One of the main sources of controversy regarding how to treat infants with this injury is the confusion existing in the literature over recovery potential of these infants. Reports of full recovery range from 30 to 95 percent. Undoubtedly this reflects the specialty of the author, with primary care physicians seeing many more infants who recovery than the referral physician called on to surgically treat the injury. Additionally, there is the question as to what constitutes a good recovery. Gjorup questioned 214 adults who had sustained injuries to their brachial plexus at birth. Of that group, 103 were subsequently examined to determine the degree of remaining disability. Of the 40 who clinically had "good" (no remaining neurological signs of injury by physician's examination) outcomes, only nine reported in their interview that they never noted any signs of injury to their arm nerves. Many had difficulty with externally rotating the shoulder with attendant difficulty in combing their hair, eating and oral hygiene. They felt they looked awkward and hesitated to eat in public because of their pattern of arm use, which caused them to frequently bump into neighboring diners.
Such conflicts in the scientific literature are sure to lead to confusion and thus hesitancy in aggressively pursuing definitive treatment. In 1972 Mallet described an assessment tool to evaluate functional disability in a child's arm with a brachial plexus injury. This test looks at voluntary movement possible at the shoulder and elbow, thus accessing the recovery of the upper part of the brachial plexus. In particular it tests the ability to actively abduct the shoulder (move the arm from the side outward then up to above the head), to externally rotate the shoulder, to move the hand to the top of the head, to move the hand to the small of the back and to get the hand to the mouth. Using these movements, the child is scored and then placed in one of three classes (II = some but little movement, III = better movement, and IV = completion of task). Tassin, in analyzing a group of untreated infants with these injuries, found that when recovery allowed movements in the deltoid (shoulder) and biceps muscles against gravity by age of 3 months, recovery would be complete. If these muscles show a flicker of contraction on examination but no obvious movement at 3 months of age and good antigravity movement at 5 months of age, then Class IV recovery is expected. If only movement is felt in the biceps muscle after the third month, Class III or II function is anticipated. These figures are what are most currently used as guidelines in determining who should undergo surgical exploration. Most also agree that if there has been absolutely no recovery of muscle contraction by 6 months, then there will be significant functional disability in the involved arm. Also, if recovery has not been complete by 6 months, then the likelihood for complete recovery is poor.