this condition is called internal hydrocephalus and may result in increased csf pressure. the production of csf continues, even when the passages that normally allow it to exit the brain are blocked. consequently, fluid builds inside the brain, causing pressure that dilates the ventricles and compresses the nervous tissue. compression of the nervous tissue usually results in irreversible brain damage. if the skull bones are not completely ossified when the hydrocephalus occurs, the pressure may also severely enlarge the head. the cerebral aqueduct may be blocked at the time of birth or may become blocked later in life because of a tumor growing in the brainstem. treatments procedures baby recovering from shunt surgery hydrocephalus treatment is surgical, creating a way for the excess fluid to drain away. in the short term, an external ventricular drain (evd), also known as an extraventricular drain or ventriculostomy, provides relief. in the long term, some people will need any of various types of cerebral shunt. it involves the placement of a ventricular catheter (a tube made of silastic) into the cerebral ventricles to bypass the flow obstruction/malfunctioning arachnoidal granulations and drain the excess fluid into other body cavities, from where it can be resorbed. most shunts drain the fluid into the peritoneal cavity (ventriculoperitoneal shunt), but alternative sites include the right atrium (ventriculoatrial shunt), pleural cavity (ventriculopleural shunt), and gallbladder. a shunt system can also be placed in the lumbar space of the spine and have the csf redirected to the peritoneal cavity (lumbar-peritoneal shunt). an alternative treatment for obstructive hydrocephalus in selected people is the endoscopic third ventriculostomy (etv), whereby a surgically created opening in the floor of the third ventricle allows the csf to flow directly to the basal cisterns, thereby shortcutting any obstruction, as in aqueductal stenosis. this may or may not be appropriate based on individual anatomy. for infants, etv is sometimes combined with choroid plexus cauterization, which reduces the amount of cerebrospinal fluid produced by the brain. the technique, known as etv/cpc, was pioneered in uganda by neurosurgeon benjamin warf and is now in use in several u.s. hospitals. hydrocephalus can be successfully treated by placing a drainage tube (shunt) between the brain ventricles and abdominal cavity. some risk exists of infection being introduced into the brain through these shunts, as they must be replaced as the person grows. external hydrocephalus external hydrocephalus is a condition generally seen in infants which involves enlarged fluid spaces or subarachnoid spaces around the outside of the brain. this condition is generally benign, and resolves spontaneously by two years of age and therefore usually does not require insertion of a shunt. imaging studies and a good medical history can help to differentiate external hydrocephalus from subdural hemorrhages or symptomatic chronic extra-axial fluid collections which are accompanied by vomiting, headaches, and seizures. shunt complications examples of possible complications include shunt malfunction, shunt failure, and shunt infection, along with infection of the shunt tract following surgery (the most common reason for shunt failure is infection of the shunt tract). although a shunt generally works well, it may stop working if it disconnects, becomes blocked (clogged) or infected, or it is outgrown. if this happens, the csf begins to accumulate again and a number of physical symptoms develop (headaches, nausea, vomiting, photophobia/light sensitivity), some extremely serious, such as seizures. the shunt failure rate is also relatively high (of the 40,000 surgeries performed annually to treat hydrocephalus, only 30% are a person's first surgery) and people not uncommonly have multiple shunt revisions within their lifetimes. another complication can occur when csf drains more rapidly than it is produced by the choroid plexus, causing symptoms of listlessness, severe headaches, irritability, light sensitivity, auditory hyperesthesia (sound sensitivity), hearing loss, nausea, vomiting, dizziness, vertigo, migraines, seizures, a change in personality, weakness in the arms or legs, strabismus, and double vision to appear when the person is vertical. if the person lies down, the symptoms usually vanish quickly. a ct scan may or may not show any change in ventricle size, particularly if the person has a history of slit-like ventricles. difficulty in diagnosing over-drainage can make treatment of this complication particularly frustrating for people and their families. resistance to traditional analgesic pharmacological therapy may also be a sign of shunt overdrainage or failure. following placement of a ventriculoperitoneal shunt there have been cases of a decrease in post-surgery hearing. it is presumed that the cochlea aqueduct is responsible for the decrease in hearing thresholds. the cochlea aqueduct has been considered as a probable channel where csf pressure can be transmitted. therefore, the reduced csf pressure could cause a decrease in perilymphatic pressure and cause secondary endolymphatic hydrops. in addition to the increased hearing loss, there have also been findings of resolved hearing loss after ventriculoperitoneal shunt placement, where there is a release of csf pressure on the auditory pathways. the diagnosis of csf buildup is complex and requires specialist expertise. diagnosis of the particular complication usually depends on when the symptoms appear, that is, whether symptoms occur when the person is upright or in a prone position, with the head at roughly the same level as the feet. standardized protocols for inserting cerebral shunts have been shown to reduce shunt infections. there is tentative evidence that preventative antibiotics may decrease the risk of shunt infections. epidemiology the hydrocephalus disease burden are concentrated in the developing world while north america and canada has the least number of cases. a systematic review in 2019 estimated that there are 180,000 childhood hydrocephalus cases from african continent alone per year, followed by 90,000 cases from southeast asia and western pacific. latin america also has high prevalence of hydrocephalus. however, data on hydrocephalus disease burden in adults are lacking. history skull of a hydrocephalic child (1800s) in the pre-historic area, there were various paintings or artifacts depicting children or adults with macrocephaly (large head) or clinical findings of hydrocephalus. however, due to lack of writing, it was unknown how the people thought of the disorder at that time and the ways to treat the disease.