BOSTON—Bright spotty lesions on MRI can help neurologists distinguish neuromyelitis optica spectrum disorder (NMOSD) from other neurologic disorders, according to data presented at the 2014 Joint ACTRIMS–ECTRIMS Meeting. These lesions may be an additional MRI indicator of NMOSD, combined with aquaporin 4 antibody, which has modest sensitivity, and longitudinally extensive transverse myelitis, which is characteristic of but not a pathognomonic feature of NMOSD.
A Series of 127 MRIs
To examine the potential relationship between bright spotty lesions and NMOSD, Jae-Won Hyun, MD, a neurologist at Research Institute and Hospital of National Cancer Center in Goyang, South Korea, and colleagues analyzed 127 spinal MRIs of patients who were having an acute myelitis attack. The study was led by Ho Jin Kim, MD, PhD, Head of the MS Clinic at Research Institute and Hospital of National Cancer Center. Of the participants, 62 had NMOSD, 32 had multiple sclerosis (MS), and 33 had idiopathic transverse myelitis. One neuroradiologist and two neurologists without knowledge of the patients’ diagnoses reviewed the spinal MRIs independently. The investigators defined bright spotty lesions as hyperintense spotty lesions with signal intensities at least as high as, but not higher than, that of the surrounding CSF on a T2-weighted image without flow void effects, and not as low as that of the surrounding CSF on a T1-weighted image.
Jae-Won Hyun, MD
The male-to-female ratio, the mean age at attack onset, and the mean age at time of MRI were higher among people with idiopathic transverse myelitis than in participants with NMOSD and those with MS. All patients with NMOSD tested positive for aquaporin 4 antibodies. Participants with MS and those with idiopathic transverse myelitis were negative for aquaporin 4 antibodies following repeated assays using three different methods. All subjects with idiopathic transverse myelitis were negative for anti-myelin oligodendrocyte glycoprotein antibody as well.
The Lesions’ Clinical Relevance Is Uncertain
The researchers found bright spotty lesions exclusively in patients with NMOSD. Of the 62 patients with NMOSD, 17 had bright spotty lesions. Dr. Hyun and colleagues identified longitudinally extensive transverse myelitis in all study participants. MRI features, including bright spotty lesions, were completely different between patients with NMOSD and those with MS. Bright spotty lesions, however, were the only MRI feature that distinguished NMOSD from idiopathic transverse myelitis.
Among patients with NMOSD, demographic data were not significantly different between individuals with and without bright spotty lesions. The investigators thus could not draw conclusions about the bright spotty lesions’ clinical relevance. To determine whether the lesions indicated attack severity, the researchers estimated the Expanded Disability Status Scale score of 36 patients with first myelitis attacks, as well as disease duration and attack numbers for all patients with NMOSD. Again, the researchers found no significant differences between patients with NMOSD with and without lesions. The investigators concluded that bright spotty lesions could not represent attack severity. In addition, other MRI findings were not significantly different between the two groups.
Dr. Hyun and colleagues followed up the patients with bright spotty lesions longitudinally. They performed 14 follow-up MRIs at two to 20 months after baseline.
No bright spotty lesions were detectable on follow-up MRI, but high signal intensities on T2 images remained for some patients. The results suggest that bright spotty lesions exist in a transient state during the acute phase of myelitis and ultimately undergo a fundamental change in properties, like contrast-enhanced lesions do, said Dr. Hyun.
—Erik Greb