Symptoms
In all spinal muscular atrophies, the primary feature is muscle weakness accompanied by atrophy of muscle. This is the result of denervation, or loss of the signal to contract that is transmitted by the motor neurons in the spinal cord. The signal is normally transmitted from the spinal cord to muscle via the motor neuron's axon, but in spinal muscular atrophies either the entire motor neuron or the motor neuron's axon loses the ability to transmit signals to muscles.
The symptoms are strongly related to the exact disease (see above) and, sometimes, to the age of onset. Certain conditions (e.g., spinal muscular atrophy or spinal and bulbar muscular atrophy) have a wide range, from infancy to adult, fatal to trivial, with different affected individuals manifesting every shade of impairment between these two extremes. Other muscular atrophies have a different and often very severe course. Some of them are extremely rare and described only in a handful of individuals. However, in all cases the majority of symptoms are a consequence of muscle weakness.
Read more about this topic: Spinal Muscular Atrophies
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