Birth Trauma: Cranial Nerve and Spinal Cord Injury

Cranial nerve and spinal cord injuries result from hyperextension, traction, and overstretching with simultaneous rotation; they may range from localized neurapraxia to complete nerve or cord transection.

Cranial nerve injury

Unilateral branches of the facial nerve and vagus nerve, in the form of recurrent laryngeal nerve, are most commonly involved in cranial nerve injuries and result in temporary or permanent paralysis.

Compression by the forceps blade has been implicated in some facial nerve injury, but most facial nerve palsy is unrelated to trauma from obstetrical instrumentation (eg, forceps). The compression appears to occur as the head passes by the sacrum.

Physical findings for central nerve injuries are asymmetric facies with crying. The mouth is drawn towards the normal side, wrinkles are deeper on the normal side, and movement of the forehead and eyelid is unaffected. The paralyzed side is smooth with a swollen appearance; the nasolabial fold is absent; and the corner of the mouth droops. No evidence of trauma is present on the face.

Physical findings for peripheral nerve injuries are asymmetric facies with crying. Sometimes evidence of forceps marks is present. With peripheral nerve branch injury, the paralysis is limited to the forehead, eye, or mouth.

The differential diagnosis includes nuclear genesis (Möbius syndrome), congenital absence of the facial muscles, unilateral absence of the orbicularis oris muscle, and intracranial hemorrhage.

Most infants begin to recover in the first week, but full resolution may take several months. Palsy that is due to trauma usually resolves or improves, whereas palsy that persists is often due to absence of the nerve.

Management consists of protecting the open eye with patches and synthetic tears (methylcellulose drops) every 4 hours. Consultation with a neurologist and a surgeon should be sought if no improvement is observed in 7-10 days.

Diaphragmatic paralysis secondary to traumatic injury to the cervical nerve roots that supply the phrenic nerve can occur as an isolated finding or in association with brachial plexus injury. The clinical syndrome is variable. The course is biphasic; initially the infant experiences respiratory distress with tachypnea and blood gases suggestive of hypoventilation (ie, hypoxemia, hypercapnia, acidosis). Over the next several days, the infant may improve with oxygen and varying degrees of ventilatory support. Elevated hemidiaphragm may not be observed in the early stages. Approximately 80% of lesions involve the right side and about 10% are bilateral.

The diagnosis is established by ultrasonography or fluoroscopy of the chest, which reveals the elevated hemidiaphragm with paradoxic movement of the affected side with breathing.

The mortality rate for unilateral lesions is approximately 10-15%. Most patients recover in the first 6-12 months. An outcome for bilateral lesions is poorer. The mortality rate approaches 50%, and prolonged ventilatory support may be necessary.

Management consists of careful surveillance of respiratory status, and intervention, when appropriate, is critical.

Laryngeal nerve injury

Disturbance of laryngeal nerve function may affect swallowing and breathing. Laryngeal nerve injury appears to result from an intrauterine posture in which the head is rotated and flexed laterally. During delivery, similar head movement, when marked, may injure the laryngeal nerve, accounting for approximately 10% of cases of vocal cord paralysis attributed to birth trauma. The infant presents with a hoarse cry or respiratory stridor, caused most often by unilateral laryngeal nerve paralysis. Swallowing may be affected if the superior branch is involved. Bilateral paralysis may be caused by trauma to both laryngeal nerves or, more commonly, by a CNS injury such as hypoxia or hemorrhage that involves the brain stem. Patients with bilateral paralysis often present with severe respiratory distress or asphyxia.

Direct laryngoscopic examination is necessary to make the diagnosis and to distinguish vocal cord paralysis from other causes of respiratory distress and stridor in the newborn. Differentiate from other rare etiologies, such as cardiovascular or CNS malformations or a mediastinal tumor.

Paralysis often resolves in 4-6 weeks, although recovery may take as long as 6-12 months in severe cases. Treatment is symptomatic. Small frequent feeds, once the neonate is stable, minimize the risk of aspiration. Infants with bilateral involvement may require gavage feeding and tracheotomy.

Spinal cord injury

Spinal cord injury incurred during delivery results from excessive traction or rotation. Traction is more important in breech deliveries (minority of cases), and torsion is more significant in vertex deliveries. True incidence is difficult to determine. The lower cervical and upper thoracic region for breech delivery and the upper and midcervical region for vertex delivery are the major sites of injury.

Major neuropathologic changes consist of acute lesions, which are hemorrhages, especially epidural, intraspinal, and edema. Hemorrhagic lesions are associated with varying degrees of stretching, laceration, and disruption or total transaction. Occasionally, the dura may be torn, and rarely, the vertebral fractures or dislocations may be observed.

The clinical presentation is stillbirth or rapid neonatal death with failure to establish adequate respiratory function, especially in cases involving the upper cervical cord or lower brain stem. Severe respiratory failure may be obscured by mechanical ventilation and may cause ethical issues later. The infant may survive with weakness and hypotonia, and the true etiology may not be recognized. A neuromuscular disorder or transient hypoxic ischemic encephalopathy may be considered. Most infants later develop spasticity that may be mistaken for cerebral palsy.

Prevention is the most important aspect of medical care. Obstetric management of breech deliveries, instrumental deliveries, and pharmacologic augmentation of labor must be appropriate. Occasionally, injury may be sustained in utero.

The diagnosis is made by MRI or CT myelography. Little evidence indicates that laminectomy or decompression has anything to offer. A potential role for methylprednisolone exists. Supportive therapy is important.

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