Monomelic amyotrophy (MMA) is a medical condition characterized by progressive degeneration and loss of motor neurons. Motor neurons are the nerve cells in the brain and spinal cord that control voluntary muscles. Also known by the names of 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.
Read more articles on Monomelic Amyotrophy.