Rare low cervical myelopathy affecting young adults. It is responsible for a pure slowly progressive distal motor impairment of the upper limbs, in the C7 to T1 metameres territory. It is caused by the movements of flexion of the neck. Imaging by magnetic resonance (MRI) in the neutral position allows detection of a possible cervical curvature abnormality, cervical spinal atrophy due to a compression, an anterior spinal hypersignal and especially a lack of posterior coalescence of the dural sac. In case of diagnostic suspicion, an MRI in cervical flexion position is performed to highlight anterior displacement of the spinal cord and the dural sac, a widening of the posterior epidural space, a flattening of the spinal cord and/or a congestion of the epidural veins. The current physiopathologic hypothesis is a disproportionate growth between the spine and the dural sac. The dural sac is attached to the spine at two precise points, the foramen magnum and C2 and C3 on one side, and the coccyx by the filum terminale on the other. In a healthy subject, there is some laxity allowing adaptation to the flexion movements of the neck. For affected patients, the range of flexibility of the spinal cord is too short compared to the length of the spine: it is thus unusually tense in the neutral position. During neck flexion, the dural sac would not be loose enough to sustain the strain induced by the lengthening of the cervical spine . The cervical spinal cord would thus be crushed by the dural sac against the posterior wall of the vertebral bodies, resulting in an increased intramedullary pressure leading to local microcirculation disorders at the level of the anterior horns of the cervical spine. Those dynamic abnormalities tend to disappear after ten years of evolution.

Anesthetic implications: 

avoid any neuraxial block

References : 

-         Dejobert M, Geffray A, Delpierre C, Chassande B, Larrieu E, Magni C.
La maladie d’Hirayama : ą propos de 3 cas.
J Radiol Diagn Intervent 2013 ; 94 : 327-31.

-        Chanson J-B, Renaud M, Echaniz-Laguna A, Koob M.
Dilation of epidural space and posterior soft tissue veins in Hirayama disease.
BMJ Case Reports 2017; doi 10.1136/bcr-2017-220787

Updated: September 2017