NeuroLearn NeuroHelp Malformations
Background Neuroimaging Gross Pathology Histopathology & Immunohistochemistry Differential Diagnosis
BACKGROUND AND CLINICAL INFORMATION:
Head
Summary: The three essential features are: agenesis of the
vermis, cystic dilatation of the fourth ventricle and enlargement of the
posterior fossa. Hydrocephalus is a frequent but inconstant finding.
Clinical features: The clinical manifestations of Dandy-Walker
syndrome are mainly those of hydrocephalus. Therefore, the diagnosis is made in
75% of cases after 3 months of age and often only by the first birthday, as
hydrocephalus usually becomes apparent by 1 year of age. Remarkably, there is no
cerebellar sign or disturbances of stance. Mental retardation is present in
30-50% of patients.
Prognosis: Prognosis is guarded and the mortality is about
27%.
Other cerebral and visceral
anomalies: it is the presene or absence of other cerebral and
viseral abnormalies that determines the prognosis of individuals. About 68% of
all cases have other developmental abnormalities of the CNS. Facial
abnormalities may also be seen.
Pathogenesis: agenesis of the vermis and cystic dilatation of
the fourth ventricle may be the two primary events. Obstruction of the foramina
of Magendie and Luschka may not be present in every cases. Other features may be
secondary to the primary events.
Prognosis: Mortality varies from 12.6% to 57%; IQ of 71% of
patients are less than 83 with no significant relationship between retardation
and associated anomalies.
Posterior fossa cyst in communication with the fourth ventricle, absence of vemian tissue, and an abnormally high insertion of the tentorium.
Dandy-Walker
syndrome as defined by Benda (1954), the person who introduced the term
"Dandy-Walker syndrome", it has six features. Not all six features are
found in each case.
a
cyst-like dilation of the fourth ventricle,
an
abnormal cerebellar vermis,
elevation
of the tentorium cerebelli and lateral and transverse sinuses and torcula (torcular
Herophilli),
lack
of patency of the foramina of Magendie and Luschka,
enlargement
of the posterior fossa,
hydrocephalus.
In
most cases, the supreior vermis may be present but the inferior vermis is
attenuated and blends with the membranous roof of the cystic fourth ventricle.
Dilatation of the lateral and third ventricle (but
to a lesser extent the fourth ventricle.
Widely
separated, hypoplastic cerebellar hemispheres, with a small
hypoplastic vermis, and rostral displacement.
Enlarged posterior fossa with high tentorium
cerebelli and transverse sinuses.
Thin
transparent membrane containing ependymal cells and occasionally cerebellar
tissue in the fourth ventricle which replaces the vermis.
Associated with the agenesis of corpus callosum.
HISTOPATHOLOGY AND IMMUNOHISTOCHEMISTRY:
Head
The cyst membrane has two layers: an outer fibrous leptomeningeal layer and an inner glio-ependymal layer sometimes including cerebellar remnants.
May be confused with a posterior fossa cyst. Identification of vermian agenesis or hypoplasia will be helpful for diagnosing Dandy-Walker syndrome.
NeuroLearn NeuroHelp Malformations For Comment: KarMing-Fung@ouhsc.edu
Background Neuroimaging Gross Pathology Histopathology & Immunohistochemistry Differential Diagnosis