Neurology: Neural Tube Defects Flashcards
What do neural tube defects result from?
Failure of normal fusion of the neural plate to form the neural tube during the first 28 days following conception
Mothers of a foetus with a neural tube defect have a … fold increase risk of having a second affected fetus
10 fold
What supplementation reduces the risk?
Folic acid
What is recommended periconceptually for women with a previously affected infant planning a further pregnancy?
High doses folic acid
What is anencephaly?
Failure of development of most of the cranium and brain
In anencephaly, what happens to the fetus?
Affected infants are stillborn or die shortly after birth
It is detected on antenatal US screening and termination of pregnancy is usually offered
What is encephalocele?
Extrusion of brain and meninges through a midline skull defect, which can be corrected surgically. However, there is often underlying associated cerebral malformations.
What are the types of spina bifida?
Spina bifida occulta
Meningocele
Myelomeningocele
Describe spina bifida occulta
Failure of fusion of the vertebral arch
Often an incidental finding on x ray
May be associated skin lesion
What skin lesions can be associated with spina bifida occulta?
Tuft of hair
Lipoma
Birth mark
Small dermal sinus
Usually in the lumbar region
In spina bifida occulta, what may happen to the cord?
Tethering, which with growth may cause neurological deficits of bladder function and lower limbs - neurosurgical relief of tethering usually indicated
What is a meningocele?
A bulge of the meninges containing CSF is visible, but the spinal cord remains in its normal anatomical location
What is a myelomeningocele?
A bulge of the meninges is visible and the spinal cord lies outside the normal location of the spinal canal, inside the bulge.
What is a myelomeningocele often associated with?
An Arnold- Chiari type II malformation
What is rachischsis?
A very severe form of spina bifida where the spine may be completely open and is often associated with anencephaly
How is spina bifida often diagnosed?
Prenatally in the womb with USS+/- raised alpha fetoprotein levels in the maternal serum or amniotic fluid
What conditions can spina bifida be associated with?
Hydrocephalus
Syringomyelia- dilation of the fluid filled cavity that runs down the centre of the spinal cord
Is it more common in females or males?
Females
Up to what percent of the population may have spina bifida occulta?
Up to 10%
Low maternal folate is a risk factor particularly between what days?
Days 17 and 30 of pregnancy (a time when many mothers not yet aware of pregnancy)
Other than low maternal folate, what other risk factors are there?
Drugs taken in pregnancy - particularly sodium valproate and carbamazepine
Maternal diabetes
Maternal alcohol exposure
Genetic component
What signs and symptoms are associated with spina bifida occulta?
Often completely asymptomatic
Usually no neurological consequences
Physical signs at site of lesion: fluid filled palpable mass, altered skin pigmentation, excess hair, asymmetrical gluteal cleft, sacral dimple
What neurological signs and symptoms are associated with spina bifida cystica (minigocele and myelomeningocele) ?
Possible paralysis and areflexia below the site of the lesion - especially if nerve roots involved
Decreased anal sphincter tone (neuropathic bowel)
Arnold chiari type 2 malformation - may be stridor, swallowing difficulties, apnoea episodes
What musculoskeletal signs and symptoms are associated with spina bifida cystica?
Muscle atrophy of lower limbs
Spine deformity and limb dislocations can result from imbalance of muscle tone
What urological problems can occur due to spina bifida cystica?
Urogenic bladder
Vesicoureteric reflux
Hydronephrosis
Recurrent UTI
What scan can detect neural tube defects?
The 18-20 week foetal anomaly scan
What post diagnosis tests should be done?
U&E to assess renal function
Urine MC+S
Urodynamics
Latex allergy test
Plain spine x rays - look for scoliosis and other spinal abnormalities
CT or MRI of brain and spinal cord - looking for chiari malformation, hydrocephalus, tethering of spine
Assessment of neurological deficit and gait
How is spina bifida occulta managed?
Often does not require any specific management
How is spina bifida cystic managed?
Any lesion usually closed after birth
Paralysis and muscle imbalance requires physio to prevent contractures
If sensory loss - skin care
Neuropathic bladder - indwelling catheter or intermittent catheterisation
Regular checks for HTN, UTI
Bowel denervation requires regular toileting and laxatives
If hydrocephalus- shunt
A lesion at and above what level is associated with worse prognosis?
Above L3 - unable to walk, have scoliosis, neuropathic bladder, hydronephrosis and frequently develop hydrocephalus
