Age / Sex : 17 / M

Hirayama disease

Discussion

Additional study during neck flexion (See the additional figures)

Findings:

 On T2 sagittal image, asymmetric spinal cord
atrophy with myelomamacic change is noted at the level of C5/6 although there
is no significant spinal stenosis or disc hernation which can cause cord
change. On the following study, enlarged vascular space and forward displacement
of the dural sac are noted in the posterior epidural space during neck flexion. 

Differential Diagnosis:

 Myelomaiacia caused by other insults such as
trauma or ischemia

Diagnosis:
 

Hirayama disease

Discussion:

***Clinical features

•       Insidious onset in Young males, 15~25
years of age

•       Predominantly unilateral upper
extremity weakness and atrophy

•       Cold paresis (increased weakness during
cold)

•       No sensory or pyramidal tract
involvement

***Pathogenesis

•      
In healthy subjects,

the dural slack compensates for the increased length in flexion and
stays in apposition with the bony canal.

•       In Hirayama Disease,

A short length of the dural canal cannot compensate for increased length of the
vertebral canal, and the dural canal becomes tight when the neck is in the
flexed position. This results in an anterior shift of the posterior dural wall,
thereby causing spinal cord compression.

***Pathogenesis

•       In neutral position

−      
Localized
lower cervical cord atrophy

−      
Asymmetric
cord flattening

−      
Parenchymal
changes in the lower cervical cord

−      
Abnormal
cervical curvature

−      
Loss of
attachment between the posterior
dural sac and subjacent
lamina.

−      
Noncompressed
intramedullary high SI on T2WI

•       In flexion position

−      
Forward
migration of the wall of the dura mater with an enlarged posterior epidural
space.

−      
Crescentic
epidural mass along posterior aspect of the lower cervical cord

−      
Curvilinear
flow void on T1WI

−      
Uniform
contrast-enhancement on T1C+

−      
Hyperintense
on T2WI

***Treatment

•       Avoidance of neck flexion can stop
progression of this disease

→ application of a cervical collar for
3~4 years generally has been advocated.

•      
Surgical
intervention, which is mainly cervical decompression and/or fusion with/without duraplasty

 References:

Chen CJ, Chen CM, Wu CL et al. Hiramaya disease:MR diagnosis.
AJNR 1998;19:368-8

Chen CJ, Hsu HL, Tseng YC et al. Hirayama flexion
myelopathy: Neutral position MR imaging findings-importance o리 oss of attachment. Radiology
2004;231:39-44

Raval M, Kumari R, Dung AA et al. MRI findings in Hirayama
disease. IJRI 2010;20:245-9