CARTA, Human Uniqueness Compared to "Great Apes": Absolute Difference Gestational age is 20 weeks, 1 day, with EDD of 09/01/2023 by the clinical dates given. If one or more sutures close early, it will cause the skull to expand in the direction of the sutures that remain open, which can result in an abnormal head shape. 1.15 and 1.16). v, lateral ventricles; solid arrow, ocular orbit with a lens within it; chevron, maxilla; open arrow, body of the mandible. xoUuf7a[Pl(uQ,|PX If it appears to be exceptionally large, it can be objectively assessed by measurement of its anteroposterior diameter in an axial section of the posterior fossa (Fig. :kDNl]w+9^R Mn9e(ng+bQjEw\Z`?:0Fdti_+J2~jOt_I@`^umWUG6h8L&@|K? /Type /XObject 1.24). This space begins to close in late gestation, a process that is completed during infancy. Fetal feet can also be identified, though evaluating the number of toes may be difficult because of their small size (Fig. Open arrow, vertebral body ossification center; solid arrow, vertebral arch ossification center. Objective: Cephalic index less than 76% Subjective: Apparently increased antero-posterior length of the head compared to width Comments: Cephalic index is the ratio of head width expressed as a percentage of head length. The use of 4D ultrasound can be used to assess facial expressions [23]. Dolichocephaly - understanding 'breech head' molding | The midwife, the mother and the breech 31/07/2015 19:13 /Width 38 Calipers, CRL measurement. Obstet Gynecol. FIGURE 1.47: Sagittal view of the spine in mid-second trimester demonstrating its normal curvature. The face, specifically lips and nose, are best examined in sagittal section (see Fig. ultrasound scans throughout the pregnancy and all neonates were found to be normal. The yolk sac becomes visible within the gestational sac by the midportion of the 6th gestational week, corresponding to an MSD of approximately 10 mm. Reference article, Radiopaedia.org (Accessed on 04 Mar 2023) https://doi.org/10.53347/rID-2020, {"containerId":"expandableQuestionsContainer","displayRelatedArticles":true,"displayNextQuestion":true,"displaySkipQuestion":true,"articleId":2020,"questionManager":null,"mcqUrl":"https://radiopaedia.org/articles/scaphocephaly/questions/1916?lang=us"}, View Frank Gaillard's current disclosures, see full revision history and disclosures. There is no direct communication between the ventricular system and CSPV; it is diffusion across the thin septi pellucidi that allows CSF to enter this space. The breech head and its ultrasound significance - PubMed FIGURE 1.2: Embryo at 6.5 weeks gestation. 1.40). NRCP report 140. FIGURE 1.24: Fetal foot (arrow) with all five toes visible (12 to 13 weeks gestation). Neuroimaging and molecular cytogenetics were used to ascertain the cause of disability in a case. We evaluated dolichocephaly, the name associated with a nonsynostotic cause to be a physiological variant having no prognostic value, to that of a similar synostotic or secondary to a. This chapter deals with normal fetal anatomy; however, frequent references to anomalies are made to underscore the pertinence of a good anatomic evaluation. A cystic midline structure that is occasionally seen located posteriorly and inferiorly to the CSV is the cavum veli interpositi (Fig. Systematic evaluation is needed to accurately distinguish between a viable intrauterine pregnancy, a miscarriage, or an ectopic pregnancy. 6 0 obj To see microcephaly during pregnancy, the ultrasound test should be done late in the 2nd trimester or early in the third trimester. It is normally small (<3 mm diameter) and may be difficult to visualize. The CSPV begins to close in the third trimester, a process that is completed in infancy. Solid arrows, frontal horns of the lateral ventricles; open arrows, caudate nuclei; o, orbit; asterisk, extra-axial fluid. In the anteroposterior axis, the spine is curved, being convex in the thoracic region and concave in the lumbosacral region. http://carta.anthropogeny.org/moca/topics/age-closure-fontanelles-sutures. FIGURE 1.35: Axial view of a fetal head at 32 weeks. Vertex Position: What It Is, Why It's Important, and How to Get There, The Age When Babies Learn to Hold Their Heads Up, Why You Shouldn't Panic If Your Baby Isn't Cute, Overview of Penile Adhesions in Babies and Young Boys, Measuring for nonsynostotic head deformities in preterm infants during NICU management: A pilot study, When a babys head is misshapen: Positional skull deformities, Treatment of cranial molding deformities in preterm infants, Cephalic index in the first three years of life: study of children with normal brain development based on computed tomography, Review of past reports and current concepts of surgical management for craniosynostosis. If one or more sutures close early, it will cause the skull to expand in the direction of the sutures that remain open, which can result in an abnormal head shape. Selected Safety Recommendations for Diagnostic Ultrasound, Ultrasound exposures that elevate fetal temperature by 4C above normal for 5 min or more have the potential to induce severe developmental defects, Apply the ALARA principle if the tissues to be exposed contain stabilized gas bodies (lung) and the MI exceeds 0.4, There is no epidemiologic support for a causal relationship between diagnostic ultrasound during pregnancy and adverse biologic effects to the fetus observed for outputs under a spatial-peak temporal-average intensity of 94 mW/cm2, The temperature of the fetus should not safely rise more than 0.5C above its normal temperature, When MI is above 0.5 or the TI is above 1.0, the NCRP recommends that the risks of ultrasound be weighed against the benefits. Another axial section routinely employed to evaluate the intracranial anatomy is the suboccipitobregmatic view: Starting with the BPD view, the posterior aspect of the probe is rotated caudally until the posterior fossa becomes visible. 4 0 obj Confirm that the fetal heart is beating. In the axial section, the three ossification centers are in a triangular arrangement. C: Section demonstrating vertebral arch ossification centers (solid arrows) only. However, many experts in the field advocate the use of additional views to improve diagnostic performance. Early Hum Dev. Trong nhng trng hp nh vy, u hp v di ra. The falx cerebri is seen as an echogenic line running in the anteroposterior direction. Babys heads are made of several soft plates that havent fully fused together at birththis flexibility helps babies pass more easily through the birth canal, and makes the rapid brain growth that happens during your babys first 12 months possible. They will let you know if any testssuch as a CAT scanare needed to better understand the way dolichocephaly may be affecting your baby, and if any specific interventions may be required. 1.9). Blickman JG, Parker BR, Barnes PD. Please Note: You can also scroll through stacks with your mouse wheel or the keyboard arrow keys. Treatment is often with a cranioplasty. Overcurvature of the thoracic spine, kyphosis, or lateral curvature of the spine, scoliosis, can be detected by careful assessment of at least two of the three standard planes. Open arrow, pulmonary artery; solid arrow, aorta; chevron, superior vena cava. 1.6). However, occasionally echolucent structures of varying complexity and size called choroid plexus cysts (CPCs) are present.9193 They can develop in any portion of the choroid plexus, but those that are 3 mm tend to be located in the glomus. FIGURE 1.12: Transverse view of the chest at 12 to 13 weeks gestation containing a four-chamber heart view. It is best to develop a systematic approach to the examination. You can find out more about our use, change your default settings, and withdraw your consent at any time with effect for the future by visiting Cookies Settings, which can also be found in the footer of the site. 1989;74 (4): 600-3. However, the presence of multiple vertebral ossification centers does obscure it to a variable degree, especially later in gestation. But what happens if your babys head is more severely misshapen? Group 2 Fifteen patients were referred with suspected fetal dolichocephaly as dened by a biparietal diameter (BPD)/occipitofrontal diameter (OFD) ratio < 0.7. This is because babies heads are meant to be moldable to accommodate the many changes that happen during gestation, birth, and the first year of life. ADVERTISEMENT: Supporters see fewer/no ads. FIGURE 1.5: Sagittal view of a 12- to 13-week fetus. Treatment of Cranial Molding Deformities in Preterm Infants 22 week US baby head was oval and stated possible dolichocephaly&nbsp; but needed repeat scan at 24 weeks. Anyone had this and how did it turn out? ASSESSING FETAL ANATOMY DURING THE SECOND AND THIRD TRIMESTERS. It can also be used to localize the DV in a right parasagittal section, allowing pulse wave assessment of this vessel for aneuploidy and cardiac screening. They invariably resolve spontaneously and do not represent a true pathologic entity. There is a tendency of the ankles to turn inward, making the diagnosis of clubfoot in the first trimester challenging. In the 11th week of gestation, the fetus begins to flex and extend its body to a degree that may significantly affect CRL; therefore, CRL measurements need to be carefully standardized from this point on (Fig. WTE Must Reads Featured Discussions Jump to Your Week of Pregnancy Pregnancy Week 1 Pregnancy Week 2 Pregnancy Week 3 20w scan - Dolichocephalic head shape - BabyCenter Canada 1 Arrow, cavum veli interpositi; cp, choroid plexus. Ultrasound findings are frequently best interpreted in combination with quantitative maternal serum hCG (human chorionic gonadotropin) with or without progesterone levels. ; C]pb Dolichocephaly Definition, Pictures, Symptoms, Causes, Treatment c, cerebellar hemispheres. stream When using Doppler during the 11 to 13+6 week scan, power indices should be reduced to a minimum, and the region of interest should be interrogated for the minimum time necessary. 3. anyone dealt with this? At the time the article was last revised Daniel J Bell had no recorded disclosures. Merz E, Bahlmann F. Ultrasound in obstetrics and gynecology. At this point, the CRL is defined as measurement between the top of the fetal head and the fetal rump along its longitudinal axis (Fig. In this section, the intracranial anatomy essentially consists of the lateral ventricles and a very thin layer of brain parenchyma. Se realiza exploracin eco-sonografica de tiroides dentro del patrn del perfil de paciente hipertenso. 1.45).106,107 In the presence of an open spine defect, this arrangement is disrupted, and the laminar ossification centers are displaced laterally, forming the shape of the letter U or V in the axial view of the spine. The index is calculated from measurement of the diameters of the skull. FIGURE 1.41: Axial view of a fetal head in the third trimester after the completion of insular operculization. A Diagnosis of Microcephaly refers to some babies having a small head when measured by ultrasound during pregnancy, and with a tape measure around the head after birth. Reference article, Radiopaedia.org (Accessed on 04 Mar 2023) https://doi.org/10.53347/rID-15495, View Yuranga Weerakkody's current disclosures, View Munyi Ambrose Ithiga's current disclosures, see full revision history and disclosures, 1. The vertebrae have three ossification centers visible prenatally: Vertebral body anteriorly and one in each of the vertebral arches (laminae) posteriorly. Some critically ill infants may be positioned supine with the head. The images can provide valuable information for diagnosing and directing treatment for a variety of diseases and conditions. A specialist must fit molding helmets. The atrium is located medially. Synonyms for dolichocephaly in Free Thesaurus. 2019;131:56-62. doi:10.1016/j.earlhumdev.2019.03.002. However, a lack of proportionality be-tween the head circumference and the biparietal diameter is more obvious to spot (e.g. Wendy Wisner is a lactation consultant and writer covering maternal/child health, parenting, general health and wellness, and mental health. Kyutoku S, Inagaki T. Review of past reports and current concepts of surgical management for craniosynostosis. Microcephaly - Symptoms and causes - Mayo Clinic FIGURE 1.48: Sagittal view of the cervical spinal cord (notched arrow) in late second trimester. Gray DL, Songster GS, Parvin CA et-al. It should also be stressed that an increased translucency and the presence of other markers, most notably tricuspid valve regurgitation and an abnormal ductus venosus (DV) Doppler waveform, increase the risk of structural abnormalities even in chromosomally normal fetuses.54. 7 0 obj Therefore, in the standard axial section at the level of the BPD, usually it is only the CSP that is visible. Abnormal curvature may be due to the presence of a hemivertebra, which is a feature of a number of genetic syndromes such as VACTERL; therefore, other anomalies known to be associated with this syndrome should be actively sought. FIGURE 1.27: Transverse/oblique section of the lower abdomen and the pelvis showing the urinary bladder (b) with two umbilical arteries coursing around it in a 12- to 13-week fetus. The fetal head and upper torso occupy the majority of the image, and the fetus is in a neutral position. Additional fetal biometry is performed if clinically appropriate. Z@N Just in case the CI is significantly lower, that suggests dolichocephaly (long head), where the sutures have closed too early. << Typical facial characteristics include dolichocephaly, downslanting palpebral fissures, enophthalmos, retrognathia, and malar hypoplasia. When a craniosynostosis is suspected, the first line imaging will be ultrasound or x-rays, depending on local expertise and preferences. In addition to the bifrontal scalloping of the cranium described earlier, open spine defects are accompanied by the Chiari Type II malformation (herniation of the cerebellar tonsils through the foramen magnum and downward displacement of the cerebellar vermis). 1.29). The third ventricle is located inferiorly to the CSP, between the paired thalami. It is a measurement of the diameter of a developing baby's skull, from one parietal bone to the other. a, atria. The inferior (temporal) horns run through the area of the temporal lobe and are difficult to identify unless they are enlarged. The four-chamber view and outflow tracts can be assessed using both grayscale and color Doppler imaging (Figs. FIGURE 1.44: A, B: Suboccipitobregmatic views of the head demonstrating a variety of normal septations within the cisterna magna (cm). 1.46). Since the cerebellar vermis is not yet fused, a large midline communication is seen between the developing fourth ventricle and the cisterna magna (CM) (Fig. The TCD is measured in an axial section using the suboccipitobregmatic view. Calipers, CRL measurement; d, diencephalon; m, mesencephalon; r, rhombencephalon. . Enlargement of the lateral ventricle (ventriculomegaly) will be recognized by measurement at this point. At the time the article was created Frank Gaillard had no recorded disclosures. The paired laminar ossification centers are slightly offset from the midline. This can lead to a false impression that the CSP is present, consequently missing the diagnosis of anomalies that can be associated with absent CSPV such as agenesis of corpus callosum, septo-optic dysplasia, lobar holoprosencephaly, and neuronal migration defects. Are Head-Shaping Pillows Safe for Babies? /Title ( D o l i c h o c e p h a l y , v a r i a n t o f n o r m a l . The genital tubercle (open arrow) points in a direction parallel to the longitudinal axis of the fetus, indicating a female gender. Placental site and cervical length can then be assessed, although true cervical assessment requires a transvaginal approach, which is best performed at the end of the examination. Note the formation of a cyst-like structure in B. Calipers, cisterna magna measurement; c, cerebellar hemispheres. FIGURE 1.23: Fetal hand with all phalangeal ossification centers visible (13 to 14 weeks gestation). Images Scaphocephaly: The head has a short laterolateral and a long anteroposterior diameter. 1.3).48 Whereas some investigators advocate using the average of three CRL measurements to establish gestational age, most use the single best measurement. Note the two juxtaposed pillars of the fornix (open arrow) with a midline echogenic division. When this occurs, the skull forms an abnormal shape. 30. The vertebral body ossification center is round and is located in the midline. MD is referring me to high risk ob for a level 2 ultrasound. Most of all, know that you are not alone, and you will get through this. Note the difference in echogenicities between the various organs. The term is derived from the Ancient Greek words "skaphe"meaning a light boat and "kephale"meaning head and describes an elongated head resembling an inverted boat. B: Axial view in a plane slightly caudal to A, where the cavum septi pellucidi (solid arrow) and cavum septi vergae (open arrow) are seen as two separate structures. As the transducer is moved caudally, the orbits can be identified. A small angle, which is essentially parallel to the longitudinal axis of the fetus, indicates a female gender, whereas an angle measuring 30 or more suggests a male gender (Figs. The Ultrasound Care specialist doctors and sonographers can use the Morphology scan for the following insights into your pregnancy and your baby. Check for errors and try again. Its common for babies heads to look slightly misshapen after birth and even in the first few weeks that follow. 1.25 and 1.26). Fetal measurements are concordant with dates, apart from BPD below 5th centile reflecting dolichocephaly. Scaphocephaly. The U.S. National Library of Medicine explains that most cases of dolichocephaly occur in preterm babies who are born at less than 32 weeks gestation, and because of the side-lying or prone (i.e., on their stomach) positions these babies are commonly placed in while they are in the NICU. A more significant deformity can also impact a person's self-esteem and confidence as they grow into adulthood. In the axial section, the contour of the fetal head is normally oval in shape. Centers for Disease Control and Prevention. However, these are often better seen in a coronal section of the face (Fig. FIGURE 1.16: Left longitudinal view of the abdomen at 12 weeks gestation demonstrating the left lung (Lu), intact diaphragm (arrow), left lobe of the liver (L), stomach (s), and small bowel (sb). Fetal anatomy is most readily assessed with a transverse sweep, running from head to toe. 1.11). It can change according to various situations such as, The usual range is variable depending on various sources and different demographic groups. /ColorSpace /DeviceRGB 1.38). anyone have a baby with this condition? Color Doppler may be used to help define the cord insertion and the number of arteries in the cord (Fig. The sacral portion of the spine usually has a more persistent curvature, with the tip of the spine pointing posteriorly (Fig. Willis S, Hsiao R, Holland RA, Lee K, Pitetti K. Measuring for nonsynostotic head deformities in preterm infants during NICU management: A pilot study. Cephalic index less than 76%. With the exception of the above-described Chiari Type II malformation, most defects affecting the posterior fossa are cystic in nature (DandyWalker malformation, Blakes pouch, arachnoid cysts, and dysgenesis of the cerebellar vermis). Normal Fetal Ultrasound Survey | Radiology Key Description Premature fusion of coronal and sagittal sutures usually leads to a tall, tower-like skull which is known as turricephaly. FIGURE 1.8: Transverse views of a fetal head at 13.5 weeks gestation demonstrating progressive development of the cerebellum. Occasionally, the third ventricle can be detected in a midcoronal section of the head (Fig. Prenatal ultrasound diagnosis of fetal craniosynostosis Nuchal translucency measurement is typically increased in fetuses affected by chromosomal abnormality. (2012) American Journal of Roentgenology. The CM is a CSF-filled structure that is located behind the cerebellum. Sagittal craniosynostosis, also called scaphocephaly or dolichocephaly, is the most common type of craniosynostosis, which occurs when bones in an infant's head fuse together abnormally.The experienced doctors at St. Louis Children's Hospital have been treating scaphocephaly for decades. Three-dimensional (3D) ultrasound can be a useful adjunct to 2D ultrasound in select circumstances and will be discussed in Chapter 2. A thin line of hair along the fetal back (arrows) is seen. Mosby Inc. (2009) ISBN:0323031250. The shape of the cerebellar hemispheres becomes somewhat flattened on its anterior surface. Scientific World Journal. 38. she as well as the dr. at the ultrasound place were happy because all measurements were right on target. 20w scan - Dolichocephalic head shape. Features of this skull deformation (dolichocephaly, a prominent occiput with a suboccipital shelf, an elongated face and a parallel-sided head) constitute the 'breech head'. Fetal anatomy is best assessed at 20 to 24 weeks gestation. >> /Producer ( Q t 4 . Retrospective analysis showed a prenatal scan reporting dolichocephaly. Has anyone experienced this, this early. PDF Dolichocephaly - understanding 'breech head' molding - CORE FIGURE 1.29: Axial view of the fetal head at the BPD level. Biparietal diameter (BPD) is one of many measurements that are taken during ultrasound procedures in pregnancy. In this rare case, surgery is very successful after birth to correct the problem. Understanding Vaginal Tears During Labor and Delivery. [/Pattern /DeviceRGB] Solid arrow, femur; open arrow, tibia; chevron, fibula. Dolichocephaly (or positional scaphocephaly) is defined as a boat-shaped or elongated anterior-posterior axis as a result of skull flattening during side-to-side head positioning of infants during hospitalization. The latter should not be mistaken for a cyst. Exposure Criteria for Medical Ultrasound, II: Criteria Based on All Known Mechanisms. It may be associated with craniosynostosis of the sagittal suture; it may be commonly seen in the premature infant and is more frequently a normal variant. At the time the article was created Yuranga Weerakkody had no recorded disclosures. endobj But most of the time, these occur after birthwithin the first 4 to 12 weeks, when babies spend a lot of time lying flat and are less mobile. 1.48). J4Wr~]RF+J7j_A@]5%"po!Y*i| $JC]l Head ultrasound was normal except marked dolicocephaly, head circumference between -1 and -2 SD, and suspected delay of sulcation. Asterisks, corpus callosum; open arrow, cavum septi pellucidi; chevron, cavum septi vergae; solid arrow, fourth ventricle; c, cerebellum; cm, cisterna magna. Note that this is a neonatal image to show the anatomy in its entirety. It should be remembered that the anterior pillars of the fornices lie in the same general area as the CSP. Appointment Center 24/7 216.445.7050. (PDF) New Screening Tool for Aortic Root Dilation in Children with Verywell Family's content is for informational and educational purposes only. Can craniosynostosis correct itself? The cerebral cortex is a hypoechoic structure, which is fairly thin and difficult to visualize at early gestations. White arrows, trigones; asterisks, choroid plexi; black arrows, section through a portion of the cerebellum. FIGURE 1.30: Sagittal view of the lateral ventricle at 24 weeks gestation. The vertebral column should be evaluated in at least two of the three planes: coronal, axial, and longitudinal (midsagittal). After 11 weeks gestation, the calvarium should be ossified and is seen as an echogenic ring around the intracranial structures (see Fig. 1.4).49,50. Arrow, fourth ventricle; c, cerebellum. In the early first trimester, the transvaginal approach is ideal to detect any adnexal pathology or free fluid. She has worked with breastfeeding parents for over a decade, and is a mom to two boys. Solid arrows, vertebral arch ossifications; open arrow, vertebral body ossification. Nuchal translucency assessment is easier to perform and more sensitive at an earlier gestation (11 to 12 weeks), whereas anatomy is best assessed at a slightly later gestation (12 to 13 weeks).8 The examination may be performed transabdominally, and if necessary transvaginally, but a combination of the two approaches often yields the best results. FIGURE 1.7: Transverse views of a fetal head at 12 weeks gestation demonstrating hindbrain appearance at various levels in descending order. It is seen as a hypoechoic structure between the cerebral peduncles and the cerebellum (Fig. Dr wants another scan at 30 weeks. FIGURE 1.1: Sagittal view of a 10- to 11-week fetus demonstrating a physiologic midgut herniation (arrow). It provides the same information as the early first trimester scan with a number of additional benefits. Dolichocephaly - ULTRASOUNDPAEDIA It has an incidence of 1 in every 4,200 babies." - Does this mean it ex Continue Reading More answers below Is ABVS ultrasound better at detecting abnormal tissues in breasts than conventional ultrasound? What is Dolichocephalic? Dolichocephalic definition and meaning - Collins Dictionary By 20 weeks most of your baby has developed such that screening of the organs is possible to assess for abnormalities. %PDF-1.4 As the spine is curved, it is common to be able to visualize the vertebral bodies at some levels and the arches at other levels in the same view (Fig. This is something your doctor will discuss with you, as the need for these interventions is case-by-case. The hemispheres develop gyri through the third trimester, which are visible on ultrasound, and the cerebellar tonsils become more elongated. Using this method, the accuracy of sex determination is only 70% at 11 weeks gestation but increases to nearly 100% at 13 to 14 weeks gestation.59. 1.30 to 1.33). The three ossification centers (solid arrows, vertebral arches; open arrow, vertebral body) are seen. Dolichocephaly Definition, Pictures, Symptoms, Causes, Treatment << Dolichocephaly has two primary causes: craniosynostosis or positioning. Ultrasound - Mayo Clinic Con transductor linear de 7,5 Mhz se visualiza imagen nodular con eco-patrn mixto ( contenido solido-liquido ), se localiza en lbulo derecho . The embryonic stage, ending at 10 weeks gestation, is a time of very rapid change in the small, developing conceptus.45 Ultrasound before 11 weeks gestation is not typically regarded as a routine part of pregnancy assessment. At this early stage, the gestational age is being estimated by determination of the mean sac diameter (MSD): the average of the sac length, width, and depth. FIGURE 1.39: Parasagittal section of the fetal head with the temporal lobe (t) visible. Assessment of the central nervous system is not complete without detailed examination of the fetal spine. The transvaginal approach should be used in all circumstances where a viable intrauterine pregnancy is not obvious on transabdominal assessment. Notched arrow, falx cerebri; cp, choroid plexus. Impacting Infant Head Shapes endobj Septations within the CM are a common finding and occasionally they can simulate a small cyst. The approach to the anatomical survey is essentially the same in both the second and the third trimesters. 3. 1010 th, temporal horn; solid arrow, color Doppler of the middle cerebral artery; open arrow, Sylvian fissure; csp, cavum septi pellucidi. FIGURE 1.11: Transverse view of the lower neck at 12 to 13 weeks gestation. {"url":"/signup-modal-props.json?lang=us"}, Gaillard F, Bell D, Zivic L, et al. Cephalic index in the first three years of life: study of children with normal brain development based on computed tomography. Our website is not intended to be a substitute for professional medical advice, diagnosis, or treatment. Biparietal diameter of the head is . Dolichocephalic Definition & Meaning - Merriam-Webster In the mid-second trimester, bifrontal scalloping occurs in >95% of open neural tube defects resulting in a lemon-shaped calvarium seen in the axial section.84,85 The occipital portion of the skull is typically flattened in trisomy 18, while the frontal and parietal portions of the skull gently slope toward one another anteriorly, creating a strawberry shape in axial view.