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| CASE REPORT |
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| Year : 2021 | Volume
: 10
| Issue : 4 | Page : 282-285 |
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Acrania-exencephaly-anencephaly sequence
Sunil Vitthalrao Jagtap1, Swati S Jagtap2, Kaushiki Varshney1, Parneet Kaur1, Ramnik Singh1
1 Department of Pathology, Krishna Institute of Medical Sciences Deemed University, Karad, Maharashtra, India
2 Department of Physiology, Krishna Institute of Medical Sciences Deemed University, Karad, Maharashtra, India
| Date of Submission | 04-Jul-2021 |
| Date of Decision | 15-Aug-2021 |
| Date of Acceptance | 15-Aug-2021 |
| Date of Web Publication | 22-Mar-2022 |
Correspondence Address:
Dr. Sunil Vitthalrao Jagtap
Department of Pathology, Krishna Institute of Medical Sciences, Deemed University, Karad, Maharashtra
India
 Source of Support: None, Conflict of Interest: None  | Check |
DOI: 10.4103/jdrntruhs.jdrntruhs_89_21
Acrania–exencephaly–anencephaly sequence is rare forms of neural tube defects. The progression is from a relatively normal-appearing exposed brain due to an absent cranium called as acrania, to an amorphous brain mass term as exencephaly. We present a case of 20 years female, nonconsaguinous marriage, G1P0A0 having amenorrhea since 3 months. On ultrasonography, a single fetus of gestational age of about 15 weeks gestation showed congenital malformation- acrania with exencephaly. Final impression on fetal autopsy given was acrania–exencephaly with deformed brain, ill-formed cervical C1, 2 spine, bilateral pulmonary immaturity- Grade II with pulmonary congestion and hemorrhage. We are presenting this rare fetal anomaly of acrania–exencephaly–anenecephaly sequence for its clinical, radio imaging, and fetal autopsy findings.
Keywords: Acrania, anencephaly, exencephaly, neural tube defects
How to cite this article:
Jagtap SV, Jagtap SS, Varshney K, Kaur P, Singh R. Acrania-exencephaly-anencephaly sequence. J NTR Univ Health Sci 2021;10:282-5 |
| Introduction | |  |
Neural tube defect occurs as a result of failure of spontaneous closure of the neural tube between the third and fourth weeks of fetal life. Acrania–exencephaly–anencephaly sequence is a rare malformation with an incidence of 3.6–5.4 for 10,000 live births.[1] Acrania and anencephaly are rare forms of neural tube defects of the fetus. Acrania is a cranial vault defect characterized by the partial or total absence of the cranial bones and the covering skin, with complete but abnormal development of the chondrocranium and the presence of brain tissue that is exposed. The progression from exencephaly to anencephaly was first described by Wilkins-Haug et al.[2] A standardized protocol in the sonographic evaluation of the developing fetus is necessary for an early prenatal diagnosis of congenital malformations. Herewith we present a case of acrania–exencephaly–anencephaly sequence.
| Case Report | | |
A 20-year-old woman, nonconsaguinous marriage, G1P0A0 having amenorrhea since 3 months. She had history of vomiting off and on since 2 months. Past menstrual history- 4-5 days/20-30 days, moderate flow, no dysmenorrheal. There was no family history of congenital anomalies. There was no history of intake of teratogenic drugs and other relevant past illnesses. The patient was non-diabetic, non-alcoholic, nonhypertensive. Her blood group was O Rh-positive. Routine investigations like complete blood count, renal and liver function tests were normal.
On ultrasonography, a single fetus of gestational age of about 15 weeks gestation showed congenital malformation- Acrania with exencephaly with deformed upper cervical spine C1, C2. Femur length, abdominal circumference were normal. No any other abnormality was detected.
Induced abortion was done. Aborted fetal autopsy examination showed a premature, male baby 120 gm, crown to heel length 15.7 cm.
The head examination revealed lack of fetal cranium. Fetal facial features were normal. Brain tissue was covered with thin membrane and present outside of cranial fossa posteriorly [Figure 1], [Figure 2], [Figure 3]. The cranial defect measured 2.4 × 2.2 cm and was covered with thin, congested membrane, in which ill-formed, distorted floating brain tissue was noted. The cervical spines C1, 2 showed a defect. The thoracic, lumbar spine appeared normal with normal morphology of the spinal canal. No facial anomalies were noted. The inter- and intraorbital distance, nasal bone, lips were normal. Intrathoracic bilateral pulmonary immaturity was noted. The intra-abdominal organs were normal. Placenta was anterior in position and was of normal thickness. The extremities were normal. Final impression given was acrania–exencephaly with deformed brain, cervical C1, 2 spine, bilateral pulmonary immaturity- Grade II with pulmonary congestion and hemorrhage. | Figure 2: Acrania- bones of the cranial vault are absent but facial structures and skull base are preserved
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 | Figure 3: Exencephalic brain is covered by a highly vascular epithelial membranous layer
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| Discussion | | |
Neural tube defects are noted frequently. The practice guidelines for the first trimester ultrasonography scan by the International Society of Ultrasound in Obstetrics and Gynecology requires identification of the fetal head, appropriate development of cranial bones, and identification of choroid-plexus and cerebral ventricle.[3] Acrania–exencephaly–anencephaly sequence is the progression from a relatively normal-appearing exposed brain due to an absent cranium called as acrania, to an amorphous brain mass term as exencephaly, to no recognizable brain tissue (anencephaly).[4] Acrania is a developmental anomaly characterized by a partial or complete absence of calvarium and presence of the exposed cerebral hemispheres with loss of its normal anatomy.[5]
The acrania is the rare fetal anomaly affecting the central nervous system with an incidence of ~1:1000 pregnancies.[4]
On embryonic development this abnormality occurs at the beginning of the fourth week of gestation when the anterior neuropores closes. The calvarium, muscles of the scalp and the dura are not formed. In the absence of induction from the neurocranium, the cerebral tissue fails to differentiate into two hemispheres.
In acrania bones of the cranial vault are absent but facial structures and skull base are preserved. The central nervous system damage occurs after formation of the retinal cusps so the retina and eyes are developed. The top of the head is wide and flat, the neck is short. The external ears are small, dysplastic and displaced in a foreword direction.
These anomalies are well detected on ultrasonography. The transvaginal approach h can detect acrania–exencephaly–anencephaly sequence at an early stage of fetal development, with the earliest at the 10–13 weeks.[6] In the first trimester, on ultrasonography the findings noted are echogenic amniotic fluid, absent of calcification of the cranial bones, lateral widening of the cerebral hemispheres -the “Mickey Mouse” sign. At 12 weeks acrania is suspected by absence of the normally ossified skull and distortion of the brain (exencephaly). At >16 weeks the brain is destroyed (anencephaly).[7]
Exencephaly can be defined as a large amount of disorganized brain tissue with loss of its normal anatomy, most of the embryo's brain is exposed or extruded through the skull. Mostly noted at the base of the skull. The exencephaly is a rare congenital anomaly that occurs in the spectrum of the acrania and anencephaly.[8]
Exencephaly is a precursor to anencephaly. It differs from anencephaly in that residual brain tissue is present and floating free in the amniotic fluid.
Hendricks et al. showed that the exencephalic brain is noted to be covered by a highly vascular epithelial layer, the gyri and sulci are shallow, flattened, and disorganized. The remaining central nervous system tissue is dysplastic, with little or no neuronal differentiation, and very little normal cortex.[9]
Anencephaly on the other hand occurs as a result of failed closure of the midbrain and forebrain, but with normal fusion at the level of the hindbrain and the cervical cord region.
Various extracranial malformations, aneuploidy and genetic syndromes associated with acrania–exencephaly–anencephaly sequence are also reported. The associated anomalies observed are limb–body wall complex, omphalocele, amniotic band syndrome, and pentalogy of Cantrell.[10],[11]
It is incompatible with survival and uniformly fatal postnatally. Various anomalies including meningoencephalocele, amniotic bands, limb–body wall complex, acalvaria, and osteogenesis imperfecta type II etc., should be carefully look for.[12]
| Conclusion | | |
Acrania-exencephaly-anenecephaly sequence is the rare fetal anomaly. It is incompatible with survival and mostly fatal. Screening methods used to identify neural tube defects at an early stage of pregnancy on ultrasonographic features in most of cases remain important.
Declaration of patient consent
The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.
Financial support and sponsorship
Nil.
Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2], [Figure 3]
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