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Hydrocephalus () is a medical condition in which there is an abnormal accumulation of cerebrospinal fluid (CSF) in the brain. This causes increased intracranial pressure inside the skull and may cause progressive enlargement of the head if it occurs in childhood, potentially causing convulsion, tunnel vision, and mental disability. It was once informally called "Water on the brain."〔(【引用サイトリンク】title=Hydrocephalus Symptoms, Causes, Treatment - What is hydrocephalus? - MedicineNet )〕 Hydrocephalus can be caused by congenital or acquired factors. Congenital causes include Spina Bifida, Arnold–Chiari malformation, craniosynostosis, Dandy–Walker syndrome, and Vein of Galen malformations. Acquired causes include hemorrhage, meningitis, head trauma, tumors, and cysts. Two types of hydrocephalus are commonly described non-communicating hydrocephalus and communicating hydrocephalus, although there is evidence that communicating forms can lead to obstruction of CSF flow in many instances. In non-communicating hydrocephalus, the CSF in the ventricles can not reach the subarachnoid space. This results from obstruction of interventricular foramina, cerebral aqueduct, or the outflow foramens of the fourth ventricle (median and lateral apertures). The most common obstruction is in the cerebral aqueduct. A block at any of these sites leads rapidly to dilatation of one or more ventricles. If the skull is still pliable, as it is in children younger than 2 years, the head may enlarge. In communicating hydrocephalus, the obstruction of CSF flow is in the subarachnoid space from prior bleeding or meningitis. This causes thickening of the arachnoid leading to blockage of the return-flow channels. In some patients, the spaces filled by CSF are uniformly enlarged without an increase in intercranial pressure. This special form of communicating hydrocephalus is called normal pressure hydrocephalus (NPH), which results specifically from impaired CSF reabsorption at the arachnoid granulations. NPH's clinical manifestations are gait abnormality, dementia, and involuntary urination. NPH usually occurs in elderly patients. ==Signs and symptoms== The clinical presentation of hydrocephalus varies with chronicity. Acute dilatation of the ventricular system is more likely to manifest with the nonspecific signs and symptoms of increased intracranial pressure. By contrast chronic dilatation (especially in the elderly population) may have a more insidious onset presenting, for instance, with Hakim's triad (Adams triad). Symptoms of increased intracranial pressure may include headaches, vomiting, nausea, papilledema, sleepiness or coma. Elevated intracranial pressure may result in uncal and/or cerebellar tonsill herniation, with resulting life-threatening brain stem compression. Hakim's triad of gait instability, urinary incontinence and dementia is a relatively typical manifestation of the distinct entity normal pressure hydrocephalus (NPH). Focal neurological deficits may also occur, such as abducens nerve palsy and vertical gaze palsy (Parinaud syndrome due to compression of the quadrigeminal plate, where the neural centers coordinating the conjugated vertical eye movement are located). The symptoms depend on the cause of the blockage, the person's age, and how much brain tissue has been damaged by the swelling. In infants with hydrocephalus, CSF builds up in the central nervous system, causing the fontanelle (soft spot) to bulge and the head to be larger than expected. Early symptoms may also include: * Eyes that appear to gaze downward; * Irritability; * Seizures; * Separated sutures; * Sleepiness; * Vomiting. Symptoms that may occur in older children can include: * Brief, shrill, high-pitched cry; * Changes in personality, memory, or the ability to reason or think; * Changes in facial appearance and eye spacing; * Crossed eyes or uncontrolled eye movements; * Difficulty feeding; * Excessive sleepiness; * Headache; * Irritability, poor temper control; * Loss of bladder control (urinary incontinence); * Loss of coordination and trouble walking; * Muscle spasticity (spasm); * Slow growth (child 0–5 years); * Slow or restricted movement; * Vomiting .〔(【引用サイトリンク】title=Hydrocephalus )〕 Because hydrocephalus can injure the brain, thought and behavior may be adversely affected. Learning disabilities including short-term memory loss are common among those with hydrocephalus, who tend to score better on verbal IQ than on performance IQ, which is thought to reflect the distribution of nerve damage to the brain. However the severity of hydrocephalus can differ considerably between individuals and some are of average or above-average intelligence. Someone with hydrocephalus may have motion and visual problems, problems with coordination, or may be clumsy. They may reach puberty earlier than the average child (see precocious puberty). About one in four develops epilepsy. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Hydrocephalus」の詳細全文を読む スポンサード リンク
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