Sporadic porencephaly is a rare disorder affecting the central nervous system. In porencephaly, cysts or cavities form on the surface of the brain. These cysts or cavities may become filled with cerebrospinal fluid, a colorless fluid that normally surrounds the brain and spinal cord to provide protection and nourishment. The severity and associated symptoms of porencephaly vary dramatically from one person to another based upon the size and exact locations of the fluid-filled cavities or cysts. Some infants develop serious complications shortly after birth; others individuals may have mild symptoms that may go undetected.
Porencephaly may be classified as sporadic or familial. Sporadic porencephaly can have many different causes including infection just before or just after birth (perinatal infection), trauma, maternal disease or sickness, maternal diabetes, or maternal use of alcohol or drugs such as cocaine during pregnancy. A distinct genetic form of porencephaly (not covered in this report) occurs due to mutations of the COL4A1 gene.
The terminology regarding porencephaly used in the medical literature has caused confusion. Some researchers break down porencephaly into type I (also known as encephaloclastic porencephaly) and porencephaly type II (also known as schizencephaly).
The symptoms and severity of sporadic porencephaly vary greatly from one individual to another based on the size and exact location of the fluid-filled cyst or cavity. Some individuals may only have minor physical complications and intelligence may be unaffected; others can have severe, disabling complications.
Symptoms that can potentially develop in association with porencephaly include delays in growth and development, diminished muscle tone (hypotonia), seizures, and microcephaly or macrocephaly, conditions in which head circumference is either smaller (micro) or larger (macro) than would be expected in a child based upon age and weight.
Additional findings that have been reported with porencephaly include poor speech development or absent speech, paralysis of one side of the body (hemiplegia), abnormal tightening or shortening of certain muscles, resulting in restricted or stiff movements (contractures) and varying degrees of intellectual disability. Some individuals develop hydrocephalus, a condition in which accumulation of excessive cerebrospinal fluid in the skull causes pressure on the tissues of the brain, resulting in a variety of symptoms.
Sporadic porencephaly is caused by damage to the cerebral hemispheres of the brain, which results in the formation of fluid-filled cavities or cysts on the surface of the brain. Researchers believe that the damage or loss of brain tissue that characterizes porencephaly results from infection, interrupted or obstructed blood flow (ischemia) to the brain, or bleeding (hemorrhaging) in the brain.
A variety of different conditions can potentially cause the localized brain tissue degeneration that ultimately leads to sporadic porencephaly. Such conditions include infection just before or shortly after birth (perinatal infection), too little oxygen in the body just before or shortly after birth (perinatal asphyxia), birth trauma, drug or alcohol use by the mother during pregnancy, maternal sickness or infection, maternal diabetes, or injury or trauma (particularly to the abdominal area) to the mother during pregnancy.
A few, rare cases, were associated with performance of diagnostic techniques known as amniocentesis and chorionic villus sampling. Amniocentesis and chorionic villus sampling may be performed during pregnancy to detect certain problems in a fetus such as chromosomal abnormalities or certain genetic disorders. During an amniocentesis procedure, a small amount of amniotic fluid is removed from the sac that surrounds the fetus and studied. During chorionic villus sampling, tissue is removed from the placenta and certain cells called chorionic villi are studied.
Disorders that increase the bleeding tendency in newborns have also been linked to porencephaly. These disorders include neonatal alloimmune thrombocytopenia, von Willebrand’s disease, and maternal use of the drug warfarin (a blood thinner). Neonatal alloimmune thrombocytopenia is a disorder in which antibodies from the mother attack a newborn’s platelets (cells that assist in forming blood clots). Von Willebrand’s disease is an inherited bleeding disorder that results in prolonged bleeding.
Most cases of porencephaly are sporadic and the risk of recurrence in subsequent pregnancies is unlikely. However, in some cases, genetic factors may play a role in the development of porencephaly. For example, porencephaly is believed to occur with greater frequency than in the general population in individuals with disorders that promote excess blood clotting (thrombophilias). Such disorders include factor V Leiden or protein C deficiency.
A specific form of porencephaly, known as autosomal dominant porencephaly type I, is a rare disorder caused by mutations of the COL4A1 gene located on chromosome 13 (see Related Disorders below).
The exact incidence of sporadic porencephaly in the general population is unknown. Some researchers believe that some cases may go undiagnosed or misdiagnosed, making it difficult to determine the disorder’s true frequency in the general population. Sporadic porencephaly affects males and females in equal numbers.
A diagnosis of sporadic porencephaly can be made before or after birth through a variety of specialized imaging tests such as an ultrasound, computed tomography (CT) scan, or magnetic resonance imaging (MRI). During an ultrasound, reflected sound waves are used to make an image of the developing fetus. During CT scanning, a computer and x-rays are used to create a film showing cross-sectional images of certain tissue structures. An MRI uses a magnetic field and radio waves to produce cross-sectional images of particular organs and bodily tissues.
The treatment of sporadic porencephaly is geared toward the specific symptoms that are present in each individual. Treatment may include physical therapy, speech therapy, anti-convulsant medications for seizures, and a shunt to treat hydrocephalus by draining excess fluid from the skull.
Early intervention is important in ensuring that children with sporadic porencephaly reach their highest potential. Services that may be beneficial for some affected individuals include medical, social, and/or vocational services such as special remedial education.
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