Embryology
- The nervous system develops from the dorsal ectoderm
- The lateral edges of the neural plate fold to form the neural groove
- Fusion of the edges of the neural groove forms the neural tube
- Fusion start cranially and progresses caudally
- Both caudal and cranial ends of the tube remain temporarily open
- The anterior neuropore closes at about 25 days
- The posterior neuropore closes at about 27 days
Spina bifida
- The term spina bifida covers a range of vertebral and neural tube defects
- Result from failure of the posterior vertebral arch to fuse
- Most commonly occur in lumbo-sacral region
Spina bifida occulta
- Commonest form of spina bifida
- True prevalence is unclear
- Isolated laminar defects are seen on about 5% of lumbar spine x-rays
- The spinal cord is usually normal
- Only clinical sign is often a tuft of hairs of skin dimple at the site of the defect
- Neurological deficit is rare
- May present with subtle neurological abnormalities such as enuresis or incontinence
Meningocele and myelomeningocele
- If meninges bulge through defect can result in a meningocele or myelomeningocele
Picture provided by Arman Matsaad, Our lady Hospital for Sick Children, Dublin, Ireland
- Meningocele does not contain spinal cord elements
- Myelomeningocele contains spinal cord and nerve routes
- May be associated with caudal displacement of medulla and cerebellum
- Can result in hydrocephalus (Arnold-Chiari malformation)
- Also associated with other abnormalities such as talipes and hip dislocation
Clinical features
- Occurs in 2-3 per 1000 live births
- Can be detected prenatally by increased serum alpha-fetoprotein
- Spinal defect is clinically obvious
- Can result in various degrees of:
- Limb weakness
- Sensory loss
- Joint dislocation and contractures
- Urinary disorders
- Of patients with a meningomyelocele
- One-third have complete paralysis and loss of sensation below the level of the defect
- One-third have preservation of distal segments below the level of the defect
- One-third have an incomplete lesion
- 90% of children develop urinary problems
Management
- Management is complicated and should involve a multidisciplinary team
- Team should include paediatrician, orthopaedic surgeon, neurologist, physiotherapist etc
- Treatment depend on level and severity of defect
- Patients with high defects and gross neurological defects many not be candidates for surgery
- If good prognosis the aim should be to achieve skin closure with 48 hours of birth
- Ventriculo-caval shunting may be required in the first week
- Early treatment of orthopaedic abnormalities is by physiotherapy
- Surgical intervention (e.g. osteotomies) may be required in the first few years of life
Bibliography
Dias M S, Li V. Pediatric neurosurgical disease. Pediatr Clin North Am 1998; 45: 1539-1578.
Drolet B A. Cutaneous signs of neural tube dysraphism. Pediatr Clin North Am 2000; 47: 813-123.
Sarawak J F. Spina bifida. Pediatr Clin North Am 1996; 43: 151-1158. |