trans congenital malformations
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Trans Congenital MalformationsTRANSCRIPT
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NEUROSCIENCE II
Congenital Malformations of the Central Nervous System
Eric C. Legaspi, MD
“That in all things God may be glorified.”
Congenital Malformations of the Central Nervous System
The human body is an intricate, marvelous mechanism…
…designed to keep the dust off the brain and take it where it wants to go.
Objectives
To review the embryology of the central nervous system
o
Gastrulation
o
Somite formation
o Neurulation
o Induction
To examine common congenital anomalies of the spine
o Spina bifida aperta
Myelomeningocoele
Meningocoele
o
Spina bifida occulta
o
The tethered cord Diastematomyelia
Dermal sinus tracts
To examine common congenital anomalies of the brain
o Hydrocephalus
o Encephalocoeles
o
Forebrain anomalies
o
Hindbrain anomalies
To review common congenital anomalies of the skull
To evaluate the social impact of congenital anomalies of the central
nervous system
References
Neurology and Neurosurgery Illustrated (3rd
edition) by Lindsay, Bone,
and Callander. 1997
Langman’s Medical Embryology (7th
edition) by Sadler. 1995
Handbook of Neurosurgery (4th edition). Greenberg. 2000
Youman’s Neurological Surgery (5th edition). 2003
Embryology
Two stages of human embryology
Embryonic stage
o
0 to 60 days after fertilization
o Bulk of neurologic malformations
o
23 stages or “horizons”
Fetal stage
o 3
rd month of gestation to birth
Early stages
Fertilization
o Day 1
Blastocyst
o Day 2 to 4
Gastrulation
o Day 12
Fertilization
Day 1
Cell division
Day 3
Blastocyst
32 cell embryo
Cavity formation
Day 4
Bilaminar blastocyst
Day 9
Two germ cell layers
o Epiblast
o Hypoblast
Day 14
How many germ cell layers are involved in the formation of the human embryo?
You, with the strange haircut, answer please.
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Three
Epiblast ectoderm
mesoderm
Hypoblast endoderm
Primitive streak
Day 14
Caudal end of bilaminar embryo
Gastrulation
Formation of three germ cell layers by invaginating cells of epiblast
Third week
Notochord formation
Day 17
Migration of a solid core of cells craniad from the primitive node
Notochord formation
Where is your notochord?
You, with the silly grin on your face.
Notochord involutes
Induction
Stimulation of a responding tissue or group of cells by an inducing
tissue
Epiblast induced to form neural plate by notochord
Neural plate
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The human CNS is based on tubular structures.
Neurulation
Neural plate folds over to form neural tube
About Day 20 to 23
Embryo at Day 20
Further neurulation
Somite – a segment of the developing body
Somite formation
Day 20
Somite
Day 21
Neurulation
Starts at Stage 9 (19-21 days) at 3rd
or 4th
somite
Complete by stage 10 (22-23 days) at about L1/L2
Accounts for formation of 21 to 29 somites
Formation of the neural tube
Is a midline phenomenon involving folding of the neural plate
Is based on individual body segments called somites
Closure of the neural tube is completed by Day 23
Formation of the brain
Cranial end of neural tube distended (by hydrostatic pressure)
Forms flexures and enlargements
Primitively divided into telencephalon, diencephalon, mesencephalon,
and rhombencephalon
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Note
Tremendous growth of the telencephalon (forebrain), leading to large,
overgrown cerebral cortex
Unmatched number and complexity of cerebral cortical convolutions
Congenital malformations result from interruptions or irregularities in the
formation of the embryo.
Period of vulnerability
Why is there a low risk of abnormalities in the early embryonic stage?
CNS anomalies
Congenital anomalies of the spinal cord
Definitions
Spinal dysraphism or spina bifida
o Defects, whether open of closed, associated with a failure of
closure of the posterior neural arch
o
Spina bifida aperta
Midline lesion communicating with the external
environement
o Spina bifida occulta
Lesion is covered by intact skin
Normal spine
Spina bifida
Failure of neurulation.
Spina bifida
Failure of closure of posterior arch
Myelomeningocoeles
a form of spina bifida aperta
1/1000 births. Regional variation
Disease of poverty
Spinal cord protrudes through a bony defect into a meningeal sac
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Myelomeningocoele
Pathologic effects?
You, the one from Laguna
Pathological effects
Nerves to lower extremities and sphincters are abnormal
CNS exposed to environment and infection
Lower extremities
Deformed due to failure of muscle tone and development
Frequent inability to ambulate
Issue: crutches versus wheelchair ambulation?
Frequent injury due to insensibility
Sphincter control
Continence one of the most complex neural interactions of spine Neurogenic bladder, usually flaccid
Prone to renal damage
Kidney failure one of major causes of death
Associated anomalies
Chiari II (or Arnold-Chiari) malformation
o
Cerebellar vermis, medulla, and 4th
ventricle extend through
foramen magnum
Hydrocephalus
Chiari II vs normal
So what?
Hindbrain dysfunction
Problems of swallowing and phonation
o
Frequent aspiration
o Poor suck
o Thin, high-pitched cry
Respiratory abnormalities
Neck rigidity
A leading cause of mortality
Hydrocephalus in myelomeningocoele
The higher the level, the higher the incidence
o
Lumbosacral defects 60%
o Thoracic defects 80%
o Cervical defects usually fatal
Common cause of mortality
Hydrocephalus Abnormal acculmulation of CSF within the brain
Intelligence
If no hydrocephalus or infection, IQ in normal range
If infections occur, IQ drops
If with hydrocephalus and infection is avoided
o
IQ falls in normal range
Verbal IQ high
Motor IQ low
o Cocktail party syndrome?
Treatment
If with hydrocephalus, shunt
Repair defect as soon as possible
o Within 48 hours of birth
Repair defect
Myelomeningocoele
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After repair
BUT, nerves still dysplastic, with abnormal function
Social implications
Often child of poverty
Physically impaired
Intellectually impaired
1/1000 live births
100 deliveries/day at Fabella
Where do they go?
Meningocoele
Much rarer
Cystic cavity lined with meninges, but no neural elements
No deficits
Operate?
Meningocoele
Operate to decrease infection
For comfort
To rule out cord tethering
Spina bifida occulta
Defect is covered by intact skin
o May have skin abnormality
5% of population have asymptomatic failure of L5 to fuseo
But, tethered cord is possible
Fawn’s tail in spina bifida occulta
Tethered spinal cord
Ascent of spinal cord
Normal cord
Normal spinal cord terminates at L1L2 interspace
End of spinal cord is fibroelastic filum terminale
On flexing neck, tip of cord a ascends 1 to 2 cm
Tethered cord
Spinal cord is fixed at an abnormally caudal location
Whenever spine is flexed, tension on cord --- cumulative damage
Progressive lower limb deformities, weakness, numbness, and
incontinence
Lipomyelomeningocoele
Pathogenesis
premature disconnection
Lipomyelomeningocoele
Fat infiltrates cord through a bifid spine
Spina bifida occulta
Effects are due to cord tethering and nerve dysplasia
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Spilt cord malformations
Diastematomyelia
o Two hemicords formed, divided by a bony spicule
Diplomyelia
o Two hemicords within one dural sheath
Problems of cord tethering
Diplomyelia
Diastematomyelia
Diastematomyelia
Bony spur in diastematomyelia
Cause problems due to cord tethering
Must remove anchoring spike
Marked by fawn’s tail
Dermal sinuses
Failure of one point to close in neurulation
A bit of ectoderm is “dragged” into CNS
Usually at lower spinal cord
Marked by tuft of hair
Malformations of the brain
Brain formation very complex
Hydrocephalus
Accumulation of large amounts of CSF due to an imbalance of
formation versus absorption
One of the most common diseases of the central nervous system
requiring treatment
A common complication of other disease processes of the CNS
CSF pathway
Absorption vs. formation
Large reserve of absorption vs. production
Constant rate of production
Effects of CSF accumulation
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Effects
Most common site of obstruction of flow
Hydrocephalus
Hydrocephalus
Anencephaly
Failure to form the anterior neural tube
Not compatible with survival
Encephalocoeles Congenital anomalies whereby parts of brain herniate out through a
defect in the skull
o Encephalocoele: contains brain, meninges and CSF
o Meningocoele: meninges and CSF only
o Cephalocoele: contents?
Failure of closure of midline
Racial variations
Encephalocoeles
Frontobasal cephalocoele
Herniation of brain, dura, CSF
out a fronto-basal skull defect
Often associated with other
intracranial anomalies
Intelligence?
Frontobasal cephalocoeles: an Asian disease
CNS infection
Hydrocephalus
Associated CNS abnormalities
Intelligence?
Repaired
Repair is to
o Prevent dysplasia of eyeball
o Cosmetic benefits
o
Prevent infection
Occipital cephalocoeles
More common in
Western population
Contain varying
amounts of brain
Not all cephalocoeles are repaired
Dermoid cysts
Communicate external environment to brain
Meningitis
o By conducting infection
o Sterile, chemical meningitis if cyst ruptures
Dermoid cyst
Holoprosencephaly
Failure of forebrain to divide
into two hemispheres Associated with midline
facial anomalies
Treatment
o Shunt?
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Schizencephaly
Cleft in brain communicates
ventricle to surface of brain
CSF flow often normal
Intellect impaired
Dandy-Walker syndrome
Dilation of lateral and third ventricles
Separated cerebellar hemispheres, hypoplastic vermis
Large posterior fossa
Widely dilated fourth ventricle
Membrane over the midline 4th
ventricle
Dandy-Walker syndrome
Associated CNS anomalies threaten intelligence
Treatment: create CSF flow
Chiari malformations
malformations of cranio-vertebral juction
Chiari I
Symptoms with adult onset
Headache, swallowing and
phonation problems
Abnormal CSF flow causes
spinal syrinx
o Often the main problem
Treatment: decompression
Chiari II
Associated with myelomeningocoele
Hydrocephalus due to abnormal
formina of Luschka and Magendie
Hindbrain dysfunction
o Swallowing
o Phonation
o Breathing
Chiari III
Herniation of cerebellum through a myelomeningocoele
Rare
Arachnoid cysts
Abnormal splitting of arachnoid
Located anywhere
Can exert pressure
Can bleed
Treatment of malformations of the brain
Relieve hydrocephalus
Prevent infections by closing
exposed CNS
Cannot grow normal brain tissue to replace the abnormal
Normal growth of skull
Ones of the skull of infant are separated by sutures
Virchow’s Law – growth of skull is perpendicular to sutures
Craniosynostosis
Premature fusion of sutures of skull
Monostotic
o Single suture involved
o
Often sagittalo
Abnormal skull shape
o Treatment is cosmetic
Can predict pattern
o Can you?
Sagittal synostosis
Scaphocephaly
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Treatment: to create an artificial suture
Multi-suture synostosis
Prevention
MRC Vitamin Study Research Group. Prevention of neural tube defects: results of
the Medical Research Council Vitamin Study. Lancet 338(8670):131-137, 1991.
Randomized double blind trial
o 1817 women with previous children with NTD
1195 completed pregnancies, 27 with NTD
o 6 in folic acid groups, 21 in groups without
Folic acid had 72% protective effect for NTD
Most common cause of congenital microcephaly?
Social issues
Counseling families of children with NTDs
Kubler-Ross: 5 stages of facing death
o Denial
o
Anger
o Bargaining
o Depression
o
Acceptance Similar stages faced when parents informed
o Death of 2 children
The normal expected child
The actual child
Counseling?
Rush to surgery to prevent infection
Comprehension down
o
~20% in other patients
o
Close to 0% in parents
Who makes the decision?
Children with myelomeningocoele
Even if socially competitive
o
More episodes of depression
o More suicidal ideation
Often not socially competitive
Social impact
Child physically disabled
Also frequently mentally disabled
Often financially disabled
Who pays?
The PCMC experience, 1995
16 cases were operated on
The hospital spent average of P70,000 on each patient
59.8% qualified free services
2.7% insurance
8.4% families
29.1% bad debt
Guess Jeans
Congenital missions