M & M conference 10/18/02

Andrea Balazs M.D.

Dept. of Pediatrics

Neural Tube Defects

Neurulation • Brain and sp.cord formation • on the dorsal aspect of the embryo• 3rd – 4th w of pregnancy• Mesoderm induce the formation of the neural plate

from the ectoderm ~18th days of gest. – neural tube - ant. closure 24th day –post.closure 26th day

Caudal neural tube formation 28-32nd day

from caudal cell mass - vacuoles - coalesc contact with the central canal - canalization

and differentation

Neural tube defects

• Craniorachischisis

• Anencephaly

• Encephalocele

• Myelomeningocele

Craniorachischisis totalis

Total failure of neurulation

Neural plate like structure, no overlying

skeleton or skin, occurs on 20-22nd day

abortion

Anencephaly

• Failure of the anterior neural tube closure• Degenarated mass of neurons, glia, vessels• Froglike appearance• Occurs on 24th day• Polyhydramnion • 75% stillborn or die during the neonatal period• Rates of occurrence 0.2/1000 live births

Anencephaly

• 4x as frequent in females than in males

• Expl.neurulation takes longer, longer vulnerable period

Encephalocele

• Herniation of the brain tissue• Location: occipital 70-80%, frontal / temporal /

parietal – less common • Protruding mass - occipital lobe / cerebellum • 50 % complicated with hydrocephalus• low occipital or high cervical EC combined with

vertebra, skull base and lower brain stem anomaly compose Arnold - Chiari III

Encephalocele

• Partial or complete agenesis of corpus callosum

• Venous drainage anomaly

• Occures before 26th day

• EC associated with visual problem,microcephaly, MR and seizure

• Meningocele – 10 - 20%, no neural element,usually no neurologic deficit

• Outcome more favorable in anterior EC (mortality 0% vs 45%, nl.outcome 42% vs 14%)

• Thx: surgery

Myelomeningocele

• Failure of the posterior neural tube closure• 80% in the lumbar region• variable dermal covering• dorsal displacement of the neural tissue, CSF leakage,

sac formation • neural plate or neural tube-like structure,

raw,velvety,flat• ventral part of the cord less affected• Axial skeleton deficiency: lack of fusion or absence of

the vertebral arches, widened spinal canal

Myelomeningocele

• Onset no later than 26th days

• Overall incidence 1:1000 live births ’89

• Risk of recurrence 3% after one affected child, 10% with 2 previous abnormal pregnancies

MyelomeningoceleClinical features: • Lesion itself• disturbances of neurological function pending on

the level (motor, sensory, and sphincter function) • Low sacral lesions: bowel and bladder

incontinence and anesthesia in the perineal area• Lesions below S1 able to walk unaided• Lesion above L2 wheelchair, later scoliosis, as

well

Myelomeningocele

• Intermediate/midlumbar lesion L3 – L4 or L5• Flaccid paralysis of the LE’s, absence of deep

tendon reflexes• Lack of response to touch and pain • Clubfeet, hip subluxation• Continuous urinary dribbling and relaxed anal

sphincter• ambulatory or primarily ambulatory with braces

or cruthces

Myelomeningocele

• Deterioriation to a lower level of ambulatory function than that expected from segmental level over time

• Hydrocephalus incidence 60% vs 90%• HC > 90% ventriculomegaly in 95% • AF, sutures status • S/s of hydrocephalus is overt by 2-3 weeks

of life

• Arnold –Chiari II malformation accompanies thoracolumbar - lumbosacral MMC Sequence of events MMC - CSF leakage - lack of normal distension of the ventricles - small posterior fossa - inferior

displacement of the medulla, IV th ventricle and cerebellum

elongation, thinning of the medulla and pons kinking of the cervical cord obstructed CSF flow - aquaeductus sten. and

hydrocephalus

Clinical features associated with A-C IImalformation:• brain stem dysfunction –feeding disturbances (reflux, aspiration), dysphagia,

apnoe, stridor, cyanotic spells onset at 3.2 months causes: brain stem malformation and displacement affects the cranial nerves

and nuclei these structures under compression from the hydrocephalus and the

increased ICP ischemic and hemorrhagic necrosis of the brain stem from the disturbed arterial architecture and caudally displaced vertebrobasilar circulation

Other anomalies of the CNS associated withMMC:Abnormal cortical development:Microgyria 55-95% intellectual deficits and seizuresImpaired neuronal migrationFalx cerebri hypoplasia, septum pellucidumAnomaliesCerebellar dysplasia

Management

• Prevention• Prenatal therapy• Human fetal surgery• Optimal means of delivery of the affected infants

-c/s vs vag. - paralysis level 3.3 segments below the anatomical level of the lesion to compare with 1.1 for babies delivered vag. - amb. or wheelch.

• Postnatal surgery - early closure - proph. Abx – VP shunt placement

Management

• Team approach – specialtiesPE :• Correlate the functional level (motor, sensory and

sphincter function and reflexes ) to the level of anatomic lesion

• Neurologic dysfunction correlates with the level of the spinal cord lesion

• Presence of anal wink and anal sphincter tone suggest functioning sacral spinal segments, prognostically important

• evaluate for other malformation

• Hydrocephalus – VP shunt – IQ better preserved• Earlier shunt placement improves the cognitive

outcome - degree of ventriculomegaly in utero or the size of the cerebral mantle during the 1st week correlates with the subsequent intelligence

• Shunt complications - deleterious effect on intellectual outcome

• Mean IQ – MMC + infected VP shunt 73 / vs MMC + VP shunt w/o infection 95

• MMC w/out hydrocephalus mean IQ 102

Rare VP shunt complication

Migration of the VP shunt tip through the patent processus vaginalis resulting in scrotal hydrocele

Complications in MMC

Orthopedic problems• Lower extremities lack innervation –

atrophied foot, knee, hip and spine deformities – result from muscle imbalance, abn. In utero positioning

• Hip dislocation/subluxation in 1 year mostly with midlumbar MMC

• contractures

Complications in MMC

Urinary tract abnormalities• Major cause of death after the 1st year• > 85% MMC located above S2 associated with

neurogenic bladder • Urinary incontinence and ureteral reflux • Hydronephrosis, chronic pyelonephritis with renal

scarring and destruction, urosepsis• Renal anomalies: agenesis, horseshoe k.,ureter

duplication

Spina bifida occulta

Neural lesions• Myelocystocele –cystic dilatation of the central canal of the

caudal neural tube• Diastematomyelia – diplomyelia – spinal cord is bifid,

occassionally separated by fibrous or bony septum originating from the vertebra

• Lipomeningocele• Epidermoid/dermoid sinus• Tethered cord• Meningocele (anterior, too)• Agenesis of distal spinal cord

Complications in MMC

• Outcome of cortical function pending on the level of lesion:

• Lumbar MMC nl. range of intelligence • Reading and spelling o.k.• Greatest deficit in arithmetic achievement and

visual – motor integration• IQ >80 with lesion below S1• IQ > 80 in 50% of pt. with thoracolumbar lesion

Spina bifida occulta

• Caudal locus L5-S1• Covered by skin• No neurological deficit• Undetected for years• Abnormal conus med. (prolonged) and

filum terminale (thickened)• “Tetherd “ or fixed at their caudal end by

fibrous bands,lipoma, dermal sinus

Spina bifida occulta

• Vertebra abnormality 85-90% • laminar defects over several segments• Widened spinal canal and sacral deformities• Skin lesion 80% - hair tufts, dimples or

tracts, hemangioma, skin tag, cutis aplasia, pigmented macula, sc. Mass, lipoma, dermal sinus (epidermoid,dermoid cyst)

• 15-20% infants of diabetic mothers

Spina bifida occulta

Clinical aspect• Neurological deficits appear later in infancy• Delay in development of sphincter control,

in walking, asymmetry of legs or abn. feet • Pain in the back or lower extremities• Recurrent meningitis• In older child: gait disturbance, foot

deformity, scoliosis, abnormal sphincter f.

Spina bifida occulta

Management

spine x – ray

spine US

if both nl. And no sy - only clinical F/U

if abn. - MRI

thx. – surgery in neonatal period to prevent neuro.deficits

New thingsFetal surgery• Goal: to prevent damage to the cord and prevent

complications related to the primary anomaly, to restore or preserve neurologic function

• Done 28-30 w , via hysterotomy• Theoretical advantage of FS: greater potential for

healing and regeneration in the fetus• Results: no improvement in motor function• Definite improvement in the cerebellar herniation – A-C

III regressed, less likely to require VP shunt – nl.CSF circulation

New things

Fetal surgery 2 pt. at risk Induction of early labor, preterm delivery,

infection, death MMC is not lethal lesion• Iatrogenic dermoid inclusion cyst in infancy• Progressive neur. deterioriation for spinal cord

tethering• Unknown, unforseen complication

Thank you for your attention

And

Than you for your help

Dr. Levin

Dr.Quattromani