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Immature Fetal Brain
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Immature Fetal Brain

Superior view of cerebral hemispheres of 18-20 week gestation fetus.
Note the lack of convolutions except for the beginning of the central fissure.
No convolutions are characteristic of this age fetus.
From this gestational age on, more and more convolutions are formed.
A normal complement is formed by 40 weeks.
(Description By:Margaret Grunnet,M.D. )
(Image Contrib. by: UCHC )
Immature infant brain
Etiology

Immature infant brains are seen as a result of spontaneous or therapeutic abortions and premature births.
Pathogenesis

See Etiology,
Epidemiology

Spontaneous abortions and premature births are seen in patients with little prenatal care and those with placental infections.
Therapeutic abortions are done for abnormal fetuses and intrauterine deaths often.
General Gross Description

Premature and very young fetuses have few convolutions. The primary sulci are the calcarine, parietal-occipital, and central sulci. They appear by about gestational age 20 weeks.
After that particularly after 25 weeks gestation secondary convolutions are formed. The pre and post central, superior temporal, and frontal gyri
After 28 weeks there is a more brain specific formation of the secondary and tertiary convolutions. The premature brain does not have any myelin except in the tegmentum of the brainstem.
Myelination of the corticospinal tracts is seen at about 39 weeks gestation. The entire premature and term infant brain appears white.
General Microscopic Description

Microscopically immature brain shows a cortex made up of small nuclei without cytoplasm or processes until 39 weeks gestation. The immature brain also has a very cellular germinal plate about the ventricles. The ventricles are the remnant of the neural canal. The germinal plate is made up of small nuclei without cytoplasm which represent neuroblasts and glioblasts which will migrate to the cortex, white matter and basal ganglia. Often premature infants develop a germinal plate hemorrhage.
Clinical Correlation

Because of immature lungs the brain is very susceptible to hypoxia, hyperoxia, and hypotension which can cause germinal plate hemorrhage, periventricular leukomalacia and periventriclar leukomalacia complex.
References

Poirer J et.al. Manual of basic neuropathology. Philadelphia: Saunders, 1990, pp. 206.
Greenfield's Neuropathology, 6th ed. Graham DI, Lantos PL (ed), New York: Arnold, 1997, pp. 558-560.
Immature infant brain
Synopsis by: Dr. MLGrunnet (TX1110M00100)[481]
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