CONGENITAL ABNORMALITIES OF CENTRAL NERVOUS SYSTEM

• The incidence of malformations is higher in children with - IUGR and multiple pregnancies

• The same anomaly may occur as a result of genetic or environmental causes

• Etiology Genetic factors Forms of microcephaly inherited as AR Sex-linked variety of hydrocephalus Hereditary congenital facial paralysis AD Some anomalies have a high risk of recurrence within families Inborn errors of metabolism Cytogenetic abnormalities

Most important group are the trisomies( e.g Down Syndrome) Translocations, deletions Maternal age Maternal infections (rubella, CMV)

• Neural tube defects

- Most congenital anomalies of CNS and result from failure of the

neural tube to close spontaneously between the 3rd and 4th wk

in utero development

Anencephaly

• Complete absence of the cerebral hemispheres• Residue of brainstem can be identified• Females > males• Additional anomalies

- folding of ears - cleft palate - congenital heart defects

• Most of the patients die within several days of birth• 50% of cases have associated polyhydramnios• Genetic basis,low socioeconomic status,nutritional and vitamin deficiency,

toxic factors

• Encephalocele and cranial meningocele

- Protrusion of brain or meninges through a cranial defect- Most frequent in the occipital region- Genetic and environmental factors may be of etiologic importance- Increased risk for hydrocephalus,chiari malformation and Dandy Walker

Syndrome- May be completely covered with skin-Risk for visual problems - microcephaly - mental retardation - seizures- Cranial meningocel-generally good prognosis- Determination of maternal serum alfa fetoprotein levels measurement- Measurement of biparietal diameter in utero

SPINA BIFIDA OCCULTA

• Midline defect of the vertebral bodies without protrusion of the spinal cord or meninges

• Most individuals are asymptomatic and lack of neurologic signs

• In some cases patches of hair lipoma discolaration of skin dermal sinus can be seen in the midline of lower back

•encephaloceleencephalocele

Neural tube defects- Spinal meningocele, myelomeningocele and myelocele

• All are associated with spina bifida

• Meningocele- Consists of herniation of both dura and arachnoid through a vertebral defect

• Meningomyelocele- Consists of the above in addition to the spinal cord being herniated as well

• Myelocele- Consists of all the above but the spinal cord is open and flat with CSF leaking on to

the exposed surface• Hydrocephaly commonly occurs in association with all of the above

MENINGOCELE

• Most are covered with skin and no threat to the patient

• Asymptomatic children with no neurological findings may have surgery delayed

• Before surgical correction plain roentgenogram,USG,MRI should be planned for determining the extent neuronal tissue involvement

MENINGOMYELOCELE• Maternal periconceptional use of folic acid supplementation reduces the incidence

of neural tube defects

• Lumbosacral region accounts 75%of cases

• Bowel and bladder incontinence

• Flaccid paralysis of the lower extremities

• Absence of DTR

• Lack of response to touch and pain

• High incidence of lower extremity deformitties

• Surgery is often done within a day of birth

•myelomeningocmyelomeningoceleele

Arnold Chiari Malformation (ACM)(1)

• Complex deformity of the brain and cerebellum– Type 1

ectopia of cerebellar tonsils– Type 2

the most common type in neonates and usually associated with lumbar myelomeningocele

Consists of lengthening of the vermis and tonsils of the cerebellum and their downward displacement through the foramen magnum in the spinal canal

Arnold Chiari Malformation (ACM)(2)

- Type 3 Consists of a cervical spinal bifida, the entire cerebellum

being herniated through the foramen magnum- Type 4

Cerebellar hypoplasiaThe malformation develops early in gestation at the age of 10

weeks

Malformations of the cerebellum

• Agenesis of the cerebellum– Very uncommon

• Hypoplasia

• Dandy Walker malformation– Occlusion of the foramina of Lushka and Magendie of 4th ventricle early in

cerebral development– Small hypoplastic cerebellum with a greatly distended 4th ventricle

• Obstructive hydrocephalus and cerebellar ataxia are the clinical presentation

• Ectopias and heterotopias

Misplaced groups of neurons

• Such as an island of gray matter in the subcortex • More common in the cerebellum than the cerebrum• Mutatons of genes directing the neurons to reach the

final destination

•Cortical Cortical heterotopiaheterotopia

–Agyria-Lissencephaly• Total absence of gyri,• rare disorder giving the appereance of a

3-4mnt fetal brain,• failure to thrive,•microcephaly,• developmental delays,• seizures,• ocular anomalies

•lisencephalylisencephaly

–Pachygyria

A few broad malformed gyri varying in size and number

•pachygyriapachygyria

–Polymicrogyria

• An increased number of gyri some of which may be abnormally small

•polymicrogyriapolymicrogyria

–Schizencephaly • Presence of unilateral or bilateral clefts within

the cerebral hemispheres.• The borders of the cleft are surrounded by

abnormal tissue• Many patients are severely mentally

retarded,seizures and spastic quadriparesis

•schizencephalyschizencephaly

–Porencephaly • Presence of cysts or cavities within brain

communicating with the subarachnoid space

• Microcephaly,encephalocele,mental retardation,spastic hemiparesis-quadriparesis,optic atrophy,seizures

–Holoprosencephaly • Defective cleavage of prosencephalon• Facial anomalies are common• Lobar

– Single ventricle+absent falx+fused basal ganglia• Semilobar • High mortality rates• Chromosomal anomalies and mutations

Microcephaly • Small brain usually associated with a small head• Head ofcircumference that measures more than 3SD below

the mean age and sex• Primary-have no other malformations

usually identified at birth familial AD

• Secondary-number of etiologic agents affects the fetus in utero or an infant during periods of rapid brain growth(in the first 2 yrs of age)

radiation,congenital inf,drugs meningitis/encep.,malnutrition metabolic,HIE

Megalencephaly

• Proportionate enlargement of the whole brain, usually associated with the presence of a variable mental aberration

- Primary - Secondary

Agenesis of corpus callosum• May be part of a complex malformation or be totally or partially

absent in an otherwise normal brain

• It develops between the 12 and 22 weeks of gestation

• Expression from severe intellectual and neurologicalabnormalities to the asymptomatic and normally intelligent individual

• Mental retardation, mild to moderate, epilepsy and cerebral palsy are common

• Diagnosis can be confirmed with a CT or MRI

•Corpus callosum agenesisCorpus callosum agenesis

Hydrocephalus • Group of conditions that result from impaired circulation and

absorbtion of CSF

- Obstructive (noncommunicating) Resulting from the obstruction within the ventricular system

- Nonobstructive (communicating) Resulting from obliteration of subarachnoid cisterns or

malformation of the arachnoid villi

• In a normal child 20ml/hr CSF is producedfrom the lateral ventricules-

3rd vent(thr foramina Monro)- 4th vent(thr aquaduct of Sylvius)- cisterns at the base of the brain(thr Luschka and

Magendie foramina) convexities of cerebral hemispheres- Absorbtion(primarily by the arachnoid villi)

• Accelerated rate of enlargement of the head

• Anterior fontanel is wide open and bulging

• Scalp veins are dilated

• Eyes may deviate downward = setting sun eye sign

• TREATMENT-ventriculoperitoneal shunt

HYDRANENCEPHALY

• Cerebral hemispheres are absent or represented by membraneous sacs

• Bilateral occlusion of the internal carotid arteries during early fetal development

• İrritable child,seizures,spastic quadriparesis,no cognitive development

CRANIOSYNOSTOSIS

• Premature closure of the cranial sutures

• Primary-closure of one or more sutures due to abnormalities skull development

• Secondary-failure of brain growth and expansion

• Skull deformity-as a result of premature suture fusion

• Prominent occiput

• Broad forehead

• Small or absent anterior fontanel

DIASTEMATOMYELIA (SPLIT SPINAL CORD MALFORMATION)

• Diastematomyelia is a division of the spinal cord in to two halves by projection of a fibrocartilagionous or bony septum originating from the posterior vertebral body

• It represent a disorder of neural tube fusion

• The defect involves the lumbar vertebrae (L1-L3) in 50% of cases

• Abnormalities of vertebral bodies

– Fusion defects– Hypoplasia– Kyphoscoliosis– Spina bifida– Myelomenıngocele

DmmCLINICAL MANIFESTATIONS

• A midline abnormality of the skin in the lumbosacral region

• In some cases the patients are asymplomatic

• Unilateral foot abnormalities

• Claw toes

• Atrophy of gastrocnemius

• Bilateral weakness and atrophy in lower extremities

• Urinary ıncontinence

• Low back pain

• Loss of pain and temperature sensation

SYRINGOMYELIA

• A cystic cavity within the spinal cord that may communicate with CSF pathways or remain localized and noncommunicating

• Communicating syringomyelia is frequently associated with the chiari type I malformation →constriction of the central canal at the level of foramen magnum during enbriogenesis

• Non communicating syringomyelia is associated with cord tumors, vascular accidents, trauma and arachnoiditis

Sm

• Syringabulbia exists when the cystic cavity extends ınto the medulla

• Syringomyelia rarely produces symptoms during childhood because of slow evolution

Sm• Asymmetric loss of pain and temperature sensation in the upper

extremities

• Muscle wasting of the hands

• Absent deep tendon reflexes

• Rapidly progressive scoliosis

• Trophic ulcers associated with vasomotor disturbances of the hands and arms----------- loss of appreciation of pain

TETHERED CORD (TC)

• During fetal development the spinal cord occupies the entire length of the vertebral column

• Due to differential growth the conus medullaris in a child ultimately assumes a position at the level of L1

• Normal regression of the distal embrionic spinal cord produces a slender, threadlike filum terminale that is attached to the coccyx

Tc

• TC results when a thickened ropelike filum terminale persists and anchors the conus at the below the L2 level

• Neurologic signs may develop as a result of abnormal tension of spinal cord

• In addition to a tight filum, sacral agenesis, intradural lipoma, myelomeningocele and dermal sinus may be associated with the tethered spinal cord syndrome

TcCLINICAL MANIFESTATIONS

• In 70% of cases inspection of the back show a midline skin lesion such as lipoma, tuft of hair, dermal sinus, portwine stain or hyperpigmentation of the skin

• Signs may be evident at birth or may be delayed until adulthood

• Infants may have asymmetric growth in foot or leg

• Cavus deformities

• Muscle wasting

Tc

• The child may be delayed in walking

• Toe walking

• Regression of lower extremity function

Tc• The lower motor neuron signs in the legs

• Abnormalities in bladder function

• Recurrent urinary tract infections

• Bowel incontinence

• Constipation

• Progressive scoliosis

• Diffuse pain in the lower extremities

Tc

• Plain roentgenogram = Lumbosacral bodies may show widening of the interpedicular distance hemivertabrae malformations the anterior spinal sagments

• MRI = outlines the level of the conus medullaris and the filum terminale