Diagnostic MR imaging features of hypomyelination of early myelinating structures: A case report

Abstract

Hypomyelination of early myelinating structures (HEMS) has recently been defined as a new genetic disorder accompanied by clinical and MR imaging characteristics. However, no studies have focused on diffusion-weighted imaging (DWI) findings of HEMS. We would like to propose a "sheep sign," which is formed by DWI hyperintensity in the medial medullary lamina along with alternating high-low-high (HLH) intensity stripes in the posterior limb of the internal capsule. We believe the presence of the "sheep sign" on DWI in combination with alternating HLH intensity stripes may be a valuable tool for diagnosing HEMS.

Keywords: Hypomyelination; diffusion magnetic resonance imaging; magnetic resonance imaging.

Figure 1.

T2-weighted imaging (T2WI; top, (a, b), and (c) and diffusion-weighted imaging (DWI; b = 1000 s/mm²; middle, (d, e), and (f). (g) The magnified image of the figure (f). (h) Schematic of the “sheep sign” T2WI and DWI exhibited hyperintensity lesions in the pons (a, d); arrows). Alternating high-low-high (HLH) intensity stripes in the posterior limb of the internal capsule are also seen on T2WI (b; arrows) and DWI (e; arrows). In addition, a symmetrical alternating HLH intensity lesion is observed at the level of the anterior commissure, which demonstrates the “sheep sign” (c, f-h; arrows). The arrows and arrowheads on the magnified DWI (g) correspond to the horns and ears of the sheep, respectively (h).