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Neural tube defects Nervous system -nervous system develops from neural plate forms into the neural folds, neural tube, & neural crest -neural tube CNS consisting of brain & spinal cord *proceeds in cranial & caudal directions until only small area of the tube remain open at both ends -around week 4 cranial and caudal ends of neural tube close -around week 9-10 lateral walls off neural tube thicken, reducing size of neural canal (central canal of the spinal cord & ventricular system of the brain) NTD causes NTD -failure of the neural tube to close spontaneously between 3rd & 4th week -precise cause remains unknown *hyperthermia, drugs (valproic acid), malnutrition, chemicals, maternal obesity or DM *genetic determinants (mutations in folate-responsive or folate-dependent enzyme pathways) *abnormal maternal nutritional state *exposure to radiation before conception -most common forms of birth defect, affecting 1/1,000 pregnancies -open neural tube defects anencephaly, myelomeningocele, meningocele -closed NTDs diastematomelia, dermal sinus, tethered spinal cord, lipomyelomeningocele -most common neural tube defects are spina bifida & anencephaly -anterior NTDs anencephaly, encephalocele Spina bifida occulta -posterior NTD spina bifida -defect in posterior vertebral body fusion occurs in L5 or S1 region -10% of otherwise normal people -no protrusion of the spinal cord or meninges most patients are asymptomatic & no neurologic signs Occult spinal dysraphism (OSD) -involves protrusion of spinal cord and/or meninges through defect in vertebral arches -cutaneous manifestations hemangioma (A), discoloration of skin, pit, lump, dermal sinus (B), or hairy patch (D) (c) human tail w/underlying lipoma -initial screening in neonate may include u/s MRI more reliable -(> 50%) dimples diagnosed w/OSD dimple with discharge needs further evaluation and neurosurgical referral! -imaging indicating subcutaneous mass or lipoma; dermal sinus, hairy patch; scar-like lesions; atypical dimples (deep, > 5mm, >25 mm from anal verge); vascular lesions (e.g. hemangioma or telangiectasia) -Gluteal cleft anomalies other than dimples also have a weak association with milder forms of OSD and warrant further evaluation Therefore, a deviated or duplicated (“split”) gluteal cleft should raise concern for OSD, whether or not a dimple is present (solitary dimple) (gluteal cleft) DERMOID SINUS -midline defect-closed neural tube defect -small skin opening, leads into a narrow duct pass through dura, acting as a conduit for spread of infection recurrent meningitis! -associated with tethered spinal cord syndrome (abnormal attachment of lower end of spinal cord to surrounding structure) & diastematomyelia (spinal cord divided into halves by a bony or cartilaginous septum, often seen in spina bifida) ASSOCIATED ORTHOPEDIC FINDINGS -clubfeet, arthrogryposis, hip dislocation, kyphosis or scoliosis Spinal bifida with meningocele Spinal bifida with myelomeningocele FURTHER EVALUATION -abnormal neurological findings chronic UTI, pain, bowel/bladder dysfunction, LE spasticity or paresis, lower limb deformity (foot drop, talipes equinovarus, dragging one foot) -cystic sac contains meninges & CSF -spinal cord & spinal roots are in their normal position -most common birth defect compatible with life *more severe & more common than meningocele -spinal cord and/or nerve roots are included in sac Myelomeningocele -about 60/100,000 births -causes both environmental & genetic factors *exposure to alcohol; hyperthermia; DM & obesity; malnutrition (especially folate deficiency); valproic aid, carbamazepine, or isotretinoin -prevalence higher among Latino & female offspring MYELOSCHISIS -most severe type of spina bifida spinal cord in affected area is open (failure of neural folds to fuse) -referral to neurosurgeon -functional levels with myelomeningocele CONSEQUENCES- BRAIN ABNORMALITIES -hydrocephalus occurs in 60% to 95% of children more common with higher-level lesions -Chiari type II malformation -agenesis of the corpus callosum -other anomalies such as hypoplasia of the cranial nerve nuclei & diffuse microstructural anomalies *learning disabilities – nonverbal learning disorder *ADHD *problems with executive function MRI brain OTHER CONSEQUENCES -overall intelligence in normal range -precocious puberty – related to a disorder of the hypothalamus -about 15% develop a seizure disorder (epilepsy) *generalized tonic-clonic *respond well to antiepileptic meds *new-onset seizures may occur as a manifestation of shunt infection or, rarely, shunt failure CONSEQENCES- SPINAL CORD ABNORMALITIES -loss of sensation *decubitus ulcers *common pressure points include the ischial tuberosities, coccyx, bony prominences of the feet & ankles *may lead to osteomyelitis *method of promoting healing is to remove pressure -loss of efferent nerve stimuli neurogenic bowel & bladder -loss of motor function *loss of mobility *MSK deformities such as flexion contractures or torsion of a bone *scoliosis & kyphosis -loss of efferent fibers in sexually mature males leads to impotence as well as to retrograde ejaculation TETHERED SPINAL CORD -weakness in LE, deterioration of gait -pain in back or legs & local swelling in the back -atrophy of muscles in LE -sensory loss or change in LE -change in DTRs -change in bowel or bladder function -new orthopedic contracture, such as pes cavus or foot- or leg-length discrepancy -rapidly progressive scoliosis & new decubitus ulcer BLADDER DYSFUNCTION -occur in almost all children who have myelomeningocele -categorized as failure to store urine or failure to empty urine may be related to bladder, external sphincter, or both -increases risk of UTI -leads to urinary reflux & hydronephrosis -infection leads to renal damage & failure over time -treatment clean intermittent catheterization (CIC); u/s at regular intervals; cystometrography (urodynamics); vesicostomy – urine to drain directly into diaper (opening the bladder & sewing on a piece of small intestine – older kids & teens); regular care from urologist NEUROGENIC BOWEL -constipation & rectal prolapse may occur *timed toileting; high in fiber diet; stool softeners or laxatives -surgical procedure – the antegrade colonic enema *daily boluses of liquids are pushed into the colon, evacuating it & preventing fecal incontinence LATEX ALLERGY -( > 50% ) of children who have myelomeningocele -risk of allergy increases as child gets older & may be life threatening -avoiding latex-containing products from time of birth is recommended PRENATAL SCREENING -alpha-fetoprotein screening at 16 to 18 weeks of gestation -high-resolution u/s -amniocentesis – AFP & acetylcholinesterase -chromosomes study NEWBORN CARE -routine care in delivery room, but lesion on back should be protected from contamination -parenteral abx until surgical closure closed surgically within 72 hrs. -neurological evaluation to determine level of lesion u/s or MRI -ventricles shunt hydrocephalus -orthopedic evaluation Prevention of NTD -urologic evaluations creatinine & BUN, renal u/s, & voiding cystourethrography -second most prevalent congenital anomaly in US -substantial morbidity & mortality -folic acid supplementation & dietary fortification decrease occurrence & recurrence of these anomalies *periconceptional folic acid supplementation can prevent 50% or more of NTDs Anencephaly -AAP, CDC, & USPHS recommendations all women capable of becoming pregnant consume 400 microgram of folic acid daily; previous NTD-affected pregnancy, 400 microgram per day beginning at least 1 month before conception & continuing through first trimester -failure of the rostral neuropore to close -incidence is 1/1,000 live births greatest incidence in Ireland, Wales, and Northern China -recurrence risk 4% and increases to 10% if a couple has had 2 previously affected pregnancies -several noxious stimuli interact on a genetically susceptible host to produce anencephaly STAR ON SLIDE -approx. 50% associated polyhydramnios -pituitary gland is hypoplastic -anomalies including folding of ears, cleft palate, & congenital heart defects in 10-20% of cases -most infants die w/in several days of birth -incidence decreasing in past 2 decades -alpha-fetoprotein levels high *definitive prenatal dx can be made with u/s between the 14th & 16th week Cranium bifidumEncephalocele -a cranial meningocele meningeal sac filled with CSF only -encephalocele contains sac plus cerebral cortex, cerebellum, or portions of the brainstem -most commonly in the occipital region, but frontal or nasofrontal prominent -inheritance & recurrence risk are similar to anencephaly ON EXAMINATION -pedunculated stalk or a large cyst like structure -may be completely covered with skin, but areas of denuded lesion can occur -require urgent surgical management -diagnosis: *transillumination of the sac can indicate presence of neural tissue *plain XR of skull & cervical spine *u/s is most helpful in determining the contents of the sac *MRI or CT further helps define the spectrum of the lesion -diagnosis in utero: *maternal alpha-fetoprotein levels may be high *u/s measurement of the biparietal diameter *ID of the encephalocele itself *fetal MRI can help -increased risk for hydrocephalus aqueductal stenosis; Arnold-Chiari malformation; dandy-walker syndrome (u/s with encephalocele) (MRI w/encephalocele) PROGNOSIS -cranial meningocele good prognosis! -encephalocele is often part of a syndrome Meckel-Gruber syndrome -risk for vision problems, microcephaly, mental retardation, & seizures Aqueductal stenosis -neural tissue w/in the sac & associated hydrocephalus have the poorest prognosis -abnormally narrow aqueduct of Sylvius -obstructive or noncommunicating hydrocephalus -neurofibromatosis & gliosis Dandy-Walker syndrome -neonatal meningitis & mumps meningoencephalitis -cystic expansion of the 4th ventricle in the posterior fossa & midline cerebellar hypoplasia -results from a developmental failure of the roof of the 4th ventricle during embryogenesis -rapid increase in head size & a prominent occiput -cerebellar ataxia & delayed motor and cognitive milestones -managed by shunting cystic cavity Arnold-Chiari malformation -structural malformation leading to downward displacement of the brainstem & cerebellum -symptoms may include dysphagia, vertigo, sleep apnea, ataxia, headache, neck pain, weakness, sensory loss, bowel or bladder dysfunction -type I cerebellar tonsils or vermis are below the foramen magnum *can become symptomatic at any time from infancy through adulthood -type II the 4th ventricle & lower medulla are pushed below the level of the foramen magnum *most common type *almost always associated with hydrocephalus & myelomeningocele -type II herniation of the cerebellum through foramen magnum Disorders of neuronal migration TYPE II -signs & symptoms *dysphagia, including difficulty swallowing, poor prolonged feeding, pooling of oral secretions *hoarseness or stridor *aspiration with or w/o pneumonitis *breath-holding spells *apnea, including disordered breathing during sleep *stiffness, weakness, & decreased function in the arms *opisthotonos -lissencephaly -schizencephaly unilateral or bilateral clefts within the cerebral hemispheres -neuronal heterotopias -polymicrogyrias -focal cortical dysplasias Lissencephaly -porencephaly -agri-smooth brain -absence of cerebral convolutions – poorly formed sylvian fissure -thin rim of periventricular white matter & numerous gray heterotopias -FTT, microcephaly, marked developmental delay, & a severe seizure disorder -ocular abnormalities – hypoplasia of the optic nerve & microphthalmia Agenesis of the corpus callosum -15% associated with Miller-Dieker Syndrome (MDS) -develops from the commissural plate proximal to the anterior neuropore *insult to this area during embryogenesis causes the agenesis -inherited as X-linked or autosomal dominant or autosomal recessive *may occur as an isolated defect – asymptomatic but it may occur with other defects – MR, seizures -assoc. with trisomy 8 & trisomy 18, single-gene mutations & metabolic disorders -dx is made with an MRI Aicardi syndrome -represents a complex disorder that affects many systems – typically assoc. with agenesis of the corpus callosuom -distinctive chorioretinal lacunae & coloboma of the optic disc -infantile spasms -almost all female -seizures 1st few months & typically resistant to anticonvulsants -mental retardation -hemiverterbra-fused vertebrae -EEG hemi – hypsarrhythmia Holoprosencephaly -most distinctive findings infantile spasms; agenesis of corpus callosum; distinctive chorioretinal lacunae -associated with maternal DM -chromosomal abnormalities -affected children with the alobar type have high mortality rates -a prenatal dx u/s after the 10th week of gestation *fetal MRI at later gestational ages gives for greater anatomic precision *look for assoc. anomalies -defective formation of the prosencephalon -3 groups lobar; semilobar; alobar, high mortality rates Microcephaly -facial abnormalities cyclopia, synophthalmia; cebocephaly, single nostril; solitary central incisor tooth; premaxillary agenesis -head circumference > 3SD below the mean for age & sex -primary (genetic) microcephaly *familial (autosomal recessive) *autosomal dominant *syndromes – Down (trisomy 21), Edward (trisomy 18) *Cri-du-chat (5 p-) *cornelia de lange *rubinstein-taybi *smith-lemli-opitz -secondary (nongenetic) *congenital infections – CMV, Rubella, toxoplasmosis *drugs – fetal alcohol, fetal hydantoin *other causes radiation – meningitis/encephalitis; malnutrition; hyperthermia; hypoxicischemic encephalopathy; metabolic maternal DM & maternal hyperphenylalaninemia CIINICAL MANIFESTATIONS & DIAGNOSIS -measure a patient’s head circumference at birth -family hx -serial head circumference measurements -head circumference of each parent & sibling -labs determined by hx & PE *mother’s serum phenylalanine, karyotype, and/or array-comparative genomic hybridization (array-CGH) study *plasma & urine amino acid analysis, serum ammonia determination, TORCH titers, HIV, CMV Hydrocephalus -MRI or CT scan -diverse group of conditions that result from impaired circulation & absorption of CSF or from increased production of CSF by a choroid plexus (rare) CSF PHYSIOLOGY -formed – choroid plexus -lateral ventricles through the foramina of Monro into the 3rd ventricle -traverses aqueduct of Sylvius to 4th ventricle -exits 4th ventricle through the paired lateral foramina of Luschka & the midline foramen of Magendie into the cisterns at the base of the brain -circulates from the basal cistern posteriorly through the cistern system & over the convexities of the cerebral hemispheres -absorbed primarily by the arachnoid villi CAUSES – COMMUNICATING -achondroplasia, basilar impression, benign enlargement of subarachnoid space, choroid plexus papilloma, meningeal malignancy, meningitis – pneumococcal & tuberculous, posthemorrhagic – subarachnoid hemorrhage CAUSES – NONCOMMUNICATING -aqueductal stenosis; infectious – toxoplasmosis, neurocysticercosis, mumps; mitochondrial; autosomal recessive, autosomal dominant; klippel-feil syndrome; chiari malformation, dandy-walker malformation; mass lesions, abscess, hematoma, tumors, & neurocutaneous disorders; vein of galen malformation CAUSES -hydranencephaly holoprosencephaly; massive hydrocephalus; porencephaly CLINICAL MANIFESTATIONS -depends on age at onset, nature of the lesion causing obstruction, & duration and rate of increase of ICP -accelerated rate of enlargement of the head -anterior fontanel is wide open & bulging -eyes might deviate downward – setting sun sign -brisk tendon reflexes, spasticity, clonus, Babinski sign -irritability, lethargy, poor appetite, vomiting, & HA -papilledema -subtle or confusing *cognitive changes, such as decline in school performance *moodiness, change in personality *signs of Chiari malformation *signs of tethered spinal cord MEGALENCEPHALY -brain weight – volume ratio > 98% percentile for age (or > = 2 SD above the mean) -usu. accompanied by macrocephaly – an occipitofrontal circcumferene (OFC) > 98th percentile -benign familial megalencephaly – most common -syndromic macrocephaly – sotos, fragile X TREATMENT -medical management use of acetazolamide & fursemide -ventriculoperitoneal shunt -endoscopic third ventriculostomy (ETV) -complications occlusion HA, papilledema, emesis, mental status changes, bacterial infection – staph epidermidis PROGNOSIS -depends on the cause and the size of the vertical mantle -developmental disabilities mean IQ reduced, abnormalities in memory function -Vision problems- strabismus, visuospatial abnormalities, visual field defects -Aggressive and delinquent behavior- some -Accelerated pubertal development -long-term follow-up in a multidisciplinary setting