**5. Present challenges with peripheral nerve surgery**

In spite of a growing number of good surgical alternatives currently available such as introduction of phrenic nerve transfer to medial root of median nerve for prehensile hand function, the restoration of function below the elbow following either partial root avulsion or total root avulsion presently remains the biggest challenge in brachial plexus surgery [8, 13, 25, 33, 39, 42]. Avulsion injuries from C5 to T1 have been shown to be amenable to restoration of good shoulder and elbow function, but the restoration of satisfactory distal function is still yet to be well demonstrated [8]. However, new techniques to circumvent this problem have recently been proposed [39, 42]. For the obstetric brachial plexus injuries, another particular challenge is the restoration of abduction and external rotation in the shoulder joint [18] which is largely limited due to developmental apraxia which occurs at a cerebral level.

Regarding investigation and preoperative planning, EMG and nerve conduction studies have their own limitations [18, 25]. EMG itself only reflects the function of the individual motor units in a nerve and not really that of the entire nerve or the cerebral retraining required to establish function [25]. Also, in severe cases with a flail anesthetic arm, the absence of SNAPs often clearly indicates damage to post-ganglionic elements but cannot exclude a mixed lesion with associated root avulsion [18].

Furthermore, there are currently only limited algorithms to guide the surgeon on carrying out nerve transfers [13, 52]. The choice of which transfer to utilize in each case is largely dependent on each surgeon's philosophy, knowledge and experience as well as patientrelated factors, a clear understanding of the involved anatomy of the brachial plexus in each patient, what is uninjured and still viable for nerve transfer repair, as well as available facilities and equipment [8, 13, 52]. A combination of long and variable recovery periods, variable patterns of injury, individual patient recovery factors and lack of uniformity in rehabilitation all lead to the overall lack of objective evidence-based guidelines for management. For pediatric patients, the criteria and timing of surgical intervention also still remains controversial [4]. Some have used the absence of recovery of the biceps muscle or shoulder function by 3 months of age as the indication for surgery in obstetric brachial plexus injury (OBPI), while others use 4 months or even 9 months as the time limit [4, 32]. In our personal experience with managing 196 cases of Erb's and Erb's plus palsies, excellent recoveries were possible in majority of cases with a proper rehabilitation programme consisting of cerebral retraining and judicious management of co-contracture deformities. Some would argue that deformities are less common with early nerve repair in OBPI, but this is yet to be proven definitively.

Finally, even though microsurgical repair of nerve injuries has advanced significantly over time, satisfactory functional recovery still remains a challenge [29]. The ultimate goal of a nerve repair should be a functional improvement that creates satisfaction for the patient in his or her daily activities and occupation and not simple improvement in the muscle power grading. This requires dedicated efforts in physical, psychological and vocational rehabilitation. Augmentation of the paralyzed limb using reanimative muscle or tendon transfer surgeries by the plastic surgeon often improves outcomes. Hence, a multidisciplinary team is ideal.
