Newborn with meroanencephaly: Surviving all odds.

Neural tube defects are a group of congenital anomalies of brain development that carry a significant risk of morbidity and mortality. Anencephaly is a serious form of this defect with a very poor prognosis. It can present in three forms - meroanencephaly, holoanencephaly, and craniorachischisis. Meroanencephaly is considered to be the classic form of anencephaly. It manifests as a lack of cranial vault bones and exposed dorsal neural tissue resulting from defective neural tube closure in the very early period of gestation. Antenatally, the diagnosis may be suggested by ultrasound examination and by elevated maternal alpha-fetoprotein level. Here, we describe a case of meroanencephaly who was discharged from the hospital in fair condition despite the life-threatening anomaly.

Introduction

Anencephaly is a devastating yet common neural tube defect which occurs due to the failure of closure of rostral pore of the neural tube that leads to exposed undifferentiated neural tissue. Anencephaly is clinically described into three types – meroanencephaly, holoanencephaly, and craniorachischisis.[1] Meroanencephaly is the classic form which presents as a lack of cranial vault bones and exposed dorsal undifferentiated dorsal neural tissue.[1] Usually, cerebral hemispheres fail to develop and only brainstem and some parts of midbrain may be present. Holoanencephaly is the more severe form in which lesion extends to hindbrain also. Craniorachischisis is the most severe variety whereby the defect extends into continuous spina bifida down to the thoracic vertebrae. Here, we present a case of meronencephaly cared for and discharged from our neonatal Intensive Care Unit.

Case Report

A male baby was born at term by vaginal delivery to a primigravida mother who did not have any antenatal visits or folic acid supplementation during pregnancy. The baby weighed 1.785 kg and did not require any resuscitation at birth. He showed gross malformation of the cranium in the form of meroanencephaly and bilateral proptosis [Figure 1a and b]. There was no prior history of similar birth defects in family. No history of teratogen exposure or any other maternal risk factor could be elicited. Antenatal ultrasound was never done which might have picked up the defect. He was on intravenous fluid for 3 days after which he was shifted to oral feeds which he tolerated well. The baby was discharged on 8 days on oral feeds. The vital need for folic acid supplementation prior to conception was advised and emphasized on the family.

Figure 1

(a-b) The affected newborn. The flat cranial vault with defective fusion and protrusion of brain matter are notable. The eyes demonstrate chemosis, conjunctival injection, and proptosis

Discussion

Neural tube defects are common congenital anomalies with worldwide incidence of 1.4–2/1000 live births.[2] The cause may be multifactorial involving genes, gender, teratogen exposure, environment, diet as well as physiological abnormalities such as hyperglycemia or hyperthermia.[2] Several studies have shown a protective role of periconceptional intake of folic acid in reducing both the occurrence and recurrence of neural tube defects.[34] Without folic acid supplementation the empirical recurrence risk after one affected child is 3–4% and after two affected children it is 10%. With supplementation, the risk after one affected child decreases by 70%.[2] Exposure to valproic acid and other antimetabolites of folic acid and other toxins like lead etc., during critical period of neural differentiation interfere with normal folate metabolism and increases the likelihood of anencephaly.[2]

Neural tube closure is the result of upward bending and eventual fusing of neural tube to form the hollow tube that becomes the brain and the spinal cord.[5] This takes place at around day 21–26 days of gestation beginning at the hindbrain/cervical boundary (Closure 1) and spreading bi-directionally into the hindbrain and spinal region. Separate closure initiation sites occur at the midbrain-forebrain boundary (Closure 2) and at the rostral extremity of the forebrain (Closure 3). However, Closure 2 found in other mammals like mice may be absent from human neurulation.

Failure of Closure 1 leads to craniorachischisis involving midbrain, hindbrain, and spinal region. Anencephaly develops if Closure 1 is completed, but the closure of the cranial neural tube is incomplete, the resulting lesion may be either confined to the midbrain (meroanencephaly) or extend into the hindbrain (holoanencephaly).[6] Failure of Closure 3 is a rare occurrence leading to anencephaly with split face.

Anencephaly can be diagnosed antenatally by ultrasound examination and by elevated maternal alpha-fetoprotein level. Anencephaly has to be differentiated from encephalocele which is a cystic extension of the brain from overlying scalp and skull defect. In addition, iniencephalocele is another differential characterized by a triad of the occipital bone defect, rachischisis, and fixed retroflexion of the head with severe cervicothoracic lordosis.[7]

Primary prevention of anencephaly involves supplementation with folic acid. The role of 0.4 mg of periconceptional folic acid in reducing the incidence of neural tube defects has been revealed by the Medical Research Council.[8] Although the prevalence of neural tube defects has decreased after preconceptional folic acid supplementation, they continue to remain common birth defects for the obstetrician to screen, diagnose, and manage in the pregnant patient. Counseling regarding folic acid supplementation is essential for all women of reproductive age.

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.

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Conflicts of interest

There are no conflicts of interest.