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Nervous System Disorders
Central nervous system (CNS) disorders are important causes of neonatal mortality and both short-term and long-term morbidity. The CNS can be injured as a result of asphyxia, hemorrhage, trauma, hypoglycemia, or direct cytotoxicity. The etiology of CNS injury is often multifactorial and includes perinatal complications, postnatal hemodynamic instability, and developmental abnormalities that may be genetic and/or environmental. Predisposing factors for brain injury include chronic and acute maternal illness resulting in uteroplacental dysfunction, intrauterine infection, macrosomia/dystocia, malpresentation, prematurity, and intrauterine growth restriction. Acute and often unavoidable emergencies during the delivery process may result in mechanical and hypoxic-ischemic brain injury.
The Cranium
Erythema, abrasions, ecchymoses, and subcutaneous fat necrosis of facial or scalp soft tissues may be noted after a normal delivery or after forceps or vacuum-assisted deliveries. The location depends on the area of contact with the pelvic bones or application of the forceps. Traumatic hemorrhage may involve any layer of the scalp as well as intracranial contents ( Fig. 120.1 ).
Caput succedaneum is a diffuse, sometimes ecchymotic, edematous swelling of the soft tissues of the scalp involving the area presenting during vertex delivery. It may extend across the midline and across suture lines. The edema disappears within the 1st few days of life. Molding of the head and overriding of the parietal bones are frequently associated with caput succedaneum and become more evident after the caput has receded; they disappear during the 1st few weeks of life. Rarely, a hemorrhagic caput may result in shock and require blood transfusion. Analogous swelling, discoloration, and distortion of the face are seen in face presentations. No specific treatment is needed, but if extensive ecchymoses are present, hyperbilirubinemia may develop.
Cephalohematoma is a subperiosteal hemorrhage and thus always limited to the surface of one cranial bone ( Fig. 120.2 ). Cephalohematomas occur in 1–2% of live births. No discoloration of the overlying scalp occurs, and swelling is not usually visible for several hours after birth because subperiosteal bleeding is a slow process. The lesion becomes a firm, tense mass with a palpable rim localized over one area of the skull. Most cephalohematomas are resorbed within 2 wk to 3 mo, depending on their size. They may begin to calcify by the end of the 2nd wk. A few remain for years as bony protuberances and are detectable on radiographs as widening of the diploic space; cystlike defects may persist for months or years. An underlying skull fracture, usually linear and not depressed, may be associated with 10–25% of cases. A sensation of central depression suggesting but not indicative of an underlying fracture or bony defect is usually encountered on palpation of the organized rim of a cephalohematoma. Cephalohematomas require no treatment, although phototherapy may be necessary to treat hyperbilirubinemia. Infection of the hematoma is a very rare complication.
A subgaleal hemorrhage is a collection of blood beneath the aponeurosis that covers the scalp and serves as the insertion for the occipitofrontalis muscle (see Fig. 120.1 ). Bleeding can be very extensive into this large potential space and may even dissect into subcutaneous tissues of the neck. There is often an association with vacuum-assisted delivery. The mechanism of injury is most likely secondary to rupture of emissary veins connecting the dural sinuses within the skull and the superficial veins of the scalp. Subgaleal hemorrhages are sometimes associated with skull fractures, suture diastasis, and fragmentation of the superior margin of the parietal bone. Extensive subgaleal bleeding is occasionally secondary to a hereditary coagulopathy ( hemophilia ). A subgaleal hemorrhage manifests as a fluctuant mass that straddles cranial sutures or fontanels that increases in size after birth. Some patients have a consumptive coagulopathy from massive blood loss. Patients should be monitored for hypotension, anemia, and hyperbilirubinemia. These lesions typically resolve over 2-3 wk.
Fractures of the skull may be caused by pressure from forceps or the maternal pelvis or by accidental falls after birth. Linear fractures, the most common, cause no symptoms and require no treatment. Linear fractures should be followed up to demonstrate healing and to detect the possible complication of a leptomeningeal cyst. Depressed fractures indent the calvaria similar to dents in a Ping-Pong ball. They are generally a complication of forceps delivery or fetal compression. Affected infants may be asymptomatic unless they have associated intracranial injury; it is advisable to elevate severe depressions to prevent cortical injury from sustained pressure. Although some may elevate spontaneously, some require treatment. Use of a breast pump or vacuum extractor may obviate the need for neurosurgical intervention. Suspected skull fractures should be evaluated with CT (3D reconstruction may be helpful) to confirm fracture and rule out associated intracranial injury.
Subconjunctival and retinal hemorrhages are frequent; petechiae of the skin of the head and neck are also common. All are probably secondary to a sudden increase in intrathoracic pressure during passage of the chest through the birth canal. Parents should be assured that these hemorrhages are temporary and the result of normal events of delivery. The lesions resolve rapidly within the 1st 2 wk of life.
Traumatic, Epidural, Subdural, and Subarachnoid Hemorrhage
Traumatic epidural, subdural, or subarachnoid hemorrhage is especially likely when the fetal head is large in proportion to the size of the mother's pelvic outlet, with prolonged labor, in breech or precipitous deliveries, or as a result of mechanical assistance with delivery. Massive subdural hemorrhage , often associated with tears in the tentorium cerebelli or less frequently in the falx cerebri, is rare but is encountered more often in full-term than in premature infants. Patients with massive hemorrhage caused by tears of the tentorium or falx cerebri rapidly deteriorate and may die soon after birth. Most subdural and epidural hemorrhages resolve without intervention. Consultation with a neurosurgeon is recommended. Asymptomatic subdural hemorrhage may be noted within 48 hr of birth after vaginal or cesarean delivery. These are typically small hemorrhages, especially common in the posterior fossa, discovered incidentally in term infants imaged in the neonatal period and usually of no clinical significance. The diagnosis of large subdural hemorrhage may be delayed until the chronic subdural fluid volume expands and produces macrocephaly, frontal bossing, a bulging fontanel, anemia, and sometimes seizures. CT scan and MRI are useful imaging techniques to confirm these diagnoses. Symptomatic subdural hemorrhage in term infants can be treated by a neurosurgical evacuation of the subdural fluid collection by a needle placed through the lateral margin of the anterior fontanel. In addition to birth trauma, child abuse must be suspected in all infants with subdural effusion after the immediate neonatal period. Most asymptomatic subdural hemorrhages following labor should resolve by 4 wk of age.
Subarachnoid hemorrhage is often clinically silent in the neonate. Anastomoses between the penetrating leptomeningeal arteries or the bridging veins are the most likely source of the bleeding. Most affected infants have no clinical symptoms, but the subarachnoid hemorrhage may be detected because of an elevated number of red blood cells in a lumbar puncture sample. Some infants experience short, benign seizures, which tend to occur on the 2nd day of life. Rarely, an infant has a catastrophic hemorrhage and dies. There are usually no neurologic abnormalities during the acute episode or on follow-up. Significant neurologic findings should suggest an arteriovenous malformation, which can best be detected on CT or MRI.
Intracranial-Intraventricular Hemorrhage and Periventricular Leukomalacia
Etiology
Intracranial hemorrhage in preterm infants usually develops spontaneously. Less frequently, it may be caused by trauma or asphyxia, and rarely, it occurs from a primary hemorrhagic disturbance or congenital cerebrovascular anomaly. Intracranial hemorrhage often involves the ventricles ( intraventricular hemorrhage, IVH ) of premature infants delivered spontaneously without apparent trauma. The IVH in premature infants is usually not present at birth but may develop during the 1st week of life. Primary hemorrhagic disturbances and vascular malformations are rare and usually give rise to subarachnoid or intracerebral hemorrhage. In utero hemorrhage associated with maternal idiopathic or, more often, fetal alloimmune thrombocytopenia may appear as severe cerebral hemorrhage or as a porencephalic cyst after resolution of a fetal cortical hemorrhage. Intracranial bleeding may be associated with disseminated intravascular coagulation, isoimmune thrombocytopenia, and neonatal vitamin K deficiency, especially in infants born to mothers receiving phenobarbital or phenytoin.
Epidemiology
The overall incidence of IVH has decreased over the past decades as a result of improved perinatal care, increased use of antenatal corticosteroids, surfactant to treat respiratory distress syndrome (RDS), and possibly prophylactic indomethacin. It continues to be an important cause of morbidity in preterm infants, as approximately 30% of premature infants <1,500 g have IVH. The risk is inversely related to gestational age and birthweight; 7% of infants weighing 1,001-1,500 g have a severe IVH (grade III or IV), compared to 14% of infants weighing 751-1,000 g and 24% of infants ≤750 g. In 3% of infants <1,000 g, periventricular leukomalacia (PVL) develops.
Pathogenesis
The major neuropathologic lesions associated with very-low-birthweight (VLBW) infants are IVH and PVL. IVH in premature infants occurs in the gelatinous subependymal germinal matrix . This periventricular area is the site of origin for embryonal neurons and fetal glial cells, which migrate outwardly to the cortex. Immature blood vessels in this highly vascular region of the developing brain combined with poor tissue vascular support predispose premature infants to hemorrhage. The germinal matrix involutes as the infant approaches full-term gestation, and the tissue's vascular integrity improves; therefore IVH is much less common in the term infant. The cerebellum also contains a germinal matrix and is susceptible to hemorrhagic injury. Periventricular hemorrhagic infarction , previously known as grade IV intraventricular hemorrhage , often develops after a large IVH because of venous congestion. Predisposing factors for IVH include prematurity, RDS, hypoxia-ischemia, exaggerated fluctuations in cerebral blood flow (hypotensive injury, hypervolemia, hypertension), reperfusion injury of damaged vessels, reduced vascular integrity, increased venous pressure (pneumothorax, venous thrombus), or thrombocytopenia.
Understanding of the pathogenesis of PVL is evolving, and it appears to involve both intrauterine and postnatal events. A complex interaction exists between the development of the cerebral vasculature and the regulation of cerebral blood flow (both of which depend on gestational age), disturbances in the oligodendrocyte precursors required for myelination, and maternal/fetal infection and inflammation. Postnatal hypoxia or hypotension, necrotizing enterocolitis (NEC) with its resultant inflammation, and severe neonatal infection may all result in white matter injury. PVL is characterized by focal necrotic lesions in the periventricular white matter and/or more diffuse white matter damage. Destructive focal necrotic lesions resulting from massive cell death are less common in the modern era. Instead, diffuse injury leading to abnormal maturation of neurons and glia is more frequently seen. The risk for PVL increases in infants with severe IVH or ventriculomegaly. Infants with PVL are at higher risk of cerebral palsy because of injury to the corticospinal tracts that descend through the periventricular white matter.
Clinical Manifestations
Most infants with IVH , including some with moderate to severe hemorrhages, have no initial clinical signs ( silent IVH). Some premature infants in whom severe IVH develops may have acute deterioration on the 2nd or 3rd day of life ( catastrophic presentation). Hypotension, apnea, pallor, stupor or coma, seizures, decreased muscle tone, metabolic acidosis, shock, and decreased hematocrit (or failure of hematocrit to increase after transfusion) may be the first clinical indications. A saltatory progression may evolve over several hours to days and manifest as intermittent or progressive alterations of levels of consciousness, abnormalities of tone and movement, respiratory signs, and eventually other features of the acute catastrophic IVH. Rarely, IVH may manifest at birth or even prenatally; 50% of cases are diagnosed within the 1st day of life, and up to 75% within the 1st 3 days. A small percentage of infants have late hemorrhage, between days 14 and 30. IVH as a primary event is rare after the 1st mo of life.
PVL is usually clinically asymptomatic until the neurologic sequelae of white matter damage become apparent in later infancy as spasticity and/or motor deficits. PVL may be present at birth but usually occurs later, when the echodense phase is seen on ultrasound (3-10 days of life), followed by the typical echolucent/cystic phase (14-20 days).
The severity of hemorrhage is defined by the location and degree of bleeding and ventricular dilation on cranial imaging. In a grade I hemorrhage, bleeding is isolated to the subependymal area. In grade II hemorrhage, there is bleeding within the ventricle without evidence of ventricular dilation. Grade III hemorrhage is IVH with ventricular dilation. In grade IV hemorrhage, there is intraventricular and parenchymal hemorrhage ( Fig. 120.3 ). Another grading system describes 3 levels of increasing severity of IVH detected on ultrasound: In grade I, bleeding is confined to the germinal matrix–subependymal region or to <10% of the ventricle (approximately 35% of IVH cases); grade II is defined as intraventricular bleeding with 10–50% filling of the ventricle (40% of IVH cases); and in grade III , >50% of the ventricle is involved, with dilated ventricles ( Fig. 120.3 ). Ventriculomegaly is defined as mild (0.5-1 cm dilation), moderate (1.0-1.5 cm dilation), or severe (>1.5 cm dilation).
Diagnosis
Intracranial hemorrhage is suspected on the basis of history, clinical manifestations, and knowledge of the birthweight-specific risks for IVH . Associated clinical signs of IVH are typically nonspecific or absent; therefore, it is recommended that premature infants <32 wk of gestation be evaluated with routine real-time cranial ultrasonography (US) through the anterior fontanel to screen for IVH. Infants <1,000 g are at highest risk and should undergo cranial US within the 1st 3-7 days of age, when approximately 75% of lesions will be detectable. US is the preferred imaging technique for screening because it is noninvasive, portable, reproducible, and sensitive and specific for detection of IVH. All at-risk infants should undergo follow-up US at 36-40 wk postmenstrual age to evaluate adequately for PVL, as cystic changes related to perinatal injury may not be visible for up to 1 mo. In one study, 29% of low-birthweight (LBW) infants who later experienced cerebral palsy did not have radiographic evidence of PVL until after 28 days of age. US also detects the precystic and cystic symmetric lesions of PVL and the asymmetric intraparenchymal echogenic lesions of cortical hemorrhagic infarction ( Fig. 120.4 ). Cranial US may be useful in monitoring delayed development of cortical atrophy, porencephaly, and the severity, progression, or regression of posthemorrhagic hydrocephalus.
Approximately 3–5% of VLBW infants develop posthemorrhagic hydrocephalus (PHH) . If the initial US findings are abnormal, additional interval US studies are indicated to monitor for the development of hydrocephalus and potential need for ventriculoperitoneal shunt insertion.
IVH represents only 1 facet of brain injury in the term or preterm infant. MRI is a more sensitive tool for evaluation of white matter abnormalities and cerebellar injury and may be more predictive of adverse long-term outcome.
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