Muscle Weakness

Muscle weakness is by far the most common symptom of ALS. Depending on the age of the person, they might attribute symptoms such as weakness in their arms or legs as growing older. Muscle weakness is caused by a decrease in the number of motor nerve cells. It will usually begin on one side of the body in a specific area and spread to other parts of the body. This weakness is not typically accompanied by pain, but fatigue is common.

Loss of muscle strength is a common symptom of ALS because it can result from the loss of both upper and motor neurons. In upper motor neuron loss, there is spasticity or stiffness and clumsiness, whereas in lower motor neuron loss, weakness is distributed to the muscles, and fasciculations or muscle tremors occur.