NEURAL TUBE DEFECT: ANENCEPHALY, SPINA BIFIDA, CRANIORACHISCHISIS, INIENCEPHALY, ENCEPHALOCELE

The Previous video Link-   • Development of Nervous system  
Normally closes at :Anterior neuropore at 25th days
Posterior neuropore at 27th days

Anencephaly: anterior neuropore not closed properly

Craniorachischisis: the neural tube fails to close properly from cranial neuropore to caudal neuropore, in which both brain and spinal cord remain open, so both anencephaly and spina bifida present.

Inienecephaly: is rare birth defect, is result in extreme retroflexion(backward bending) of the head combined with severe distortion of the spine, no standard treatment and as preventive medicine giving the folic acid supplements.

Encephalocele: is NTD by sac-like protrusion of the brain and the meninges that cover it through opening in the skull
Classified as
Occipital: between lambdoid suture and foramen magnum
Parietal: between bregma and lambdoid suture
Anterior :between the bregma and the ethmoid bone
More common is occipital and parietal
Open and closed bifida caudal neuropore not
closed properly

ANENCEPHALY

Baby born with underdeveloped brain and an incomplete skull
It’s disorder of neural tube defect
Upper part of neural tube closes it helps to form the baby’s brain and skull.
Due to neural tube fails to close properly the developing brain and spinal cord are exposed to the amniotic fluid which is surrounding the fetus in womb.
This exposure causes the nervous tissue to break down (degenerate)
So due to degeneration person with anencephaly are missing large parts of the brain, Cerebrum and cerebellum
This brain regions are necessary for thinking, hearing,vision, emotion and coordinating movement.
because anencephaly is so severe ,they are not compatible for extra uterine environment , almost all babies with anencephaly die before birth or within a few hours or days after birth

SPINA BIFIDA =split spine
A birth defect in which a developing baby’s spinal cord fails to develop properly
Lower part (caudal neuropore) of neural tube closes it helps to form spinal cord and back bones.

TYPES:
Spina bifida occulta
Meningocele(meningeal cyst)
Myelomeningocele ( meningomyelocele)

Spina bifida occulta

Most common/ least severe/ mild
Hidden because prenatal test often don’t detect it
Spinal cord and meninges not protrude
No spinal cord damaged
Usually no s/s
Often found accidentally in later life:
hair, dimple or birthmark on the back

Meningocele(meningeal cyst)

Least common
Defect or absence of vertebral arches due to
failure of mesoderm to organize
Only meninges protrude not spinal nerve
Spinal cord not damaged
No severe s/s

Myelomeningocele ( meningomyelocele)

Most severe
Spinal cord and meninges protrude out and
opening bony vertebral skin may or may
not intact on back
No skin
Spinal cord exposed and damaged
Develops risk of infection
loss of sensation
Paralysis
Bladder and bowel movement problems
Seizures
Leg and foot deformities
Meningomyelocele also associated with Arnold chiari II malformation

Arnold chiari II malformation
Where cerebellar and brainstem tissue slip down into foramen magnum
s/s related to cerebellum
Hydrocephalus (accumulation of csf in brain)

CAUSES:

Unknown
Risk factors
Folate deficiency( vit.B9): How to prevent?
Foods: especially grain products such as cereals and bread added
with folic acid(fortified)
Supplement: give folic acid as prenatal vitamin to prevent developmental Abnormalities dose 400 micrograms (mcg) daily
When should take folic acid supplements: 2 to 3 months before
conceive and until 12 week of GA

Obesity
Poorly controlled diabetes

DIAGNOSTIC TEST:

For myelomeningocele
Often done prenatally :MSAFP test( maternal serum alpha fetoprotein)
increased alpha fetoprotein in mother’s serum, Can be increased in other conditions like down syndrome

Other blood tests:
Human chorionic gonadotropin(hcg)
Inhibin A
Estriol

USG

MRI

Amniocentesis: sample from amniotic sac (in most severe cases)

Medication that interfere with folic metabolism (Eg: anti-seizure medication)

TREATMENT:

Prenatal surgery:
Close myelomeningocele
Can be dangerous
Postnatal surgery:
Days within birth
Minimize risk of meningitis
Additional intervention:
Urinary catheterization
Wheelchair or crutches (Spinal nerves can’t be repaired)