Intrinsic cervical spinal cord deformation on MRI: "the distorted 'H' sign"

Extrinsic and intrinsic pathologic processes involving the spinal cord can affect its gross morphologic appearance. Contour-related abnormalities of the spinal cord can be determined by both noninvasive and invasive imaging techniques. Detailing internal dysmorphism of the spinal cord is more difficult to determine because the internal architecture of the cord is not usually visualized. Now magnetic resonance (MR) imaging can readily demonstrate the central "H" configuration of the normal spinal gray matter on axial T2* gradient-recall echo pulse sequences; thus, it should also be capable of demonstrating distortions of it. We initially reviewed 55 abnormal cervical spine 1.5-T MR imaging studies. Of 37 large lesions, 31 deformed the "H" whereas 18 small lesions did not. To compare potential differences in visualization of the "H" by MR scanners of different field strengths (1.5-0.5 T), a total of 125 additional patients were reviewed at different State University of New York (SUNY) sites. Visualization of the "H" varied from 51.4% at 1.5 T to 18.4% at 0.5 T. As resolution of the spinal cord increases on MR imaging, it becomes possible to more accurately map the altered cord "interior," which may have a detectable clinical (neurologic) counterpart.