Neural Tube Defects (NTDs)

What are Neural Tube Defects (NTDs) according to the summary?

The most common congenital malformations of the central nervous system (CNS). Summary 1

When do Neural Tube Defects (NTDs) typically develop during pregnancy?

Between the 3rd and 4th weeks of pregnancy. Summary 2

What is a common cause of Neural Tube Defects (NTDs)?

Folate deficiency, resulting in improper closure of the neural tube in the embryo, mainly at the caudal or cranial ends. Summary / Etiology 3

What is the more common location for NTD formation, and what is it known as?

Formation of defects at the caudal end is more common and is known as spina bifida. Summary 4

How might spina bifida occulta present clinically?

It may occur without any apparent clinical features. Summary / Overview 5

How does myelomeningocele manifest?

With protrusion of the meninges and, potentially, the spinal cord through a gap in the vertebrae. Summary / Overview 6

What are predominant symptoms of myelomeningoceles?

Symptoms of sensory and motor function loss, such as bladder dysfunction and paraplegia. Summary / Overview 7

What is the most severe manifestation of NTDs at the cranial end, and is it compatible with life?

Anencephaly, which is incompatible with life. Summary / Overview 8

How are Neural Tube Defects (NTDs) often diagnosed during pregnancy?

Via ultrasound and detection of elevated alpha-fetoprotein (AFP) levels in the maternal serum or amniotic fluid. Summary / Diagnosis 9

What does treatment for Neural Tube Defects (NTDs) typically involve postnatally?

Prophylactic administration of antibiotics and rapid surgical closure of the defect to avoid CNS infections. Summary / Treatment 10

What is an important preventative measure for Neural Tube Defects (NTDs)?

Supplementation with folic acid. Summary / Prevention 11

Who is recommended to take daily folic acid due to high rates of unplanned pregnancies?

All individuals capable of pregnancy. Summary / Prevention 12

What folic acid recommendation is given for individuals with a personal, family, or partner history of NTD?

A higher folic acid dose is recommended. Summary / Prevention 13

How are Neural Tube Defects (NTDs) generally defined?

Congenital malformations of the central nervous system (CNS), spine, and cranium, caused by incomplete closure of the neural tube during neurulation (3rd-4th weeks post-conception). Definitions 14

How do cranial NTDs typically occur?

Due to incomplete closure of anterior neuropores, leading to cranial cleft formation (mostly open defects) with involvement of the skull and brain. Definitions 15

How do spinal NTDs typically occur, and where are they most common?

Due to incomplete closure of posterior neuropores, leading to bone defects of vertebral arches (mostly lower lumbar or sacral region), possibly with herniation of spinal neural tissue/meninges. Definitions 16

What are open Neural Tube Defects (NTDs)?

Meninges and/or neural tissue are uncovered and therefore exposed to the surroundings (e.g., amniotic fluid). Definitions 17

What are closed Neural Tube Defects (NTDs)?

The defect is covered by skin and/or connective tissue. Definitions 18

Which are the two most frequent Neural Tube Defects (NTDs)?

Spina bifida and anencephaly. Epidemiology 19

What is the combined incidence of spina bifida and anencephaly in the US?

Approximately 6.5 per 10,000 live births per year in the US. Epidemiology 20

What is the most common cause of folate deficiency leading to NTDs?

Insufficient folic acid supplementation in pregnancy. Etiology 21

Name two types of drugs that interfere with folate metabolism and are risk factors for NTDs.

Methotrexate, anticonvulsants (valproate, carbamazepine), sulfonamides, or trimethoprim. (Any 2) Etiology 22

Name two maternal conditions (besides folate deficiency) that are risk factors for NTDs.

Pregestational diabetes mellitus, obesity, or fever/hyperthermia during the first trimester. (Any 2) Etiology 23

Name two fetal causes or associated conditions that are risk factors for NTDs.

Chromosomal aberrations (trisomy 13, trisomy 18), other genetic factors, amniotic band syndrome, or Chiari II malformation. (Any 2) Etiology 24

What is spina bifida occulta?

Most common closed NTD; vertebral bone defect without herniation; spinal cord, meninges, and overlying skin remain intact. Most common in lower lumbar/sacral region. Overview (Spinal) 25

What are the clinical features of spina bifida occulta?

Often asymptomatic (incidental finding). Possible symptoms: lumbar skin dimple, collection of fat, patch of hair at vertebral defect level. Normal AFP. Overview (Spinal) 26

What is a lipomyelomeningocele?

A myelomeningocele that also contains fat tissue and is covered by skin. Overview (Spinal) 27

What are the clinical features of a meningocele?

Neurological symptoms vary (motor loss, sensory deficits, bladder/bowel dysfunction - rare flaccid paralysis). Hydrocephalus common. Associated skeletal malformations. Developmental delays. Elevated AFP. Overview (Spinal) 28

What is a myelomeningocele?

Meninges and parts of the spinal cord herniate through the vertebral bone defect. Characteristic of Chiari II malformation. Associated with maternal diabetes/folate deficiency. Elevated AFP. Overview (Spinal) 29

What is myeloschisis (rachischisis)?

Most severe subtype; portions of neural tube completely fail to fuse, leading to bare, exposed neural tissue without coverage of meninges, bones, or skin. Elevated AFP. Overview (Spinal) 30

What is anencephaly?

Rostral neuropore remains open, leading to absence of the forebrain and an open cranial vault. Associated with polyhydramnios. Incompatible with life. Elevated AFP. Overview (Cranial) 31

What is an encephalocele?

Brain tissue herniates through an occipital or frontal bone defect; covered by skin. Malformations/neurological deficits vary. Lethal in severe cases. AFP usually not elevated. Overview (Cranial) 32

What screening test is used for NTDs at 16-18 weeks' gestation, and what does it detect for open NTDs?

Maternal serum alpha-fetoprotein (MSAFP). Elevated AFP in maternal serum indicates an open NTD. Diagnosis (Prenatal) 33

Is MSAFP elevated in spina bifida occulta?

No, MSAFP is not elevated in spina bifida occulta (as it is a closed defect). Diagnosis (Prenatal) 34

What are characteristic ultrasonography findings in anencephaly?

Cranial vault and brain tissue absent; residual disorganized cerebellar/brainstem tissue may be present; bulging eyes; underdeveloped forehead; associated polyhydramnios. Diagnosis (Prenatal) 35

What findings in amniotic fluid confirm an open NTD if MSAFP is elevated but ultrasound is inconclusive?

Elevated AFP and elevated Acetylcholinesterase (AChE) in amniotic fluid. Diagnosis (Prenatal) 36

What postnatal physical examination findings might suggest spina bifida occulta?

Lumbar skin dimple or tuft of hair. Diagnosis (Postnatal) 37

What imaging modalities are used postnatally for NTDs, and what are their purposes?

Cranial ultrasonography (to monitor hydrocephalus). CT scans and/or MRI (to monitor hydrocephalus, evaluate bone defects/neural tissue lesions, plan surgery). Diagnosis (Postnatal) 38

What is tethered cord syndrome?

A functional neurological disorder caused by abnormal stretching of the spinal cord due to adhesions or obstructions attaching the caudal spinal cord to the spinal canal. Differential Diagnoses 39

What is the most common cause of tethered cord syndrome?

Myelomeningocele or lipomyelomeningocele. Differential Diagnoses 40

What are clinical features of tethered cord syndrome?

Lower back pain (aggravated by flexion), sensory/motor deficits of lower limbs (weakness, spasticity, abnormal reflexes), bladder/bowel dysfunction, skeletal malformations, visible lesions on lower back. Differential Diagnoses 41

What is a congenital dermal sinus?

Mostly lumbar/lumbosacral fistulae extending from skin surface to spinal canal, frequently ending in a dermoid or epidermoid cyst. Caused by incomplete separation of neural/dermal ectoderm. Differential Diagnoses 42

What is the general postnatal management for an open NTD immediately after birth?

Cover defect with sterile, wet compresses (avoid pressure); prophylactic administration of broad-spectrum antibiotics. Treatment (Postnatal) 43

When should surgery ideally be performed for open NTDs, and why?

Within 72 hours after delivery, to reduce the risk of CNS infection. Treatment (Postnatal) 44

What intervention is considered for hydrocephalus associated with NTDs?

Placement of a ventriculoperitoneal shunt. Treatment (Postnatal) 45

What does long-term care for individuals with NTDs often involve?

Complex treatment, possibly involving physical therapy, rehabilitation programs, and specific treatment of neurological disorders (e.g., neurogenic bladder dysfunction). Treatment (Postnatal) 46

What is the standard preventative folic acid supplementation dose recommended for all individuals capable of pregnancy?

Oral folic acid 0.4-0.8 mg once daily, continued until 12 weeks' gestation. (Start ≥4 weeks before conception if planning). Prevention 47

Why does the USPSTF recommend daily folic acid for all individuals capable of pregnancy?

Because of the high rate of unplanned pregnancies. Prevention 48

What is the recommended high-dose folic acid supplementation for individuals at increased risk of NTD-affected pregnancy?

Oral folic acid 4 mg daily, recommended from 3 months before conception until 12 weeks' gestation. (Standard dose recommended throughout reproductive life otherwise). Prevention 49

What factors place an individual at high risk for an NTD-affected pregnancy, warranting high-dose folic acid?

Previous pregnancy with NTD (birthing parent or partner), partner history of NTD, or personal history of NTD. Prevention 50