Mechanical birth-related trauma to the neonate: An imaging perspective
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Mechanical birth-related injuries to the neonate are declining in incidence with advances in prenatal diagnosis and care. These injuries, however, continue to represent an important source of morbidity and mortality in the affected patient population. In the United States, these injuries are estimated to occur among 2.6% of births. Although more usual in context of existing feto-maternal risk factors, their occurrence can be unpredictable. While often superficial and temporary, functional and cosmetic sequelae, disability or even death can result as a consequence of birth-related injuries. The Agency for Healthcare research and quality (AHRQ) in the USA has developed, through expert consensus, patient safety indicators which include seven types of birth-related injuries including subdural and intracerebral hemorrhage, epicranial subaponeurotic hemorrhage, skeletal injuries, injuries to spine and spinal cord, peripheral and cranial nerve injuries and other types of specified and non-specified birth trauma. Understandably, birth-related injuries are a source of great concern for the parents and clinician. Many of these injuries have imaging manifestations. This article seeks to familiarize the reader with the clinical spectrum, significance and multimodality imaging appearances of neonatal multi-organ birth-related trauma and its sequelae, where applicable.
• Mechanical trauma related to birth usually occurs with pre-existing feto-maternal risk factors.
• Several organ systems can be affected; neurologic, musculoskeletal or visceral injuries can occur.
• Injuries can be mild and transient or disabling, even life-threatening.
• Imaging plays an important role in injury identification and triage of affected neonates.
KeywordsNeonate Mechanical trauma Macrosomia Instrumental delivery Cephalopelvic disproportion
The process of birth, whether spontaneous or assisted, is inherently traumatic for the newborn. Birth-related injuries encompass both mechanical and hypoxic-ischemic events. This review focuses mostly on mechanical trauma sustained by the neonate owing to the forces of labor and delivery. For conciseness of this review, birth-related hypoxic-ischemic injuries to the neonate will not be separately addressed.
Trauma related to birth may affect several organ systems of the neonate (ESM_1). The exact incidence of mechanical trauma of birth may be somewhat underestimated. Incidence is 0.82%, prevalence has been estimated at 9.5 per 1000 live births . Less than 2% of neonatal deaths result from birth trauma .
Birth-related trauma can occur without identifiable risk factors; however, it is more common in context of predisposing feto-maternal risk factors. Risk factors can be fetal (macrosomia-birth weight > 4500 g, malpresentation or shoulder dystocia (defined as passage of more than 60 s between the delivery of the head and body , resulting in requirement of additional obstetric maneuvers for delivery of fetal shoulders )); maternal (diabetes, primiparity, small pelvis); or obstetric (epidural analgesia, induced or instrumental delivery).
Over the following paragraphs, we discuss the clinical context and imaging findings of birth -related injuries categorized by different portions of the neonate’s anatomy.
Injuries to the head and face
Based on a study of asymptomatic neonates following full-term spontaneous vaginal birth , the prevalence of intracranial hemorrhage was estimated to be 26%. These hemorrhages were not associated with signs of overt trauma. The majority of these hemorrhages were found to be subdural and infratentorial. These were found to be without clinical consequence [8, 9]. Also, these hemorrhages were all of the same age . The pterion is a large, relatively unprotected sutural confluence, which makes this site vulnerable for injury . MR is superior to CT for evaluation of extracerebral and posterior fossa hemorrhages . Susceptibility weighted imaging is especially useful for delineation of both intra- and extraaxial hemorrhages . Supratentorial intracerebral hemorrhages are well seen and can be dated with both CT and MR, although ultrasound can be useful for initial bedside evaluation .
Retinal hemorrhages are seen among one-quarter of otherwise normal deliveries, but instrumental delivery and cord around the neck have been identified as risk factors . Spontaneous vaginal delivery, prolonged second stage of labor and neonatal intracranial hemorrhage can exacerbate these hemorrhages [12, 13]. In one prospective study , all detected birth-related retinal hemorrhages resolved by 1 month of age . Coexistence of these hemorrhages with skull fractures/intracranial hemorrhages secondary to mechanical birth trauma can lead to confusion with nonaccidental trauma.
Passage through the birth canal may lead to facial trauma including mostly abrasions of the face, although traumatic luxation of the nose  and neonatal nasal septal deviation  have been reported as a consequence of birth-related trauma.
Injuries to the spinal cord and neck
Forceful hyperextension of the neck can occasionally result in ligamentous injuries at the craniocervical junction .
Carotid dissection has been described as a rare accompaniment of dystocic labor ; CT, Doppler ultrasound and MR may all have a role in diagnosis . CT and MR of the brain may reveal findings of a stroke involving a carotid vascular territory; color Doppler of the carotid may reveal an intravascular flap suggesting dissection .
Peripheral nerve injuries
Involvement of C5/6 results in Erb’s palsy and lack of Moro’s reflex, whereas involvement of C7/T1 results in Klumpke’s palsy (Fig. 13b-f) and lack of Moro and grasp reflexes. Additionally, injury to T1 sympathetic fibers can lead to Horner’s syndrome. Complete plexus injury results in atonic limb and Horner’s sign .
This entity most commonly affects the upper trunk nerve components of the brachial plexus (C5-T1) . This results in stretching, or less commonly avulsion of nerve roots. Avulsions, when they occur, usually localize to the C5 and C6 nerve roots and clinically manifest as Erb’s palsy . High resolution heavily T2-weighted MR can show a traumatic pseudomeningocele (Fig. 13b-e), absent rootlets or roots (Fig. 13d-e) and abnormal spinal cord signal [6, 27].
Ultrasound has a role in preoperative evaluation of postganglionic brachial plexus in children with neonatal brachial plexus palsy; it demonstrated 68% sensitivity and 40% specificity for lower trunk involvement in a recent retrospective cohort study . A small neuroma involving the upper trunk of the brachial plexus in an infant presenting with brachial plexus palsy was also recently described .
Radial nerve palsy can occur in context of a humeral shaft fracture .
Traumatic facial nerve injury can occur as a consequence of difficult extraction, particularly in context of forceps use. Prognosis for recovery is excellent; 90% recover completely .
Application of excessive traction to the head during breech delivery can result in unilateral recurrent laryngeal nerve injury and abductor paralysis. Left recurrent laryngeal nerve tends to be involved more often due to its longer course . Prognosis for unilateral injuries is good, most usually resolve in 6 weeks, bilateral injuries tend to have a variable prognosis and some may require tracheostomy.
Musculoskeletal injuries encompass both bony fractures and soft tissue injuries. Birth-related fractures in the newborn period, though overall rare, are important to recognize due to non-specific signs or symptoms, increased likelihood of missing them due to unossified cartilage and necessity of differentiating these from abusive trauma. These include fractures of both flat and long bones .
Rib fractures have been described to be associated with dystocic birth. Based on a recent case series, birth-related rib fractures tend to be mid-posterior in location .
Operative intervention or botulinum toxin injection are considered in the rare circumstance where physical therapy fails .
Tracheal rupture can be anterior subglottic or distal tracheal in location. This rare and potentially fatal entity can occur in context of dystocic birth, and should be promptly suspected in neonates who develop subcutaneous emphysema or pneumomediastinum shortly after birth [51, 52]. Bronchoscopy should be expeditiously performed, and open surgical repair undertaken if necessary, especially in cases of distal tracheal rupture .
Mechanical trauma related to birth can affect different organ systems of the neonate. While often of little clinical consequence, traumatic events can lead to cosmetic deformity, functional impairment and in extreme circumstances, even death. Imaging is important for detection, assignment of prognostic significance and follow-up, making it important for radiologists to be familiar with the imaging manifestations of these entities and their sequelae.
The authors wish to thank Margaret Kowaluk, Nadezhda Kiriyak and Gwen Mack from the Graphics Section, Department of Imaging Sciences, University of Rochester Medical Center, Rochester NY, USA for their help with radiographic images and original artwork in this article.
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