Transcript 2013 Malformations

CNS Malformations
Ben Bly
2013
I am posting Eric Adelman’s slides which
were much better than mine.
Cavum Septum Pellucidum
Normal finding
Arachnoid Cysts
• Pocket of fluid within
arachnoid
• Walls are arachnoid
membrane
• Occur close to cisterns,
often near sylvian
fissure
– Do not communicate
with CSF spaces
– Present in 0.5% at
autopsy
Arachnoid Cysts
• Clinical Findings
– Asymptomatic
– Global disturbances
• Headache, signs/symptoms of increased ICP, enlarged
HC, seizures, developmental delay
– Focal neurologic symptoms related to location
• Treatment
– If symptomatic: surgical decompression, shunt
Arachnoid cyst
Porencephaly
• Porencephalic cysts = cavity
within brain parenchyma
– Injury during development
• Infarct / trauma
– Or faulty induction and
neuronal migration
• Smooth walls, radially
oriented gyri
• May be in distribution of a
cerebral artery
• May or may not
communicate with ventricle
• May require shunting if
enlarging or progressive
RITE 2008: question 318
Porencephaly
Hydranencephaly
• Complete or near complete
destruction of cerebral
hemispheres with extreme
dilation of ventricles
• Catastrophic injury to brain
< 28 weeks gestation
• Multiple possible causes: in
utero carotid occlusion,
CMV or toxoplasma
infection
• Unlike anencephaly,
cranium is intact
Mega Cisterna Magna
aka Retrocerebellar Arachnoid Pouch, Blake’s Cyst
• Enlarged cisterna
magna
• Communicates with
subarachnoid spaces
• Posterior fossa = normal
size
• Unlike arachnoid cysts:
– No mass effect on 4th
ventricle
Mega Cisterna Magna
• ?Normal Variant
• Often an incidental finding
Dandy Walker Malformation
Core features:
• Absence (partial or
complete) of the
cerebellar vermis
• Cyst like dialation of the
4th ventricle
Commonly present:
– Cerebellar hemispheres
underdeveloped,
displaced superiorly
– Hydrocephalus
RITE 2008 question 317
Dandy Walker Malformation
Dandy-Walker Malformation
Dandy Walker Malformation
Clinical Findings
• Usually evident in infancy
• Apnea, hypo/hypertonia, motor delays, nystagmus,
titubation, hydrocephalus
• Sudden unexpected death, without herniation (vascular
compromise from local ICP increases?)
• Treatment
• Cysto-/Ventriculo- peritoneal shunt
• Many associated syndromes
Walker-Warburg Syndrome
• Dandy-Walker plus ocular Abnormalities
– On 9q31, likely AR
Other features:
• Hydrocephalus
• Lissencephaly
Craniorachischisis
Neural tube closure defects
• Neural plate is
converted into a
closed neural tube
during 3-4th weeks of
development
Neural tube closure defect
• Craniorachischisis:
– Most severe type of
NTD in which brain and
spinal cord are exposed
to amniotic fluid and
undergo degeneration
– May have well
developed forebrain
and optic nerves
Myelomeningocele
Neural Tube Closure Defects
• Myelomeningocele:
– 95% associated with Chiari II malformations,
hydrocephalus may occur
– Malformations in spinal cord above the defect are
common
Anencephaly
• Absence of both
cerebral hemispheres
• Failure of neural tube to
close anteriorly
• Infants are stillborn or
die shortly after birth
RITE 2010 question 319
Neural Tube Closure Defects
• Anencephaly:
– Absent or hypoplastic calvarium, “bat wing”
deformity of sphenoid bone, only minimal cranial
nerves II-V are present,
pons/cerebellum/midbrain are grossly absent,
aplasia of descending tracts
– May be associated with visceral anomalies
including a large thymus and hypoplastic lungs
Anencephaly
Encephaloceles
• Herniation of
intracranial contents
through a skull defect
• Fluctuant balloony mass
covered by a membrane
or normal skin, may
pulsate
• Occipital 75%, Frontal
25%
• Seen with other
malformations and in
syndromes
Encephalocele
Neural tube closure defects
• Encephalocele:
– In anterior version, herniation occurs through frontoethmoidal junction and appears as hypertelorism or bulging
tissue
– May expand into nasal cavity (30%), pharynx, or orbit
– Seen in 90% of patients with Meckel-Gruber syndrome
• MG Syndrome –AR, lethal renal dysplasia, CNS malformations,
polydactyly, pulmonary hypoplasia, hepatic developmental problems
Defective prosencephalization
Forebrain develops between 25-30 days
gestation from a midline vesicle that is
generated from the closed anterior neuropore.
Holoprosencephaly
Holoprosencephalic children
Hypoteloric
Proboscis
RITE 2010: question 310
Holoprosencephalic
cat
Holoprosencephaly
• Defective clevage
• No division of prosencephalon (forebrain)
– No interhemispheric fissure
– Telencephalon = single lobe
– No olfactory bulbs or tracts
– Absence of midline structures
Holoprosencephaly
Craniofacial dysplasia
• Cyclopia (single median eye)
• Ethmocephaly: nose replaced by a proboscis
located above hypoteloric eyes
• Cebocephaly: hypotelorism and a nose with a
single nostril
• Premaxillary agenesis: hypotelorism, flat nose,
midline cleft lip
Holoprosencephaly
• Failure of prosencephalon to cleave into
symmetric cerebral hemispheres
• Variable severity
• Alobar
• Semilobar
• Lobar
Semilobar Holoprosencephaly
• Some differentiation of hemispheres,
posteriorly
• Diencephalon/Forebrain still fused in midline
Semilobar Holoprosencephaly
Lobar Holoprosencephaly
• Hemispheres separated (interhemispheric
fissure present)
• Absent septum pellucidum
• Fused thalami
• Diffuse pachygyria
• Interdigitation of frontal gyri
Lobar Holoprosencephaly
Agenesis of the Corpus Callosum
Agenesis of the Corpus Callosum
• Corpus Callosum forms front to back;
myelinates back to front
• If CC is partially absent, most likely posterior
portion
• Anterior part alone can be absent in
holoprosencephaly, frontal schizencephaly, frontal
porencephalic cysts
• Thin CC: insult after completely formed (like
PVL)
Agenesis of the
Corpus Callosum
Agenesis of the Corpus Callosum
RITE 2008: question 254; RITE 2009 question 269
Schizencephaly
• Clefts in the cerebral hemispheres
• Flawed development of cortical mantle during
cell migration in first trimester
• Genetic vs. acquired
Schizencephaly
• Most clefts near sylvian fissures
• Clefts extend from surface of cortex into a
ventricle
• Neighboring gyral pattern abnormal
• Lips are formed by dysplastic gray matter
– (Porencephalic cyst lined by white matter)
Schizencephaly
• Open Lip: Lips of cleft are separated by CSF
• Closed Lip: Lips of cleft are in contact
Closed Lip Schizencephaly
Closed Lip Schizencephaly
Open Lip Schizencephaly
Schizencephaly
Clinical Findings
• Often presents with seizures
• Can be focal or generalized; infantile spasms
• Hemiplegia
Hemimegalencephaly
• Brain volume increased from errors in
neuroepithelial proliferation
• Histology: increase in number of cells
(neurons and glia) and cell size
• Association of hemimegalencephaly with
neuro-cutaneous disorders
– Linear sebaceous nevus syndrome and
hypomelanosis of Ito
Hemimegalencephaly
• Macrocephaly at birth
• May have accelerated head growth in first few
months of life
• Present with seizures, developmental delay,
hemiparesis, hemihypertrophy
• Seizures sometimes require hemispherectomy
or callosotomy
Hemimegalencephaly
Joubert Syndrome
• Molar Tooth Sign
• Complete agenesis of
cerebellar vermis
• 4th ventricle enlarged
(batwing shape)
• Other cerebral
malformations,
especially occipital
encephaloceles
Joubert Syndrome
Chiari Malformation
Chiari Malformations
Chiari I
Extension of cerebellar tonsils (sometimes
posterior vermis) into upper cervical canal
• Associated with syrinx
Chiari II
Displacement of cerebellar vermis (? medulla) in upper
cervical canal
• Associated with lumbar myelomeningocele
Chiari III
Occipital encephalocele
Chiari IV
Absence of cerebellum
Chiari I with Syrinx
Chiari III
Lissencephaly
• Disorder of neuronal migration
• Abnormal migration of post-mitotic neurons
from the ventricular zone to form the cortical
plate
• Smooth cerebral surface: absence of gyri,
abnormally thick cortex, abnormal
lamination
Lissencephaly
Defects of cellular migration
Miller-Dieker syndrome
– Lissencephaly
– Microcephaly
– Characteristic facies
• Upturned nares,
micrognathia, high
forehead, thin upper
lip, low set ears
– Deletion on
chromosome 17
X-linked defects of cellular
migration (DCX mutation)
Boys
• Lissencephaly
Girls
• Subcortical band
heterotopia
– Gray matter in the wrong
places
RITE 2009: question 257
Polymicrogyria
• Too many small abnormal gyri
• Convolutions may not have sulci, or sulci
might be bridged by fusion of overlying
molecular layer which may give smooth
appearance on surface
• Gray-white interface not distinct
Polymicrogyria
Clinical findings depend on extent of
abnormality
• Diffuse: severe developmental delay and
hypertonia
• Focal deficits if focal
• Seizures common
Heterotopias
• Collections of normal-appearing neurons in an
abnormal location
• Proposed mechanisms
• Damage to radial glial fibers
• Premature transformation of radial glia into astrocytes
• Radial glial surface molecule deficiency
• Isolated/multiple/diffuse
• Usually no cause apparent
Heterotopias
• Periventricular Nodular Heterotopias
– X-linked dominant (females only, lethal in males)
– Filamin A, aka Filamin 1
– Failure of neuronal migration at an early stage
from ventricular zone
– Filamin A anchors membrane proteins to actin
cytoskeleton
Mobius syndrome
Facial diplegia,
bilateral abducens
palsy, often
involvement of other
lower cranial nerves
– Pathogenesis:
selective ischemia of
midline and
paramedian zones of
developing brainstem