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Cerebral white matter lesions seen in the perinatal period include periventricular leukomalacia (PVL), historically defined as focal white matter necrosis, and diffuse cerebral white matter gliosis (DWMG), with which PVL is nearly always associated. The first use of the term PVL was by Banker and Larroche in 1962, although the gross and microscopic features had been noted by others (reviewed in Haynes and Folkerth, 2018 ). More recently, the broader terms white matter injury (WMI) or diffuse white matter injury (DWMI) have been in use, in part because it refers to the increasingly more common pattern of DWMG, with or without microscopic necroses, reflecting the trend toward decreasing macroscopically visible (or sonographically detectable) “cystic” lesions. This decrease in perinatal brain injury is in turn attributed to improvements in supportive care of preterm neonates, at especial risk for fluctuations of blood pressure (and often cerebral perfusion pressure), and respiration/oxygenation .
After completion of all macroscopic and microscopic investigations, one must synthesize the data with the other information already gathered (clinical history, radiographic, microbiologic, genetic, or other ancillary data) to formulate a coherent final interpretation which best fits all the findings. Rarely will any finding stand alone or trump all others.
Miscarriage is defined as the loss of an embryo or fetus before the 20th week of pregnancy (1). Stillbirth in general refers to a natural loss of the products of conception after the 20th week of gestation. However, the administrative and legal definitions of stillbirth vary. For example, the US Centers for Disease Control uses the definition “fetal deaths whose birth weight is of 350 g or more, or if weight is unknown, of 20 completed weeks gestation or more, calculated from the date last normal menstrual period,” whereas other jurisdictions use 24 weeks (typical limit of viability) or 28 weeks as cutoffs (2–4). Notwithstanding the varied definitions, the rate of stillbirth is approximately 4 per 1000 total births in high-income countries, and up to 35 per 1000 births in sub-Saharan Africa and South Asia, with a general decline in frequency during the past three decades (5, 6).
The cerebellum has a growth program sharing some features with, but differing importantly in tempo and sequence from, that of the cerebrum. This chapter provides a brief overview; select details of the molecular genetic mechanisms underlying human cerebellar development are discussed here, and when relevant to human malformations are further highlighted in Chapter 40.
Mechanical nervous system trauma in neonates mainly encompasses blunt impact injury and rotational acceleration/deceleration injury, whether accidental (such as in falls from height or motor vehicle collisions) or nonaccidental (i.e., at the hands of another). The distinction between accidental and nonaccidental patterns of injury is the crux of the issue in examining a deceased infant with clinical or autopsy evidence of trauma, and will be the focus of this chapter. Penetrating projectile and sharp force injury to the brain and spinal cord are sufficiently rare as to be outside the scope of this discussion. Likewise, deaths due to suffocation, drowning, and arson are not covered here, in part because neuropathologic changes are not specific (see Table 65.1).
The placenta is best considered a vital organ of the fetus, as essential as the heart or lungs. In addition, it serves as the “diary” of the pregnancy, often indicating antepartum (maternal and exogenous) influences. It should be examined as a matter of routine in every stillbirth or adverse neonatal outcome for clues to underlying contributing factors.
As mentioned previously, review of any prenatal imaging (transabdominal ultrasonography, or maternal/fetal MR imaging) of fetal cases, or antemortem studies of liveborns, will assist greatly in the planning of the prosection. In addition, postmortem imaging (whether of the whole infant or of the isolated brain specimen) may be desirable in certain circumstances, assuming the consent for examination includes this as a diagnostic technique, and has the obvious advantage of lack of movement artifact
Spinal muscular atrophy (SMA) refers to a group of progressive neurodegenerative conditions primarily involving spinal anterior horn cells, as well as select bulbar motor neurons. Onset may be in infancy, childhood, or teen years (historically classified into Types 1, 2, and 3; see Table 50.1). Adult-onset (type 4) SMA is not discussed further here.
The developing cerebellum is susceptible in unique ways to disruptions, both in utero and after birth. This is in part because of its relatively late and prolonged program of neuronal migration and differentiation, as compared to those of the hemispheres, brainstem, and spinal cord (see Chapters 20 and 23). As in other neuroanatomic sites, selective vulnerability is in play in the immature external granule cells which, while derived from the rhombic lip, are analogous in many ways to the immature cells of the germinal matrix originating from the ventricular zone. Thus, the external granule cells are thought to be the cerebellar elements at risk of injury from hypoxia-ischemia and/or hemorrhage, resulting in free radical toxicity, neuroinflammation, and excitotoxicity. The short-term effect is an irreversible injury to or delayed function of these precursor cells of the cerebellar cortex, and the long-term result is overall underdevelopment of the cerebellum (hypoplasia) .