MS PEDIA - Neural Tube Defects

Pre-embryonic stage

Weeks 1-2 of development; insults can cause spontaneous abortion or death.

Embryonic stage

Weeks 3-8; period where morphologic abnormalities and neural tube defects may occur.

Fetal period

Weeks 9-38; insults cause functional defects, growth retardation, or minor anomalies.

Blastocyst

Structure formed when morula absorbs fluid; contains inner cell mass, trophoblast, and blastocoel.

Inner cell mass

Part of the blastocyst that becomes the embryo.

Trophoblast

Forms the placenta and supports the embryo.

Blastocoel

Fluid-filled cavity of the blastocyst.

Bilaminar disc

Embryonic disc composed of epiblast and hypoblast.

Gastrulation

Process forming the three germ layers: ectoderm, mesoderm, endoderm.

Primary neurulation

Folding and fusion of the neural plate to form the neural tube.

Anterior neuropore

Opens to the amniotic cavity; closes on day 25.

Posterior neuropore

Opens to the amniotic cavity; closes on day 28.

Secondary neurulation

Formation of lower lumbar, sacral, and coccygeal spinal cord segments.

Neural crest cells

Cells that give rise to melanocytes, Schwann cells, dura mater, dorsal root ganglia, and autonomic ganglia.

Sonic hedgehog

Signaling factor involved in neural induction.

Conus medullaris

Tapered end of the spinal cord.

Filum terminale

Extension of pia mater attaching to the coccyx.

Central canal

Channel running through the spinal cord, open superiorly and closed inferiorly.

Dorsal column

Ascending pathway for vibration, proprioception, and 2-point discrimination.

Lateral spinothalamic tract

Ascending pathway for pain and temperature.

Spina bifida

Defect in posterior neuropore closure.

Spina bifida occulta

Hidden bony defect without herniation; usually lumbosacral.

Meningocele

Herniation of meninges without neural tissue.

Myelomeningocele

Herniation of meninges and neural tissue; most common spina bifida cystica.

Rachischisis

Severe defect where neural folds fail to join, exposing the spinal cord.

Occult spinal dysraphism

Closed spinal cord malformations such as syringomyelia, diastematomyelia, or tethered cord.

Tethered cord

Abnormal distal fixation of the spinal cord causing neurologic and orthopedic symptoms.

Caudal regression syndrome

Absence of sacrum and parts of lumbar spine; associated with maternal diabetes.

Diastematomyelia

Sagittal split of the spinal cord, often with a bony spur.

Syringomyelia

Tubular cavity within the spinal cord, common in cervical region and in myelomeningocele patients.

Chiari type II malformation

Herniation of medulla, pons, elongated 4th ventricle, and cerebellar vermis into cervical spine; associated with hydrocephalus.

Hydrocephalus

Enlargement of ventricles due to increased intracranial pressure.

Cushing's triad

Hypertension, bradycardia, and irregular respirations due to increased ICP.

Monro-Kellie principle

Skull is a fixed-volume space of brain, blood, and CSF; increase in one requires compensation.

Polymicrogyria

Increased number of small, irregular gyri.

Heterotopias

Abnormal neural tissue nodules; associated with epilepsy.

Agenesis of corpus callosum

Partial or complete absence of corpus callosum.

Quad screen

Prenatal test (AFP, hCG, estriol, inhibin A) used in second trimester to detect abnormalities.

AFP elevation

Suggests possible neural tube defect.

Lemon sign

Anterior scalloping of the skull on ultrasound.

Banana sign

Herniation of cerebellar vermis through foramen magnum.

Nonverbal learning disorder (NVLD)

Deficits in visual-spatial reasoning, organization, and processing speed seen in spina bifida.

PROM (Passive range of motion)

Exercises to maintain joint mobility in paralyzed regions.

Dynamic stander

Early mobility equipment for thoracic and high lumbar levels.

Neurogenic bladder

Bladder dysfunction due to neurologic impairment.

Neurogenic bowel

Bowel dysfunction due to distal nerve involvement.

Osteoporosis in NTD

Low bone mass and high fracture risk due to immobility and other factors.

Precocious puberty

Early puberty due to loss of inhibitory hypothalamic-pituitary control.

ETV (Endoscopic third ventriculostomy)

Procedure creating communication between the third ventricle and subarachnoid space.

Latex allergy

Common in repeated surgical exposures, though incidence is decreasing.

Vocational counseling

Planning for functional career paths starting in secondary school.