Neonatal brachial plexus palsy

Disease/Disorder

Also known as: Erb's palsy, obstetric brachial plexus palsy, birth brachial plexus palsy

Anatomy or system affected: Arms, nervous system

Definition: A motor disability evident early in life that manifests as weakness of the affected arm due to stretching or compression of the nerves of the brachial plexus during the perinatal period, with passive range of motion greater than active.

Key terms:

brachial plexus: complex of nerves that carry motor and sensory function to the arm

contractures: permanent shorting of muscles or joints

Erb's palsy: stereotyped clinical presentation of neonatal brachial plexus palsy resulting from injury to the C5, C6, and sometimes C7 spinal nerve roots

Horner's syndrome:ptosis (eyelid drooping), miosis (abnormal constriction of the pupil of the eye), and anhydrosis (decreased sweating on the face)

incidence: the rate at which a certain event occurs or the number of new cases of a specific disorder occurring during a certain period in a population at risk

pan-plexopathy: a form of neonatal brachial plexus palsy comprising of injury to all of the spinal nerve roots manifesting as a flaccid arm

perinatal period: the period immediately before and after birth, commencing at 20 weeks of gestation and ending at 28 weeks after birth (140 days total)

range of motion: movement of a joint from full flexion to full extension

shoulder dystocia: diagnosed when the delivery of the fetal head is not followed by the emergence of the shoulder due to impaction of the fetus' shoulder in the birth canal

Causes and Symptoms

Children with neonatal brachial plexus palsy (NBPP) have a weak or paralyzed arm, and their passive range of motion is greater than their active range of motion. NBPP becomes evident early in life and usually results from stretching or compression of the nerves of the brachial plexus during the perinatal period. NBPP occurs with an incidence of 1.5 cases per 1,000 live births, with or without shoulder dystocia at the time of both vaginal and cesarean delivery. Risk factors for NBPP include abnormal positioning of the fetus, labor abnormalities, artificial labor induction, large fetus, and shoulder dystocia. However, except for shoulder dystocia, none of these risk factors are statistically significant clinical predictors for the occurrence of NBPP.

Compression or stretching of the nerves of the brachial plexus can occur during development in the uterus or during the descent and emergence of the fetus from the uterus and pelvis with maternal pushing and naturally expulsive forces. Biomechanically, nerve injury can result from forces applied by clinicians, or natural physical events that move the fetus from the uterus through the birth canal and out of the mother's pelvis. No one force or factor seems to be responsible for the cause of NBPP, but the available data do suggest that the occurrence of NBPP may be a multifactorial event.

The brachial plexus is a very complex structure that connects the spinal nerves in the neck to their terminal branches in the arm and is divided into 5 zones: (1) C5 through T1 spinal nerve roots; (2) upper, middle, and lower trunks; (3) anterior and posterior divisions of each trunk; (4) lateral, posterior, and medial cords; and (5) terminal branches. These nerves carry the signals necessary for the normal movement and sensation in the entire arm. The brachial plexus is analogous to a set of intersecting highways with overpasses, underpasses, and multiple merging traffic intersections, with several roads leading into (analogous to the spinal nerve roots) and out of (analogous to the terminal branches) the intersections. However, for simplicity, the nerve roots can be indexed to the muscles in the following fashion: C5-shoulder movement, C6-elbow flexion, C7-elbow extension, C8/T1-hand and finger movement.

Not all cases of NBPP are the same, and the symptoms may be radically different depending on which parts of the brachial plexus are injured. The intricate intersecting nature of the brachial plexus implies that thousands of potentially different palsies can ensue, but in reality, only a few variations actually occur. The most useful classification scheme for clinical presentation of NBPP is the Narakas Grade system that represents the extent of the spinal nerve root injury: only C5 and C6 nerve roots are injured in Grade 1, C5, C6, C7 nerve roots in Grade 2, and C5 through T1 injured in Grade 3 (without Horner's syndrome) and Grade 4 (with Horner's syndrome). When this classification system is used in two- to four-week old affected babies, it may guide the prognosis for spontaneous recovery, since up to 90 percent of the patients with Grade 1 NBPP regain functional use of the affected arm, but less than 5 percent of the patients with Grade 4 NBPP regain functional use without medical and/or surgical intervention.

Other classification systems are based on the clinical manifestations of NBPP. Erb's palsy, the most common type of NBPP, is synonymous with an “upper” plexus palsy that specifically results from damage to C5, C6, and sometimes C7 spinal nerve roots. Patients with Erb's palsy present a “waiter's tip” posture when their affected arm is pulled toward the midline of the body, an internally rotated shoulder, flexed wrist, extended fingers that result from loss of both shoulder control and elbow bending. Contrastingly, the extremely rare Klumpke's palsy is synonymous with a “lower” plexus palsy characterized by a flaccid hand attached to an otherwise active arm. Total plexus palsy or pan-plexopathy is equivalent to Narakas Grade 3 and 4 and is recognized by loss of total function of the arm.

Treatment and Therapy

Lack of normal arm movement observed during the perinatal period warrants confirmation of the diagnosis of NBPP by a specialist. Possible skeletal injuries or fractures should be confirmed by clinical and radiographic evaluation since these injuries may preclude early occupational/physical therapy. Immobilization of the arm is not recommended except in the case of skeletal injuries.

With regard to the specific motor function of the affected arm, the treating physician assesses the passive and active range of motion of the affected arm. Available assessment scales of motor function in NBPP are used to determine the extent and severity of nerve injury, to prognosticate potential functional recovery, and to guide and assess the outcomes from further treatment. Traditional scales focus only upon the affected arm, but more recently, assessment methods are focusing upon the overall function of the child. Supplementing the physical examination with electrodiagnostic, electromyographic (EMG) and radiographic (magnetic resonance imaging, MRI) findings are helpful to decide whether surgical nerve reconstruction will be beneficial.

Early referral of those babies with severe or extensive NBPP to interdisciplinary specialty clinics can improve overall functional outcomes as the baby grows. Regardless of the need for surgical intervention, rehabilitation management is critical. Occupational/physical therapy to maintain the normal passive range of motion in all upper extremity joints (especially shoulder external rotation and forearm rotation) facilitates successful functional recovery. Parents and caregivers should consider themselves to be the patient's primary therapist by performing range of motion exercises regularly, with multimedia assistance if available (e.g., during every diaper change). Reinforced use of the affected arm while constraining the normal arm (similar to patching a lazy eye) can aid the child's recognition of the arm and strengthen the arm through increased arm use during age-appropriate activities. Normal childhood development milestones must be encouraged, including crawling. Splinting may be used during sleep to avoid contractures or to protect floppy joints. As the child grows, recreational activities like swimming, dance, sports, and potentially therapist-designed video game platforms can help to sustain the goals of formal occupational/physical therapy.

For NBPP patients who do not recover with conservative management, surgical nerve reconstruction may be an option, usually occurring between three to nine months of age. Although the indications and timing for nerve reconstruction have not been absolutely established, most practitioners agree that babies with the extensive total brachial plexus palsy and those with the severe Erb's palsy will benefit from nerve surgery. The goal of nerve reconstruction is not to regain a normal arm, but surgical intervention is a step towards a functional arm with adequate movement, if not power. Nerve repair using autologous nerve graft and/or nerve transfer (using a good nerve to re-innervate an injured one) constitute the primary options for reconstructing the function of the brachial plexus. As nerve repair and transfer rely upon regrowth of the normal portions of the nerve through the residual pathways after injured nerve is cleared away (Wallerian degeneration), and as this nerve regeneration is very slow, the ultimate functional outcome from nerve reconstruction surgery may not be apparent for one to three years.

Toddlers and older children with incomplete recovery following neurosurgical or conservative treatment may have functional limitations because of residual muscle weakness and soft tissue contractures, especially around the shoulder and elbow. MRI imaging can guide the decision to pursue orthopedic intervention. Internal rotation contracture of the shoulder is most common and can be associated with progressive shoulder joint deformity and instability. Indications for surgical intervention include persistent internal rotation contracture despite aggressive nonsurgical therapy, progressive joint deformity, and obvious joint dislocation. Surgical options include muscle lengthening combined with tendon transfers, corrective bone surgery (osteotomies), and open or arthroscopic reduction of the shoulder joint.

For children with residual elbow, forearm, and hand problems, secondary procedures by a hand surgeon may be appropriate. These procedures include soft tissue releases, joint fusions, muscle transfers, and corrective osteotomies. The usual age for secondary reconstruction of the elbow/forearm function is 4–6 years of age, and for wrist/hand function is 6–13 years of age.

For all surgical interventions, the most important factor in producing the optimal result is a cooperative child with intense investment from assertive parents/caretakers. The parents must understand the objectives of the surgical procedure and work hard with their children in postoperative rehabilitation-and maintenance of function by being their children's primary therapists. Surgery alone without subsequent rehabilitation management and therapy is unlikely to yield the desired outcome.

Perspective and Prospects

Overall, the majority of infants with NBPP have a good prognosis for recovering adequate functional use of the affected arm-with rehabilitation management and therapy, supplemented with surgical intervention when and where appropriate and desired by the patient and parents/caretakers. Early occupational/physical therapy can support the spontaneous recovery of function and minimize consequent musculoskeletal comorbidities along with more efficient recovery of function after surgery. Despite the similar incidence of NBPP to cerebral palsy, public awareness of this perinatal disorder and its lifelong implications (medical and psychosocial) for the more extensively/severely affected children are significantly lacking. Similarly, published research studies regarding NBPP number only a fraction of that regarding cerebral palsy. Therefore, current efforts exist not only to find new medical treatment techniques but also to increase awareness, to address and improve the quality of life for patients with NBPP via traditional and recent technology-assisted modalities. Early referral to an interdisciplinary specialty brachial plexus clinic can avail the patient of the most current treatment paradigms to achieve the optimal outcome.

Bibliography

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