Hydrocephalus refers to an abnormal increase or accumulation of cerebrospinal fluid circulating in the subarachnoid space surrounding the brain and spinal cord, resulting in an abnormal increase in intracranial pressure. This is usually caused by an obstruction of cerebrospinal fluid flow in the ventricles or subarachnoid space at the base of the brain. In severe cases, excessive accumulation of cerebrospinal fluid may compress the brain and damage the medulla oblongata through the foramen ovale, leading to death. Pathology Increased intracranial pressure may cause brain atrophy, leading to brain damage and other complications. hydrocephalus is a Greek word meaning “watery brain”. Hydrocephalus is a common birth defect, occurring in 1 in 500 safe births, and is more common than Down syndrome or deafness. According to the NIH website, hydrocephalus affects an estimated 700,000 children and adults in the United States and is the most common pediatric brain surgery procedure. There are more than 180 different causes, one of the most common being cerebral hemorrhage that occurs with preterm birth. One of the most effective treatments for hydrocephalus, shunt surgery, was not developed until 1960. A shunt must be performed through brain surgery to access the patient’s brain, a procedure that itself can cause brain damage. It is estimated that 50% of people with shunts fail within 2 years and require another shunt procedure. Almost half of the children shunted have IQs below 80 on standardized IQ tests, and only half of children with hydrocephalus enter mainstream schools. In the United States, more than a billion dollars is spent annually on treating hydrocephalus, but it is still far less than research on other diseases such as juvenile diabetes. Symptoms Symptoms caused by increased intracranial pressure may include headache, vomiting, nausea, optic nerve papilloedema, drowsiness or coma. Increased intracranial pressure may lead to brain herniation of the temporal lobe or cerebellar tonsils, resulting in life-threatening brainstem atrophy. Etiology of hydrocephalus Hydrocephalus may be caused by weakened cerebrospinal fluid (CSF) flow, weakened reabsorption, or excessive production of cerebrospinal fluid. Normal intracranial pressure is the balance between cranial pressure and blood pressure, cerebrospinal fluid and parenchymal pressure (cranial pressure = cerebral pressure + cerebrospinal fluid pressure + blood pressure). The most common cause of hydrocephalus is obstruction of the flow of cerebrospinal fluid through the ventricular system and the subarachnoid space (e.g., stenosis of the cerebral aqueduct or interventricular foramina obstruction – foramina of Monro secondary to tumor, hemorrhage, infection or congenital malformation). infection or congenital malformation). Hydrocephalus may also be caused by an excess of cerebrospinal fluid (e.g., papilloma of choroid plexus).