Diffusion-weighted imaging (DWI) technique might help distinguish spinal cord infarction (SCI) from neuromyelitis optica spectrum disorder (NMOSD), according to a recently published study in BMC Neurology.
Although magnetic resonance imaging is currently the gold standard for SCI diagnosis, most of the time, MRI-detected lesions are not specific and can easily be mistaken for NMOSD lesions due to the fact that both conditions can produce longitudinally extensive lesions around the grey matter. Furthermore, the frequency of pathognomonic radiological signs in T2 weighted images, such as the “owl’s eyes sign,” is currently unknown.
Evidence suggests that DWI could be a very valuable tool for SCI diagnosis, particularly in the early stages. Acute SCI appears as high-intensity lesions with low-intensity regions on apparent diffusion coefficient (ADC) maps. However, the literature regarding DWI findings in other inflammatory myelopathies like NMOSD is scarce.
Read more about NMOSD diagnosis
The authors aimed to assess the effectiveness of DWI in distinguishing between SCI and NMOSD through a retrospective study including a population of 27 patients with either NMOSD or SCI. The study compared the clinical characteristics and MRI findings of both groups. Researchers then used the mixed-effects logistic regression analysis to analyze factors influencing T2 and DWI abnormalities.
There was no significant difference in the median age of both groups; however, the proportion of female patients was significantly higher in the NMOSD group. The prevalence of comorbidities such as obesity, hypertension, and diabetes was higher in the NMOSD group. Interestingly, there was no significant difference in the frequency of motor paresis and sensory disturbances.
Regarding DWI comparison, both groups had DWI hyperintensities, albeit with a higher frequency in the SCI group (100% vs 60%). Yet, there was a noteworthy difference in the ACD maps, revealing corresponding hypointensities in the SCI hyperintensities and isointensities in NMOSD lesions.
T2 weighted images revealed that, on average, lesion length was shorter in SCI, and focal involvement in T9–L2 vertebral level was observed only in the SCI group. Surprisingly, owl’s eyes sign and pencil-like hyperintensities in T2 weighted images, regarded as suggestive of SCI, were only observed in 3 patients.
“DWI and ADC maps help distinguish SCI from NMOSD,” the authors wrote. “The time from symptom onset, imaging sequence, and imaging plane should be considered when MRI findings are interpreted in patients with suspected SCI.”
Kobayashi, M. The utility of diffusion-weighted imaging in patients with spinal cord infarction: difference from the findings of neuromyelitis optica spectrum disorder. BMC Neurol. Published online October 11, 2022. doi: 10.1186/s12883-022-02903-y