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Unformatted text preview: CNS Congenital Anomalies
CNS Congenital Anomalies
.Jamous M, M.D
Dept. of Neurosciences, School of Medicine, JUST Objectives
Review the normal CNS developmentReview the normal CNS development
study the common causes of CNS study the common causes of CNS congenital anomalies
study the common congenital study the common congenital anomalies, its presentations, diagnosis, and treatment Etiology of Congenital Brain Etiology of Congenital Brain Malformations Chromosomal (6%) Single gene (2%) Environmental (maternal) Nutrition: folic acid deficiency Disease: diabetes Toxins: alcohol, smoking Infections: rubella, toxoplasmosis, CMV, syphilis Radiation Unknown (most cases) CNS development
CNS development Primary neurolation 34 weeks
Secondary neurolation 4 weeks after birth
Prosencephalic development 23 months
Neural proliferation 34 months
Neuronal migration 35 months
Organization 5 months postnatal Myelination birth years postnatal Primary neurolation
Primary neurolation Occur in 3-4 week gestation
It ends by the creation of the neural
tube (NT) internally which will give
rise to the CNS above S2 segment ,
epidermis externally & neural crest
(NC) at the junction of NT &
NC: mesoderm cells which migrate a
way from the neural tube and give
rise to the PNS,skull, facial and jaw
bones, pigment cells, adrenal
medulla Neural tube closure
Neural tube closure Start at the cervical area (cervico
Extend cranially and caudally
Cephalic neuropore correspond to the commissural plate and lamina terminalis and it close around day 25
Caudal neuropore closes around day 29 and correspond to S2 segment Disorders of primary neurolation
Disorders of primary neurolation Split cord syndrome
Craniorachischisis Neuroenteric cyst
Arnold chiari malf.
encephalocele Disorders of primary neurolation
Disorders of primary neurolation diplomyelia
Dermal sinus (Split cord syndrome (Diplomyelia
Split cord syndrome (Diplomyelia splitting of the notochord around an adhesion between the endoderm and the ectoderm
the formation of two neural tubes and subsequently two hemicords
notochord also influences the vertebrae formation and thus it is common to have associated segmentation anomalies at the site of diastematomyelia
In twothirds of cases the overlying skin shows nevi, hypertrichosis, lipomas, dimples or hemangiomas. Symptoms are nonspecific and similar to other causes of cord tethering. Myeloschisis & Craniorachischisis
Myeloschisis & Craniorachischisis a flattened, platelike mass of nervous tissue with no overlying skin or membrane the neural folds fail to meet and fuse Most aborted Dermal sinus tract
Dermal sinus tract result from incomplete disjunction of
neuroectoderm from cutaneous ectoderm
The sinus tracts extend deep into the
subcutaneous tissues, reaching the spinal
canal in one-half to two-thirds of cases.
it may be attached to the dura, causing
tenting of the thecal sac.
When they pass intradurally, they may end
in the subarachnoid space, conus
medullaris, filum terminale, a nerve root, a
fibrous nodule on the surface of the cord, or
a dermoid or epidermoid cyst.
about 50% of the dermal sinuses end in
dermoid or epidermoid cysts. Conversely,
20% to 30% of dermoid cysts and dermoid
tumors have associated dermal sinus tracts.
Cause cord tethering in 50 % of cases
There may be a history of meningitis from extension of bacteria along the tract or from chemical irritation if the cyst ruptures. :Anencephaly
Failure of anterior neuropore to close Brain and calvarium are absent & Replaced by a cerebrovasculorum a tangle of glial and connective tissue Remnants of brainstem and pituitary may be present &so infant is born alive Geographic variability Ireland – high U.S – intermediate Japan – low Most severe case defect from level of lamina terminalis to foramen magnum (holocrania/holoanencephaly); if defect does not extend to foramen magnum meroacrania/meroanencephaly ).Chiari II malformation (Arnold Chiari Malf
Chiari II malformation (Arnold Chiari Malf The cerebellar vermis and part of brain stem herniate below foramen magnum One unifying theory suggests that the posterior neuropore remains open too long, thereby decompressing the ventricular system and allowing the bony posterior fossa to close too early forming a small compartment
More than 90 percent of these patients develop hydrocephalus within the first six months following closure of the spinal defect
Syringomyelia, the common finding
associated with CM
associated Meningocele and Meningocele and myelomeningocele 1. Primary failure of neural tube closure –Myelomeningocele Meningocele
mesenchyme destined to form the posterior elements remains trapped laterally, causing a wide spina bifida.
Most frequently located in the thoracolumbar area.
Rule of 80's (80% have hydrocephalus, 80% require shunt, and 80% will have IQ >80 ) Lipomeningocele
caused by premature separation of the neural ectoderm from the cutaneous ectoderm.which allows the mesench to enter the ependymalined canal of the neural tube inducing fat formation Three types: intradural lipomas (4%) lipomyelomeningoceles (84%), fibrolipomas of the filum terminale
May have symptoms related to associated abnormalities such as tethering of cord or neural element compression. Include motor and sensory deficits, reflex changes, gait abnormalities, bowel/bladder problems, musculoskeletal problems. Encephalocele
Encephalocele Bony defects in midline Brain tissue can protrude through hole Most common in occipital region Prognosis depends on quantity of cerebral tissue that herniates into the defect CNS development
CNS development At the time of closure of the anterior neuropore,
three dilatations or vesicles develop in the rostral
aspect of the neural tube: prosencephalon
(forebrain), mesencephalon (midbrain), and
These are separated by the cephalic, pontine
Cervical flexure separate rhombencephalon from
the cervical cord
Pontine flexure is the last to develop Prosencephalic development
Peak time 23 months Notochord & Prechordal mesoderm will cause ventral induction of the forebrain to develop the prosencephalon Prosencephalon cleavage will give:
1paired optic and olfactory structure
2telencephalon cerebral hemisphere, Caudate & putamen
3diencephalons thalamus, hypothalamus & Basal Ganglia Midline prosencephalic development Midline prosencephalic development will give rise to corpus callosum, septum pellucidum, optic nervechiasm and hypothalamus Disorder of prosencephalic development
Disorder of prosencephalic development
Aprosencephaly/ atelencephaly Prosencephalic cleavage
Holoprosencephaly/ holotelencephaly Midline prosencephalic development
Agenesis of corpus callosum
Agenesis of septum pellucidum Neuronal proliferation
Neuronal proliferation Peak time 34 months
Neuroblast proliferate in ventricular and subventricular zones which will produce proliferative units by symmetrical divisions
The proliferative units enlarge by asymmetrical divisions Neuronal proliferation & migration
Neuronal proliferation & migration Disorders of neuronal proliferation
Disorders of neuronal proliferation Micrencephaly Macrencephaly
Isolated Associated with growth disturbance
Unilateral (hemimegalencephaly) Disorders of neuronal migration
Disorders of neuronal migration Lissencephaly pachygyria (smooth brain)
Mental Retardation, Intractable epilepsy Hydrocephalus
enlargement of the ventricles
often due to obstruction or
overproduction or poor
absorption of cerebrospinal
-It can be communicating or
-Incidence of 1 in 1,000 births
1. Increasing head circumference.
2. Irritability, lethargy, poor feeding, and vomiting.
3. Bulging anterior fontanelle.
4. Widened cranial sutures.
5. McEwen's cracked pot sign with cranial percussion.
6. Scalp vein dilation (increased collateral venous
7. Sunset sign (forced downward deviation of the eyes, a
neurologic sign almost unique with hydrocephalus).
8. Epidsodic bradycardia and apnea. Hydrocephalus
4. Decreased level of consciousness.
5. Focal neurological deficit. Hydrocephalus
-Dandy Walker malformation
-Chiari II malformation
-Intrauterine viral infection (CMV, mumps, rubella)
-Vein of Galen aneurysms
-Chromosomal anomalies (trisomy 13 and 18) Treatment of hydrocephalus
Treatment of hydrocephalus Observation in borderline cases
Shunting (ventriculoperitoneal) Endoscopic Third ventriculostomy Types of CSF shunting
Complications of shunting Craniosynostosis
Craniosynostosis Premature closure of the cranial sutures, 1/2000 birth
Abnormal skull shape
Vs. Lazy suture Presentation
Timing of surgery ...
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This note was uploaded on 12/24/2011 for the course STEP 1 taught by Professor Dr.aslam during the Fall '11 term at Montgomery College.
- Fall '11