Myelodysplasia

Question 1

Pathoembryology

Answer 1

Can be related to 2 different processes in nervous system development:
1. Abnormal Neurolation
Neurulation- the folding of the ectoderm on each side of the notochord to form a tube that extends from the hindbrain to the second sacral veterbra, begins before day 28 of gestation
- meningoceles can occurs both over the skull and along spinal cord
Encephaloceles- containing brain if along the midline of skull
Myelomeningoceles- SC from C1-S2 vertebrae

Encephalocele and myelomeningoceles- result from a failure of complete entubulation with associated abnormal mesoderm development

2. Canalization- developmental of SC distal to S2
   - cells distal to SC in dorsal central midline of mesoderm become nerve cells, cells clump together into masses which join for form canals which later connect to the SC
   - failure of proper canalization–results in skin covered lesions–meningoceles, lipoma and myelocystoceles—-> all most frequently develop below L3

Question 2

Etiology

Answer 2

Cause of canalization disorders is unknown

Neurulation, specifically myelomeningocele (MM)

• Genetics- often associated with genetic abnormalities, often associated with a syndrome, recurrence btwn siblings = 2-3%, varies among races and regions, African Amer = lowest incidence, high incidence = celts, spanish
• Teratogens- excess maternal alcohol, ingestion of valporic acid (seizure med)
• Nutritional deficiencies- inadequate folic acid
• – only concern with folic acid is that supplementing with it may mask pernicious anemia resulting from cobalamin deficiency (b12 deficiency)

Question 3

Incidence and prevalence

Answer 3

overall there has been a decrease worldwide in incidence of MM

prenatal dx allows parents to opt for c-section to decrease damage to neural sac–results in less paralysis or potential CNS infection

Improved medical care has improved survival rates

US per 1000

• 4. 18 hispanic
• 3.37 non hispanic white
• 2.90 non hispanic black mothers

Question 4

Perinatal Mgmt

Answer 4

Alpha-fetoprotein screening and US allow for detection early on in pregnancy
- screening does not detect skin covered neural defects

US in 2nd trimester can detect SB and other neural tube defects, more accurate in detecting abnormalities of the cranial formation than with issues of the spine

• Lemon Sign- overlapping of frontal bones, lemon sign detected in 83%
• Banana Sign- abnormally shaped midline and elongated cerebellum in Chiari malformation, banana sign detected in 93%

Canalization defects not usually associated with cranial malformations

Amniotic fluid analysis- done when neural tube defect is found, assists with prenatal decision making–allows for genetic testing for syndromes, etc.

Perinatal dx allows for repair of MM in-utero
- some report decreased need for shunt following in-utero surgery