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

encephalocele

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

myelomeningocele

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 hypoplasia The 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 heterotopia

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

lisencephaly

Pachygyria A few broad malformed gyri varying in size and number

pachygyria

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

polymicrogyria

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

schizencephaly

Porencephaly Holoprosencephaly 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 agenesis

Hydrocephalus - Obstructive (noncommunicating) 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 produced from 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

(SPLIT SPINAL CORD MALFORMATION) 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

CLINICAL MANIFESTATIONS Dmm CLINICAL 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

CLINICAL MANIFESTATIONS Tc CLINICAL 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