Glossary in Congenital Malformations
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A B C D E F G H I J K L M N O P Q R S T U V W X Y Z
#Malformation: a morphological defect, including absence, of an
organ, or larger region of the body resulting from an intrinsically abnormal
phenomenon (jaw-winking): this is
a congenital phenomenon that is characterized by
elevating or drooping eyelids associated with jaw movement, smilling,
swallowing, or speaking; can be acquired or congenital. It is thought to be due
to misconnection between the third and fifth, and other cranial nerves. See also
anormalous axonal connection (guidance) syndromes,
#Macrocephaly (megalocephaly): excessive occipitofrontal circumference without
regard to cause or brain size.
#Membranis reuniens dorsalis
of von Recklinghausen: During
closure of the vertebral column, the dorsal part of the spinal cord is first
composed of a mass of connective tissue and cartilage. The two lateral processes
grow medially and eventually fuse. The membranis renuiens dorsalis of von
Recklinghausen is the deepest part of this tissue mass that separates the spinal
cord from the overlying connective tissue and epithelium.
#Meningocele: Herniation of the meninges through a defect in the
cranium or vertebral column.
this includes atretic meningocele, heterotopic neural rest, ectopic glial
tissue, congenital head tumor, epicranial arachnoidal cyst, primary cutaneous
meningioma, and meningocele without
central connection. They are not attached to cerebral structures. They are
more commonly seen in the head than in the spine. Typically, they appear either
as small skin-covered plaques or nodules without
either hair or skin appendages and lack
neuronal and glial elements. They may become cystic despit not connected to
the spinal canal or the absence of choroid plexus.
#Meningomyelocele: Both meninges and spinal cord herniate thorugh a
large vertebral defect. The spinal cord or nerve roots are frequently involved
in the formation of the wall and the dorsal part of the spinal cord often
remains open. Meningomyelocele above T12 have increased tendency to be
associated with malformations in other systems whereas lower meningomyeloceles
#Metopic: relating to the forehead or anterior portion of
#Microencephaly: Abnormally small head.
#Microdysgenesis: Subtle structural abnormalities of cortical
#Microgyria: Microgyria is characterized by small gyri. The
underlying cortex is normal and there is no fusion of molecular layer between
two adjacent gyri.
#Micromelia: Abnormally small and short limbs.
#Multicystic encephalopathy: multiple cortical and subcortical cystic spaces
secondary to necrosis. The spaces are lined by gliotic tissue. The surrounding
tissue generally shows varying degrees of ischemic-hypoxic-type lesions
associated with cytoarchitectonic abnormalities.
#Muscle-eye-brain syndromes: These syndromes are characterized by a variety of
cerebral and/or cerebellar cortical malformation, abnormal cortical vascular
architecture, and congenital muscular dystrophy. The eyes are frequently
affected. They include, in decending order of severity, Fowler syndrome, Walker-Warburg
syndrome, Fukuyama congenital muscular dystrophy, and muscle-eye-brain disease
of Santavuori. In common, they have smaller than normal brain, abnormal cerebral
cortical vessels and abnormalities in muscle. Neuronal migration disorders are
#Myelocystocele: a localized, cystic dilation of the central canal
of the spinal cord that may be associated with dorsal or ventral meningoceles of
the cervicothoracic or lumbroscral spine.
#Myelodysplasia: Myelodysplasia may be due to imperfect closure of
the neural plate but it can also be present in a closed spinal cord.
Histologically, there is a variety of anomalies in the area of the central canal
and in the white and gray matters, although more or less complete closure of the
neural plate had taken place. The more common clinical features include
persistent enuresis, mild sensory disturbances in the lower portions of the body
and inconspicuous reflex anomalies.
#Myeloschisis: cleft spinal cord resulting from failure of the
neural folds to close normally in the formation of the neural tube, inevitably
spina bifida is a sequel. The open neural plate ("open book"
neuroplate) is not covered by skin, meninges, or vertebral arch.
Syndromes and Sequences: Head
#Meckel-Gruber Syndrome (Meckel
Autosomal recessive and is lethal. It
seems that the mutant gene in Merkel-Gruber syndrome is variable. This condition
is a neural tube defect. It consists of a variable cranial and CNS malformation
with or without cranial rachischisis and occipital encephalocele, microcephaly,
and eye anomalies with cystic dysplasia of the kidneys and malformation of other
organs with the most consistent ones include hepatic fibrosis, hepatic "ductal
plate malformation" and severe hypoplasia of the male genitalia associated
Definition of Meckel-Gruber syndrome: "cystic kidney dysplasia plus at least two
other defects which include relevant anomalies of brain (usually), heart, liver,
genitalia, spleen, eye, urinary system or lip”.
CNS malformations: the
most common "triad" includes prosencephalic dysgenesis, occipital
encephalocele, and rhombic roof dysgenesis. Other neuronal migration defects are
also common. The most consistent findings include:
arhinencephaly-holoprosencephaly and other midline anomalies,
taking the form of extrusion of parts of the rhombic roof through the posterior
notably supracerebellar cyst, vermal agenesis, stenosis of the aqueduct and
flattening and dysplasia of the brain stem.
#Miller-Dieker Syndrome (17p syndrome):
Miller-Dieker syndrome is a migration disorder characterized by lissencephaly.
Deletion or translocation of chromosome 17p13.3 is the salient feature, however,
Miller-Dieker syndrome is a continuous gene syndrome and probably involves
deletion of more than one gene. It typically comes with characteristic facial
dysmorphism and other features. The critical gene is PAFAH1B1 (b-subunit of platelet activating factor
acetylhydrolase, brain isoform Ib; formerly known as lissencephaly-1 or LIS1),
located on a 350 kb critical region on chromosome 17p13.3. The most common
genetic abnormality is complete deletion. The deletion is heterogenous, that
means half the dosage of the gene product is not sufficient for normal
development. This gene is related to Miller-DIeker syndrome and isolated
lissencephaly syndrome. See also isoloated lissencephaly sequence.
the infants are often severely spastic, with infantile spasm, and oblivious to
their envrionement, and profound mental retardation. Usually die in the first
two years of life. Characteristic facial dysmorphism with bitemporal hollowing
and small jaw, short nose withupthurned nares, and a long and protuberant upper
lip with thin vermillion border and relatively flattened midface. Other
malformations may also be seen.
the spectrum varies from diffuse agyria to frontal pachygyria with
parietooccipital agyria to diffuse pachygyria. Typically the posterior part of
the brain, in contrast to X-linked lissencephaly, is more affected. Large
ventricles, and sometimes, ventricular heteropia are also seen.
the cerebral cortex show abnormal architecthre. They may have a molecular layer,
then a broad band where cortical neurons show a marked radial arrangement, then
deep to that a band of neurons randomly arranged. The inferior olivary nuclei
are poorly convoluted, and heterotopic remnants of these nuclei lie in the
migrator track of these nuclei from the rhombic lip whtere the young olivary
neurons are generated. Cerebellum may show mild dysplasia, subcortical Purkinje
cell heterotopias, and Purkinje cell lost.
Syndrome: a congenital facial paralysis characterized by
facial diplegia (facial paralysis) typically associated with bilateral abducens
palsy (internal strabismus) and, occasionally, with involvement of several
cranial nerves, especially the lower cranial pairs. Möbius
syndrome has been used to describe a variety of heterogenous syndrome with
features of 6th and 7th cranial nerve palsy. But according to Margret Norman's
book, the term Möbius
syndrome should only be used in patients with bilateral 6th and 7th cranial
nerve palsy that is fully conscious, have no central respiratory depression, and
in whom limb or muscle defects are absent or minimal. The etiology of Möbius syndrome is unknown. In most cases it probably
is the result of a focal destructive lesion in the brain stem that may be
resulted from hypoxic-ischemic, hemorrhagic or even thromboembolic. The combined
presentation of 6th and 7th nerve palsy may be resulted from the close location
of these two cranial nerve nuclei. Also, the 7th nerve wraps around the abducen
#Multiple lethal pterygia
syndrome: joints are fixed and skin webs form at the fixed
joint. A pterygium can form at a single joint or at more than one joint and not
be lethal. Pterygia form when the age of onset is between 9 to 12 weeks.
This is a migration disorder. A rare, lethal, probably autosomal recessive
syndrome comprising severe intrauterine growth retardation, extreme microcephaly
(the size of the brain is about 1/10 to 1/20 of normal), characteristic
grotesque facies, flexion deformities of the limbs, short neck, scaly skin
(sometimes described as ichthyosis or hyperkeratosis), edema of hands and feet,
and hypoplasia of various organs. CNS
the brain is smooth or has mild grooving. Many structures are poorly developed
or rudimentary, these include the hippocampus, olfactory and optic nerves, roof
of the third and fourth ventricles, spinal cord, and cerebellum. The cortical
neurons are small and closely packed and have failed to grow or mature and there
is a paucity of primitive neuroectodermal cells in the subependymal regions.
Corpus callosum is usually absent.
may be resulted from excessive or premature cell death in the ventricular zone.
NeuroLearn NeuroHelp Malformations General Syndromes For Comment: KarMing-Fung@ouhsc.edu