Aetiology of cerebral palsy

Infections and other inflammatory conditions

The etiology of cerebral palsy and other related perinatal brain injuries is poorly understood. Infections of the central nervous system are rare but important causes of neurodisability. Recent evidence suggests that infections and other inflammatory conditions apparently limited to the placenta are also associated with an increased risk of neurologic impairment. A major hypothesis to explain this connection is that cytokines, activated inflammatory cells, and other mediators of the innate immune response are released into the fetal circulation where they can directly or indirectly affect the development or integrity of the central nervous system. This review surveys the organisms, mediators, and placental lesions that have been associated with perinatal brain injury.

Placental pathology and cerebral palsy

Recent classification systems of cerebral palsy call for an assessment of the timing and etiology of brain injury. The placenta is an underused resource for addressing these important questions. An expert assessment of the placental pathology can provide temporally and mechanistically specific data not available from any other source. Key concepts for an understanding of the role of placental pathology are the "sentinel lesion," the high prevalence of thromboinflammatory lesions affecting large fetal placental vessels, the significance of underlying placental reserve, and the realization that placental findings can serve as markers for processes occurring in the mother or fetus.

Comparison of fetal behavior in low- and high-risk pregnancies

Meta-analyses were conducted on archival data of human fetal behavior to identify differential behavior among high-risk fetuses in pregnancies complicated by threatened preterm delivery, maternal hypertension or diabetes compared with low-risk fetuses in uneventful pregnancies, delivering as healthy, full-term infants. Data for a total of 493 fetuses (260 high risk, 233 low risk) from 23 weeks' gestation to term who participated in a study using a standardized protocol including observations of spontaneous and auditory-induced behavior were retrieved from our laboratory database. There were no differences in spontaneous behaviors when scored using clinical criteria for the nonstress test and biophysical profile; however, there were differences in the magnitude of the behaviors measured in the tests. Developmental differences were observed between those threatening to deliver early and the fetuses of hypertensive and diabetic mothers. The latter two groups differed little from one another but differed from low-risk fetuses in their response to auditory stimulation. We concluded that differences in behavior among high-risk groups suggest that atypical fetal behaviors may represent adaptation to condition specific insult rather than a generalized response to insult per se. The finding that high-risk fetuses showed atypical responses to auditory stimuli indicates a need to examine the relation between fetal auditory function and later language acquisition.

Fetal Neurobehavioral Development: A Tale of Two Cities

Longitudinal neurobehavioral development was examined in 237 fetuses of low-risk pregnancies from 2 distinct populations--Baltimore, Maryland, and Lima. Peru--at 20, 24, 28, 32, 36, and 38 weeks gestation. Data were based on digitized Doppler-based fetal heart rate (FHR) and fetal movement (FM). In both groups. FHR declined while variability, episodic accelerations, and FM-FHR coupling increased, with discontinuities evident between 28 and 32 weeks gestation. Fetuses in Lima had higher FHR and lower variability, accelerations, and FM-FHR coupling. Declines in trajectories were typically observed 1 month sooner in Lima, which magnified these disparities. Motor activity differences were less consistent. No sex differences in fetal neurobehaviors were detected. It is concluded that population factors can influence the developmental niche of the fetus.

Longitudinal study of fetal body movements: nomograms, intrafetal consistency, and relationship with episodes of heart rate patterns a and B

Our objective was to investigate the longitudinal development of incidence parameters of fetal body movements to define normal reference ranges, to relate them to episodes of fetal heart rate patterns A and B, and to determine the intrafetal consistency for these parameters. Twenty-nine fetuses were studied longitudinally from 24 wk of gestation. Fetal body movements and heart rate were recorded at fortnightly intervals between 24 and 36 wk of gestation and weekly from 36 wk of gestation. Data were analyzed using multilevel analysis. Reference ranges were constructed for the percentage of observation time that movements were present, the number of movement bursts per hour, the mean burst duration, and the median onset-onset interval. The median percentage incidence of fetal body movements decreased from 17% at 24 wk to about 7% near term. The developmental course was the same during active episodes. Body movements also decreased during episodes of relative quiescence, in the course of pregnancy. Intrafetal variance was on average 40-80% of the total range of the four movement parameters. Normal reference ranges were developed for incidence parameters of fetal body movements from 24 wk of gestation onward. The overall decline in the incidence of movements during pregnancy appeared to be a developmental phenomenon and not due to progressively increasing episodes of fetal quiescence. Individual fetuses showed a degree of consistency in the percentage incidence of body movements, but intra- and interfetal variances were generally high, resulting in wide ranges.

Maturation of human fetal responses to airborne sound in low- and high-risk fetuses

The purpose of the study was to characterize the onset and maturation of airborne sound-elicited responses in low- and high-risk preterm fetuses. In Study 1, a total of 91 low-risk fetuses at 27, 30, 33, and 36 weeks GA received three sound trials at 90, 100, 105 and 110 dB and three no-stimulus control trials. The onset of cardiac acceleration and body movement responses occurred at 30 weeks GA. Maturation of the cardiac response was observed with a decrease in threshold from 105-110 dB at 33 weeks GA to 100-105 dB at 36 weeks GA. In Study 2, the procedure was similar except that the 43 high-risk fetuses at 27, 30 and 33 weeks GA did not receive sounds at 90 dB. For the high-risk fetuses, the onset of cardiac and motor responses also occurred at 30 weeks GA. At 33 weeks GA, those high-risk fetuses subsequently born at term showed an increased magnitude of the cardiac acceleration response compared to low-risk fetuses. The results indicate that both low- and high-risk fetuses begin responding to sounds at the same gestational age. Differential responses observed over gestation in the high-risk group most likely indicate differential functional development of the auditory-response system.

Hyperthermic injury of oligodendrocyte precursor cells: implications for dysmyelination disorders

Although 6 h of exposure to 41 degrees C did not affect the viability of oligodendrocyte precursors in culture, a 2-h exposure to 42 degrees C caused them to die. In contrast, astrocytes could tolerate 42 degrees C for at least 6 h. There was an increase in lipid peroxidation following the 42 degrees C insult, particularly in the oligodendrocyte precursors. These findings may be of relevance in understanding certain dysmyelination disorders in humans.