along ependymal layers on FLAIR images in two patients ((a) and (b)).