Master MRCPCH Part-2: Essential Study Guide

Ans- a/ spina bifida

Explanation

This is a classic presentation of occult spinal dysraphism (e.g., tethered cord) — the sacral dimple with a tuft of hair is a cutaneous marker of an underlying spinal cord anomaly.

Let’s break it down:

🧠 Reasoning

• Age & symptoms: 10-year-old with daytime urinary symptoms + occasional fecal incontinence → suggests neurogenic bladder/bowel.
• Cutaneous marker: Sacral dimple with tuft of hair → high suspicion for spinal dysraphism.
• X-ray normal: Plain radiographs often miss spinal cord anomalies — they only show bony defects, not cord pathology.
• Next step: Need detailed imaging of the spinal cord to confirm diagnosis and plan management.

📌 Best Investigation

• MRI spine ✅
  • Gold standard for detecting tethered cord, lipomeningocele, diastematomyelia, or other occult lesions.
  • Non-invasive, no radiation, excellent soft tissue detail.

❌ Why not the others?

• MRI brain: Not indicated unless there are CNS symptoms/signs above the foramen magnum.
• USG: Useful in neonates (before posterior elements ossify), but at 10 years old, bone blocks ultrasound view.
• CT scan: Good for bone, poor for cord/soft tissue; involves radiation.
• Maternal Serum AFP: Prenatal screening — irrelevant postnatally.

✅ Correct answer: a. MRI spine

*** Exam Pearl

Spina bifida

Spina bifida describes a congenital malformation where the vertebral column is open. Spinal dysraphism is the term used for the spectrum of congenital anomalies associated with defects in the neural arch that cause herniation of neural tissue or the meninges. Where a defect is not visible, there may be neurocutaneous markers on the skin in the midline such as a tuft of hair (Figure 26.5), dermal sinus, lipoma or a patch of dysplastic skin. The most common and clinically important manifestation is myelomeningocele leading to postnatal exposure of neural tissue. The condition is commonly detected antenatally on routine ultrasonography and further assessed by foetal MRI imaging (Figure 26.6).

Many babies born with myelomeningocele will also have a coexisting Arnold-­Chiari malformation resulting in cerebellar tonsillar herniation through the foramen magnum. Hydrocephalus due to obstruction of cerebrospinal fluid at the level of fourth ventricle may occur and requires the insertion of a ventriculoperitoneal shunt.

Children with myelomeningocele will have motor and sensory deficits below the level of the lesion (Figure 26.7) with a lower-­level lesion being associated with an improved motor outcome. Intellectual disability may be associated with complications of hydrocephalus.

Treatment and management

Foetal repair for open spina bifida has recently become available. Immediate postnatal management requires the defect to be wrapped in plastic wrap film to prevent infection and surgical repair is then undertaken in the first few days of life. CSF diversion surgery with a ventriculoperitoneal shunt may also be required. Urodynamic studies will frequently show evidence of urinary retention, overflow and ureteric reflux and consequently intermittent catheterisation is often necessary. Orthopaedic surveillance and intervention may be necessary for spinal, hip, leg and foot deformities.