Clinical features of progressive muscular atrophy

The clinical features of progressive muscular atrophy are:

• atrophy and weakness - often the wasting suggests a greater weakness than is actually present
• fasciculations are a noticeable feature - if not evident, can usually be evoked by tapping the muscle sharply
• muscle cramps are common

The hand is often affected first. The patient may become aware of stiffness and difficulty in performing fine movement. Gradually, a "guttered" or skeletal appearance develops as a result of prominence of the 1st dorsal interosseous muscle and tendons. One hand may be affected before the other or both may deteriorate together. The forearms tend to be affected next, the flexors before the extensors.

The lower limbs are rarely affected early. Bilateral foot drop may occur. Weakness of the muscles of the trunk and of respiration are a late feature.