Brachial Plexus Injury in Growing Children: Disability Trajectory
In most children with brachial plexus injury, the disability itself does not worsen with growth; however, the functional gap between the affected and unaffected limbs often becomes more apparent as the child develops, creating what appears to be worsening disability due to growth-related deformities and developmental challenges rather than progressive nerve damage.
Understanding the Natural History
The key distinction here is between nerve recovery versus functional development. The nerve injury itself typically stabilizes or improves in the first 1-2 years after injury, with the majority of spontaneous recovery occurring within the first 3 months of life in obstetric cases 1. However, what changes dramatically is how the injury manifests functionally as the child grows.
Primary Mechanisms of Apparent Worsening
Growth-related musculoskeletal deformities develop as the child ages, even when the nerve injury remains stable. These include:
- Glenohumeral joint deformity: The shoulder joint develops abnormally due to muscle imbalance, with stunted muscle growth, denervation effects, and limb disuse disrupting normal joint development 2
- Bone growth abnormalities: The affected limb experiences growth retardation, creating increasing length and size discrepancies 3
- Secondary contractures: Muscle imbalances lead to progressive joint contractures that worsen with skeletal growth
Developmental Apraxia Component
Beyond the physical nerve damage, children with persistent brachial plexus injury develop impaired motor unit activation—a form of developmental apraxia caused by defective motor programming in early infancy 4. This means that even when muscles are reinnervated, the brain's ability to properly activate and coordinate those muscles remains impaired, contributing to persistent functional limitations that become more evident as complex motor tasks are required during development.
Clinical Trajectory by Injury Severity
Mild Injuries (Neuropraxia)
- 70-90% recover spontaneously within 3 months 1
- Minimal long-term disability
- Growth-related issues are uncommon
Moderate to Severe Injuries
- 13.2% develop disability lasting >1 year 5
- Risk factors for persistent disability include:
The Critical Distinction: Preganglionic vs Postganglionic
Preganglionic injuries (nerve root avulsion) have worse prognosis and different developmental consequences than postganglionic injuries (nerve rupture), yet they present similarly initially and are often treated identically due to diagnostic limitations 2. This contributes to variable outcomes and the perception of worsening disability in some children.
What Actually Worsens vs What Stays Stable
Does NOT Worsen:
- The nerve injury itself (damage is static after initial trauma)
- Sensory recovery (83.3% of children with initially insensate hands recover to S3 sensation) 6
- Pain (notably, children with brachial plexus injuries have high incidence of root avulsions but no pain complaints) 6
DOES Worsen or Become More Apparent:
- Functional gap: As unaffected limb develops normally, the affected limb falls progressively behind in strength, coordination, and size
- Skeletal deformities: Glenohumeral dysplasia, scapular winging, and limb length discrepancy become more pronounced with growth 2
- Activity limitations: As age-appropriate activities become more complex (sports, writing, dressing), the functional limitations become more disabling
- Psychosocial impact: Body image concerns and participation restrictions increase during school years 7
Critical Clinical Implications
Early intervention is essential but timing flexibility exists: Unlike adult injuries, functional recovery in children does not correlate significantly with delay to surgery 6. However, this should not delay appropriate evaluation and treatment planning, as secondary deformities are easier to prevent than correct.
The 3-month window remains critical for decision-making: Absence of biceps function at 3 months and global palsy are the main indications for early microsurgery 1. After this point, the focus shifts to managing developmental consequences.
Long-term rehabilitation is mandatory: The complexity of functional impairment—including sensorimotor disturbances, CNS reorganization, upper limb underuse, and psychological factors—necessitates interdisciplinary long-term management 7. This is not a "fix it and forget it" condition.
Common Pitfalls to Avoid
- Assuming spontaneous recovery means complete recovery: Even children who regain movement may develop significant functional limitations and deformities during growth
- Treating all injuries the same: Preganglionic and postganglionic injuries require different surgical approaches and have different prognoses 2
- Stopping follow-up too early: Growth-related deformities may not manifest until school age or adolescence
- Neglecting the central component: The developmental apraxia component means that peripheral nerve repair alone may not restore normal function 4