The pattern of muscle involvement in poliomyelitis of the upper limb.

The pattern of muscle paralysis and paresis in the upper limb has been studied in 31 children with poliomyelitis. The incidence of involvement of the upper limb alone is the same as of the upper and lower limbs together, and of the spine and upper limb. The left arm was more commonly affected than the right. The muscle most frequently paralysed was the deltoid. When complete paralysis of the whole deltoid occurred and was associated with paralysis of the rotator cuff muscles, the shoulder often subluxed downwards. The next most commonly affected muscles were the elbow flexors and extensors. In the hand the opponens pollicis was most often involved. As far as the spinal segments are concerned, C5 involvement was usually associated with paralysis and C7 with paresis.