Fetal Anomalies Kuldeep Singh
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Head and Brain (Normal Anatomy)Chapter 1

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CRANIAL BIOMETRY (TRANSTHALAMIC VIEW)
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Fig. 1.1: Section for cranial biometry consisting of the thalamus, the third ventricle and the cavum septum pellucidum. The biparietal diameter is the side to side measurement from the outer table of the proximal skull to the inner table of the distal skull. The head perimeter is the the total cranial circumference, which includes the maximum anteroposterior diameter. The occipito-frontal diameter is the front to back measurement from the outer table on both sides
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VENTRICULAR ATRIUM (TRANSVENTRICULAR VIEW)
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Fig. 1.2: Choroid plexus (CP) seen occupying the whole of the body of the lateral ventricle (LV). The anterior horn of the lateral ventricle (solid arrow) seen on the left side and posterior horn of the lateral ventricle (dashed arrow) seen on the right side are not filled by the choroid plexus
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Fig. 1.3: Choroid plexus seen in the lateral ventricles on both sides
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Fig. 1.4: The choroid plexus quite often does not occupy the whole of the body of the lateral ventricle and the frontal and the posterior horn also are not filled by the choroid plexus (stars)
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Fig. 1.5: The width of the body of the lateral ventricle, the interhemispheric distance and the ratio of the width of the body of the lateral ventricle to the interhemispheric distance is calculated (Normal value < 50%). This is not sensitive for early hydrocephalus. The width of the body, anterior horn and posterior horn of the lateral ventricle are taken (Normal value < 08 mm, borderline 08-10 mm and > 10 mm abnormal)
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Fig. 1.6: When the choroid plexus does not occupy the whole of the body of the lateral ventricle see for the measurement of the medial separation (arrow) of the choroid plexus from the wall of the lateral ventricle (Normal value < 02 mm, borderline 02-03 mm and > 03 mm is abnormal)
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CEREBELLUM (TRANSCEREBELLAR VIEW)
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Fig. 1.7: The cerebellum is seen as a ‘W’ turned 90 degrees. The cerebellar hemispheres (C) and the cerebellar vermis (within the circle) should be appreciated for posterior cranial fossa abnormalities
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Fig. 1.8: The cerebellar transverse diameter (CTD) is measured from the edges of both cerebellar hemispheres. The CTD in mm from 14-22 weeks is equal to the gestational age of the fetus in weeks
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CISTERNA MAGNA
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Fig. 1.9: The cisterna magna is seen posterior to the cerebellar vermis and anterior to the occipital bone (solid arrow) (Normal value < 08 mm, borderline 08-10 mm and > 10 mm abnormal). Few strands seen traversing the cisterna magna are normal. Carefully check for any communication between the fourth ventricle and the cisterna magna with an abnormal cerebellar vermis. If there is any communication at gestational age less than 16 weeks revaluate the fetus after 2 weeks