A brachial plexus birth injury occurs when the network of nerves in a baby’s neck and shoulder is damaged during childbirth. This injury can result in weakness or paralysis, impacting the infant’s ability to move their affected limb.
Understanding the Brachial Plexus and Injury Causes
The brachial plexus is an arrangement of nerves originating from the spinal cord, from nerve roots C5 through T1 in the neck. These roots merge to form trunks, divisions, cords, and finally branch out into the main nerves that supply the shoulder, arm, forearm, and hand. This neural network is responsible for both motor function and sensory function throughout the upper limb.
The least severe brachial plexus injury is a stretch injury, or neurapraxia, where the nerve is stretched but not torn, often healing spontaneously within a few months. A neuroma involves scar tissue forming around a damaged nerve, which can press on healthy nerve fibers and interfere with signal transmission. More severe injuries include a rupture, where the nerve is torn but not from the spinal cord, and an avulsion, the most severe type, where the nerve is completely torn from the spinal cord.
These injuries often occur during delivery when there is excessive stretching or pulling of the baby’s head and neck relative to the shoulders. A frequent cause is shoulder dystocia, a situation where the baby’s shoulder becomes lodged in the birth canal after the head has delivered. Other contributing factors include a large birth weight (macrosomia), breech presentation (feet or buttocks first), prolonged or difficult labor, and the use of assistive devices like forceps or vacuum extractors during delivery.
Identifying Signs and Diagnosis
Parents might observe signs in an infant with a brachial plexus injury shortly after birth. These include a limp or floppy arm, a lack of movement in one arm or hand, or the arm being held in an unusual position, such as straight at the elbow and tucked close to the body, sometimes described as a “waiter’s tip” posture. A decreased grip strength in the affected hand or the absence of the Moro reflex (a baby’s startle response) on the injured side can indicate an injury.
Medical professionals diagnose a brachial plexus birth injury through a physical examination, assessing the infant’s range of motion, reflexes, and muscle strength in the affected arm. To determine the extent and location of the nerve damage, further diagnostic tests may be performed. These can include Electromyography (EMG) and Nerve Conduction Studies (NCS), which evaluate the electrical activity of muscles and the speed of nerve signals. Magnetic Resonance Imaging (MRI) can provide detailed images of the nerves and surrounding tissues, helping to visualize the injury. In some cases, a CT myelography, which involves injecting contrast dye, might be used if MRI provides insufficient information.
Treatment Approaches
Treatment for a brachial plexus birth injury typically begins with non-surgical approaches, especially given that many mild injuries can heal spontaneously. Physical therapy and occupational therapy are often initiated early to maintain the baby’s range of motion, prevent muscle stiffness and contractures, and encourage functional use of the affected limb. Therapists guide parents through exercises, positioning techniques, and daily activities to support recovery and promote neural development.
If significant recovery does not occur with conservative management, surgical interventions may be considered, often between 3 to 6 months of age for better outcomes. Nerve grafting involves removing a damaged nerve segment and replacing it with a healthy nerve segment from another part of the body, creating a bridge for nerve regeneration. Nerve transfers involve rerouting a healthy, less important nerve to power a paralyzed muscle, which can lead to faster muscle reinnervation, especially in cases of nerve root avulsion.
For older children who may have developed muscle imbalances or joint deformities, tendon transfers might be performed. This procedure involves reattaching a functioning tendon to a paralyzed one to restore specific movements, such as external rotation of the shoulder. Other supportive care may include pain management, if necessary, and ongoing monitoring by a multidisciplinary team of specialists to track progress and adjust the treatment plan.
Recovery and Prognosis
The recovery trajectory for a brachial plexus birth injury varies widely, influenced by several factors including the type and severity of the nerve damage, the age at which the injury was diagnosed, and consistent adherence to therapy. Mild stretch injuries (neurapraxia) often show full spontaneous recovery within three to six months, with some improvement noted even within weeks. For more severe injuries, the recovery process can be prolonged, potentially taking many months or even years.
Early intervention, particularly with physical and occupational therapy, is associated with better outcomes, helping to maintain joint mobility and muscle strength as nerves regenerate. If spontaneous recovery of specific functions, such as biceps strength, does not begin by around three to five months of age, surgical options are often explored to prevent permanent muscle atrophy and improve functional results. While many children regain full or significant function in the affected arm, some may experience residual weakness, limited range of motion, or other long-term effects despite treatment. Continued rehabilitation and ongoing support systems for families are important throughout the child’s development to maximize their potential and adapt to any lasting challenges.