Amniotic Band Syndrome Associated with Exencephaly: A Case Report and Literature Review.

Amniotic band syndrome (ABS) is a rare congenital disease with variable manifestations ranging from simple constriction rings at the extremities to major defects such as exencephaly. Here we report the case of a female baby born full term (39 weeks) from a 35-year-old primiparous mother by cesarean section. In addition to the constriction rings at the extremities (fingers), the newborn presented facial malformations and a cranial anomaly suggestive of exencephaly. Supportive treatment was chosen because of the poor prognosis, and the child died 5 months later. Depending on the anomaly associated with ABS and its complexity, as in our case, genetic studies should be performed whenever possible, and the parents should be informed about the possibility of recurrences and incompatibility with life.

Introduction

Amniotic band syndrome (ABS) is a rare congenital disorder with several manifestations from simple constriction rings to major defects that may even lead to miscarriage. Its incidence ranges from 1:200 to 1:500 live births.[1] It affects both sexes equally, and its frequency is slightly higher in the people of the Afro-Caribbean descent.[2] The first report on this type of malformation was published in 1685 by Portal. The first description of its etiopathogenesis was proposed by Montgomery in 1832.[3] Although studies by Orioli et al.[4] showed that the extremities are more affected by this disease, Guzmán-Huerta et al.[5] reported craniofacial abnormalities in 78% of the cases and defects of the extremities in 70%. Cranial changes range from encephalocele to acrania.[6] Exencephaly is a type of acrania, with disorganized brain tissue arising from the base of the skull.[7] We report the case of a newborn with ABS and exencephaly.

Case Report

A female newborn was delivered by a 35-year-old primigravida mother at term (39 weeks) by a cesarean section. The mother reported a consanguineous marriage and no history of teratogenic medication, diabetes, hypertension, recent infection, or drug exposure during pregnancy. Antenatal ultrasound (28 weeks) led to the diagnosis of frontal encephalocele.

On physical examination, the newborn weighed 3500g and had difficulty in breathing and showed partial absence of the skull bones (left parietal, left temporal, and frontal bones).

Owing to this defect, protruded abnormal brain tissue was covered only by a membrane similar to the dura mater. There were malformations along the facial midline, such as bilateral cleft lip and palate and nasal deformity. Bilateral proptosis was also noted. Changes in the extremities included the following: her right hand had hypoplastic second and third fingers conjoined by a fibrous tissue (syndactyly) and left hand had constriction rings around the third and fifth fingers, with amputation of the distal phalanx of the fourth finger. Congenital clubfoot was noted [Figure 1].

Figure 1

Coronal CT scan, protruding malformed brain tissue through the skull bone defect caused by the partial absence of the frontal, left temporal, and left parietal bones (arrows)

Cranial computed tomography (CT) evidenced a great amount of protruding malformed brain tissue through the skull bone defect caused by the partial absence of the frontal, left temporal, and left parietal bones, suggesting exencephaly [Figure 2].

Figure 2

Right hand, hypoplastic second and third fingers conjoined by a fibrous tissue (syndactyly). Left hand, constriction rings around the third and fifth fingers, with amputation of the distal phalanx of the fourth finger

No other malformations were found. ABS was diagnosed on the basis of the clinical picture.

Only support treatment was provided because of the severity of the condition and the poor prognosis, including feeding via an orogastric tube and tracheostomy for improved breathing. However, the child died from acquired comorbidities 5 months after birth.

Discussion

ABS comprises a group of anomalies that correspond to 1%–2% of the congenital malformations in the general population. This disorder is not hereditary, and no risk of recurrence is observed.[8]

Its etiology is unknown. Several theories have been suggested to explain its etiopathogenesis, and the most accepted ones are as follows: (1) the intrinsic theory proposed by Streeter in 1930, which establishes that congenital constriction is a germplasm defect with vascular disruption and change of morphogenesis during gastrulation, forming the fibrous bands and causing limb necrosis[139] and (2) the extrinsic theory proposed by Torpin in 1965, which associated the defects of the extremities or limb amputations with amniotic rupture and compression of the bands.[3]

There are multifactorial and genetic factors that cause amniotic rupture: direct abdominal trauma, induced abortion, amniocentesis, maternal exposure to drugs, bacterial infection of the amniotic membranes, and oligohydramnios.[8]

According to Higginbottom, there are three mechanisms that could explain the role of bands in the genesis of the malformation: (1) interruption of morphogenesis, (2) deformation due to compression of fetal parts by the fetus itself or entrapment of fetal parts by the band, and (3) injury of already formed and developed fetal parts such as constrictions found in the extremities.[10]

Van Allen et al., in 1987, also contributed with the theory of vascular disruption, preceded by Kino who conducted experiments in animal models in 1975.[3]

Hunter et al. proposed another theory based on a defect or primary deficiency in the ectoderm of the embryonic disc. The area affected and the severity of the results varied according to the location of the defect. In particular, craniofacial abnormalities were classified as follows: (1) exencephaly/encephalocele with amniotic connections and without facial cleft; (2) similar cranial lesions, with facial clefts and with or without amniotic bands; (3) abdominoschisis and thoracoabdominoschisis; and (4) limb abnormalities.[3]

Exencephaly is a malformation incompatible with extrauterine life.[11] This condition is the partial or complete absence of the calvaria (acrania) associated with protrusion of an abnormal brain tissue through the defect. Some studies have shown that it is an embryological precursor of anencephaly, resulting from the degeneration of the unprotected brain tissue affected by mechanical and chemical trauma when exposed to the amniotic fluid.[712]

The diagnosis of ABS is difficult and occurs in only 29%–50% of cases.[3] The craniofacial deformities are often bizarre, and the internal organ abnormalities are rare.[2]

Exencephaly may be diagnosed using the measurement of alpha-fetoprotein level in the amniotic fluid and maternal blood. Ultrasound may be used at gestational week 11, which may indicate the absence of bone coverage in the cranial vault.[1113]

The prognosis of ABS varies according to the associated anomalies. In this case, despite the complex anomaly (exencephaly) and poor prognosis, supportive measures were chosen and the survival period was 5 months. The complications from this disease are severe; therefore, genetic studies should be performed whenever possible, and the parents should be informed about the potential risk of recurrences and incompatibility with life.

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Conflicts of interest

There are no conflicts of interest.