Obstetrical brachial plexus palsy is a traction neural injury sustained during the course of the birth process. The incidence of obstetric brachial plexus palsy (OBPP) ranges globally from 0.5 to 2 per 1000 births with the higher numbers in under developed countries. Perinatal risk factors include large birth weight infants with macrosomia, multiparous pregnancies, assisted (vacuum or forceps) deliveries, and shoulder dystocia. A majority of them progress to complete recovery. Others may improve slowly but incompletely. The rate of complete, spontaneous recovery varies in the literature from 30 % to 95 %.
There is a great disparity among experts in the determination of surgical indications in partial palsies. This is attributed to relatively incomplete understanding of the natural history of obstetric palsy. Physicians still advise the parents to adhere to the physiotherapy programme, that ultimately leaves many children with significant disabilities. Contrary to this, in total palsy, the general consensus is towards an early surgical reconstruction.
Timing of surgery
Gilbert and Tassin recommend surgical intervention if there is no return of biceps function by 3 months of age. They believe that ultimate shoulder function is poor if biceps function is not regained by 3 months. Other workers have adopted a more conservative approach and prefer to delay surgery by a month or two. Clarke and Curtis advocate that failure to perform a ‘cookie test’ by 9 months of age is an indication for surgery. Contrary to partial palsy, there is a common consensus for surgical intervention in total palsy.
With the baby placed in supine position, an exploration of brachial plexus is performed under general anaesthesia through a reverse C-shaped incision starting along the posterior border of lower part of sternocleidomastoid muscle and then continuing above and parallel to the clavicle.
The upper brachial plexus spinal nerves are generally present in the space between the anterior and middle scalene muscles. Their absence suggests root avulsion. This is correlated with the presence of characteristic pseudomeningoceles on MR myelography. A common finding is presence of neuroma-in continuity. Use of nerve stimulator helps in establishing their proximal integrity. For the infraclavicular exposure an incision is made in the deltopectoral groove and extended in to the medial aspect of proximal arm.
Nerve related procedures
Neurolysis- Neurolysis is indicated for neuroma- in continuity which is conducting on electrical stimulation.
Nerve Grafts- Nerve grafts are used to bridge the nerve defects once the nonconducting neuromas are resected. In C5, C6 injuries, to prevent cocontractions, grafts are preferably directed from C5 nerve root to the posterior division and C6 nerve root to the anterior division of the upper trunk. In high grade injuries grafts are placed between the intact nerve root or roots and the distal infraclavicular targets. Fibrin glue was used in graft fixation.
Nerve Transfers– Nerve transfers are indicated in avulsion and irreparable nerve root injuries. Multiple donor nerves are used to reactivate the distal targets. Spinal accessory nerve is routinely transferred through a dorsal approach to the suprascapular nerve in restoration of shoulder abduction and external rotation. This approach allows nerve transfer close to the target muscles (supraspinatus and infraspinatus muscles) without affecting upper trapezius muscle function.
Infraclavicular plexus is explored through an incision just medial to the deltopecteral groove and extending into the inner arm. For the identification of posterior cord and the axillary nerve, the axillary artery is taped and pulled aside. A semicircular incision is extended from the incision at the anterior border of the axilla on to the infraareolar region to gain access to the intercostal nerves. The deep central branches of the third, fourth and fifth intercostals nerves are used for transfer to the musculocutaneous nerve.
Oberlin transfer (partial transfers of the ulnar nerve) is made through a longitudinal incision on the anteromedial aspect of upper arm. The musculocutaneous nerve is identified after it had traversed the coracobrachialis muscle. The ulnar nerve is identified at the same level, and a longitudinal epineurotomy is made. One or two ulnar nerve fascicles are minimally dissected, sectioned and coapted to the biceps motor branch with 10-0 nylon suture or fibrin glue.
In all cases, nerve dissections are performed under 4x loupe magnification, and nerve coaptations are made under the operating microscope with 10-0 nylon sutures or fibrin glue.
Post-operative care and assessment – Post-operatively, the baby is immobilised in a custom made plaster helmet with the arm flexed and strapped to the chest for a period of 4 weeks. After that gradually increasing passive exercises were started in the shoulder, elbow, wrist and finger joints.
Discussion – Historically, obstetric brachial plexus palsy was treated conservatively because surgical intervention produced poor functional results. In obstetric palsy late surgical results are unsatisfactory because there is a critical time period of approximately 2 years during which motor fibers must innervate the appropriate muscles. Although most of the injuries improve spontaneously with good functional results, the temptation to wait is outweighed by the time constraints imposed by degenerative changes in the motor end plates. Therefore, children who will ultimately require surgery should be treated as early as possible to optimize re-innervation of denervated muscles. Over the years, surgeons have devised clinical algorithms to guide them in deciding whether and when surgical intervention is required. Gilbert et al concluded that if there is no biceps function at the three months of age, surgical intervention should not be delayed further. Other surgeons prefer to operate at 4 months of age. After 12 months of age the results are disappointing. Therefore, indications for the primary repair are total root avulsion without recovery by three months of age, absent motor function in one or more muscle units (deltoid, biceps, triceps) at three to six months of age, and muscle grade I to II with no progress at 6 months of age. Microsurgical reconstruction usually incorporates nerve graft and nerve transfer procedures.
An upper truncal injury with weak elbow flexion but good hand function is not an urgent indication for early exploration. These cases should be observed for 4 to 6 months period of time. However, a total hand palsy with positive Horner sign is an urgent indication for an early nerve surgery within 3 months.