Trans Congenital Malformations

7/21/2019 Trans Congenital Malformations

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Trans by: Marjorie Santillan Cruz

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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


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


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

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Trans Congenital Malformations