Disorders of Neural Tube Closure

Dr Malith Kumarasinghe (MBBS)

Review of Neuroembryology• Dorsal induction• Primary neurolation: 3-4 wks

gestation Brain and upper spine• Secondary neurolation: 4-5 wks

gestation Distal spine

Disorders of neural tube closure• Chiari I-IV• Encephaloceles• Anencephaly• Corpus Callosum Agenesis• Spinal Dysraphism (Spina bifida)• - Menigoceles• - Myelomeningoceles• Tethered chord

Enephaloceles• Anatomy• Failure of the anterior neural tube to

close due to genetic, infection, or toxic reasons.

• 1/1000• Distorted parts of the (covered) brain

protruding extracalvarially

EncephaloceleAnatomyOccipital 90%Parietal 10%TranssphenoidalFrontoethmoidal Nasal

Encephaloceles• Parietal

encephalocele

• Frontoethmoidal encephalocele

Encephaloceles• ClinicalDepends on involvement

• TreatmentSurgical excision of sac with water-

tight dural closure

Anencephaly• 1/1000 • Anencephaly is a defect in the

closure of the neural tube during fetal development.

• Large defect of the calvarium, meninges, and scalp.

• Incompatible with life.

Anencephaly

Corpus callosum• Location?• Functions?

Lateralization of Function• Lateralization of function refers to

the idea that each hemisphere of the brain is specialized for different functions.

• Each hemispheres controls the contralateral (opposite) side of the body.– Example: skin receptors and muscles

mainly on the right side of the body.– Each hemisphere sees the opposite

side of the world.

Lateralization of Function• The left and right hemisphere

exchange information primarily through a set of axons called the corpus callosum.

• Other areas that exchange information include:– The anterior commissure.– The hippocampal commissure.– A few other small commissures.

• Information crosses to the other hemisphere with only a brief delay.

Fig. 14-2, p. 418

Corpus Callosum Agenesis• Expansion of third ventricle• May present with HCP, seizures• May be incidental finding without any

clinical significance

Spinal Dysraphism (spina bifida)• Spina bifida occulta: 20-30% in North

Americans, often incidental, cutaneous manifestations

• Spina bifida aperta:• Meningocele • Myelomeningocele

Spinal Dysraphism• Spina bifida occulta

Spinal Dysraphism• Meningocele

Spinal Dysraphism• Myelomeningocele

Meningocele• 1-2/1000• 1/3 have neurological deficits• Surgical repair with water-tight dural

closure

Meningomyelocele• 1-2/1000 live birth• Failure of complete

closure of caudal neural tube

• 85% occur in lumbar region

Meningomyelocele

Meningomyelocele

Myelomeningocele• Clinical• Mild to complete paralysis• Ruptured vs unruptured• Urinary incontinence• Skeletal abnormalities

Myelomeningocele• Treatment• If open, Gent and Naf IV• Prone, bottom up• Telfa with wet gauze over lesion• Surgical closure within 36hrs• Shunt if overt HCP• Urologic and Orthopaedic

consultation

Lipomyelomeningocele• Present with back mass, bladder

problems, paralysis• Cutaneous stigmata• Treatment is surgical decompression