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Neonatal pathology nonrelated to prematurity, birth asphyxia or infection

3  Neonatal pathology

3.7  Neonatal pathology nonrelated to prematurity, birth asphyxia or infection

3.7.1  Congenital anomalies in liveborn infants

Introduction:

3% of newborns have a major anomaly defined as an anomaly having either cosmetic or functional significance.

Some are detected ar birth but some such as cardiac defects or renal anomalies may not become clinically apparent until years.

The most common malformation among liveborn infants in the Czech republic are various heart defects (40% of all anomalies diagnosed in the first year of life). Hypospadia and cryptorchidism are common in males, malformations of limbs and congenital luxation of hip joint are common in females. The most common chromosomal abnormality is Down syndrome which affects approximately 0.5 % liveborn infants/45 newborns annually. Renal anomalies and cleft lip and palate are also frequent.

Clinical signs:

  • congenital anomalies as a cause of death
  • congenital heart defects
  • major CNS malformations
  • chromosomal syndromes
  • pulmonary anomalies  —  lung hypoplasia, diaphragmatic hernia

Pictures

Transpositon of great arteries in term newborn who died several hours after birth with signs of severe cyanosis:
Transposition of the great arteries, Macro, autopsy (73890)

Hypoplasic left heart syndrome, the baby died at the age of 4 weeks:
Hypoplastic left heart syndrome, Macro, autopsy (73889)

Early neonatal death from severe lung hypoplasia and diaphragmatic malformation:
Hypoplasia of the lungs, Macro, autopsy (73817)
Hypoplasia of the lungs, Macro, autopsy (73816)

Early neonatal death in premature newborn born at 32 week's gestation with birth weight 1200 g. Death occured early after birth because of lung hypoplasia with eventration of the diaphragm. Chromosomal aberation was suspected because of abnormal phenotype but unofortunatelly postmortal examination of karyotype was unsuccesful.
Chromosomal abberation, Macro, autopsy (73885)
Chromosomal abberation, Macro, autopsy (73886)

3.7.2  Kernicterus

Introduction:

Kernicterus is bilirubin staining of the deep gray matter nuclei of the brain and brainstem. It is an anatomic diagnosis made at autopsy. Bilirubin is neurotoxic. Kernicterus was originally described in mature infants who died of severe Rh isoimmunization (such a case is rarely seen today). Extremely premature sick infants are at higher risk of kernicterus than mature infants.

Etiology:

  • Hyperbilirubinemia as a result of increased bilirubin production and decreased bilirubin elimination
  • Immature blood-brain barrier of the neonates  —  the barrier is less well developed in the neonatal period than in adulthood. The integrity of the barrier may be further disrupted by hypercarbia, hypoxia, acidosis, hypoglycemia, infection (meningitis).
  • Total serum bilirubin comprises a conjugated fraction and an unconjugated fraction. The unconjugated fraction is composed of bound bilirubin (bound to albumin) and free bilirubin. Only free bilirubin is available to cross the blood-brain barrier and cause neurotoxicity. The blood-brain low plasma albumin or displacement of bilirubin from albumin by certain drugs or lipid emulsions may increse the proportion of free bilirubin which can enter the brain.
  • The precise bilirubin level which causes kernicterus is unpredictable. Classic kernicterus was recognized with blood bilirubin level greater than 20 mg/dl. In premature infants the level causing neuronal damage may be considerable lower.
  • Well-known risk conditions
    • Hemolytic disorders  —  Rh isoimmunization, ABO incompatibility, glucose-6-phosphate-dehydrogenase deficiency
    • Birth trauma  —  significant bruising, cephalohematoma, subgaleal hemorrhage
    • Sepsis
    • Extreme prematurity
    • Rare  —  galactosemia, congenital hypothyroidism, Crigler-Najjar syndrome (congenital defect of bilirubin conjugation)

Clinical signs:

Acute bilirubin toxicity appears in the first few days of life in term infants. Preterm infants are at risk for slightly longer.

Classic kernicterus (mature infants):

  • Acute bilirubin encephalopathy (first week of life): decreased alerteness, hypotonia, poor feeding. Babies may also present with retrocollis or opisthotonus. Some infants have no neurologic signs.
  • Chronic bilirubin encephalopathy: athetosis, chorea, hearing abnormalities, delayed psychomotoric developement, cerebral palsy (in preterm babies kernicterus is just one of determining factors)
  • Prevention of hyperbilirubinemia and its neurotoxicity  —  phototherapy, exchange transfusion

Macroscopic appearance:

Prominent yellow staining of specific regions: Basal ganglia, lateral thalamic nucleus, hippocampus, geniculate bodies, nuclei of brainstem and floor of the fourth ventricle, dentate nucleus, inferior olive, anterior horn of spinal cord, cuneate and gracilis nuclei.

Histology:

Vacuolization of cytoplasm, colouration (in frozen section)  —  early microscopic lesions. Loss of neurons and reactive astrocytosis.

3.7.3  Hemorrhagic disease of the newborn

Introduction:

Vitamin K deficiency bleeding.

Etiology:

  • Vitamin K is required for production of coagulation factors II., VII., IX. and X. in the liver
  • Newborns are relatively vitamin K deficient because of
    • low vitamin K stores at birth
    • low levels of vitamin K in the breast milk
    • sterility of the intestine

Clinical signs:

Bleeding from umbilicus, mucous membmranes, gastrointestinal tract, venipunctures, large cephalhematoma or skin bruising. Intracranial bleeding is rare.

Bleeding is a problem exlusively in breastfed infants. Formulas contain supplemental vitamin K.

The occurence is rare due to routine prophylaxis (intramuscular administration of vitamin K immeditely after birth, regular administration of vitamin K per os to all breastfed infants in the neontal period).

  • Early onset disease  —  less than 24 hours after birth, occurs rarely with maternal medication that interferes with vitamin K
  • Classic onset  —  2 – 7 days after birth in breastfed neonates
  • Late onset  —  after 2 weeks of life, risk factors besides breastfeeding include diarrhea, hepatitis, cystic fibrosis, absence of prophylaxis. Late onset disease tends to be more serious with higher occurence of intracranial bleeding.

3.7.4  Spontenous gastric perforation in a neonate

Etiology:

Ischemia of the gastric wall secondary to severe birth asphyxia with shunting of blood away from the splanchnic organs.

Clinical signs:

  • rare occurance with high mortality
  • more common in preterm infants
  • occurs in the first days after birth
  • linear tears on the greater curvature

Pictures

Gastric perforation which occured at 9 days of age in a premature neonate with history of significant birth asphyxia. There is a linear tear on the great curvature measuring 18 mm. Diffuse peritonitis was the cause of death.
Perforation of the stomach, newborn, Macro, autopsy (73865)
Perforation of the stomach, newborn, Macro, autopsy (73864)
Perforation of the stomach, newborn, Macro, autopsy (73863)


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