Spasticity is a condition in which there is an abnormal increase in muscle tone or stiffness of muscle, which might interfere with movement, speech, or be associated with discomfort or pain. Spasticity is usually caused by damage to nerve pathways within the brain or spinal cord that control muscle movement. (Source: NIH)
In about two-thirds of people with motor neurone disease, the first symptoms occur in the arm or leg. This is sometimes called limb-onset disease. These symptoms include:
a weakened grip, which can cause difficulties picking up or holding objects
weakness at the shoulder, making lifting the arm above the head difficult
tripping up over a foot because of weakness at the ankle or hip
These symptoms are usually painless and may be accompanied by widespread twitching of the muscles (fasciculations) or muscle cramps.
Hyperreflexia (or hyper-reflexia) is defined as overactive or overresponsive reflexes. Examples of this can include twitching or spastic tendencies, which are indicative of upper motor neuron disease as well as the lessening or loss of control ordinarily exerted by higher brain centers of lower neural pathways (disinhibition).