June 13, 2024
A 23-year-old man presents with weakness and tingling in the left upper limb for 18 months. On examination, there is atrophy of the thenar muscles of the left hand.
Hirayama Disease
- Background:
- Hirayama, et al reported 12 cases of predominantly young males with progressive monoparesis and acral wasting of the upper limb in 1959. Thus, Hirayama disease, also known as juvenile unilateral muscular atrophy of the upper extremity, occurs due to dynamic changes during neck flexion in adolescence with forward displacement of the thecal sac due to prominent posterior epidural space.
- Clinical Presentation:
- Gradually progressive upper limb muscle weakness and atrophy. There is oblique amyotrophy, ie, wasting of forearm muscles with sparing of brachioradialis.
- Key Diagnostic Features of MRI:
- Neutral position
- Abnormal T2 signal in the cervical cord at the site of the maximum forward shift without an apparent cause.
- Flexion
- Forward shifting of the posterior dural wall. The posterior epidural space appears prominent (crescent-shaped) with hyperintensity on T1- and T2-weighted images and flow voids.
- Widened laminodural space
- Neutral position
- Differential Diagnosis:
- Amyotrophic lateral sclerosis: spine MRI would show spinal cord atrophy and, on brain MRI, hyperintensity of corticospinal tracts. There would be no forward dural displacement on flexion MRI of the spine. ALS occurs between 40–60 years of age and progresses relentlessly with death after 3 to 5 years of symptom onset. Hirayama disease progresses over 3 to 5 years and then stabilizes.
- Longitudinally extensive transverse myelitis is characterized by extensive cord signal, while in Hirayama disease, there is a localized cord signal with focal atrophy.
- Treatment:
- Generally self-limiting. However, early recognition and using a cervical collar to avoid neck flexion are recommended to prevent disease progression.
- Teaching Point:
- In any young male patient with unilateral muscular weakness of the upper extremity, an additional flexion view of the cervical spine in the sagittal section should be acquired.
