Hirayama disease

Editor-In-Chief: Prab R Tumpati, MD
Obesity, Sleep & Internal medicine
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W8MD medical weight loss NYC and sleep center NYC

Hirayama disease
Cervical spine MRI showing features of Hirayama disease
Synonyms	Monomelic amyotrophy, juvenile muscular atrophy of distal upper extremity
Pronounce	N/A
Specialty	Neurology
Symptoms	Muscle weakness, muscle atrophy in the hand and forearm
Complications	N/A
Onset	Adolescence or early adulthood
Duration	Progressive over several years, then stabilizes
Types	N/A
Causes	Spinal cord compression due to forward displacement of the posterior dural sac
Risks	Male gender, age 15-25
Diagnosis	MRI, clinical examination
Differential diagnosis	Amyotrophic lateral sclerosis, spinal muscular atrophy, cervical spondylotic myelopathy
Prevention	N/A
Treatment	Physical therapy, cervical collar, surgical intervention in severe cases
Medication	N/A
Prognosis	Generally good, with stabilization of symptoms
Frequency	Rare, more common in Asia
Deaths	N/A

Hirayama Disease

Modern 3T MRI machine used for diagnosing Hirayama disease

Hirayama disease, also known as monomelic amyotrophy, is a rare neurological disorder characterized by muscle weakness and atrophy in the distal upper limbs. It predominantly affects young males and is considered a type of motor neuron disease.

Pathophysiology

Hirayama disease is believed to be caused by a dynamic compression of the cervical spinal cord during neck flexion. This compression leads to ischemia and subsequent damage to the anterior horn cells, which are responsible for innervating the muscles of the hand and forearm.

Clinical Presentation

Patients with Hirayama disease typically present with insidious onset of unilateral or asymmetric weakness and atrophy of the hand and forearm muscles. The condition is often painless and progresses slowly over several years before stabilizing.

Diagnosis

The diagnosis of Hirayama disease is primarily clinical, supported by imaging studies. MRI of the cervical spine is crucial for diagnosis, as it can demonstrate the forward displacement of the posterior dural sac and the loss of attachment to the vertebral bodies during neck flexion.

Treatment

There is no definitive cure for Hirayama disease. Management focuses on preventing further progression and alleviating symptoms. Patients are often advised to avoid neck flexion and may be fitted with a cervical collar. Physical therapy can help maintain muscle strength and function.

Prognosis

The prognosis for Hirayama disease is generally favorable, with many patients experiencing stabilization of symptoms after a few years. However, some degree of muscle weakness and atrophy may persist.

See also

• Motor neuron disease
• Spinal cord
• Muscle atrophy