Neural tube defects and spinal dysraphism: SAQ

This boy has an open lumbosacral myelomeningocele with the Chiari II malformation and early hydrocephalus. The exposed neural placode with the cerebrospinal fluid leak is the classic open lesion, and the motor level, which is around L2 to L3 given that he moves his hips but not his knees or ankles, predicts a significant motor deficit. The full fontanelle and the head circumference on the 97th centile point to the hydrocephalus that complicates most myelomeningoceles. The priorities are the latex-free protection, the neurosurgical closure within 24 to 72 hours, and the management of the hydrocephalus and the neurogenic bladder. [1]

Question 1 (10 marks)

Outline the immediate neonatal management, the investigations, and the definitive care for this boy, including the time frame for the closure and the approach to the hydrocephalus. [1]

I would treat this as a neurosurgical emergency in a latex-free environment. My first move is to call the neonatal and the neurosurgical teams at the outset, because the definitive treatment is the operative closure. I would keep the boy in a latex-free environment from the first contact, because the latex sensitisation that complicates spina bifida begins with the early exposure, and the latex-free status would be documented and flagged at every admission. [1]

I would place the boy prone or lateral to keep the pressure off the sac, and I would cover the lesion with a sterile saline-soaked dressing that is changed regularly to keep the placode moist and clean. I would start the broad-spectrum antibiotics that cover the skin flora, such as a first-generation cephalosporin, while awaiting the closure. I would secure the intravenous access and check the bedside glucose, because the mother has type 1 diabetes and the boy is at risk of the hypoglycaemia. [1]

The investigations would run in parallel. I would order a cranial ultrasound or a magnetic resonance imaging of the brain to map the Chiari II malformation and the hydrocephalus, with the downward herniation of the cerebellar vermis and the brainstem through the foramen magnum and the ventriculomegaly. I would order a spinal magnetic resonance imaging to map the level and the extent of the lesion and to look for the diastematomyelia, the lipoma, and the dermal sinus that may accompany it. [7]

The definitive care is the neurosurgical closure within 24 to 72 hours of birth. The surgeon frees the neural placode from the surrounding tissue, reconstructs the neural tube, closes the meninges, and brings the muscle and the skin over the defect. The early closure prevents the infection and preserves the remaining neurological function. The hydrocephalus is managed with the ventriculoperitoneal shunt, placed when the ventriculomegaly progresses, either at the time of the lesion closure or soon after. I would watch for the stridor, the swallowing difficulty, and the apnoea of the Chiari II, which would need the posterior fossa decompression once the shunt malfunction is excluded. [7]

Question 2 (10 marks)

Discuss the primary prevention of neural tube defects, including the folic acid doses and the evidence behind them, the prenatal screening, and the counselling for this mother's next pregnancy. [5]

The primary prevention rests on the periconceptional folic acid supplement. The neural tube closes at the third and fourth week of embryogenesis, before most women know they are pregnant, which is why the supplement is taken before conception and not after the pregnancy is confirmed. The United States Preventive Services Task Force reaffirmed the grade A recommendation in 2023 that all women planning a pregnancy take 400 to 800 micrograms of folic acid daily, started at least one month before conception and continued through the first trimester. [5]

For the high-risk woman, the dose is higher. The Medical Research Council Vitamin Study, reported in 1991, showed that the 4 milligram folic acid supplement reduced the recurrence of the neural tube defects by about 72 percent in the women with a previous affected pregnancy, and it established the high-dose supplement for the high-risk group. This mother is high-risk because she has a child with a myelomeningocele, and because her diabetes is poorly controlled. For her next pregnancy I would prescribe the 4 milligram folic acid, started at least one month before the conception and continued through the first trimester, taken separately from the routine multivitamin to avoid the excess of the other vitamins. [3]

I would also address the diabetes. The maternal diabetes raises the neural tube defect risk through the teratogenic effect of the hyperglycaemia, and the woman with the diabetes needs the tight glycaemic control, with the haemoglobin A1c in the target range, before and through the pregnancy. I would work with the diabetes team to optimise the control before the next conception, because the periconceptional control is the one that matters for the organogenesis. [2]

For the next pregnancy, the prenatal screening would include the maternal serum alpha-fetoprotein at 15 to 20 weeks, where a value above two and a half multiples of the median raises an open defect, and the detailed fetal ultrasound at 18 to 20 weeks, which looks for the spinal defect, the lemon and banana signs of the Chiari II, and the ventriculomegaly of the hydrocephalus. I would counsel the mother that the folic acid and the diabetic control lower the risk but do not eliminate it, that the prenatal screening finds most open defects, and that the team would walk the journey with her whatever the outcome. [2]