Hirayama is a rare disease of the nervous system that affects the cervical spine. Keizo Hirayama first identified this condition in 1959. Juvenile muscular atrophy of the distal upper extremity is also known as monomyelic atrophy (MMA). In adolescent and early adulthood, it typically affects males.
Typically, the young patient initially reports writing difficulties (can not take up examinations), holding objects in his hands. Typically in one hand, it begins and then progresses to involve the other. The hands get thinner later in the course of the disease and develop a claw deformity with a useless function.
Another characteristic aspect of this disorder is the worsening of cold symptoms. Typically, there is no sensory disturbance and no trouble in passing the urine or stools. The shoulder muscles and lower limb muscles are rarely involved in the disease.
Atrophy typically develops slowly and plateaus for many years. At that time, the hands are totally useless and have no capacity to work. With a strong male predominance, it is more common in Asia. In India, these cases are seen primarily in individuals from the eastern and northeastern regions.
The cause of this condition is not well known, but it has been postulated that the neck is overly flexible, resulting in cervical spinal cord compression when the neck is bent, causing weakening of the limb.
Until recently, with despondency and nihilism, this disease was looked at with no specific treatment. The treatment choice available was a cervical collar with watchful expectation along with physiotherapy. This resulted in minimal improvement in the disease's natural history, which is one of the constant progression of hand weakness, stabilising only after major wasting and weakness occurred in both hands.
Over the last few decades, it has become obvious that surgical intervention may give this often hopeless condition some hope. The surgery involves extracting the offending cervical disc and using a plate and screws to repair a section of the cervical spine.
This decreases the degree of bending of the neck and avoids further damage to the cervical spine. The disease stabilises after surgery in most patients, along with significant improvement in hand bulk and strength.