Monomelic amyotrophy (MMA) is a medical condition in which there is a progressive degeneration and loss of motor neurons. Motor neurons are the nerve cells in the brain and spinal cord that control voluntary muscles. Also referred to as Hirayama disease and juvenile non-progressive amyotrophy, MMA is not considered to be hereditary. Unlike other lower motor neuron conditions, fasciculations (involuntary muscle twitches) are rare.
Focal motor neuron disease primarily affects young (15–25 year old) population. As far as diagnosis goes, EMG tests reveal loss of the nerve supply, or denervation, in the affected limb. Increased sweating, coldness and cyanosis are some of the complaints reported by few patients. While MMA will cause weakness and/or wasting in only one limb, EMG and NCV tests often show signs of reinnervation in the unaffected limbs.
As of now, there is no cure for MMA. The treatment is supportive, involving muscle strengthening exercises and training in hand coordination.
The symptoms of MMA usually progress slowly for one to two years before reaching a plateau, and then remain stable for many years. Disability is generally slight. Rarely, the weakness progresses to the opposite limb. There is also a slowly progressive variant of MMA known as O'Sullivan-McLeod syndrome, which only affects the small muscles of the hand and forearm and has a slowly progressive course.
Read more articles on Monomelic amyotrophy.
Monomelic amyotrophy (MMA) is characterized by progressive degeneration and loss of motor neurons and can be diagnosied with help of medical history and physical examination.read more
Although the causes of MMA are still to be know, there are few reports which believe that traumatic or radiation injury may be linked to MMA.read more