Abstract
This chapter is focused on injuries of extracranial, cranial, intracranial, spinal cord, and peripheral nervous system structures, with emphasis on those disorders that appear to be related primarily to mechanical trauma. Extracranial hemorrhage consists of three major lesions: caput succedaneum, subgaleal hemorrhage, and cephalhematoma. These lesions are generally not serious, except for several uncommon complications. Skull fracture, the principal bony lesion of the newborn, may be linear, be depressed, or consist of occipital osteodiastasis. Intracranial hemorrhage, not unexpectedly, may result from mechanical factors, although among all types of intracranial hemorrhage, trauma per se is a prominent pathogenetic factor principally only for epidural and some cases of subdural hemorrhage. Subdural hemorrhage is discussed in Chapter 22 . Spinal cord injury is the most serious CNS parenchymal lesion related primarily to mechanical factors. Two major sites of injury are upper to mid-cervical, occurring mainly in cephalic deliveries and relating primarily to torsional factors, and lower cervical to upper thoracic, occurring mainly in breech deliveries and relating primarily to longitudinal or lateral tractional factors. MRI has proven valuable for both diagnosis and prognosis. Improvements in obstetrical practice have led to declines in incidence. Management is difficult, but new pharmacological, cellular, and rehabilitative interventions are on the horizon. Traumatic injury to peripheral nervous system structures is particularly dominated by brachial plexus injury. The mechanical forces underlying most cases are usually some combination of exogenous factors, such as downward lateral traction involving delivery of the head in a breech delivery or of the shoulder in cephalic deliveries and endogenous factors, such as very strong maternal expulsion forces. Other injuries to peripheral nervous system structures individually are uncommon but collectively are relatively common.
Keywords
mechanical trauma, extracranial hemorrhage, skull fracture, intracranial hemorrhage, spinal cord injury, brachial plexus injury
This chapter focuses on injuries of extracranial, cranial, intracranial, spinal cord, and peripheral nervous system structures. In particular, the emphasis is on those disorders that appear to be related primarily to mechanical trauma. The adverse mechanical events occur principally during labor and delivery. Unfortunately such events often lead to criticism of obstetrical management. Such criticism generally is unwarranted, because the mechanical factors are most often beyond the control of the obstetrician. Indeed, in many well-documented instances, apparent traumatic lesions are related to unknown antepartum events or to developmental or acquired lesions evolving in utero. Nevertheless perinatal mechanical traumatic events do occur, result in well-defined clinical syndromes, and require recognition and appropriate management. The chapter is organized into extracranial, cranial, intracranial, spinal cord, and peripheral nervous system lesions.
A brief caveat concerning terminology is important to note in the introduction to this chapter. The terms perinatal trauma and birth injury have been given definitions so broad as to be confusing and nearly meaningless. Indeed, a commonly used definition of birth injury is considered to be any condition that affects the fetus adversely during labor or delivery. In this discussion, however, perinatal trauma refers to those adverse effects on the fetus during labor or delivery and in the neonatal period that, as noted earlier, appear to be caused primarily by mechanical factors. Thus specifically excluded are the disturbances of labor and delivery that lead principally to hypoxic-ischemic brain injury (see Chapter 17 , Chapter 18 , Chapter 19 , Chapter 20 ). (Nevertheless, potential overlap between mechanical trauma and the occurrence of hypoxic-ischemic cerebral injury is important to recognize because perinatal mechanical insults may result also in hypoxic-ischemic cerebral injury, perhaps secondary to disturbances of placental or cerebral blood flow. The precise mechanistic relationships remain largely unknown.)
The incidence of traumatic brain injury is difficult to establish conclusively. Nevertheless, it is clear that there have been drastic reductions in the occurrence of traumatic injuries to central and peripheral nervous structures, primarily because of improved obstetrical management. Specific examples are apparent in the subsequent discussions, but recurring themes are the rational use of cesarean section and improved techniques of manual and instrumental vaginal deliveries.
Major Varieties of Perinatal Trauma
The major varieties of perinatal trauma are outlined in Table 36.1 . These include extracranial hemorrhage, skull fracture, intracranial hemorrhage, cerebral contusion, cerebellar contusion, spinal cord injury, and several types of injuries to the peripheral nervous system—for example, nerve roots and cranial or peripheral nerves. The injuries to extracranial, cranial, and central nervous system structures are discussed first.
Extracranial hemorrhage
Skull fracture
Intracranial hemorrhage
| Cerebral contusion Cerebellar contusion Spinal cord injury Peripheral nervous system injury
|
Injury to Extracranial, Cranial, and Central Nervous System Structures
Extracranial Hemorrhage
The three major varieties of extracranial hemorrhage are caput succedaneum, subgaleal hemorrhage, and cephalhematoma. These lesions occur in different tissue planes between the skin and the cranial bone ( Fig. 36.1 and Table 36.2 ).
| LESION | FEATURES OF EXTERNAL SWELLING | INCREASES AFTER BIRTH | CROSSES SUTURE LINES | MARKED ACUTE BLOOD LOSS |
|---|---|---|---|---|
| Caput succedaneum | Soft, pitting | No | Yes | No |
| Subgaleal hematoma | Firm, fluctuant | Yes | Yes | Yes |
| Cephalhematoma | Firm, tense | Yes | No | No |
Caput Succedaneum
This term refers to the hemorrhagic edema that is very commonly observed after vaginal delivery. Compression on the presenting part, exerted by the uterus or cervix, is the most common pathogenesis. Caput and related scalp injuries have been reported in 10% to 20% of deliveries by vacuum extraction. The usual site of caput formation is the vertex, and marked molding of the head is a common accompaniment. The edema is soft, superficial, and pitting in nature and crosses sites of suture lines (see Table 36.2 ). The lesion steadily resolves over the first days of life, and no intervention is necessary.
Subgaleal Hemorrhage
Subgaleal hemorrhage refers to hemorrhage beneath the aponeurosis covering the scalp and connecting the frontal and occipital components of the occipitofrontalis muscle (see Fig. 36.1 ). (Understandably this lesion also is termed subaponeurotic hemorrhage.) Blood may spread beneath the entire scalp and even dissect into the subcutaneous tissue of the neck. The pathogenesis of subgaleal hematoma is related to a combination of external compressive and dragging forces, occasionally aided by a coagulation disturbance (e.g., vitamin K deficiency). A strong association with delivery by vacuum extraction is suggested by available data. In one series approximately 90% of the lesions were associated with vacuum extraction. In a prospective series of 71 infants with subgaleal hemorrhage and delivery by vacuum extraction, a strong relationship was observed with maternal nulliparity and placement of the vacuum cup over the sagittal suture or less than 3 cm from the anterior fontanel. The last two factors would cause the vacuum extractor to exert traction forces with a slanting or shearing effect on the scalp, considered to be central to the rupture of the emissary veins in the subgaleal space. The infants presented at 1 hour of age and had an appreciable incidence of hypovolemic shock (10%), requirement for volume expansion or inotropic support (35%), need for transfusion for anemia (35%), secondary coagulopathy (50%), and hyperbilirubinemia (35%). In a unique study of 27 affected infants by computed tomography (CT) scan, 14 infants demonstrated various angulation abnormalities of the parietal bones; such abnormalities suggest that the lesion can result from bleeding caused by one or more of three mechanisms (linear skull fracture, suture diastasis, and fragmentation of the superior margin of the parietal bone) illustrated in Fig. 36.2 . This lesion is much less common than caput succedaneum, although the precise incidence is unknown. In contrast to uncomplicated caput, subgaleal hematoma presents as a firm, fluctuant mass, increases in size after birth, and may be present in the subcutaneous tissue of the posterior neck (see Table 36.2 ). Because of the findings noted earlier, infants must be watched carefully for signs of blood loss, coagulopathy, and the development of hyperbilirubinemia. Urgent blood transfusion may be necessary. After the acute phase, the lesion resolves over 2 to 3 weeks.
Cephalhematoma
Cephalhematoma refers to a circumscribed region of hemorrhage overlying the skull and confined by cranial sutures.
Incidence.
Cephalhematoma occurs in approximately 1% to 2% of live births. The lesion is nearly twice as common in males as in females and is more frequent in children of primiparous than multiparous mothers. The use of forceps or vacuum extraction in delivery sharply increases incidence. In one large earlier series the incidence of cephalhematoma after the use of outlet forceps was 4.3%; after low forceps, 7.4%; and after midforceps, 9.5%. More recent data indicate that these incidences have declined considerably. Vacuum extraction increases the likelihood of cephalhematoma over threefold relative to the incidence with forceps deliveries. In one careful series of term infants, cephalhematoma occurred in approximately 10% of vacuum-assisted deliveries. Among premature infants the incidence was 20%.
Pathology.
The hemorrhage is subperiosteal in cephalhematoma, as opposed to the edema and blood in caput succedaneum and subgaleal hemorrhage, which are located over the periosteum in either the subcutaneous or subaponeurotic spaces (see Fig. 36.1 ). The subperiosteal locus explains the confinement of the hematoma by cranial sutures (see Table 36.2 ). By far the most common locus of cephalhematoma is over the parietal bone and unilateral. The rare occipital cephalhematoma, midline in location because of confinement by the lambdoid sutures, may mimic occipital encephalocele (cranial ultrasound scan is a convenient means to make this distinction). An underlying linear skull fracture is detected in 10% to 30% of cases of cephalhematoma. The presence of a skull fracture increases the possibility of accompanying intracranial hemorrhage. In one series, 9 of 10 infants with cephalhematoma associated with skull fracture also had intracranial hemorrhage, including subdural and epidural hemorrhage.
Pathogenesis.
Cephalhematoma is caused by mechanical forces—that is, is clearly a traumatic lesion in nearly all cases. The most reasonable formulation for pathogenesis implicates generally unavoidable obstetrical factors relating to the size of the skull and birth canal and to the use of forceps or vacuum, causing tight apposition of subcutaneous structures to the periosteum but separation of periosteum from bone by external dragging forces.
Clinical Features.
The lesion usually increases in size after birth and presents as a firm, tense mass that does not transilluminate (see Table 36.2 and Fig. 36.3 ). The elevated periosteum palpable at the margin of the hematoma causes the palpating finger to appreciate a ridge at the margin of the lesion and a recessed center. This finding is readily mistaken for a depressed skull fracture. Rarely, contiguous cephalhematomas will appear to cross suture lines and thus will be mistaken for subgaleal hematoma ( Fig. 36.4 ). Cephalhematoma is rarely of clinical significance from the neurological standpoint unless a complicating intracranial lesion is present. As noted earlier, linear skull fracture is an occasional accompaniment of cephalhematoma, and in this setting there is a clear association of linear skull fracture and intracranial hemorrhage. I have seen one infant with an infected cephalhematoma and meningitis. Rare additional complications are hyperbilirubinemia, late-onset anemia, and osteomyelitis.
Essentially all cephalhematomas resolve in a few weeks to months. The few that calcify and result initially in hard skull protuberances gradually disappear over many months of skull growth and remodeling.
Management.
No specific therapy is indicated. The degree of acute blood loss rarely requires urgent intervention. Evacuation of the lesion is contraindicated. Treatment of unusual complications, especially large intracranial hemorrhage, may be necessary.
Skull Fracture
Three principal bony lesions of the newborn are categorized appropriately under the designation skull fracture . These lesions are linear and depressed skull fractures and occipital osteodiastasis (see Table 36.1 ). In fact, only with linear skull fracture is there loss of bony continuity and therefore true fracture.
Linear Fracture
Linear skull fracture refers to a nondepressed fracture and is most commonly parietal in location ( Fig. 36.5 ).
Incidence.
Linear skull fractures are relatively common in newborns; however, incidence is difficult to determine precisely because identification of the lesion depends particularly on the frequency of radiographic studies and the diligence of examination. In one older series (1975), the incidence was 10%, but more recent data indicate an incidence less than 3%. The incidence after vacuum-assisted delivery is approximately 5%.
Pathology.
Linear skull fracture may be associated with extracranial (e.g., cephalhematoma) and intracranial (e.g., epidural and subdural hemorrhage and cerebral contusion) complications. It should be emphasized, however, that the more serious, intracranial complications are uncommon concomitants of linear skull fracture in the newborn. Also rarely, the fracture is associated with a tear of the dura and subsequent development of a leptomeningeal cyst. Leptomeningeal cyst may also occur after an unusual type of linear fracture—that is, coronal suture diastasis, particularly secondary to vacuum extraction.
Pathogenesis.
Linear skull fracture is principally a traumatic lesion. Direct compressive effects are probably most important in genesis of the fracture.
Clinical Features.
No clinical feature is associated with the fracture per se. The important clinical point is that the fracture should alert the physician to the possibility, however remote, of a more serious intracranial traumatic lesion. The development of a leptomeningeal cyst over the weeks or months subsequent to fracture can be suspected at the bedside by the finding of increased transillumination of the affected region and defined in more detail by CT or MRI.
Management.
No therapy is indicated. Follow-up skull radiographs at several months of age are useful to document that healing has occurred and that a widened defect indicative of an enlarging leptomeningeal cyst has not developed.
Depressed Fracture
Depressed skull fracture in the newborn usually refers to the “ping-pong” lesion associated with inward buckling of the unusually resilient neonatal bone, usually without loss of bony continuity ( Fig. 36.6 ).
Incidence.
In one large series of 270 infants “injured at birth,” 32 exhibited depressed skull fracture. The use of forceps was common; thus, in 28 of these 32, forceps were known to have been used. In a more recent series, 50 of 68 cases of depressed skull fracture occurred after instrument-related delivery.
Pathology.
The most common site of depressed fracture is the parietal bone. Although in the vast majority of cases there is no visible fracture, occasionally bone fragments may be seen. Rarely, epidural or subdural hemorrhage or cerebral contusion is associated.
Pathogenesis.
Depressed fracture is almost certainly a result of localized compression of the skull. The compressing force is generated by either forceps or pressure against maternal pelvic structures during labor. A prolonged second stage of labor followed by forceps delivery was the most common sequence in one large series. Rarely, depressed skull fracture may occur in utero.
Clinical Features.
The obvious and palpable bony defect calls immediate attention to the lesion ( Fig. 36.7 ). Neurological accompaniments are unusual and relate to associated intracranial traumatic complications. Neurological complications are rare in spontaneous depressed skull fracture but are relatively common in fractures related to forceps deliveries. Indeed, in the latter group, epidural or subdural hemorrhage complicates 30% of cases and subsequent neurological sequelae occur in 4%.
Management.
Traditionally depressed fractures were considered an indication for neurosurgical elevation. This view has been challenged by the observation in several cases of spontaneous elevation of the deformity. Indeed, the natural history of neonatal depressed skull fracture is unclear and the incidence of spontaneous elevation unknown. This fact and the reports of elevation by digital pressure or the use of a breast pump or obstetrical vacuum extractor suggest that neurosurgical intervention may be indicated less commonly than is currently done. The combination of a transparent breast pump shield attached to a vacuum extractor appears to be particularly useful ( Fig. 36.8 ). Nevertheless 85% of 68 cases in one series were said to “require neurosurgery.”
The most reasonable approach to depressed fracture is careful radiological assessment of the lesion—including CT, MRI, or both—to rule out the presence of extradural or subdural clot or bone fragments, as well as careful neurological surveillance to ensure that acute complications do not develop. This approach could then be followed by a trial of the nonsurgical modalities noted previously. If that is unsuccessful, consideration of neurosurgical intervention is then appropriate. However, small uncomplicated “ping-pong” fractures, on the basis of current information, do not seem to warrant prompt neurosurgical intervention.
Occipital Osteodiastasis
Occipital osteodiastasis, or separation of the squamous and lateral parts of the occipital bone, may result in posterior fossa subdural hemorrhage, cerebellar contusion, and cerebellar-medullary compression without hemorrhage or gross contusion. The evolution of the lesion by skull radiography is shown in Fig. 36.9 . Its consequences are discussed primarily in Chapter 23 .
Intracranial Hemorrhage
Major Varieties
The major varieties of intracranial hemorrhage associated with cranial trauma in the perinatal period include epidural hemorrhage, subdural hemorrhage (acute, subacute, and chronic), primary subarachnoid hemorrhage, intraventricular hemorrhage, intracerebral hemorrhage, and intracerebellar hemorrhage (see Table 36.1 ). Pathogeneses other than trauma play more important roles in several of these varieties of intracranial hemorrhage. Trauma appears to play the dominant pathogenetic role in epidural and subdural hemorrhage and may contribute to pathogenesis of the other varieties of intracranial hemorrhage. Except for epidural hemorrhage, the neuropathology, clinical features, management, and other features of neonatal intracranial hemorrhage are discussed in detail in Chapter 22 , Chapter 23 , Chapter 24 .
Epidural Hemorrhage
An epidural hemorrhage refers to hemorrhage in the plane between the bone and the periosteum on the inner surface of the skull (see Fig. 36.1 ). It represents the intracranial analogue of a cephalhematoma (which is often associated).
Incidence.
Epidural hemorrhage is a rare lesion in the newborn and constitutes only about 2% of all cases of neonatal intracranial hemorrhage observed at autopsy. This relative rarity may relate to the fact that in the newborn the dura is unusually thick and largely contiguous with the inner periosteum.
Pathology.
Bleeding into the epidural space stems either from branches of the middle meningeal artery or from major veins or venous sinuses. Fractures across suture lines are likely to be associated with the venous sinuses. Linear skull fracture is present in the majority of cases but not all. Cephalhematoma is also a frequent accompaniment.
Pathogenesis.
When epidural hemorrhage is accompanied by linear skull fracture, overriding of fracture segments and tearing of branches of the middle meningeal artery or a large venous sinus are the probable reasons for the hemorrhage. In the infant without fracture, the reason for the hemorrhage is unclear. The dura can be separated from the bone when “the skull is bent inward or outward” at autopsy, and it is possible that this separation in vivo could cause tears of arteries running in the richly vascularized dural-periosteal layer of the neonatal cranium. Several cases have been associated with neonatal in-hospital falls.
Clinical Features.
Most affected infants have experienced a traumatic labor or delivery and exhibit signs of increased intracranial pressure (bulging anterior fontanel) from the first hours of life. A delay in onset of signs also may occur, perhaps when a venous origin is present. In approximately half of the reported cases, seizures were also present. Signs of uncal herniation—for example, a fixed, dilated ipsilateral pupil—may occur. Suspicion of the lesion is an indication for emergency CT or MRI, which will demonstrate the hemorrhage effectively. The convex, lentiform appearance of the lesion is characteristic (see Figs. 36.6B and 36.10A ). Untreated infants often die within 24 to 48 hours. Surgical evacuation and survival, often with normal outcome, have been reported frequently. Moreover, survival after nonsurgical therapy has also been documented (see Fig. 36.10 ).
Management.
Although epidural hemorrhage is a rare lesion, it should be considered in any infant who has experienced a traumatic labor or delivery or exhibits signs of increased intracranial pressure in the first day of life. Rapid diagnosis by CT or MRI and prompt intervention should improve the outcome. Although surgical evacuation has been the most common therapy, in one series three infants treated by aspiration of an accompanying cephalhematoma recovered without sequelae. In each case the epidural hematoma disappeared after aspiration of the cephalhematoma, apparently because of communication of the two lesions through a fracture site (see Fig. 36.10 ). In a fourth case without cephalhematoma, the hematoma resolved with no direct therapy. In a recent series of four infants, all were normal on follow-up, two after surgical evacuation, one after needle aspiration, and one after conservative therapy.
Cerebral Contusion
Cerebral contusion refers to a focal region of necrosis and hemorrhage usually involving the cerebral cortex and subcortical white matter.
Incidence
Cerebral contusion is an apparently uncommon lesion in the newborn, although the precise incidence is unknown because of past difficulty in establishing the diagnosis in vivo. The reason for the relatively low incidence perhaps relates to the uncommon occurrence in the perinatal period of focal blunt trauma and to the relative resiliency of the neonatal cranium and cerebral mantle. These properties render less likely acceleration-deceleration movements of brain, which result in cerebral contusion at later ages.
Pathology
The term cerebral contusion describes the pathology of focal necrosis and hemorrhage, typically observed in older children, involving particularly cerebral cortex and subcortical white matter. Such lesions are usually found in coup and contrecoup, as well as inferior orbital, frontal, and temporal locations. This characteristic topography is observed only rarely in the newborn. Another variety of cerebral contusion described in newborns and young infants, albeit rarely, consists of slit-like tears in hemispheric white matter that may extend into the cerebral cortex or even the walls of the lateral ventricle.
Pathogenesis
Focal areas of cortical necrosis and hemorrhage result from direct compressive effects in the newborn. Studies in neonatal rat pups implicate excitotoxic effects, mediated at the N -methyl- d -aspartate (NMDA) receptor, in the final pathway to tissue injury and show protective effects of NMDA antagonists administered 30 minutes or 1 hour after the insult. The tears of white matter are attributed to shearing forces within subcortical cerebral parenchyma produced by rapid and extreme deformation of brain. The latter is made possible by the pliability of the newborn skull. An additional predisposing factor may relate to the relative lack of myelin in the developing cerebral white matter.
Clinical Features
Cerebral contusion probably constitutes the substrate for some of the focal cerebral signs associated with serious perinatal traumatic injury. Thus seizures, often focal, motor deficits, especially hemiparesis or monoparesis, and deviation of eyes to the side of the lesion (but movable with the “doll’s eyes” maneuver) represent particularly characteristic cerebral signs. Diagnosis is made best by MRI.
Management
No specific therapy is indicated.
Cerebellar Contusion
Cerebellar contusion may occur with occipital osteodiastasis. More often the contusion that results is associated with infratentorial subdural hematoma or intracerebellar hemorrhage. These lesions are discussed in Chapters 22 and 23 .
Spinal Cord Injury
Spinal cord injury incurred during delivery results from excessive traction or rotation and is unlike the compression injury that is characteristic of most cord injuries encountered in older patients. Spinal cord injury secondary to obstetrical disturbances and apparent mechanical trauma is readily distinguished from the rare spinal cord injuries that occur postnatally in association with vascular occlusion, observed with umbilical artery catheterization or accidental injection of air into a peripheral vein. More difficult to distinguish are the intrauterine cord injuries related to a variety of vascular, malformative, and other factors (see the section on diagnosis , later). These last disorders occur in infants born after atraumatic vaginal or cesarean deliveries.
Incidence
The true incidence of spinal cord injury is difficult to determine, in part because the spinal cord is examined at autopsy only uncommonly. It is likely that injury to the spinal cord is more common than expected. Indeed, in one early series Pierson identified intraspinal hemorrhages in 46% of infants of breech deliveries examined at autopsy. The clinical significance of such lesions is not clear. The most widely cited neuropathological observations are those of Towbin, who concluded in the 1960s that spinal cord injury was a causal factor in approximately 10% of neonatal deaths. Friede cautions against overinterpretation of these data and suggests distinguishing clearly clinically significant lesions from “the often observed minor perivascular petechiae in the cord and from the extreme congestion or hemorrhagic imbibition of the epidural adipose tissue of newborns,” which are presumably of little clinical importance.
Pathology
Two major sites of injury can be identified ( Table 36.3 ). One site occurs principally with breech delivery and involves the lower cervical and upper thoracic regions ; the other site occurs principally with cephalic delivery and involves the upper to midcervical regions. In one large series, the latter site was involved more than twice as often as the former.
| Major sites of injury |
|
| Major neuropathological changes |
|
The dominant acute lesions are hemorrhages, especially epidural and intraspinal, and edema. The intraspinal hemorrhages particularly involve dorsal and central gray matter. These hemorrhagic lesions are usually associated with varying degrees of stretching, laceration, disruption, or total transection. The dura not infrequently is torn, but complete cord transection may occur with an intact dura. Only uncommonly do lesions of the vertebral column appear. Such lesions consist of vertebral fractures or dislocations and separation of the vertebral epiphysis.
The acute lesions of the spinal cord are followed by striking subacute and chronic changes— for example, formation of fibrotic adhesions between dura, leptomeninges, and cord; focal areas of necrosis with cystic cavities within the cord; syringomyelia; drastically disrupted architecture of the cord; and, often, total separation of transected cord segments. Vascular occlusions, perhaps developing as a posttraumatic event, may cause ischemic infarction of cord segments caudal to the level of the primary lesion ( Fig. 36.11 ). This posttraumatic vasopathy may be related causally to the persistence of the clinical state of spinal shock in certain patients (see subsequent section).
Pathogenesis
Central to the pathogenesis of neonatal spinal cord injury is the fact that the large majority of cases are associated with excessive longitudinal or lateral traction of the spine or excessive torsion. (The term excessive must be interpreted cautiously because spinal cord injury has been described in multiple reports after apparently atraumatic deliveries [see earlier].) Traction is more important in breech deliveries, which account now for the minority of cases, and torsion in cephalic deliveries, which account now for the majority of cases.
The critical factors in pathogenesis relate to the relative elasticities of the vertebral column with its associated ligamentous and muscular structures, the dura, and the spinal cord. In the newborn the bony vertebral column is nearly entirely cartilaginous and very elastic, as are the associated ligaments. Similarly, the muscles are relatively hypotonic, and the tone may be depressed further by maternal drugs or anesthesia. The dura is somewhat less elastic. However, least elastic is the neonatal spinal cord, which is anchored above by the medulla and the roots of the brachial plexus and below by the cauda equina. Thus it is easy to understand why excessive longitudinal traction results in marked stretching of the vertebral column and rupture of the dura (the snap often heard at delivery of the aftercoming head in such cases) and the spinal cord. The cord ruptures at the sites of particular mobility and anchoring — that is, in the lower cervical to upper thoracic region. With extreme rotational maneuvers, as with forceps rotation in difficult cephalic deliveries, the site of particular cord mobility and most frequent rupture is in the upper to midcervical region. In a series of 15 cases of high cervical cord injury, the nearly invariable feature was a forceps rotation of 90 degrees or more from the occipitoposterior to occipitotransverse position. The infant’s spine is particularly susceptible to rotational forces because the bony processes (“uncinate processes”) of one vertebral body that articulate with corresponding processes of the adjacent vertebral body and thereby limit rotation are not well developed in the newborn.
Recent insight into pathogenesis at the vascular, cellular, and molecular levels has been gained from studies of adult animals and humans. Thus an early posttraumatic disturbance in cord perfusion may result from local disturbances in cord microcirculation and from systemic hypotension. Release of excitatory amino acids from injured neurons may lead to local excitotoxic mechanisms of cell death, as described in Chapter 13 . The final common pathway of ischemic and neurotransmitter injury includes increases in cytosolic calcium, release of arachidonic acid, production of vasoactive prostanoids and free radicals, lipid peroxidation, membrane injury, and cell death. Potential interventions (e.g., glutamate blockers, corticosteroids, lipid peroxidation inhibitors) are suggested from these findings, and one such intervention, early steroid therapy, has been shown to be of modest benefit in human adults (see the section on management , further on).
Clinical Features
Clinical Settings.
Of paramount importance in the clinical setting are obstetrical factors, particularly breech or midforceps deliveries, which are present in the majority of recognized neonatal spine injuries. In addition, a frequent contributing feature is fetal depression secondary to maternal drugs or anesthesia or to intrauterine asphyxia.
Basic Clinical Syndromes.
The clinical syndromes of spinal cord injury in the newborn are principally threefold ( Table 36.4 ). First, stillbirth or rapid neonatal death with failure to establish adequate respiratory function occurs, particularly in cases with lesions involving the upper cervical cord, lower brain stem, or both. Second, severe respiratory failure may develop in the first days of life and lead to death. (This development may be delayed by mechanical ventilation, which presents major ethical difficulties in the ensuing weeks.) Third, the infant may exhibit neurological phenomena in the neonatal period but survive, with weakness and hypotonia of limbs as the prominent features. The nature of the neonatal neurological syndrome may not be recognized, and the possibility of a neuromuscular disorder or transient hypoxic-ischemic encephalopathy is often considered. Most of these infants later develop spasticity and may be mistakenly considered to have cerebral lesions (“cerebral palsy”).
| Three basic clinical syndromes |
|
| Neurological features |
|
Neurological Features.
The typical infant is born after a difficult delivery. In the lower cervical–upper thoracic injury, the following neurological features are apparent to varying degrees in the first hours or days of life: flaccid weakness with areflexia of lower extremities and variable involvement of upper extremities (see subsequent discussion); sensory level in the region of the lower neck or upper trunk; respiratory disturbance with diaphragmatic breathing and paradoxical respiratory movements or even diaphragmatic paralysis; paralyzed abdominal muscles with a soft, sometimes bulging abdomen; atonic anal sphincter; and distended bladder that usually empties with gentle suprapubic pressure (see Table 36.4 ). a
a References .
Involvement of the upper extremities may reflect concomitant brachial plexus injuries or, if only distal portions of the upper extremities are affected, injury to anterior horn cells at the segmental levels of the spinal cord injury. Horner syndrome is occasionally present and relates to involvement of either cord neurons in the intermediate column of gray matter or exiting roots (especially T-1) destined for the sympathetic ganglia. The major additional neurological feature with mid- or upper-cervical injury is respiratory failure and the need for mechanical ventilation because innervation of the diaphragm emanates from cervical segments 3, 4, and 5, especially 4.Detection of a sensory level is critical and is accomplished readily if the examiner observes both the quantity and quality of movement and the presence of grimace or affective facial response elicited by pinprick. Stimulation should be performed slowly, and low-level reflex movements without facial response, probably mediated at a spinal level, should be recognized.
Coexistence of the clinical features of hypoxic-ischemic encephalopathy (see Chapter 20 ) in the acute neonatal period is not unusual in those infants with upper cervical lesions and the need for mechanical ventilation. In the largest series of such cases reported to date ( n = 14), 9 infants exhibited such signs. Similarly, cognitive deficits, presumably of cerebral origin, were observed later in approximately 40% of infants with upper cervical spinal injury who survived more than 3 months. With improvements in mechanical ventilation, these sequelae appear to be less frequent.
Subsequent Course.
The neonatal neurological syndrome is followed primarily by one of two courses. First, and less commonly, the state just described, sometimes characterized as spinal shock, persists. This state may relate to secondary ischemia (see the section on posttraumatic vasopathy, described earlier) or to degenerative changes in the caudal segment of cord. Second and more commonly, as edema and hemorrhage subside over the ensuing several weeks to months, the state of spinal shock subsides and evolves to a state of enhanced reflex activity. Tendon reflexes become hyperactive and Babinski signs appear. Hypotonia gives way to spasticity, and lower limbs may assume a position of triple flexion —that is, flexion of the hips, knees, and ankles. However, newborns usually do not develop spasticity as severe as that observed later in older children and adults with spinal cord injury. Changes in the upper extremities depend on the level of the lesion. If anterior horn cells or the brachial plexus is involved, these limbs remain flaccid and areflexic. If the lesion is at the midcervical level or higher, spasticity and hyperreflexia supervene in upper extremities as in lower extremities. Persistent respiratory failure and a need for mechanical ventilation also are present in such mid- or upper cervical cases. Reflex emptying of the bladder occurs, often as part of mass reflex activity elicited by cutaneous or other stimulation. Higher-level motor or affective responses to sensory stimulation below the level of the lesion, however, do not develop. Disturbances of autonomic function—for example, sweating and vasomotor phenomena—may lead to wide fluctuations in body temperature, especially in young infants. Trophic disturbances of muscle and bone may become prominent. The orthopedic and urinary tract complications that dominate the clinical course of these patients in the years after infancy are appropriately discussed in other texts.
Diagnosis
Diagnosis is often not difficult in the typical case. In less severely affected newborns or infants born after an apparently atraumatic delivery, differentiation is necessary from an occult dysraphic state (see Chapter 1 ); cervical arachnoid cyst ; an intravertebral, extramedullary mass, such as abscess, neuroblastoma, or hemorrhage ; an intramedullary lesion, such as syringomyelia, hemangioblastoma, or hemorrhage ; bony abnormalities ; apparent intrauterine traumatic lesions related to maternal abdominal trauma ; infarction occurring prenatally or caused postnatally by a vascular catastrophe associated with an indwelling catheter ; or a neuromuscular disorder (see Chapters 32 and 33 ). Radiographs of the spine and a search for cutaneous dimples, sinus tracts, hemangioma, and abnormal hair should aid in the differential diagnosis of occult dysraphic state, cervical arachnoid cyst, or bony abnormality. Demonstration of a sensory level rules out a neuromuscular disorder, such as Werdnig-Hoffmann disease. Differentiation from other extramedullary or intramedullary lesions requires an imaging study.
The principal choices for imaging of the cord are ultrasonography, CT, or MRI. Ultrasonography is useful because the infant need not be moved, and the modality demonstrates cord size and configuration and echogenic blood or edema within the cord or blood in the extramedullary space. Although blood is more echogenic than is edema, this critical distinction can be difficult with ultrasonography. Serial studies are carried out readily. I consider ultrasonography the initial imaging modality of choice in the acute situation. However, MRI provides superior resolution and should be used promptly subsequently. In the acute period, hemorrhage and edema can be distinguished by utilization of gradient-echoacquisition sequences. In the subacute and chronic periods, MRI provides superb resolution of parenchymal changes ( Figs. 36.12 and 36.13A ). CT is useful when bony detail is required. CT or air myelography is generally not used now because of the superiority of MRI. Diffusion tensor MRI techniques show promise for the delineation of fiber tracts in the neonatal spinal cord. Current MRI data indicate that the worst prognosis for subsequent cord function in the infant with traumatic spinal cord injury is associated with the finding of intramedullary hemorrhage. The prognosis is better with edema over several segments and best with edema involving one segment or less.
Management
Prevention.
The most important element of management is prevention ( Table 36.5 ). Of paramount importance is appropriate management of breech presentations and any other obstetrical situation that might lead to dysfunctional labor. Particularly, pharmacological augmentation of dysfunctional labor, ill-advised use of instrumentation, and the production of fetal depression by inappropriate use of maternal drugs or anesthesia should be avoided. Because a substantial proportion of neonatal spinal cord injuries are associated with breech delivery, careful radiographic assessment of fetal position and size and of the maternal pelvis is necessary.
| Prevention |
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| Therapy |
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Hyperextension of the fetal head represents a fetal position that carries a very high risk for the development of spinal cord injury if the infant is delivered by the vaginal route. It is critical to recognize that approximately 5% of all breech presentations are associated with a hyperextended fetal head. (This dangerous fetal position may also be present with a transverse lie.) Vaginal delivery of a fetus with a hyperextended head and breech presentation is associated with death or survival with severe spinal cord injury in approximately 20% to 25% of cases. Thus, in a composite series of 73 such infants delivered vaginally, 15 experienced significant spinal cord injury, whereas none of 35 infants delivered by cesarean section experienced such injury. That is, the beneficial role of cesarean section in preventing spinal cord injury is exemplified exceptionally well in this clinical setting. Nevertheless, a small minority of fetuses with hyperextended heads in utero may sustain serious cord injury before delivery and exhibit quadriplegia and respiratory failure despite cesarean section. A decrease in fetal movement in the last weeks of gestation may herald the occurrence of cord injury in the fetus with a hyperextended head. The cord lesions have been upper cervical in location, and one careful neuropathological study suggests intrauterine vascular injury. The likely intrauterine mechanism (see the section on pathogenesis , earlier) is subluxation and dislocation of upper cervical vertebrae, shown at autopsy to occur with hyperextension of the head with compromise of the vertebral arteries, the vascular supply for upper cervical cord via the anterior spinal artery. Thus, although cesarean section for the fetus in breech position with hyperextended head is critically important, spinal cord injury may, uncommonly, already have occurred. Indeed, as noted earlier, other examples of spinal cord injury occurring in utero and observed after cesarean section have been recorded.
Therapy.
When a newborn infant has already sustained a serious cord injury, no specific therapy can be offered (see Table 36.5 ). It is critical to rule out a surgically approachable lesion—such as an occult dysraphic state, vertebral fracture, dislocation, or other extramedullary lesion—as previously discussed. A careful history, physical examination, radiographs of the spine, and ultrasonography may be sufficient to rule out such lesions. However, when there is any doubt about the nature of the lesion or the possible presence of an extramedullary block, MRI should be carried out promptly. Intramedullary block, secondary usually to marked cord edema, is demonstrable in a small minority of cases, but surgical intervention is generally not indicated. In the rare case of extramedullary block, exploration may be reasonable to rule out a surgically remediable lesion or a major epidural hemorrhage that might be contributing seriously to a traumatic lesion of the cord. Nevertheless, it must be emphasized that there is little evidence that laminectomy and decompression have anything to offer these unfortunate infants in view of the basic nature of the cord lesion. Further data, however, are needed on this issue.
A potential role for methylprednisolone in the acute management of spinal cord injury was suggested by the results of randomized, controlled trials in adult patients. However, on balance, the increased likelihood of complications and the modest beneficial effects have led to a lack of enthusiasm for this approach. Many other interventions, suggested by study of experimental models—for example, GM-1 ganglioside, neurotrophic factors, antiexcitotoxic agents, antiinflammatory drugs, neural stem cells, and others—have either not yet been studied in humans or have not shown clear benefit. Proof of benefit (without major risk) is difficult to obtain in infants because of the relatively small number of cases available for study. Moreover, the correct diagnosis is usually delayed for many hours or days in infants (see earlier discussion).
Supportive therapy is important and is directed at ventilation, maintenance of body temperature, maintenance of perfusion, and prevention of urinary tract infection and contractures.
Major ethical issues are raised when infants are unable to sustain adequate ventilation without mechanical support. Prediction of outcome in the neonatal period is very difficult and clearly essential for decisions to withdraw life support. Certain tentative conclusions can be reached at 24 hours of age and 30 days of age. Thus, in one series of nine infants with spinal cord injury above the level of C-4 and requiring mechanical ventilation and who had survived at least 3 months, the only two patients who survived with a favorable outcome (independent daytime breathing, good motor function) had breathing movements on day 1. Of the seven survivors who took their first breath after the first day of life, all still required mechanical ventilation (although one infant required only nocturnal mechanical ventilation) 8 months to 9 years later. All four survivors who were totally apneic beyond 30 days of age required long-term mechanical ventilation and had severe motor disability. It should also be noted that in this study five additional patients with upper cervical lesions had no respiratory movements in the first days of life and had life support withdrawn at 4 to 10 days of age. Nevertheless, although these data are useful in predicting outcome, the numbers of infants studied is relatively small and conclusions remain tentative. Moreover, some rehabilitative centers report that improvements in home mechanical ventilatory systems have been associated with relatively low long-term mortality rates and intercurrent morbidities and with successful reintegration into schools and the community. Additionally, newer rehabilitative approaches—such as peripheral sensory level electrical stimulation and surface electromyography (EMG) triggered stimulation—have been reported to lead to surprising improvements in motor function.
Injury to Peripheral Nervous System Structures
Traumatic injury to peripheral structures—for example, nerve roots, plexuses, and peripheral and cranial nerves—may result in serious and sometimes fatal disorders. In this section I review, first, the four most common or serious of these injuries—that is, brachial plexus palsies, diaphragmatic paralysis, facial paralysis, and median nerve injury. Next, a variety of less common peripheral traumatic injuries of nerve roots, plexuses, and trunks are discussed.
Brachial Plexus Injury
Brachial plexus injury is weakness or total paralysis of muscles innervated by the nerve roots that supply the brachial plexus—that is, cervical roots 5 to 8 (C-5 to C-8) and thoracic root 1 (T-1) ( Fig. 13.14 ).
Incidence
Brachial plexus injury is distinctly more common than spinal cord injury. In the largest reported series of traumatic birth injuries, brachial plexus injuries occurred 10 to 20 times more commonly than did spinal cord injuries. The incidence has varied generally between 0.5 and 2.5 per 1000 live births. Attesting further to the relatively common occurrence of brachial plexus injury, albeit not necessarily severe, I have been impressed with the relative frequency with which subtle but definite evidence for plexus injury can be ascertained by meticulous examination of infants at risk for such traumatic injury (see the section on pathogenesis , later). My observations have not been made in a systematic or quantitative fashion; indeed, the clinical significance is probably minimal because the subtle deficits invariably resolve in a matter of days.
Pathology
Although the term brachial “plexus” injury is consistently used, it should be recognized that the major pathology often involves the nerve roots that supply the plexus, particularly at the site where the roots form the trunks of the plexus (a similar site is observed in stretch injuries to the brachial plexus in adults) (see Fig. 36.14 ). In the most severe neonatal lesions, actual avulsion of the root from the cord and, often, associated cord injury are present. A collection of cerebrospinal fluid (CSF) not confined by dura—that is, pseudomeningocele—usually accompanies avulsion. In the much more common, less severe lesions, hemorrhage and edema consequent to injury to the nerve sheath or axon are prominent. In the most common form of brachial plexus palsy, the involvement of the proximal upper extremity, or Erb palsy, is caused particularly by a lesion at the point (Erb’s point), where the fifth and sixth cervical nerve roots unite to form the upper trunk of the brachial plexus. Involvement of the distal upper extremity, that is, Klumpke palsy, is caused particularly by a lesion at the point where the eighth cervical and first thoracic nerve roots unite to form the lower trunk of the plexus.
The general relationships between the nature of the gross pathology and outcome are summarized in Table 36.6 . Injury to the nerve sheath with associated hemorrhage and edema but with intact axons ( neurapraxia ) secondarily impairs axonal function, primarily by compression, but recovery is complete. Severance of axons or roots is more serious . Rupture of roots is associated with essentially no chance of spontaneous recovery. Similarly, axonal rupture when associated with severance of the nerve sheath and thus loss of a guide for regenerating axons (“neurotmesis”) is associated with a poor spontaneous outcome. However, axonal rupture with an intact nerve sheath is intermediate in severity; axonal regeneration occurs at a rate of approximately 1.8 mm per day, somewhat faster than the rate of approximately 1 mm/day in older individuals.
| SEVERITY OF LESION | NERVE SHEATH | AXONS | ROOTS | LIKELIHOOD OF SPONTANEOUS RECOVERY |
|---|---|---|---|---|
| Mild | Intact a | Intact | Intact | Good |
| Moderate | Intact | Severed | Intact | Fair |
| Severe | Severed | Severed | Intact | Poor |
| Severe | Intact | Intact | Severed | Poor |
a Nerve sheath intact but injured; injury usually consists of edema and hemorrhage with secondary impairment of axonal function.
Pathogenesis
Brachial plexus injury is thought to result from stretching of the brachial plexus, with its roots anchored to the cervical cord, by downward lateral traction. The forces underlying injurious lateral traction may be endogenous, or related to strong maternal and uterine expulsion forces and an impacted shoulder, or they may be exogenous, or related to the process of delivering the head, or likely commonly, by both endogenous and exogenous forces. Endogenous forces are considered generally to be stronger than exogenous forces. With delivery, the traction is exerted via the shoulder in the process of delivering the head with breech deliveries and via the head in the process of delivering the shoulder in cephalic deliveries. The upper roots of the plexus are most vulnerable, but with marked traction all roots are affected and total paralysis results. The relatively uncommon occurrences of intrauterine injury to the brachial plexus have been secondary to abnormalities of fetal position or of uterine structure, congenital cervical bone abnormalities, congenital tumors, or, most commonly, unknown intrauterine factors.
The most common pathogenetic events just mentioned occur secondary to especially, obstetrical factors and large fetal size. a
a References .
(It should be noted that obstetrical factors relate principally to such issues as fetal position, forces of labor, and characteristics of delivery; they should not be construed as those factors that are always under the control of the obstetrician.) In Gordon’s large, essentially unselected series, abnormal presentations occurred in 56% of cases; this group consisted of 14% breech and 42% abnormal vertex presentations (occiput posterior and occiput transverse). Shoulder dystocia was present in 51% of all vertex deliveries and in 30% of all breech deliveries. Labor was augmented in 50% of these cases. In a large series ( n = 276) studied in the United Kingdom and Ireland, 65% had shoulder dystocia. In several earlier series of shoulder dystocia, approximately 20% of infants sustained some degree of brachial plexus injury. More recent studies suggest that this value is less than 10%. Birth weight of affected infants exceeds 3500 g in 50% to 85% of cases. bb References .
In a large Swedish series, the incidence of brachial plexus palsy was 45-fold greater at a birth weight of greater than 4500 g than at a birth weight of less than 3500 g. In a careful earlier study, intrauterine asphyxia with fetal depression was suggested by the signs of fetal distress in 44% and Apgar score at 1 minute of less than 4 in 39%. Thus a large depressed infant with an abnormal labor and delivery appears to be at particular risk.Clinical Features
Clinical Setting.
The typical clinical setting comprises obstetrical and fetal factors that predispose the infant to traumatic injury, particularly by downward lateral traction. Thus, as noted previously, abnormal presentations, dysfunctional labor, augmented labor, large fetal size, and perhaps fetal depression occur to varying degrees in most cases of brachial plexus injury.
Neonatal Varieties.
In standard writings on brachial plexus injury, two basic types are recognized: the upper type, or Erb palsy, and the lower type, or Klumpke palsy ( Figs. 36.15 and 36.16 ). In neonatal patients, approximately 90% of cases of brachial plexus injury involve the proximal upper limb and correspond to Erb palsy. a
a References .
A true Klumpke palsy—that is, weakness of distal upper extremity only —in my experience does not occur in the newborn period; infants with distal involvement also exhibit proximal involvement. These neonatal patients with essentially total brachial plexus palsy often are described, appropriately or not, as Klumpke palsy.
