CNS – Neural Tube Defects and Craniosynostosis

Dr. Kalpana MallaMD Pediatrics

Manipal Teaching Hospital

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CONGENITAL ANOMALIES

• NTD – Spina Bifida Occulta Meningocele Meningomyelocele Encephalocele Anencephaly

CONGENITAL ANOMALIES• Defects of Neuronal Migration – Lissencephaly

Porencephaly Schizencephaly Holoprosencephaly

• Craniosynostosis • Agenesis of Corpus Callosum• Microcephaly• Hydrocephalus

MORPHOGENESIS

Abnormal Organisation Of Cells In Tissue

DYSPLASIA

Unusual Forces On Normal Tissue

DEFORMATION

Poor FormationOf Tissue From Begining

MALFORMATION

Breakdown OfNormal Tissue

DISRUPTION

Neural tube defects

• Neural tube defect - Failure of closure of Neural tubes

Neural tube defects - ETIOLOGY:

Folic acid deficiency:Drugs antagonizing folic acid:Valproic acid, CBZ, phenytoin, phenoba., alcohol,

thalidomide, irradiation, maternal diabetesSyndromal disorders: trisomy 18, 13,

Malnutrition – zn , folate def.

EMBRYOLOGY

Nelson.

A single sheet of cells – midline ectoderm

Ectodermal plate enlarges

Neural folds become elevated and fuse forming Neural tube

Fusion occurs in cervical region and proceed both caudally and cephalic, by secondary neuralization

Cephalic completed by 23rd dayCaudally completed by 28th day Thus neural tube formation completed by 4th week

EMBRYOLOGY

TYPES OF NTD

PRIMARY -95% of all NTD Primary failure of closure/disruption of NT

btw 18-28 days.

Eg. -Myelomeningocele Encephalocele

Anencephaly

TYPES OF NTDSECONDARY

-5% of all NTD. Abnormal deve. of lower sacral seg. during

secondary neuralisation• Skin is usually intact• Involves lumbo sacral regionEg. Spina Bifida Occulta Meningocele

Spina bifida occulta:

• Midline defect of vertebral bodies without protrusion of spinal cord / meninges.

• Asymptomatic , usually of no consequence• Presents as patch of hair, lipoma, dermal sinus

in low back – underlying spinal malf.• Level - L5 & S1.• May be associated with tethered cord.• May present as recurrent meningitis – look for

dermal sinus.

Meningocele

Sac + CSF + intact skin + No nervous tissue + usually no hydrocephalus-Small sac which increases on crying - Usually no neurological abnormality

Meningocele• Inv.-• CT HEAD – r/o hydro• MRI SPINE – R/O (i)Diastematomyelia – division of spinal

cord into two halves by projection of fibrocartilagenous or bony septum from post vertebral body

(ii) Tethered cord – slender threadlike filum terminale attached to coccyx conus here is below L2 instead L 1

• Treatment – • Skin intact – surgery in infancy• Skin lacerated – urgent treatment• Look for recto vaginal fistula

Meningomyelocele

Sac + CSF + neural element + discontinuous skin + hydroce(80%). TYPE – 94% of all NTD - Lumbo sacral- Area of well developed skin at periphery With thin apex covered by glistening arachnoid membrane- Usually CSF oozing +

Meningomyelocele

• Check for reflexes, muscle power of LL. Check for SPHINTER and ANAL reflexes

TREATMENT:• SURGERY• MULTIDIS. APPROACH• Look for other anomalies• Treat hydroceph, Club foot• Bladder and bowel care

LOBERS CRITERIA 1972 - FOR SELECTIVE SURGERY

SURGERY NOT DONE IF – • Severe praplegia below L3 with bladder

paralysis• Gross Hydrocephalus• ASSOCIATED LIFE THREATENING GROSS CONG.

MALFORMATION.

LOBERS CRITERIA 1972 - FOR SELECTIVE SURGERY

SURGERY NOT DONE IF – • Kyphosis• Associated gross congenital anomalies• Very large lesions• Infection of sac ormeningitis

Myelomeningocele

ANENCEPHALY• Failure of closure of rostral neuropore.• Large defect of calvarium, meninges, scalp

associated with rudimentary brain.• Cerebral hemisphere and cerebellum

usually absent• Associated anomalies-• In pregnancy – polyhydroamnios• Die at birth or few days• Etiology – genetic, environmental toxins,

nutrition

ENCEPHALOCELE• Contains sac + cerebral cortex +

cerebellum + brain stem• – OCCIPITAL region, Can also occur in

frontal or nasofrontal• ↑ risk of arnold chiari or dandy walker

malformation• ↑ risk of hydroceph.• Visual problems, microcephaly, mental

retardation, seizures associated features.

Diagnosis in pregnancy

Amniocentesis - to diagnose chromosomal disorders and open neural tube defects (ONTDs)

Alpha-fetoprotein screening

• Measures the level of AFP in mothers' blood during pregnancy.

• Abnormal levels of AFP - Open neural tube defects (ONTD) Down syndrome Other chromosomal abnormalities Defects in the abdominal wall of the fetus Twins - more than one fetus is making the

protein

Neural tube defects – prevention

Folic acid deficiency:If previous history of NTD in family :4mg – 1 month before preg. To 3 months

thereafter

Else for every other women of child bearing age :0.4mg – 1 month before conception till 12 weeks

gestation.

Defects of Neuronal Migration

• Lissencephaly – absence of cerebral convolution due to faulty neuroblast migration

• Porencephaly – cysts or cavities within the brain

Defects of Neuronal Migration

• Schizencephaly – uni or bilateral cleft within cerebral hemisphere

• Holoprosencephaly – defective cleavage of procencephalon – single ventricle,absent falx,fused basal ganglia

CRANIOSYNOSTOSIS

• Craniosynostosis – premature closing of sutures causing problems with normal brain and skull growth

Plagiocephaly - coronal synostosis

- Fusion of either rt or lt side of the coronal suture-Causes the normal forehead and the brow to stop growing-Produces flattening of the forehead and the brow on the affected side, with the forehead tending to be excessively prominent on the opposite side

SCAPHOCEPHALY/DOLICHOCEPHALY

Early closure or fusion of the sagittal suture

Fusion causes a long, narrow skull .Prominent occiput and forehead

Usually only craniosynstosis which is relatively harmless

TRIGONOCEPHALY Fusion of the metopic (forehead) suture

Fusion result in a prominent ridge running down the forehead -looks pointed, like a triangle, with closely placed eyes (hypotelorism).

• Turriencephaly – cone shaped head . Fusion of coronal and speno frontal or fronto

ethmoid sutures.• Brachycephaly – premature closure of coronal

suture expands skull parallel to coronal suture , thus broadening of forehead with short AP diameter. Eg – in many syndromes like Downs

TYPES OF CRANIOSYNOSTOSIS

Primary • Closure of sutures due to abnormality of skull

development. Eg – genetics.

Secondary • Occurs from failure of brain growth and

expansion. Therefore causing premature fusion.

CLINICAL

• Palpation of suture reveals prominent bony ridge.

• Fusion may be confirmed by x-ray skull• Associated syndromes – Crouzon , Alperts,

Carpenter,

TREATMENT

• Premature fusion of single suture rarely causes any neurological deficit . Thus, in this situation the only indication is cosmetics.

• 2 or more suture fusion – more complications eg. ↑ ICT, hydrocephalus,

optic atrophy, DNS, choanal atresia --- operative surgery essential – craniectomy with craniofacial correction.

• Usually good prognosis with non syndromic infants……………

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