Monomelic amyotrophy (also known as MMA, Hirayama's disease, Sobue disease or Juvenile nonprogressive amyotrophy) is an untreatable, focal, lower motor neuron disease that primarily affects young (15 - 25 year-old) males in India and Japan. Lower motor neurons ( LMNs) are the Motor neurons connecting the Brainstem and Spinal cord to Muscle fibers, bringing the nerve India, officially the Republic of India (भारत गणराज्य inc-Latn Bhārat Gaṇarājya; see also other Indian languages) is a country For a topic outline on this subject see List of basic Japan topics. MMA is marked by insidious onset of muscular atrophy, which stabilizes at a plateau after two to five years from which it neither improves nor worsens. Atrophy is the partial or complete Wasting away of a part of the Body. There is no pain or sensory loss associated with MMA. Unlike other lower motor neuron diseases, MMA is not believed to be hereditary and fasciculations (involuntary muscle twitches) are rare. The motor neurone diseases (or motor neuron diseases) (MND are a group of progressive neurological disorders that destroy Motor neurones the cells that control voluntary A fasciculation (or "muscle Twitch " is a small local involuntary Muscle contraction (twitching visible under the skin arising from the spontaneous discharge
EMG tests reveal loss of the nerve supply, or denervation, in the affected limb without conduction block (nerve blockage restricted to a small segment of the nerve). Electromyography (EMG is a technique for evaluating and recording the activation signal of muscles Increased sweating, coldness and cyanosis have been reported for a few patients, indicating involvement of the sympathetic nervous system. Cyanosis is a blue coloration of the Skin and mucous membranes due to the presence of deoxygenated Hemoglobin in Blood vessels near the skin surface The Sympathetic Nervous System ( SNS) is a branch of the Autonomic nervous system along with the Enteric nervous system and Parasympathetic nervous
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. Electromyography (EMG is a technique for evaluating and recording the activation signal of muscles A nerve conduction study (NCS is a test commonly used to evaluate the function especially the ability of Electrical conduction, of the motor and Sensory nerves When a Motor nerve dies a nearby nerve can grow a new Axon to the affected muscle in order to take over the functionality of the dead nerve
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Treatment
There is no cure for MMA. Treatment consists of muscle strengthening exercises and training in hand coordination.
Prognosis
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.
Epidemiology
MMA occurs in males between the ages of 15 and 25. Onset and progression are slow. MMA is seen most frequently in Asia, particularly in Japan and India; it is much less common in North America.
External links
- monomelic_amyotrophy at NINDS
- MND Association
- Overview at Washington University
- Gourie-Devi M, Nalini A (2001). The National Institute of Neurological Disorders and Stroke is a part of the U "Sympathetic skin response in monomelic amyotrophy". Acta Neurol. Scand. 104 (3): 162-6. doi:. A digital object identifier ( DOI) is a permanent identifier given to an Electronic document. PMID 11551236.
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