Abstract
Background Hirayama disease is a cervical myelopathy, characterized by painless progressive unilateral or bilateral asymmetric amyotrophy of C7-T1 myotomes, with sparing of the brachioradialis and proximal upper limb muscles, without objective sensory or lower limb involvement. Clinical progression is usually self-limited. Patients have characteristic abnormal forward-shifting of the posterior dura detected only on dedicated neck flexion cervical spine MRI.
Case C.D. is a 15-year-old, active male, with no past medical history, presenting with a 2 year history of progressive distal right upper limb weakness, which has plateaued over the past 6 months.
Examination reveals right distal upper limb wasting and weakness (oblique amyotrophy), with preservation of proximal strength and normal sensory examination.
Initial nerve conduction studies (NCS) of the right upper limb showed prolonged distal motor latencies (DMLs), reduced motor amplitudes and absent f-waves, with normal sensory studies. Left upper limb studies were normal.
C.D. was treated with IVIG for possible multifocal motor neuropathy, without clinical improvement. Repeat NCS revealed normalisation of distal motor latencies and f-wave latencies, but impersistent f-waves. MRI cervical spine with neck flexion showed widening of dorsal epidural space and mild focal atrophy of right hemicord C5-C7.
IVIG has since been ceased, and NCS and motor function remains stable.
Discussion C.D.’s clinical features are most in keeping with Hirayama disease. We present atypical neurophysiology findings for Hirayama disease, so as not to misdiagnose this condition, and have patients on ineffective treatments.
