Familial Porencephaly

Heterogenous group of extremely rare familial malformative disorders characterized by intracerebral cerebrospinal fluid (CSF)-filled cavitations associated with various malformations and neurologic impairments.

Infantile Hemiplegia with Porencephaly.

Type I: encephaloclastic porencephaly; Type II: schizencephalic porencephaly.

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.

An autopsy review showed an incidence of 22:1000 infants with intracerebral injuries.

Infantile hemiplegia with porencephaly is transmitted as an autosomal dominant trait.

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.

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.

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.

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 because any respiratory depression further compromises cerebral perfusion.

Carefully position the hemiplegic or tetraplegic patient to prevent trauma to the spastic limbs. Neuromuscular junction monitoring should be performed on the unanalyzed limb, to prevent administration of excessive doses of muscle relaxants. In spastic tetraplegic patients with respiratory muscle involvement, problems of weaning from artificial ventilation postoperatively may occur. The anesthetic technique for patients with raised intracranial pressure should consider a smooth induction with total control of the hemodynamic changes. Rapid reversibility of the effects of anesthetics must be considered so that an adequate neurologic assessment may be performed at the end of the operation. In addition, perioperative institution of cerebral protective maneuvers (such as mannitol and hyperventilation) must be evaluated.

Hemiplegia has been associated with resistance to nondepolarizing muscle relaxants and hyperkalemia following the administration of succinylcholine. Tetraplegia, on the other hand, is known to have increased sensitivity to nondepolarizing muscle relaxants in the affected muscles. The intravenous induction anesthetic agents decrease intracranial pressure via a reduction in the cerebral metabolic rate and blood flow. Ketamine remains the exception because it increases both cerebral blood flow and cerebral oxygen consumption. Volatile inhalational agents are potent cerebrovasodilators and cause uncoupling of the relationship between cerebral blood flow and cerebral metabolic rate. Narcotics should be administered with care because they result in some degree of respiratory depression and increase CSF production, which may have significant effects on intracranial pressure. Succinylcholine is contraindicated in the presence of hemiparesis or quadriparesis.

Bonnemann Meinecke Syndrome (Porencephaly-Cerebellar Hypoplasia-Internal Malformations Syndrome): Autosomal recessive disorder characterized by bilateral porencephaly, cerebellar hypoplasia (including absence of the vermis), and internal malformations, including severe congenital heart anomalies (e.g., tetralogy of Fallot, total situs inversus, atrial septal defect). In cases of extensive bilateral porencephaly, the term “basket brain” has been coined, referring to the remaining parasagittal tissue that gives the brain the appearance of a basket with a handle.