Congenital Malformations

Question 1

What types of defects are there?

Answer 1

• Failure of neural tube closure
• CSF accumulation
• Problems with Gyri Formation
• Corpus Callosum
• Head size
• Cysts/cavities
• Clefts/slits
• Split cord
• Intelluctual

Question 2

List some abnormalities caused by failure of the neural tube?

Answer 2

Anencephaly (Ant neuropore doesnt close)

Encephalocoele (Rostral neural tube failure)

Spina Bifida (Caudal neuropore doesn’t close right leading to non-fused vertebral arches)

Question 3

How does Anencephaly develop?

Answer 3

Anterior neuropore doesnt close so the skull doesnt form over the brain and (exposed to the outside) it degenerates –> Death

Question 4

How does Encephalocoele develop?

Answer 4

The rostral neural tube fails causing a defect in the skull through which cerebral tissue herniates.
This can cause a varying degree of neurological deficits based on location and level of herniation

Question 5

How does spina bifida develop?

Answer 5

Caudal neural tube fails to close properly so you end up with non-fused vertebral arches
(Often has herniation out the spinal column in the lower back)

Question 6

What is the most minor form of spina bifida?

Answer 6

Spina Bifida Occulta

This occurs in 10% of peoples L5/6 vertebrae with usually no clinical symptoms.
Sometimes it has a dimple with a tuft of hair there.

Question 7

What are the types of protrusion through the defect in spina bifida?

Answer 7

Collectively called Spina Bifida Cystica.

• Spina Bifida with Meningocele (Protrusion of meninges & CSF)
• Spinal Bifida with Meningomyelocle (Nerve roots/spinal cord also protrude causing loss of sensation and paralysis below lesion)
• Myeloschisis (Spinal cord open due to failure of neural folds to fuse - Complete loss of function/sensation below the lesion causing lower limb paralysis and bladder problems)

Question 8

How can we prevent neural tube malformations?

Answer 8

• Screening

- Folic Acid Supplements (Very important to neural tube for no apparent reason)

Question 9

What screening methods are there for neural tube malformations?

Answer 9

Maternal Blood Screening:

• Raised Serum Alpha Fetoprotein
• AFP from foetal liver leaks into amniotic fluid through open neural tube and into maternal blood

Amniocentesis:
- Raised AFP in amniotic fluid

Ultrasound:
- Anencephaly and Spina Bifida

Question 10

What risk factors are there for neural tube malformations?

Answer 10

• Genetic Predisposition
• Nutrional (e.g. too little folate or too much Vit A)
• Environmental e.g. Hyperthermia or Drugs (e.g. Na Valproate)

Question 11

What is Hydrocephalus?

Answer 11

CSF cant drain so it builds up resulting in an enlarged brain and cranium, usually due to blocked cerebral aqueduct.

Question 12

What causes hydrocephalus?

Answer 12

• Genetic
• Prenatal Viral Infection
• Intraventricular Haemorrhage
• Spina Bifida Cystica

Question 13

What do we call it if the Gyri/Sulci fail to develop?

Answer 13

Lissencephaly or “smooth Brain”.

Question 14

What causes Lissencephaly?

Answer 14

Defective Neuronal Migration

Question 15

What happens in Lissencephaly?

Answer 15

• Severe Mental Impairment
• Failure to Thrive
• Seizures
• Abnormal Muscle Tone

(Many die before 10)

Question 16

Other than lissencephaly what conditions affect the gyri?

Answer 16

Polymicrogyria

An excessive number of small gyri with a variable degree of neurological problems

Question 17

What causes microcephaly and how does it present?

Answer 17

Genetics, drugs and infection e.g. Zika

Intellectual impairment
Delayed Motor function/speech
Seizures
Balance/Co-ordination problems
Hyperactivity

Question 18

What congenital malformation affects the Corpus Callosum?

Answer 18

Agenesis of the Corpus Callosum (Partial or incomplete)

Effects range from subtle cognitive/social difficulties up to severe impairment, seizures and hypotonia etc

Question 19

What causes CSF filled Cysts or cavities?

Answer 19

Porencephaly

Due to postnatal stroke or infection

Question 20

What causes Clefts or slits in the brain?

Answer 20

Genetics, in utero stroke or infection.

Called Schizencephaly

Question 21

Define Diastematomyelia?

Answer 21

Spinal cord split longitudinally in two, associated with other vertebral anomalies.

Causes loss of sensation, weakness, scoliosis, hairy lower back and foot deformities.