Case Report Hirayama’s Disease in a Young Belgian Male: Case Report and Review of Literature

Hirayama’s disease, also known as juvenile non-progressive amyotrophy, is a rare neurological pathology characterized by an asymmetric distal amyotrophy of the upper limb affecting myotomes C7 to T1 in young males. Hirayama’s disease is most commonly observed in Asian population. The aim of this article is to report disease in a young European patient and to describe the clinical presentation and investigations


Introduction
Hirayama's disease, also termed juvenile non-progressive amyotrophy, or monomelic amyotrophy, first described by Hirayama et al in 1959 [1], is a rare type of cervical myelopathy related to flexion movements of the neck causing an asymmetric distal weakness or amyotrophy of muscles innervated by C7 to T1. It is most commonly in Asia, and it mainly affects young men in their second or third decade. The pathogenesis of this disease is not fully clarified. Dynamic cervical magnetic resonance imaging (MRI) is fundamental for the diagnosis. Conservative treatment with cervical collar and physiotherapy is effective in most cases but some severe cases require surgical treatment. This article reports a case of a 17-year-old male who was diagnosed with Hirayama's disease, and describe the clinical presentation and investigations.

Case Presentation
A previously healthy Caucasian 17-year-old male patient developed for several months progressive weakness in the right upper limb associated with amyotrophy involving the muscles of the hand, forearm and triceps. There was neither context of trauma nor family history of neuromuscular disorders. He did not report any sensory disturbance or associated cramp or fasciculations. He had no complaints of neck pain. Furthermore, he reported no disorders in the left upper limb, nor the lower limbs. Clinical examination revealed an atrophy of the hypothenar, thenar and interosseous muscles. There was no pyramidal syndrome. Examination of the cranial pairs, cervical spine and other limbs was normal. Blood biology was normal including anti-GM1 antibodies. Cerebrospinal Fluid (CSF) analysis showed normal cytochemistry and an absence of specific IgG oligoclonal band Electromyography (EMG) showed a purely motor neurogenic disease of C7 to D1 associated with signs of acute denervation with fibrillations and fasciculations. There was a reduction in the distal motor amplitude, which was clearly predominant in the first interosseous muscle compared to the short abductor muscle of the thumb. The left upper limb showed more moderate motor abnormalities. The lower limbs resutls were normal Cervical spine X-Ray was normal. However, we noted a disappearance of cervical lordosis ( Figure 1).
The course of Hirayama's disease is progressive with an insidious onset, followed by spontaneous resolution over 2 to 5 years.
It usually affects young men in their second to third decade.
The clinical features include unilateral or asymmetric weakness and amyotrophy in the forearm and the hand, with sparing of brachioradialis, giving the appearance of oblique amyotrophy. It can be associated with autonomic dysfunction causing cold paresis and muscle cramps. Conventional radiographic of the cervical spine may show loss of lordosis but is often aspecific [13]. MRI is the best diagnostic tool to confirm the diagnosis and exclude other spinal cord disorders.
Cervical MRI in neutral position is not always contributory but may reveal localized atrophy of the cervical cord, T2 hyperintensity signal, loss of lordosis, and loss of attachment of the dorsal dural sac to the subjacent lamina.
MRI in flexion is critical to confirm diagnosis and shows anterior migration of the posterior wall of the dura and an enlarged, crescent shaped and enhancing posterior epidural space, best appreciated with T2-weighted [14].
Electromyography (EMG) and Nerve Conduction Studies (NCS) reveal chronic denervation changes in C7-T1 myotomes and absence of sensory involvement. The reduction of the distal amplitudes predominates in the cubital territory compared to the Median [15], which was also noted in this case.
Autopsy findings demonstrate that the main pathology is asymmetrically located in the cervical anterior horn and anterior roots, with a central necrosis and decrease in nerve cells without macrophage infiltration at the C7-C8 levels [16].
The exact pathogenesis of this disease is still controversial. Many theories have been formulated. The causal factor is the forward displacement of the posterior lower cervical dura during neck flexion. The pathophysiological theories leading to Hirayama's disease include: The prognosis of Hirayama's disease is good compared to other motor neuron disorders such as SMA, ALS, PLS, with longer survival and fewer morbidity. The complications remain rare and involve chronic atrophy of the muscles and permanent contractures sometimes associated with spaticity.

Consent for Publication
Patient consent for case report

Availability of Data and Materials
The datasets analysed during the current case report are available in the GHDC XCare repository