From the Guidelines
The placement of lesions in Multiple Sclerosis (MS) has a significant impact on the body, with lesions typically developing in specific white matter regions, such as the periventricular and juxtacortical white matter, the corpus callosum, infratentorial areas, and the spinal cord 1.
Key Characteristics of MS Lesions
- Lesions are usually round to ovoid in shape and range from a few millimeters to more than one or two centimeters in diameter
- They should be at least 3 mm in their long axis to satisfy diagnostic criteria
- Lesions are often small, covering less than two vertebral segments and usually less than half of the cord area
- On axial images, most lesions are located in the periphery of the spinal cord, mainly in the lateral or dorsal columns ### Distribution of Lesions
- MS lesions tend to affect specific white matter regions, such as the periventricular and juxtacortical white matter, the corpus callosum, infratentorial areas, and the spinal cord 1
- The distribution of lesions is often mildly asymmetric in the early stages
- Lesions can occur in any CNS region, but some areas are more commonly affected than others ### Red Flags for Spinal Cord Lesions
- Longitudinally extensive lesions extending over three or more vertebral segments
- Prominent involvement of the central grey matter
- Swelling of the spinal cord
- Leptomeningeal or nerve root involvement
- Cavitation or evidence of micro/macrobleeds 2 ### Clinical Implications
- The presence of multiple short-segment spinal cord lesions is highly specific for MS and only rarely occurs in other inflammatory CNS diseases 2
- Spinal cord lesions are not seen with normal ageing or in the majority of common neurological disorders, such as migraine and cerebrovascular diseases 2
- Brain MRI is more sensitive than spinal cord MRI for detecting disease activity, and serial spinal cord imaging may add little to brain imaging for monitoring of disease activity and progression 3
From the Research
Impact of Lesion Placement on the Body in Multiple Sclerosis (MS)
- The location of lesions in the brain may predict disability in patients with primary progressive multiple sclerosis (MS) 4.
- Lesions in the periventricular, (juxta)cortical, and infratentorial regions are part of the diagnostic criteria for MS, while lesions in the subcortical region are a marker of disease activity 5.
- The spatial location of lesions can affect the severity and type of disability in MS patients, with periventricular regions in temporal, frontal, and limbic lobes being predictive of impairment 6.
Lesion Location and Disability
- Lesions in the occipital lobe have been shown to have a significant reduction in myelin water fraction (MWF) compared to other lobes, which may contribute to ongoing demyelination in this region 7.
- The location of lesions can affect different physical and cognitive abilities, probably due to the impact on commissural and long projection fibers, which are relevant white matter pathways supporting many different brain functions 6.
- New lesions in the periventricular, juxtacortical, and infratentorial regions are associated with the number of lesions in the respective regions at baseline, while new lesions in the subcortical region are more closely related to periventricular lesions 5.
Methodological Considerations
- The choice of spatial registration algorithm can substantially affect conclusions regarding lesion localization, and methods for dealing with confounding factors due to differences in disease duration and local lesion volume are necessary 8.
- Voxel-wise regression approaches can be extended by introducing a metric that measures the distance between a patient-specific lesion mask and the population prevalence map 8.