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Heterogenous group of extremely rare familial
malformative disorders characterized by intracerebral cerebrospinal fluid (CSF)-filled cavitations
associated with various malformations and neurologic impairments.
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Infantile Hemiplegia with Porencephaly.
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Type I: encephaloclastic porencephaly; Type II:
schizencephalic porencephaly.
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A developmental defect of the brain, porencephaly is
defined as any cavitation or CSF-filled cyst in the brain that communicates
directly with the ventricular system. It may occur prenatally or
postnatally. Berg et al. provided the first description of familial
porencephaly in 1983.
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An autopsy review showed an incidence of 22:1000 infants
with intracerebral injuries.
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Infantile hemiplegia with porencephaly is
transmitted as an autosomal dominant trait.
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Type I, or encephaloclastic porencephaly, is an acquired and usually unilateral
condition thought to occur in the third trimester. It can result from fetal
vascular occlusion, birth trauma, ventricular puncture, inflammatory
processes, coxsackie virus infection, hemorrhage, or embolism. Type II, or schizencephalic porencephaly, usually
is symmetrical, is thought to occur during the second trimester, and
represents a primary defect in morphogenesis of the neuroectoderm. Later
findings indicate that deficiencies in the protein C anticoagulant pathway
have an important role in the etiology of congenital porencephaly.
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Prenatal and postnatal ultrasonography and MRI can
demonstrate characteristic images of porencephaly. Cranial transillumination
may be positive. Types I and II are distinguishable both anatomically and
histopathologically. Type I usually presents as a unilateral cyst, whereas
type II usually is bilateral, located around the sylvian fissure, and often
communicating with the lateral ventricles. Angiographically, type I
porencephaly shows preexisting vessels, which cross the cavitation, whereas
type II is noted for the continuity between the cortical vessels and the
subependymal vessels. Histologic findings in type I reveal that the cavity
is lined by a cicatricial glial membrane, whereas the type II cavity is
lined by ependymal tissue.
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Patients with infantile hemiplegia and
porencephaly usually present with permanent neurologic disabilities. Prognosis generally
depends on the extent of the lesion. In most patients, symptoms begin in the
first decade of life. A few patients develop only minor neurologic signs and
have normal intelligence. The character and etiology of porencephaly,
congenital or acquired, is diversiform and often difficult to recognize.
Classically, those with type I lesions have severe impairment, ranging from
mental retardation and seizures to spastic hemiparesis or tetraplegia and
blindness. Infants with type I cysts have a more variable course. The use of
cocaine during pregnancy is associated with a higher risk (four times
normal) of porencephaly. Progressive hydrocephalus may require a shunt
procedure.
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Detailed neurologic assessment,
documenting any raised intracranial pressure and the presence of other
neurologic deficits. Look for seizures, the presence of bulbar involvement,
feeding difficulties, and recurrent pulmonary aspiration syndrome. Evaluate
the respiratory system, especially in tetraplegic patients. Investigations
include complete blood count, serum electrolytes, arterial blood gas, and
chest radiography. Avoid sedative premedications in patients with raised
intracranial pressure ...