Download congenital anomalies of the central nervous system

CONGENITAL ANOMALIES OF
THE CENTRAL NERVOUS
SYSTEM
SUBMITTED BY:
Nicole Christianne Mae B. Bacayo
BSOT-IV
SUBMITTED TO:
Dr. Gerrard Dennis Uy
A. Neural Tube Defects
Neural tube defects (NTDs) account for the largest proportion of congenital anomalies of the
CNS and result from failure of the neural tube to close spontaneously between the 3rd and 4th
wk of in utero development. Precise cause of NTDs remains unknown, but evidence suggests
that many factors can adversely affect normal development of the CNS from the time of
conception. These include the following: including hyperthermia, drugs (valproic acid),
malnutrition, chemicals, maternal obesity or diabetes, and genetic determinants (mutations in
folate-responsive or folate- dependent enzyme pathways). In some cases, an abnormal
maternal nutritional state or exposure to radiation before conception increases the likelihood of
a congenital CNS malformation. The major NTDs include spina bifida occulta, meningocele,
myelomeningo-cele, encephalocele, anencephaly, caudal regression syndrome, dermal sinus,
tethered cord, syringomyelia, diastematomyelia, and lipoma involving the conus medullaris
and/or filum terminale and the rare condition iniencephaly.
The human nervous system originates from the primitive ectoderm that also develops into the
epidermis. The ectoderm, endoderm, and mesoderm form the three primary germ layers that
are developed by the 3rd wk. The endoderm, particularly the notochordal plate and the
intraembryonic mesoderm, induces the overlying ectoderm to develop the neural plate in the 3rd
week of development. Failure of normal induction is responsible for most of the NTDs, as well
as disorders of prosencephalic development. Rapid growth of cells within the neural plate
causes further invagination of the neural groove and differentiation of a conglomerate of cells,
the neural crest, which migrate laterally on the surface of the neural tube. The notochordal plate
becomes the centrally placed notochord, which acts as a foundation around which the vertebral
column ultimately develops. With formation of the vertebral column, the notochord undergoes
involution and becomes the nucleus pulposus of the intervertebral disks. The neural crest cells
differentiate to form the peripheral nervous system, including the spinal and autonomic ganglia
and the ganglia of cranial nerves V, VII, VIII, IX, and X. In addition, the neural crest forms the
leptomeninges, as well as Schwann cells, which are responsible for myelination of the
peripheral nervous system. The dura is thought to arise from the paraxial mesoderm. In the
region of the embryo destined to become the head, similar pat-terns exist. In this region, the
notocord is replaced by the precordal mesoderm.
In the 3rd wk of embryonic development, invagination of the neural groove is completed and the
neural tube is formed by separation from the overlying surface ectoderm. Initial closure of the
neural tube is accomplished in the area corresponding to the future junction of the spinal cord
and medulla and moves rapidly both caudally and rostrally. For a brief period, the neural tube is
open at both ends, and the neural canal communicates freely with the amniotic cavity. Failure of
closure of the neural tube allows excretion of fetal substances (α-fetoprotein [AFP],
acetylcholinesterase) into the amniotic fluid, serving as biochemical markers for a NTD. Prenatal
screening of maternal serum for AFP in the 16th-18th wk of gestation is an effective method for
identifying pregnancies at risk for fetuses with NTDs in utero. Normally, the rostral end of the
neural tube closes on the 23rd day and the caudal neuropore closes by a process of secondary
neurulation by the 27th day of development, before the time that many women realize they are
pregnant.
The embryonic neural tube consists of three zones: ventricular, mantle, and marginal. The
ependymal layer consists of pluripotential, pseudostratified, columnar neuroepithelial cells.
Specific neuroepithelial cells differentiate into primitive neurons or neuroblasts that form the
mantle layer. The marginal zone is formed from cells in the outer layer of the neuroepithelium,
which ultimately becomes the white matter. Glioblasts, which act as the primitive supportive
cells of the CNS, also arise from the neuroepithelial cells in the ependymal zone. They migrate
to the mantle and marginal zones and become future astrocytes and oligodendrocytes. It is
likely that microglia originate from mesenchymal cells at a later stage of fetal development when
blood vessels begin to penetrate the developing nervous system.
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Spina Bifida Occulta (Occult Spinal Dysraphism)
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Spina bifida occulta is a common anomaly consisting of a midline defect of the vertebral
bodies without protrusion of the spinal cord or meninges.
Most patients are asymptomatic and lack neurologic signs.
The condition is usually of no consequence.
Spina Bifida Occulta
- Merely a posterior vertebral body fusion defect
- Does not have an associated spinal cord malformation
Occult Spinal Dysraphism
- Term used for other clinically more significant form of this closed spinal cord
malformation
- In most of these cases, there are cutaneous manifestations such as a
hemangioma, discoloration of the skin, pit, lump, dermal sinus, or hairy patch.
- There is no abnormality of the meninges, spinal cord, or nerve roots.
- Is often associated with more significant developmental abnormalities of the
spinal cord
- Diagnosis:
 Spine roentgenogram- shows a defect in closure of the posterior vertebral
arches and laminae, typically involving L5 and S1
 All cases of occult spinal dysraphism are best investigated with MRI.
 Initial screening in the neonate may include ultrasonography.
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A dermoid sinus usually forms a small skin opening, which leads into a narrow
duct, sometimes indicated by protruding hairs, a hairy patch, or a vascular nevus.
Dermoid sinuses occur in the midline at the lumbosacral region or occiput,
respectively.
Dermoid sinus tracts can pass through the dura, acting as a conduit for the
spread of infection.
Recurrent meningitis of occult origin should prompt careful examination for a
small sinus tract in the posterior midline region, including the back of the head.
Lower back sinuses are usually above the gluteal fold and are directed
cephalad.
Tethered spinal cord syndrome may also be an associated problem.
Diastematomyelia commonly has bony abnormalities that require surgical
intervention along with untethering of the spinal cord.
Imaging of the spine in cutaneous lesions:
CUTANEOUS LESIONS ASSOCIATED WITH OCCULT SPINAL
DYSRAPHISM
IMAGING INDICATED
Subcutaneous mass or lipoma
Hairy patch
Dermal sinus
Atypical dimples (deep, >5 mm, or >25 mm from anal verge)
Vascular lesion, eg., hemangioma or telangiectasia
Skin appendages pr polypoid lesions, eg., skin tags, tail-like appendages
Scarlike lesions
IMAGING UNCERTAIN
Hyperpigmented patches
Deviation of the gluteal fold
IMAGING NOT REQUIRED
Simple dimples (<25 mm from anal verge)
Coccygeal pits
Meningocele
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A meningocele is formed when the meninges herniate through a defect in the posterior
vertebral arches or the anterior sacrum.
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The spinal cord is usually normal and assumes a normal position in the spinal canal,
although there may be tethering, syringomyelia, or diastematomyelia.
A fluctuant midline mass that might trans-illuminate occurs along the vertebral column,
usually in the lower back.
Most meningoceles are well covered with skin and pose no immediate threat to the
patient.
An anterior meningocele projects into the pelvis through a defect in the sacrum.
Symptoms of constipation and bladder dysfunction develop due to the increasing size of
the lesion.
Female patients might have associated anomalies of the genital tract, including a
rectovaginal fistula and vaginal septa.
Careful neurologic examination is mandatory.
Orthopedic and urologic examination should also be considered.
Examinations:
- plain x-rays, ultrasonography, CT scan and MRI
 Determine the extent of neural tissue involvement, if any, and associated
anomalies, including diastematomyelia, lipoma, and possible clinically
significant tethered spinal cord
 Plain x-rays demonstrate a defect in the sacrum
 CT scanning or MRI outlines the extent of the meningocele and any
associated anomalies.
 A CT scan or MRI of the head is recommended for children with a
meningocele because of the association with hydrocephalus in some
cases.
- Urologic evaluation, usually including cystometrogram (CMG)
 Identifies children with neurogenic bladder who are at risk for renal
deterioration
Treatment:
- Patients with leaking cerebrospinal fluid (CSF) or a thin skin covering should
undergo immediate surgical treatment to prevent meningitis.
- In asymptomatic children with normal neurologic findings and full thickness skin
covering the meningocele, surgery may be delayed or sometimes not performed.
Myelomenigocele
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Myelomeningocele represents the most severe form of dysraphism, a so-called aperta or
open form, involving the vertebral column and spinal cord.
Epidemiology:
- Occurs with an incidence of approximately 1/4,000 live births
- The risk of recurrence after one affected child is 3-4% and increases to 10% with 2 prior
affected children.
- Hydrocephalus in association with a type II Chiari malformation develops in at least
80% of patients with myelomeningocele.
- Certain drugs, including drugs that antagonize folic acid, such as trimethoprim and the
anticonvulsants carbamazepine, phenytoin, phenobarbital, and primidone, increase the
risk of myelomeningocele.
- The anticonvulsant valproic acid causes NTDs in approximately 1-2% of pregnancies
when administered during pregnancy.
Etiology:
- The cause of myelomeningocele is unknown.
- A genetic predisposition exists, as with all neural tube closure defects including
anencephaly.
- The risk occurrence and the presence of substantial familial aggregation of
anencephaly, myelomeningocele, and craniorachischisis indicate heredity, on a
polygenic basis, as a significant contributor to the etiology of NTDs.
- Nutritional and environmental factors have a role in the etiology of myelomeningocele
as well.
- Folate is intricately involved in the prevention and etiology of NTDs.
 Folate functions in single-carbon transfer reactions and exists in many
chemical forms.
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Folic acid (pteroylmonoglutamic acid), which is the most oxidized and stable
form of folate, occurs rarely in food but is the form used in vitamin
supplements and in fortified food products, particularly flour.
 Most naturally occurring folates (food folate) are pteroylpolyglutamates, which
contain 1-6 additional glutamate molecules joined in a peptide linkage to the
γ-carboxyl of glutamate.
 Folate coenzymes are involved in DNA synthesis, purine synthesis,
generation of formate into the formate pool, and amino acid interconversion;
the conversion of homocysteine to methionine provides methionine for the
synthesis of S-adenosyl-methionine (SAM-e, an agent important for in vivo
methylation).
 Mutations in the genes encoding the enzymes involved in homocysteine
metabolism include 5, 10 methylenetetrahydrofolate reductase (MTHFR),
cystathio-nine β-synthase, and methionine synthase.
 An association between a thermolabile variant of MTHFR and mothers of
children with NTDs might account for up to 15% of preventable NTDs.
 Maternal periconceptional use of folic acid supplementation reduces the
incidence of NTDs in pregnancies at risk by at least 50%.
 To be effective, folic acid supplementation should be initiated before
conception and continued until at least the 12th wk of gestation, when
neurulation is complete.
 The mechanisms by which folic acid prevents NTDs remain poorly
understood.
Clinical Features and Manifestations
- Myelomeningocele produces dysfunction of many organs and structures, including the
skeleton, skin, and gastrointestinal and genitourinary tracts, in addition to the peripheral
nervous system and the CNS.
- A myelomeningocele may be located anywhere along the neuraxis, but the
lumbosacral region accounts for at least 75% of the cases.
- .A lesion in the low sacral region causes bowel and bladder incontinence associated
with anesthesia in the perineal area but with no impairment of motor function.
- Newborns with a defect in the midlumbar or high lumbothoracic region typically have
either a saclike cystic structure covered by a thin layer of partially epithelialized tissues
or an exposed flat neural placode without overlying tissues.
- Examination of the infant shows a flaccid paralysis of the lower extremities, an absence
of deep tendon reflexes, and a lack of response to touch and pain, and a high incidence
of lower extremity deformities (clubfeet, ankle and/or knee contractures, and
subluxation of the hips).
- Some children have constant urinary dribbling and a relaxed anal sphincter.
 Other children do not leak urine and in fact have a high-pressure bladder and
sphincter dysynergy.
- A myelomeningocele above the midlumbar region tends to produce lower motor neuron
signs due to abnormalities and disruption of the conus medullaris and above spinal cord
structures.
- These infants sometimes have an associated kyphotic gibbus that requires neonatal
orthopedic corrections.
- Patients with a myelomeningocele in the upper thoracic or cervical region usually have
a very minimal neurologic deficit and, in most cases, do not have hydrocephalus but
they can have neurogenic bladder and bowel.
- The possibility of hydrocephalus developing should always be considered, no matter
what the spinal level.
- Ventricular enlargement may be indolent and slow growing or may be rapid causing a
bulging anterior fontanel, dilated scalp veins, setting-sun appearance of the eyes,
irritability, and vomiting associated with an increased head circumference.
- About 15% of infants with hydrocephalus and Chiari II malformation develop symptoms
of hindbrain dysfunction, including difficulty feeding, choking, stridor, apnea, vocal cord
paralysis, pooling of secretions, and spasticity of the upper extremities, which, if
untreated, can lead to death.
- This Chiari crisis is due to downward herniation of the medulla and cerebellar tonsils
through the foramen magnum as well is endogenous malformations in the cerebellum
and brainstem.
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Prevention:
- The U.S. Public Health Service has recommended that all women of childbearing age
and who are capable of becoming pregnant take 0.4 mg of folic acid daily.
- If, however, a pregnancy is planned in high-risk women (previously affected child),
supplementation should be started with 4 mg of folic acid daily, beginning 1 mo before
the time of the planned conception.
- The modern diet provides about half the daily requirement of folic acid.
- To increase folic acid intake, fortification of flour, pasta, rice, and cornmeal with 0.15
mg folic acid per 100 g was mandated in the United States and Canada in 1998.
- The added folic acid will be insufficient to maximize the prevention of preventable
NTDs.
- Therefore, informative educational programs and folic acid vitamin supplementation
remain essential for women planning a pregnancy and possibly for all women of
childbearing age.
- In addition, women should also strive to consume food folate from a varied diet.
- Certain drugs, including drugs that antagonize folic acid, such as trimethoprim and the
anticonvulsants carbamazepine, phenytoin, phenobarbital, and primidone, increase the
risk of myelomeningocele.
- The anticonvulsant valproic acid causes NTDs in approximately 1-2% of pregnancies
when administered during pregnancy.
- Some epilepsy clinicians recommend that all female patients of childbearing potential
who take anticonvulsant medications also receive folic acid supplements.
Treatment:
- Management and supervision of a child and family with a myelomeningocele require a
multidisciplinary team approach:
 Surgeons, physicians, and therapists, with one individual (often a
pediatrician) acting as the advocate and coordinator of the treatment
program.
- Surgery is often done within a day or so of birth but can be delayed for several days
(except when there is a CSF leak) to allow the parents time to begin to adjust to the
shock and to prepare for the multiple procedures and inevitable problems that lie
ahead.
- Evaluation of other congenital anomalies and renal function can also be initiated before
surgery.
- After repair of a myelomeningocele, most infants require a shunting procedure for
hydrocephalus.
 If symptoms or signs of hindbrain dysfunction appear, early surgical
decompression of the posterior fossa is indicated.
- Clubfeet can require taping or casting, and dislocated hips can require operative
procedures.
- Careful evaluation and reassessment of the genitourinary system are some of the most
important components of the management.
 Regular catheterization of a neurogenic bladder is a crucial step in
maintaining a low residual volume and bladder pressure that prevents urinary
tract infections and reflux leading to pyelonephritis, hydronephrosis, and
bladder damage.
 Latex-free catheters and gloves must be used to prevent development of
latex allergy.
 Periodic urine cultures and assessment of renal function, including serum
electrolytes and creatinine as well as renal scans, vesiculourethrograms
(VCUGs), renal ultrasonography, and cystometrograms (CMGs), are obtained
according to the risk status and progress of the patient and the results of the
physical examination.
 Some children can become continent with surgical implantation of an artificial
urinary sphincter (these are used less often) or bladder augmentation at a
later age.
 Although incontinence of fecal matter is common and is socially unacceptable
during the school years, it does not pose the same organ-damaging risks as
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urinary dysfunction, but occasionally fecal impaction and/or megacolon
develop.
 Many children can be bowel-trained with a regimen of timed enemas or
suppositories that allows evacuation at a predetermined time once or twice a
day.
 Special attention to low anorectal tone and enema administration and
retention is often required.
 Appendicostomy for antegrade enemas may also be helpful.
- Functional ambulation is the wish of each child and parent and may be possible,
depending on the level of the lesion and on intact function of the iliopsoas muscles.
 Almost every child with a sacral or lumbosacral lesion obtains functional
ambulation; approximately half the children with higher defects ambulate with
the use of braces, other orthotic devices, and canes.
 Ambulation is often more difficult as adolescence approaches and body mass
increases.
 Deterioration of ambulatory function, particularly during earlier years, should
prompt referral for evaluation of tethered spinal cord and other neurosurgical
issues.
 In utero surgical closure of a spinal lesion has been successful in a few
centers.
- Preliminary reports suggest a lower incidence of hindbrain abnormalities and
hydrocephalus (fewer shunts) as well as improved motor outcomes.
 This suggests that the defects may be progressive in utero and that prenatal
closure might prevent the development of further loss of function.
 In utero diagnosis is facilitated by maternal serum α-fetoprotein screening
and by fetal ultrasonography.
Prognosis:
- Mortality rate is 10-15%
 Children with aggressive treatment
- Most deaths occur before age 4 yr, although life-threatening complications occur at all
ages.
- At least 70% of survivors have normal intelligence, but learning problems and seizure
disorders are more common than in the general population.
- Previous episodes of meningitis or ventriculitis adversely affect intellectual and
cognitive function.
- Because myelomeningocele is a chronic disabling condition, periodic multidisciplinary
follow-up is required for life.
- Renal dysfunction is one of the most important determinants of mortality.
Encephalocele
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A cranial meningocele consists of a CSF-filled meningeal sac plus cerebral cortex,
cerebellum, or portions of the brainstem.
Microscopic examination of the neural tissue within an encephalocele often reveals
abnormalities.
The cranial defect occurs most commonly in the occipital region at or below the inion, but in
certain parts of the world, frontal or naso-frontal encephaloceles are more prominent.
These abnormalities are one tenth as common as neural tube closure defects involving the
spine.
Etiology:
- Etiology is presumed to be similar to that for anencephaly and myelomeningocele.
- Infants with a cranial encephalocele are at increased risk for developing
hydrocephalus due to aqueductal stenosis, Chiari mal-formation, or the DandyWalker syndrome.
Examinations and Diagnosis:
- Examination might show a small sac with a pedunculated stalk or a large cyst like
structure that can exceed the size of the cranium.
- Transillumination of the sac can indicate the presence of neural tissue.
- A plain x-ray of the skull and cervical spine is indicated to define the anatomy of the
vertebrae.
- Ultrasonography is most helpful in determining the contents of the sac.
- MRI or CT further helps define the spectrum of the lesion.
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Fetal MRI can help define the extent of associated CNS anomalies and the
degree of brain herniated into the encephalocele.
- Determination of maternal serum α-fetoprotein levels and ultrasound measurement
of the biparietal diameter as well as identification of the encephalocele itself can
diagnose encephaloceles in utero.
Prognosis:
- Patients with an encephalocele are at risk for:
 vision problems, microcephaly, mental retardation, and seizures
- Generally, children with neural tissue within the sac and associated hydrocephalus
have the poorest prognosis.
- Cranial encephalocele is often part of a syndrome.
 Meckel-Gruber syndrome is a rare autosomal recessive condition that is
characterized by an occipital encephalocele, cleft lip or palate, microcephaly,
microphthalmia, abnormal genitalia, polycystic kidneys, and polydactyly.
Anencephaly
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An anencephalic infant presents a distinctive appearance with a large defect of the
calvarium, meninges, and scalp associated with a rudimentary brain.
Anencephaly results from failure of closure of the rostral neuropore, the opening of the
anterior neural tube.
The cerebral hemispheres and cerebellum are usually absent, and only a residue of the
brainstem can be identified.
The pituitary gland is hypoplastic, and the spinal cord pyramidal tracts are missing owing to
the absence of the cerebral cortex.
Additional anomalies include folding of the ears, cleft palate, and congenital heart defects in
10-20% of cases.
Etiology:
- Genetics
- Low socioeconomic status
- Nutritional and vitamin deficiencies
- Environmental factors
- Toxic factors
 It is very likely that several noxious stimuli interact on a genetically susceptible host
to produce anencephaly.
Epidemiology:
- The incidence of anencephaly approximates 1/1,000 live births
- The greatest incidence is in Ireland, Wales, and Northern China.
- The recurrence risk is approximately 4% and increases to 10% if a couple has had
two previously affected pregnancies.
- The incidence of anencephaly has been decreasing in the past 2 decades.
- Approximately 50% of cases of anencephaly have associated polyhydramnios.
- Couples who have had an anencephalic infant should have successive pregnancies
monitored, including amniocentesis, determination of AFP levels, and ultrasound
examination between the 14th and 16th wk of gestation.
Course and Prognosis
- Most anencephalic infants die within several days of birth.
B. Disorders Of Neuronal Migration
Disorders of neuronal migration can result in minor abnormalities with little or no clinical
consequence (small heterotopia of neurons) or devastating abnormalities of CNS structure
and/or function (mental retardation, seizures, lissencephaly, and schizencephaly, particularly the
open-lip form). One of the most important mechanisms in the control of neuronal migration is the
radial glial fiber system that guides neurons to their proper site. Migrating neurons attach to the
radial glial fiber and then disembark at predetermined sites to form, ultimately, the precisely
designed six-layered cerebral cortex. Another important mechanism is the tangential migration
of progenitor neurons destined to become cortical interneurons. The severity and the extent of
the disorder are related to numerous factors, including the timing of a particular insult and a host
of environmental and genetic contributors.
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Lissencephaly
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Lissencephaly, or agyria, is a rare disorder that is characterized by the absence of cerebral
convolutions and a poorly formed sylvian fissure, giving the appearance of a 3-4 mo fetal
brain.
Etiology:
- The condition is probably a result of faulty neuroblast migration during early
embryonic life and is usually associated with enlarged lateral ventricles and
heterotopias in the white matter.
- In some forms, there is a four-layered cortex, rather than the usual six-layered one,
with a thin rim of periventricular white matter and numerous gray heterotopias visible
by microscopic examination.
- Doublecortinis, an X chromosome gene that causes lissencephaly when mutated in
males and subcortical band heterotopia when mutated in females.
Clinical Features:
- These infants present with failure to thrive, microcephaly, marked developmental
delay, and a severe seizure disorder.
- Ocular abnormalities are common, including hypoplasia of the optic nerve and
microphthalmia.
- Lissencephaly can occur as an isolated finding, but it is associated with Miller-Dieker
syndrome (MDS) in about 15% of cases.
 These children have characteristic faces, including a prominent forehead,
bitemporal hollowing, anteverted nostrils, a prominent upper lip, and
micrognathia.
 About 90% of children with MDS have visible or submicroscopic
chromosomal deletions of 17p13.3.
 The gene LIS-1 (lissencephaly 1) that maps to chromosome region 17p13.3
is deleted in patients with MDS.
- Other important forms of lissencephaly include the Walker-Warburg variant and other
cobblestone cortical malformations.
Examinations:
- CT and MRI scans typically show a smooth brain with an absence of sulci.
Schizencephaly
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Schizencephaly is the presence of unilateral or bilateral clefts within the cerebral
hemispheres owing to an abnormality of morphogenesis.
The cleft may be fused or unfused.
There is notable absence of cerebralsulci iand the mal-developed sylvian fissure as
associated with enlarged ventricles.
Unilateral schizencephaly shown, if unilateral and large, may be confused with a
porencephalic cyst.
Not infrequently, the borders of the cleft are surrounded by abnormal brain, particularly
microgyria.
Etiology:
- It remains controversial whether genetic causes of schizencephaly exist.
Examination tools:
- MRI is the study of choice for elucidating schizencephaly and associated
malformations.
Clinical Features:
- Many patients are severely mentally retarded, with seizures that are difficult to
control, and microcephalic, with spastic quadriparesis when the clefts are bilateral.
- Some cases of bilateral schizencephaly are associated with septo-optic dysplasia
and endocrinologic disorders.
- Unilateral schizencephaly is a common cause of congenital hemiparesis.
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Neuronal Heterotopias
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Subtypes of neuronal heterotopias include:
- Periventricular nodular heterotopias
- Subcortical heterotopia (including band-type)
- Marginal glioneuronal heterotopias
Etiology:
- Several genes have been identified that are a cause of these conditions.
Clinical Features:
- Intractable seizures are a common feature.
Polymicrogyrias
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Polymicrogyria is characterized by an augmentation of small convolutions separated by
shallow enlarged sulci.
Etiology:
- Several genes have been identified that cause several of the forms of this condition.
Clinical Feature:
- Epilepsy, including drug-resistant forms, is a common feature.
Focal Cortical Dysplasias
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Focal cortical dysplasias consist of abnormal cortical lamination in a discrete area of cortex.
High-resolution, thin-section MRI can reveal these areas sometimes in the setting of drugresistant epilepsy.
Porencephaly
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Porencephaly is the presence of cysts or cavities within the brain that result from
developmental defects or acquired lesions, including infarction of tissue.
True porencephalic cysts are most commonly located in the region of the sylvian fissure and
typically communicate with the subarachnoid space, the ventricular system, or both.
They represent developmental abnormalities of cell migration and are often associated with
other malformations of the brain, including microcephaly, abnormal patterns of adjacent gyri,
and encephalocele.
Pseudoporencephalic cysts characteristically develop during the perinatal or postnatal
period and result from abnormalities (infarction, hemorrhage) of arterial or venous
circulation.
These cysts tend to be unilateral, do not communicate with a fluid-filled cavity, and are not
associated with abnormalities of cell migration or CNS malformations.
Clinical Features:
- Affected infants tend to have many problems, including mental retardation, spastic
hemiparesis or quadriparesis, optic atrophy, and seizures.
Etiology:
- Mutations in the COL4A1gene have been described in cases of familial
porencephaly.
Risk Factors:
- Several risk factors for porencephalic cyst formation have been identified including:
 hemorrhagic venous infarctions
 various thrombophilias such as protein C deficiency and factor V Leiden
mutations
 perinatal alloimmune thrombocytopenia
 von Wille-brand’s disease
 maternal warfarin use
 maternal cocaine use
 congenital infections
 trauma such as amniocentesis
 maternal abdominal trauma
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