Presentation
Bilateral upper limb weakness
Patient Data
Axial and sagittal MRI in neutral position are normal.
Flexion MRI reveals anterior translation of posterior dura with epidural soft tissue (red), dura is represented by a thin hypointense line (blue). T1: note the anterior dural translation in dorsal canal as well with epidural fat prominence (findings easier to appreciate on T1WI). T2: cord is displaced by the epidural soft tissue. Similar findings on a more inferior section, thin dura (blue) well seen to be displaced anteriorly.
Case Discussion
Hirayama disease is a form of muscular dystrophy seen in the 2nd-3rd decades. It is thought to be due to disproportionate growth between the bony spinal canal and canal contents resulting in a lax dura in extension and vice versa.
Contrast-enhanced spinal MRI may be done to demonstrate findings better but is not essential. A dynamic MRI should definitely be done in every suspected case.