55. CNS Congenital Malformations

Question 1

What are the 6 key steps of CNS development and when do they occur?

Answer 1

1. Neural Tube Formation (D16-22)
2. Neural Tube Closure (D22-28)
3. Segmentation (W4-5)
4. Neuronal Proliferation (W5)
5. Neuronal Migration - inside-out
6. Neuronal Differentiation (W12-20)

Question 2

What is a biomarker for neural tube defects?

Answer 2

alpha feto-protein

Question 3

Anencephaly

• cause
• effects

Answer 3

C: failure of closure of anterior neural tube = absent forebrain
E: incompatible with life

Question 4

Encephalocele

• cause
• effects

Answer 4

C: failure of anterior neuropore closure = herniation of brain parenchyma through midline skull defect
E: needs surgical correction, ventricular peritoneal shunt, intellectual/motor delays, microcephaly

Question 5

Myelomeningocele

• cause
• effects

Answer 5

C: neural tube defect - herniation of SC/meninges thru midline defect
E: neuro deficits at lesion level (flaccid paralysis, sensory deficits)
Dx: alpha feto-protein!

Question 6

Chiari II Malformation (Arnold-Chiari Malformation)

• what it is
• clinical features
• tx

Answer 6

Hindbrain malformation - traction of mid/hind brain = lower cerebellum displaces into foramen magnum (+ myelomeningocele 80% associated)
CF: sx of hydrocephalus and brainstem dysfx (apnea, feeding difficulty, stridor, CN abnormalities, quadriparesis, dyscoordination, ataxia, seizures)
tx: fetal surgical repair W22-26, surgical correction w/in 1st days of life (survives til 18yo), ongoing mgmt from neurosurgery, ortho, urology

Question 7

Holoprosencephaly

-what it is

Answer 7

Defect in prosencephalon formation and induction of forebrain structures
-facial anomalies: cyclopia, single nostril, single incisor
Single ventricle/hemisphere or fusion of CC dysgenesis

Question 8

Septo-Optic Dysplasia

-what it is

Answer 8

failure of prosencephalic/midline structure formation - hemispheres divide but problems with optic nerve, septum pellucidum, CC, pituitary gland

Question 9

Agenesis/Dysgenesis of CC

-what it is

Answer 9

most common CNS defect after spina bifida
Assoc with other malformations
due to genetics, alcohol exposure

Question 10

Lissencephaly

-what it is

Answer 10

agyria = absence of cerebral convolutions

-due to faulty neuroblast migration - less layers of cortex formed

Question 11

Polymicrogyria/Schizencephaly

-what it is, cause?

Answer 11

excessive gyration with large clefts due to abnormal cortical organization/layering
DUE TO CMV

Question 12

Focal Cortical Dysplasia

-what it is

Answer 12

mildest form of cortical later misdevelopment

• disrupted cortical lamination and cytological abnormalities
• widely variable spectrum of microscopic changes

Question 13

Dandy Walker Malformation

• what it is
• constellation of findings

Answer 13

Most common cerebellar malformation

• cystic dilation of 4th ventricle
• hypoplastic cerebellar vermis
• hydrocephalus
• elevated torcular/tentorium

Question 14

Joubert Syndrome

-key sign

Answer 14

“Molar tooth” sign with elongated cerebellar peduncles and vermis hypoplasia

Question 15

Cerebral Palsy

• what it is
• Classification

Answer 15

Permanent motor disorder (activity limitation or posture abnormality) due to nonprogressive disturbance in developing fetal/infant brain
Classified by-
Distribution: regional hemiplegia vs. global quadriplegia
Physiologic Type: spastic, dyskinetic, dystonic, athenoid
Pyramidal (CS tract) vs extrapyramidal (BG/midbrain)

Spectrum of involvement/ability
Need multidisciplinary sx mgmt (no curative tx)