Brachial Plexus Birth Palsy

The obstetric palsy is the same anatomy with a different clock. The levels, trunks and branches are on brachial plexus anatomy, and the adult traction injury on adult brachial plexus injury - but the two behave nothing alike. Most birth palsies recover spontaneously and the adult ones do not, which is why this page is organised around an observation window and a decision point rather than around early exploration. The other difference is that a growing shoulder remodels around the imbalance, so the late problem here is glenohumeral deformity rather than simple weakness. The nerve surgery itself is on nerve repairs and the biology that sets its timing on nerve injury and regeneration; the birth injury most often confused with it is a clavicle fracture, which also gives a pseudoparalytic arm but resolves in days.

Definition. Brachial plexus birth palsy (BPBP), also known as obstetric brachial plexus injury (OBPI), is a stretch injury to the brachial plexus occurring during delivery. It results from lateral flexion of the head away from the shoulder, which puts traction on the plexus.

Who it happens to. The incidence is 1-2 per 1000 live births, and the risk factors are these.

• Shoulder dystocia
• Macrosomia
• Forceps or vacuum delivery
• Breech presentation

Which part of the plexus. The pattern of the lesion sets both the posture and the prognosis.

• Upper plexus (Erb's, C5, C6 +/- C7) - the most common pattern and the best prognosis
• Lower plexus (Klumpke's, C8, T1) - rare in isolation, and associated with Horner's syndrome
• Total plexus (C5-T1) - a flail arm, and the worst prognosis

The plexus. It is formed by the ventral rami of C5-T1 and built in five steps: roots, trunks, divisions, cords and branches. C5 and C6 make the upper trunk, C7 continues as the middle trunk, and C8 and T1 make the lower trunk; each trunk divides into an anterior and a posterior division, and the divisions regroup into the lateral, posterior and medial cords.

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What each nerve powers. Reading a weak arm back to a level depends on the outputs.

• Musculocutaneous - biceps
• Axillary - deltoid
• Radial - triceps and wrist extensors
• Median - forearm flexors and thenar muscles
• Ulnar - intrinsics and hypothenar muscles

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How the nerve fails. Traction produces three lesions, and they do not behave alike.

1. Stretch (neurapraxia) - a temporary conduction block, with full recovery expected
2. Rupture - the nerve is disrupted distal to the dorsal root ganglion and scars; grafting may be needed
3. Avulsion - the root is torn from the spinal cord. There is no spontaneous recovery, and a nerve transfer is required

Why the shoulder deforms later. Strong internal rotators working against weak external rotators is a muscle imbalance, and in a growing shoulder the imbalance runs a predictable course.

• Internal rotation contracture
• Posterior subluxation of the glenohumeral joint
• Glenoid retroversion and posterior humeral head flattening
• Glenohumeral dysplasia (GHD)

Waters and colleagues defined a CT/MRI grading of the glenohumeral deformity that progresses with an untreated internal-rotation contracture. The grade directs whether the joint can be rebalanced with soft tissue alone or needs a bony procedure.

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How the numbers are taken. Two measurements describe the joint: the percentage of the humeral head lying anterior to the mid-glenoid, and the glenoid version. Both are read off the axial image rather than estimated.

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The posture names the level. An upper-trunk palsy holds the shoulder adducted and internally rotated, the elbow extended, the forearm pronated and the wrist and fingers flexed - the waiter's tip. The weak C5-C6 muscles, deltoid, infraspinatus, biceps, supinator and the wrist extensors, are overpowered by the intact adductors and internal rotators, triceps and pronators, and the limb settles where the working muscles put it.

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The newborn examination. Four things are looked for, and none of them needs equipment.

• Posture - waiter's tip, flail, or claw
• Passive range of motion - full in the newborn, so a restricted range means a contracture or a fracture
• Reflexes - Moro, in which the abducted arm does not follow, and grasp if the lower plexus is involved
• Horner's syndrome - ptosis, miosis and anhidrosis

Serial assessment. One examination says what is weak; repeated examinations say whether it is recovering, and that is the observation the whole pathway turns on. Score active movement with the Active Movement Scale (AMS), 0-7 per muscle, at every visit.

• Biceps recovery is the milestone - antigravity biceps by 3-6 months predicts a good recovery (Gilbert)
• Shoulder range - watch for the internal rotation contracture, which declares itself as an external rotation deficit
• Later - the Mallet classification, for shoulder function

Mallet grading. The Mallet score grades shoulder function - abduction, external rotation, hand to mouth and the rest. Grade I is a flail shoulder and grade V is normal, with grades II to IV in between, and the shoulder operations are indicated against it.

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Radiographs. Clavicle and humerus at the first assessment. Always radiograph the shoulder girdle.

MRI of the plexus. Requested if there is no recovery by 3 months. It is read for two things: a pseudomeningocele at a root, which indicates avulsion, and a neuroma.

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Ultrasound of the shoulder. For the child who has developed an internal rotation contracture: it assesses the glenohumeral joint for posterior subluxation and glenoid retroversion.

CT of the shoulder (3D). For surgical planning in the older child with established glenohumeral dysplasia.

Electrodiagnostics. EMG and nerve conduction studies can differentiate neurapraxia from axonotmesis or avulsion, and are often used to supplement the clinical examination. Timing matters: 3-4 weeks after the injury, which is when fibrillation potentials appear.

The flaccid or under-moving newborn arm has several mimics. The single most important step is to exclude a painful pseudoparalysis (fracture, infection) before attributing weakness to plexopathy.

Birth plexus palsy rarely occurs in isolation - the same difficult delivery often injures neighbouring structures, and some associations carry prognostic weight.

• Clavicle and humeral fractures - the commonest association; they produce a painful pseudoparalysis that mimics, and can coexist with, the palsy
• Facial (VII) nerve palsy - from forceps pressure or the same lateral traction; usually neurapraxic and self-limiting
• Cephalohaematoma or subgaleal haemorrhage, and congenital muscular torticollis, from the birth trauma

Phrenic nerve palsy. The phrenic nerve (C3-C5) leaves the plexus very proximally, so a hemidiaphragm paralysis is an important association of high, proximal (C5) and total lesions. It can cause neonatal respiratory distress or recurrent atelectasis: look for unexplained respiratory difficulty and confirm it with a sniff test - fluoroscopy or ultrasound showing paradoxical upward diaphragm motion on inspiration. Persistent symptomatic paralysis may need diaphragm plication.

Glenohumeral dysplasia is the major late complication, and a joint left subluxated ends in osteoarthritis.

After nerve surgery. A sling or shoulder immobiliser, then gentle range of motion at 4-6 weeks. Recovery is expected over 12-18 months.

After tendon transfer or release. External rotation immobilisation in a spica, brace or shoulder immobiliser for 6 weeks, followed by intensive physiotherapy.

After osteotomy. A sling, with range of motion as tolerated and bone healing at 6-8 weeks.

What recovery looks like. Approximately 80-90% recover spontaneously, often fully or with minimal residual deficit. That headline figure depends heavily on how recovery is defined: methodologically rigorous natural-history data suggest full recovery may be closer to two-thirds, with a meaningful minority left with deficits, and over-reassurance risks late referral.

The severe end. A total palsy (Narakas III-IV) does badly, and permanent deficits are common. Nerve surgery improves function significantly but rarely restores it to normal.

Global Epidemiology:

• Incidence approximately 1-2 per 1000 live births, falling in high-resource settings. A Swedish national registry recorded a decline from 3.1 to 1.0 per 1000 cephalic vaginal births between 1997 and 2019 despite rising recognition of shoulder dystocia (PMID 36345990).
• Risk factors: shoulder dystocia, fetal macrosomia, maternal gestational diabetes, instrumental (forceps/vacuum) delivery, prolonged second stage, and breech delivery. Notably, a proportion of cases occur without documented dystocia (including caesarean births), implicating in-utero maladaptation.
• Upper-trunk (Erb's) pattern accounts for roughly 80-90% of cases and carries the best prognosis.

Side-by-Side Guidance:

Service Organisation & Resource Variation:

• High-resource settings: dedicated multidisciplinary plexus clinics (paediatric hand/peripheral-nerve surgery, physiotherapy, occupational therapy), early MRI and microsurgical capability, and structured glenohumeral surveillance.
• Limited-resource settings: emphasis on prevention (dystocia training, gestational diabetes screening), parent-delivered range-of-motion therapy, and clear referral pathways; advanced microsurgery and secondary reconstruction may be regionally centralised or unavailable, making timely triage critical.
• Universal principles: exclude a fracture, protect passive range of motion, document serial active movement, refer early if recovery stalls, and monitor lifelong for shoulder dysplasia regardless of setting.

When to operate on the nerve. No biceps by 3 months (Gilbert/Paris), a multi-movement composite at 3 months (Toronto/Clarke), or waiting to 6 months for partial recovery: no randomised trial has resolved the optimal threshold, and practice varies by centre.

Microsurgery versus watchful waiting. The absence of randomised data comparing primary nerve reconstruction with continued observation in incomplete upper-trunk lesions remains the field's biggest evidence gap. Decisions rest on cohort data and serial examination.

How early to intervene for the shoulder. Botulinum toxin, closed reduction and casting, arthroscopic versus open release, and the place of glenoid osteotomy are all debated for posterior subluxation. Earlier joint reduction may remodel the glenoid, but the thresholds are not standardised.