MR Imaging Features of Critical Spinal Demyelinating Lesions Associated with Progressive Motor Impairment

Abstract

Background and purpose: Progressive MS is typically heralded by a myelopathic pattern of asymmetric progressive motor weakness. Focal individual "critical" demyelinating spinal cord lesions anatomically associated with progressive motor impairment may be a compelling explanation for this clinical presentation as described in progressive solitary sclerosis (single CNS demyelinating lesion), progressive demyelination with highly restricted MR imaging lesion burden (2-5 total CNS demyelinating lesions; progressive paucisclerotic MS), and progressive, exclusively unilateral hemi- or monoparetic MS (>5 CNS demyelinating progressive unilateral hemi- or monoparetic MS [PUHMS] lesions). Critical demyelinating lesions appear strikingly similar across these cohorts, and we describe their specific spinal cord MR imaging characteristics.

Materials and methods: We performed a retrospective, observational MR imaging study comparing spinal cord critical demyelinating lesions anatomically associated with progressive motor impairment with any additional "noncritical" (not anatomically associated with progressive motor impairment) spinal cord demyelinating lesions. All spinal cord MR images (302 cervical and 91 thoracic) were reviewed by an experienced neuroradiologist with final radiologic assessment on the most recent MR imaging. Anatomic association with clinical progressive motor impairment was confirmed independently by MS subspecialists.

Results: Ninety-one individuals (PUHMS, 37 [41%], progressive paucisclerosis 35 [38%], progressive solitary sclerosis 19 [21%]) with 91 critical and 98 noncritical spinal cord MR imaging demyelinating lesions were evaluated. MR imaging characteristics that favored critical spinal cord demyelinating lesions over noncritical lesions included moderate-to-severe, focal, lesion-associated spinal cord atrophy: 41/91 (45%) versus 0/98 (0%) (OR, 161.91; 9.43 to >999.9); lateral column axial location (OR, 10.43; 3.88-28.07); central region (OR, 3.23; 1.78-5.88); ventral column (OR, 2.98; 1.55-5.72); and larger lesion size of the axial width (OR, 2.01;1.49-2.72), transverse axial size (OR, 1.66; 1.36-2.01), or lesion area (OR, 1.14; 1.08-1.2). Multiple regression analysis revealed focal atrophy and lateral axial location as having the strongest association with critical demyelinating lesions.

Conclusions: Focal, lesion-associated atrophy, lateral column axial location, and larger lesion size are spinal cord MR imaging characteristics of critical demyelinating lesions. The presence of critical demyelinating lesions should be sought as these features may be associated with the development of progressive motor impairment in MS.

FIG 1.

Patient ascertainment algorithm.

FIG 2.

Axial spinal cord columns. A, Axial T2 spinal cord imaging. B, Superimposed schematic of axial columns on axial MR image. C, Schematic diagram of axial columns of spinal cord.

FIG 3.

Examples of critical T2-hyperintense demyelinating lesions on sagittal T2-weighted images. Imaging composite of sagittal T2-weighted images in patients with critical lesions with corresponding axial images. A right C1 T2-hyperintense lesion with focal atrophy (A, arrow). A left C4 T2-hyperintense lesion with focal atrophy (B, arrow). A right-sided upper thoracic spine; T2-hyperintense lesion with focal atrophy (C, arrow). A left-sided C4-C5 T2-hyperintense lesion with focal atrophy (D₁, arrow). An additional noncritical lesion is noted at the C6 level (D₂, arrow).

FIG 4.

Examples of critical T2-hyperintense demyelinating lesions on axial T2-weighted images. Imaging composite of axial T2-weighted images in patients with critical lesions, corresponding to sagittal images and clinical details. The corresponding axial images reveal a T2-hyperintense lesion in the right lateral column with focal atrophy (A, arrow), a T2-hyperintense lesion in the left lateral column with focal atrophy (B, arrow), a T2-hyperintense lesion in the right lateral column with focal atrophy (C, arrow), a T2-hyperintense lesion in the left lateral column with focal atrophy (D₁, arrow), and a T2-hyperintense lesion in the right lateral column without focal atrophy (D₂, arrow).