A Glossary of Hydrocephalus Related Words



acquired hydrocephalus: hydrocephalus that develops after birth, caused by a factor such as an intraventricular hemorrhage, meningitis, head injury, or a brain tumor.

adjustable (programmable) valves: shunt valves whose settings can be noninvasively adjusted during an office visit.

aqueduct of Sylvius (cerebral aqueduct): a narrow channel allowing the flow of cerebrospinal fluid in the midbrain. The aqueduct of Sylvius connects the third and fourth ventricles.

amblyopic: also called lazy eye. Undeveloped central vision in one eye that leads to the use of the other eye as the dominant eye. Strabismus is the leading cause, followed by anisometropia. There are no symptoms. The patient may be found squinting and closing one eye to see; there may be unrecognized blurred vision in one eye and vision loss.

aqueductal stenosis: a narrowing of the aqueduct of Sylvius. Aqueductal stenosis is one cause of obstructive hydrocephalus and the most common cause of congenital hydrocephalus.

arachnoid cysts: cysts filled with cerebrospinal fluid that may occur anywhere in the brain. Some arachnoid cysts are self-contained, while others may be connected by a passageway with the ventricles or the subarachnoid space. The entrapped fluid may block the CSF pathways, producing hydrocephalus.

arachnoid granulations: arachnoid villi.

arachnoid membrane: the middle of the three meninges, lying between the dura mater and the pia mater. The arachnoid membrane covers the brain and spinal cord smoothly without conforming to the irregularities of their surfaces.

arachnoid villi (arachnoid granulations): small projections in the dura mater that protrude into the dural venous (blood) sinuses. Cerebrospinal fluid is reabsorbed from the arachnoid space by passing through the arachnoid villi and entering the venous system.

astigmatism: a condition when the cornea, and sometimes the lens, curves differently in different directions. This causes light to bend differently when it focuses on the retina. The image is thus blurred or ghosted unless corrected by contact lenses or spectacles.

ataxis: ataxia is the shaky and unsteady movements that result from the brain’s failure to regulate the body’s posture and the strength and direction of movements. Ataxia is most often caused by disease activity in the cerebellum.

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brain stem: the part of the brain that connects the spinal cord with the cerebrum and cerebellum. The brain stem controls basic functions like heart rate, breathing, and blood pressure.

brain tumor: an abnormal growth of tissue in the brain that can be benign or malignant. The tissue, which results from rapid cell growth, serves no physiological purpose. Brain tumors can cause acquired hydrocephalus.

bursa: a bodily pouch.

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catheter: a flexible, hollow tube used to shunt fluid. Shunts used to treat hydrocephalus include inflow (proximal) catheters and outflow (distal) catheters.

central nervous system (CNS): the part of the nervous system that includes the brain and the spinal cord. The CNS coordinates the activity of the entire nervous system.

cerebellum: a part of the brain located between the brain stem and the back of the cerebrum.The cerebellum controls muscle coordination and maintains bodily equilibrium.

cerebral aqueduct: aqueduct of Sylvius.

cerebral cortex: the surface layer of gray matter of the cerebrum. The cerebral cortex functions chiefly to coordinate sensory and motor information.

cerebral hemispheres: the two hollow lateral halves of the cerebrum.

cerebrospinal fluid (CSF): a clear, colorless liquid secreted primarily by the choroid plexus and contained within the ventricles and the subarachnoid space. CSF functions primarily to nourish and protect the brain and spinal cord.

cerebrum: the upper part of the brain, which overlies the rest of the brain and includes the cerebral hemispheres and their connecting structures. The cerebrum is thought to control conscious mental processes.

Chiari II malformation: a cause of congenital hydrocephalus in which part of the cerebellum and the fourth ventricle push downward through the opening at the base of the skull, blocking CSF’s flow out of the fourth ventricle and thus producing hydrocephalus. This condition is often referred to as spina bifida.

choroid plexus: the structures in the lateral, third, and fourth ventricles that produce cerebrospinal fluid.

cistern: a sac or cavity in the body that contains fluid (such as cerebrospinal fluid).

CNS: central nervous system.

cocktail party syndrome: a hyperverbal condition, found in some children with hydrocephalus, in which a childseems to never stop talking, while content is usually superficial or inappropriate. It can mask learning difficulties such as an inability to listen or to understand the relevant aspects of a situation.

communicating hydrocephalus: hydrocephalus in which the openings between the ventricular spaces,and between the fourth ventricle and the subarachnoid space, are functioning.

computerized tomography (CT) scan: a type of brain scan that creates a picture of brain using x-rays and a special scanner. It takes about 15 minutes to perform.

congenital hydrocephalus: hydrocephalus caused by a problem that is present at birth. Hydrocephalus that develops later in life, even in adults, but is caused by a condition that existed at birth, is still considered a form of congenital hydrocephalus. Congenital hydrocephalus can be caused by aqueductal stenosis, a neural tube defect, arachnoid cysts, or Dandy-Walker syndrome.

CSF: cerebrospinal fluid.

CSF shunt: a tube surgically placed in the body that channels cerebrospinal fluid away from the brain or spinal cord into another part of the body, where it can be absorbed and transported to the bloodstream.

CT scan: computerized tomography scan.

cyst: closed sac with a distinct membrane that develops abnormally in a bodily cavity or structure.

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Dandy-Walker syndrome: a cause of congenital hydrocephalus in which the fourth ventricle becomes enlarged because its outlets are partly or completely closed, and part of the cerebellum fails to develop. Dandy-Walker syndrome sometimes leads to aqueductal stenosis.

decompensated congenital hydrocephalus: hydrocephalus that may have been present at birth, and perhaps even treated in early childhood, but remained largely compensated and asymptomatic for many years.

distal (outflow) catheter: outflow (distal) catheter.

dura mater (dura): one of the three meninges.The dura mater, the outermost and heaviest layer of the meninges, lies closest to the skull.

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echolalia: a learning disability sometimes manifested by children with hydrocephalus in which the child repeats what someone else has said, rather than responding appropriately.

endoscopic third ventriculostomy (ETV): a surgical operation that creates an opening through the membranous floor of the third ventricle, permitting cerebrospinal fluid to exit the third ventricle and flow directly into the subarachnoid space at the base of the brain.

ETV: endoscopic third ventriculostomy.

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fontanel: a membrane-covered opening in the skull of an infant or young toddler.

foramen magnum: the opening in the skull through which the spinal cord passes.

foramen of Monro (interventricular foramen): an opening between a lateral ventricle and the third ventricle allowing cerebrospinal fluid to flow from the lateral ventricle into the third ventricle.

foramina: any small opening.

foramina of Luschka and Magendie: small opening in the brain that allows cerebrospinal fluid to flow out of the fourth ventricle, into the subarachnoid space.

fourth ventricle: a cavity within the brain that is situated between the brain stem and the cerebellum. Cerebrospinal fluid enters the fourth ventricle from the cerebral aqueduct; it exits via the foramina of Luschka and Magendie, flowing into the subarachnoid space.

frontal bossing: Frontal bossing is the descriptive term for a prominent forehead. Sometimes the brow (just above the eyes) is also heavier than normal as seen in acromegaly.

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hematoma: a localized collection of blood, usually clotted.

hemorrhage: the escape of blood from blood vessels.

hemostasis: the arrest of bleeding.

hydrocephalus: an abnormal condition that occurs when there is an imbalance between the rate of cerebrospinal fluid production and the rate of absorption, leading to gradual accumulation of CSF.

hydrostatic: relating to fluids, such as cerebrospinal fluid, when they’re at rest or to the pressures they exert or transmit.

hygroma: a sac, cyst, or bursa distended with fluid; a subdural hygroma is a collection of fluid between the brain and the skull.

hypothalamus: a part of the brain that forms the floor of the third ventricle. The hypothalamus includes vital autonomic (involuntary) regulatory centers.

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ICP: intracranial pressure.

idiopathic: without known cause.

IEP: individualized education plan.

inflow (proximal) catheter: shunt catheter that drains cerebrospinal fluid away from the ventricles or the lumbar subarachnoid space.

individualized education plan (IEP): a personalized program that takes into account a child’s strengths and weaknesses, targeted educational goals, and approaches to help him or her reach these goals. An IEP, designed to maximize a child’s academic and personal potential, is created by a team including child care workers, neuropsychologists, teachers, other appropriate professionals, and parents.

intracranial pressure (ICP): pressure caused by a build-up of cerebrospinal fluid, resulting in hydrocephalus.

interventricular foramen: foramen of Monro.

intraventricular hemorrhage: bleeding into the ventricles.

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kinesthetic proprioceptive: the unconscious perception of movement and spatial orientation arising from stimuli within the body itself.

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lateral ventricle: one of two normal cavities within the cerebral hemispheres that contains cerebrospinal fluid. CSF flows from the lateral ventricles into the third ventricle via the foramen of Monro.

lumbar: relating to the vertebrae between the thoracic vertebrae (between the neck and the abdomen) and the sacrum (the part of the vertebral column that is connected with the pelvis).

lumbar puncture: spinal tap. Clinicians sometimes use a lumbar puncture to help diagnose hydrocephalus, removing cerebrospinal fluid to see whether hydrocephalus symptoms are relieved.

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magnetic resonance imaging (MRI) scan: a type of brain scan that uses radio signals and a powerful magnet to create a picture of brain. It is the most widely used test in diagnosing hydrocephalus because it provides more specific details about the size of the ventricles than a computerized tomography (CT) scan does. It takes approximately 30 minutes to perform.

meninges: the three membranes covering the brain and spinal cord, including the dura mater, the arachnoid membrane, and the pia mater.

meningitis: inflammation of the meninges. Meningitis can result from a bacterial or a viral infection. Scarring of the arachnoid membrane resulting from meningitis can restrict or block cerebrospinal fluidflow and absorption.

meningomyelocele: congenital defect of the central nervous system of the baby. Membranes and the spinal cord protrude through an opening or defect in the vertebral column.

MRI: magnetic resonance imaging.

myelomeningocele: type of neural tube defect in which the spinal cord is exposed at birth and is often leaking cerebrospinal fluid. It usually leads to the Chiari II malformation.

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neural tube defect (NTD): birth defect of the brain or spinal cord. A neural tube defect can cause hydrocephalus.

NLD: nonverbal learning disorder

noncommunicating hydrocephalus: hydrocephalus in which the ventricular pathways are blocked. Noncommunicating hydrocephalus is caused by the obstructed flow of cerebrospinal fluid through the cerebral aqueduct or from the fourth ventricle to the subarachnoid space.

nonverbal learning disorder (NLD): a specific type of learning disability that has been identified in children with hydrocephalus. It affects both academic progress and social and emotional development.

normal pressure hydrocephalus (NPH): type of adult-onset hydrocephalus whose symptoms usually include difficulty walking, mild dementia, and impaired bladder control. This form of hydrocephalus occurs most often in people over age 60.

NPH: normal pressure hydrocephalus.

nystagmus: involuntary, rhythmic side-to-side or up and down (oscillating) eye movements that are faster in one direction than the other.

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obstructive hydrocephalus: hydrocephalus caused by a blockage along the pathway allowing the flow of cerebrospinal fluid.

opisthotonos: opisthotonos is a condition of abnormal posturing that involves rigidity and severe arching of the back, with the head thrown backward. If a person with opisthotonos were laid on his or her back, only the back of the head and the heels would touch the supporting surface. Opisthotonos may occur in infants with meningitis, where it is a sign of irritation of the membranes surrounding the brain and spinal cord (meninges). It may also occur as a sign of depressed brain function or injury to the nervous system.

outflow (distal) catheter: shunt component that drains cerebrospinal fluid from the valve to the peritoneum, the heart, or another suitable drainage site.

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papilledema: swelling around the optic nerve, usually due to pressure on the nerve by a tumor. Papilledema is optic disc swelling that is caused by increased intracranial pressure. The swelling is usually bilateral and can occur over a period of hours to weeks. Papilledema occurs in approximately 50% of those with a brain tumor.

parietal: related to the upper posterior (back) wall of the head.

peritoneum: thin membrane that lines the abdominal cavity. Cerebrospinal fluid is sometimes shunted to the peritoneum, which can act as a suitable drainage site.

pia mater: one of the three meninges. The pia mater is the layer closest to the brain.

porencephaly: congenitally deficient development of the cerebral cortex and gray matter so that cystic cavities communicate with the brain surface.

posterior fossa: small space at the back of the brain. The posterior fossa houses the brain stem and the cerebellum.

prenatal hydrocephalus: hydrocephalus that is diagnosed before birth.

preservation: a learning disability sometimes manifested by children with hydrocephalus in which the child repeats the same thing over and over again.

prominent: unusually full. Prominent scalp veins may be a sign of hydrocephalus in infants.

proximal (inflow) catheter: inflow catheter.

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sac: bodily pouch that often contains fluid (such as cerebrospinal fluid).

sacrum: the part of the vertebral column that is connected with the pelvis.

sagittal sinus: a large vein close to the suture between the parietal bones of the skull.

shunt: a hallow plastic tube (catheter) that is placed in the ventricle of the brain. The tube is attached to a valve and is then threaded under the skin from the brain to either the abdomen (Ventricular-Peritoneal shunt) or heart (Ventricular-Atrial shunt).

SHYMA: syndrome of hydrocephalus in young and middle-aged adults.

spina bifida: a condition caused by the Chiari II malformation in which part of the cerebellum and the fourth ventricle push downward through the opening at the base of the skull, blocking the flow of cerebrospinal fluid out of the fourth ventricle and thus producing hydrocephalus.

Staphylococcus Epidermidis: member of the bacterial genus Staphylococcus mainly found on the skin and mucous membrane of humans and animals. They are a common cause of medical device-associated infections.

stenosis: obstruction.

strabismus: eye misalignment caused by extraocular muscle imbalance: one fovea is not directed at the same object as the other.

subarachnoid pathways: pathways in the space under the arachnoid membrane that normally allow the flow of cerebrospinal fluid.

subarachnoid space: the space under the arachnoid membrane.

subdural hygroma: a collection of fluid between the brain and the skull.

sunsetting sign: downward turning of the eyes. The sunsetting sign can be a symptom of hydrocephalus in infants.

syncope: fainting, loss of consciousness. In some cases of adult-onset hydrocephalus, syncope can result from insufficient blood flow to the brain.

symptom of hydrocephalus in young and middle-aged adults (SHYMA): type of adult-onset hydrocephalus whose symptoms usually include difficulty walking, mild dementia, and impaired bladder control, along with chronic headaches, visual problems, and fainting ( syncope). This form of hydrocephalus occurs most often in younger adults.

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thalamus: a part of the brain that lies deep in the forebrain. There is one thalamus on either side of the brain. The thalamus chiefly relays impulses, especially sensory impulses, to and from the cerebral cortex.

third ventricle: a midline cavity within the brain that is situated between the right and left thalamus. Cerebrospinal fluid enters the third ventricle from each lateral ventricle via the foramen of Monro; it exits the third ventricle via the aqueduct of Sylvius.

thoracic vertebrae: vertebrae between the neck and the abdomen.

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ultrasonography: a noninvasive diagnostic technique that uses sound waves to image internal body structures. Ultrasonography can be used to diagnose hydrocephalus prenatally or after birth, before the skull’s suture lines have closed.

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valve: a shunt component that regulates differential pressure or controls CSF flow through the shunt tubing.

ventricle: a cavity within the brain that contains cerebrospinal fluid.

ventriculo-atrial (VA) shunts: a shunt that is placed into a brain ventricle to drain cerebrospinal fluid (CSF) from the ventricular system into the heart.

ventriculo-peritoneal (VP) shunts: a shunt that is placed into a brain ventricle to drain cerebrospinal fluid (CSF) from the ventricular system into the abdomen.

ventricular lining: the lining of the ventricles.

vertebral column: spinal column.

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