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(a) Sagittal view fetal MRI demonstrating the absence of the calvarium with large mass of brain tissues hanging outside of the skull base and an incomplete layer of vascular epithelium covering the deformed brain. (b) Coronal view fetal MRI showing the intact skull base with normal appearing orbits and nasal cavity. (c) Sagittal view fetal MRI depicting the absence of the calvarium but intact orbits and skull base. The spine is normal without evidence of myelomeningocele. (d) Coronal view fetal MRI demonstrating exencephaly with grossly intact body organs.
Source publication
We present the fetal MRI characteristics of exencephaly, a rare malformation of the cranium. The fetus was initially misdiagnosed as anencephaly at 14 weeks of estimated gestational age (EGA) and later mislabeled as acrania at 20 weeks of EGA by ultrasound. A confirmatory magnetic resonance imaging (MRI) at 29 weeks of EGA demonstrated findings con...
Similar publications
Acrania is a rare congenital malformation with partial or
total absence of skull of human fetuses. It is often associated
with anencephaly and is usually fatal in very short time.
There are some prenatal markers and the ultrasound is the
gold-standard diagnostic method. The authors review aspects
of the epidemiology, pathophysiology, ultrasound dia...
Citations
... 8,9 The characteristic fetal MRI for exencephaly include (i) supra-orbitally no calvarium and scalp, (ii) skull which is unflawed and standard development of the face (eyes, nose, and mouth) (iii) disruption of parenchyma of brain with poor demarcation of landmarks, (iv) fragmentary membranous or bleary matter covering the brain tissue, (v) disproportion of the cerebellum and brain stem. 10 • With the aid of 3 D USG, 11 early detection by 8 weeks has been described. ...
Acrania–exencephaly–anencephaly sequence has an incidence of 3.6–5.4 for 10,000 live births and has been reported in literature. Exencephaly, described here is a defect of the neural tube which occurs due to the absence of closure of the neural fold. The main diagnostic ultrasound features include that are characterized by acrania, decreased size of cranial pole in comparison with the chest, irregular cranial surface, with increased amniotic fluid echogenicity due to the damaged brain tissue. Associated with amniotic band syndrome, Pentalogy of Cantrell, limb anomalies and ventral body wall defects. It is incompatible with life. Conducting programs training the budding neuro-sonographers about the knowledge in detection, diagnosis of NTD according to the Carnegie Classification is crucial to look forward in pathogenesis and application in the clinical scenario.
... The brain is covered with a thick layer of soft tissue and unossified bones; bowing or shortening of the long bones is generally found in osteogenesis imperfecta. Foetal ultrasound results can be inconclusive in the diagnosis of cranial vault defects especially during early pregnancy and foetal MRI can be used for confirmatory diagnosis in such cases [18] . There is a notable elevation in alpha-fetoprotein levels, coupled with the absence of detectable unconjugated estriol during pregnancy [1,2] . ...
... Irrespective of the specific malformation, the outlook for cranial vault defects is generally unfavourable, as a significant proportion of pregnancies end in stillbirths [18,21] . The longest-living cases of this fatal anomaly have been reported as being severely mentally retarded and disabled requiring specialized medical and social care. ...
Introduction and importance
Acalvaria is a rare congenital malformation in which the flat bones of the cranial vault, dura mater, and associated muscles are absent while the central nervous system usually remains unaffected. It is an extremely rare congenital anomaly with only a handful of cases being reported in literature.
Case presentation
The authors report a case of a 2-month-old male infant with acalvaria who was delivered at home and brought to our centre with the complaint of an abnormally soft skull. He was evaluated in a primary centre in rural Nepal. Parietal bones were missing bilaterally but no other abnormalities were found during the physical examination and investigations. Major differential diagnoses like anencephaly, cephalocele, osteogenesis imperfecta type II, and hypophosphatasia were ruled out with the help of history, physical examination, and available investigations and the case was diagnosed as acalvaria.
Clinical discussion
Acalvaria is a post-neurulation defect which is associated with anomalies of various organ systems. Radiological diagnosis, with supportive laboratory investigations, is the most reliable method of antenatal diagnosis.
Conclusion
Acalvaria is known to have a dismal prognosis and all the living cases with long-term follow-up are mentally retarded and physically disabled. Early and reliable antenatal diagnosis can reduce the economic, physical, and psychological burden associated with this fatal disease, especially in low-income countries.
... 8,9 Acrania is often used as the synonym of acalvaria but in this condition, the absence of the skull bones may extend beyond the vault bones and is often accompanied by anencephaly. 8,10 The pathophysiology of acalvaria is still unclear but a deficit in the mesenchymal migration is the most accepted hypothesis. 1-3 Normally, mesenchymal migration occurs after the neural tube closure around the fourth week of the embryonic development. ...
Acalvaria is a rare and lethal congenital malformation characterized by the absence of the cranial vault bones, dura mater and associated muscles with complete cranial content. We report a 5-year-old Malian girl seen at 20 months old for facial dysmorphia, hemiparesis, and a cranial bone defect that improved progressively.
... The (3-T) MRI scans suggest that there is no structured nervous tissue. The other most prominent feature of anencephaly which can be observed in this specimen are the bulging eyes [Sharif and Zhou, 2016]. Unfortunately, the fetus had previously been dissected, and all the abdominal and thoracic organs were removed. ...
The number of human embryology collections is very limited worldwide. Some of these comprise the Carnegie Collection, Kyoto Collection, and the Blechschmidt Collection. One further embryonic collection is the Hinrichsen Collection of the Ruhr University Bochum, Germany, which also contains very well-preserved embryos/fetuses, along with approximately 16,000 histological sections. The digitization of this collection is indispensable to enable conservation of the collection for the future and to provide a large group of embryologists, researchers, and physicians access to these histological slides. A small selection of these scans is available at the website of the Digital Embryology Consortium [https://human-embryology.org/wiki/Main_Page].
Neuroimaging in the pregnant patient is tailored to evaluating the neuraxis of either the patients themselves or their underlying gestation(s). Imaging indications can range from outpatient follow-up and pre-scheduled gestational anatomic surveys to emergent indications affecting either the expectant patient or fetus.
Acalvaria is a rare cranial vault defect characterized by the presence of the cerebellum and cerebral cortex with the absence of the calvarium above the orbits, intact facial structures, and the presence of dura mater. Unfortunately, this diagnosis comes with a dim prognosis that is not compatible with life long-term. First-trimester diagnosis with ultrasonography can establish the diagnosis. If imaging is equivocal, advanced imaging with fetal MRI has a role to aid in distinguishing between similar cranial vault defects that fall on the spectrum including anencephaly, exencephaly, and acrania. We present the case of a term male infant with known acalvaria diagnosed incidentally on prenatal ultrasound that was delivered by cesarean section to a G3P3 mother at the time of delivery with two prior uncomplicated pregnancies. Maternal history was rather insignificant except for gestational diabetes and gestational hypertension well-controlled without medication. After initiation of comfort measures only, the infant expired on day of life two.
Abstrak Amniotic band syndrome(ABS) merupakan kelainan non genetik dengan spektrum luas dari konstriksi dan amputasi sederhana pada jari ekstremitas hingga kelainan kraniofasial mayor hingga defek visera bahkan kematian. Beberapa laporan kasus menyebut anensefali merupakan contoh defek kraniofasial yang dihubungkan dengan ABS. Sonografi membantu diagnosis eksensefali sebagai kondisi peralihan menuju kondisi terminal anensefali sebagai kondisi yang lebih sering ditemukan yaitu kondisi otak janin sudah habis teresorbsi oleh cairan serebrospinal. Fetus dengan eksensefali tidak dapat bertahan hidup, sebagian besar berakhir dengan abortus, intrauterine fetal death dan stillbirth sehingga jika terdeteksi perlu dipertimbangkan untuk dilakukan terminasi kehamilan. Berdasar laporan kasus persalinan spontan Bracht di kamar bersalin RS Hasan Sadikin pada 1 Desember 2016, Ny RA 33 tahun, G3P1A1 gravida 30-31 minggu, letak sungsang, eksensefali, anemia. Pada laporan kasus ini ditemukan membran amniotik berfusi dengan kranium bayi dan absennya tulang tengkorak pada tempat perlekatan membran amnion. Eksensefali pada kasus ini diperkirakan diawali oleh residu selaput korion berupa jaringan fibrosa yang membentang cavum korionik dan menekan kranium sehingga migrasi membran neurokranium tergganggu dan berakhir dengan akalvaria. Ekstremitas yang berkembang sempurna namun cacat pada beberapa segmen terutama tempat perlekatan membran amnion dan kranium sesuai letak kejadian cincin konstriksi mendukung teori Torpin. Kata kunci: amniotic band syndrome; acrania Exencephaly as One of Amniotic Band Syndrome Complication Abstract Amniotic Band Syndrome includes a spectrum of non-genetic anomalies, varying from simple digital band constriction to major craniofacial and visceral defects, and even fetal death. Anencephaly represents the most common neural tube defect. Sonographic as well as pathologic evidence points to a close link between exencephaly (also frequently referred to as “acrania”) and anencephaly. It has been proposed that the brain tissue of exencephalics may gradually degenerate due to the exposure to amniotic fluid in combination with mechanical trauma. ABS is an aetiological factor in exencephaly. Appropriate counselling for affected families needs to be given after prenatal diagnosis. Based on medical report Mrs RA 33 years old , G3P1A1 30-31 weeks of pregnancy, breech presentation, exencephaly, anemia that delivered her baby on Delivery Room Hasan Sadikin General Hospital at December 1,2016. Amniotic membrane found fused with fetal cranium and on its attachment found that the cranium was absent (acrania) In the case reported here, the amniotic membrane was well fused to the scalp, and skull bones were absent on the site of attachment of the amniotic membrane. This case supports Torpin’s hypothesis of early amnion rupture, with failure of the cranial bones to develop at the site of attachment of the amniotic band as “early amnion disruption sequence.”. The fibrous strands would entangle and entrapped the fetal head, resulting in faulty migration of the membranous neurocranium which leads to exencephaly on this case. Keywords: Amniotic band syndrome; exencephaly
