The ventricles the the mind are a connecting network of cavities filled v cerebrospinal fluid (CSF) and also located in ~ the mind parenchyma. The ventricular system is written of 2 lateral ventricles, the 3rd ventricle, the cerebral aqueduct, and the 4th ventricle (see the images below). The choroid plexuses arelocated in the ventricles develop CSF, which filling the ventricles and subarachnoid space, complying with a bicycle of constant production and also reabsorption.

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Brain, coronal view.
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Meninges and ventricles that the brain.
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The ventricular system is embryologically derived from the neural canal, forming beforehand in the advance of the neural tube. The 3 mind vesicles (prosencephalon or forebrain, mesencephalon or midbrain, and rhombencephalon or hindbrain) type around the end of the an initial gestational month. The neural canal dilates within the prosencephalon, leading to the formation of the lateral ventricles and third ventricle. The cavity that the mesencephalon forms the cerebral aqueduct. The dilation that the neural canal within the rhombencephalon forms the fourth ventricle.


The lateral ventricles interact with the third ventricle v interventricular foramens, and also the third ventricle communicates through the fourth ventricle through the cerebral aqueduct (see the image below). <1> throughout early development, the septum pellucidum is created by the thinned walls of the 2 cerebral hemispheres and contains a fluid-filled cavity, named the cavum, which might persist.


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The ventricular system of the human being brain.

Tufts that capillaries invaginate the roofs of prosencephalon and rhombencephalon, forming the choroid plexuses of the ventricles. Cerebrospinal liquid (CSF) is secreted by the choroid plexuses, pour it until it is full the ventricular system. CSF flows out of the fourth ventricle through the 3 apertures created at the roof the the fourth ventricle by 12 weeks" gestation. <1>


Lateral ventricles

The largest cavities the the ventricular system are the lateral ventricles. Every lateral ventricle is divided into a central portion, developed by the body and atrium (or trigone), and also 3 lateral expansions or horns that the ventricles. <1, 2> The central portion or the human body of the ventricle is situated within the parietal lobe. The roof is created by the body callosum, and also the posterior section of the septum pellucidum lies medially. The anterior part of the body of the fornix, the choroid plexus, lateral dorsal surface ar of the thalamus, stria terminalis, and also caudate nucleus, kind the floor the the lateral ventricle. <2> watch the picture below.


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Ventricles and the boundaries of significant adjacent anatomy.

The interventricular foramen is located in between the thalamus and anterior tower of the fornix, in ~ the anterior margin of the body. The 2 interventricular foramens (or foramina that Monro) affix the lateral ventricles v the third ventricle. The body of the lateral ventricle is associated with the occipital and also temporal horns by a large area called the atrium. <1, 2>


The anterior or frontal horn is located anterior come the interventricular foramen. The floor and also the lateral wall are developed by the head of the caudate nucleus, the corpus callosum constitutes the roof and anterior border, and the septum pellucidum delineates the medial wall. <2> The posterior or occipital horn is located within the occipital lobe. The yarn of the body callosum and also the splenium kind the roof. The forceps significant is located on the medial side and also forms the pear of the occipital horn. <1, 2>


The inferior or temporal horn is located within the temporal lobe. The roof is developed by the yarn of the temporal lobe; the medial border has the stria terminalis and tail of the caudate. The medial wall and the floor are created by the hippocampus and its associated structures. The amygdaloid facility is situated at the anterior finish of the inferior horn. <1, 2>


Capillaries that the choroid arteries indigenous the pia mater project right into the ventricular cavity, forming the choroid plexus of the lateral ventricle (see the image below). The choroid plexus is attached to the adjacent brain structures through a double layer the pia mater referred to as the tela choroidea. The choroid plexus extends native the lateral ventricle right into the worse horn. The anterior and posterior horn have actually no choroid plexus.


The choroid plexus the the lateral ventricle is connected with the choroid plexus of the contralateral ventricle and also the 3rd ventricle v the interventricular foramen. The anterior choroidal arteries (branch of interior carotid artery) and also lateral posterior choroidal arteries (branch of the posterior cerebral artery) kind the choroid plexus. Venous it is provided from the choroidal veins drainpipe into the cerebral veins. <2>


Third ventricle

The 3rd ventricle is the narrow vertical cavity the the diencephalon. A thin tela choroidea provided by the medial posterior choroidal arteries (branch the posterior cerebral artery) is created in the roof of the 3rd ventricle. The fornix and also the corpus callosum are situated superiorly. The lateral walls are formed by the medial thalamus and hypothalamus. The anterior commissure, the lamina terminalis, and also the optic chiasm delineate the anterior wall. The floor that the 3rd ventricle is developed by the infundibulum, which attaches the hypophysis, the tuber cinereum, the mammillary bodies, and also the upper end of the midbrain. The posterior wall surface is developed by the pineal gland and also habenular commissure. The interthalamic adhesions room bands that gray issue with unknown functional significance, which cross the cavity that the ventricle and attach come the exterior walls. <1, 2>


Fourth ventricle

The 4th ventricle is connected to the 3rd ventricle through a narrow cerebral aqueduct. The 4th ventricle is a diamond-shaped cavity located posterior come the pons and also upper medulla oblongata and anterior-inferior to the cerebellum. The exceptional cerebellar peduncles and the anterior and also posterior medullary vela form the roof that the 4th ventricle. The apex or fastigium is the expansion of the ventricle up into the cerebellum. The floor that the 4th ventricle is named the rhomboid fossa. The lateral recess is an extension of the ventricle top top the dorsal worse cerebellar peduncle.


Inferiorly, that extends right into the main canal that medulla. The 4th ventricle communicates through the subarachnoid space through the lateral foramen of Luschka, located near the flocculus that the cerebellum, and also through the median foramen the Magendie, situated in the roof of the ventricle. Many of the CSF outflow passes through the medial foramen. The cerebral aqueduct contains no choroid plexus. The tela choroidea that the 4th ventricle, i m sorry is provided by branches of the posterior inferior cerebellar arteries, is situated in the posterior medullary velum. <1, 2>


Cerebrospinal fluid

CSF is a clear, watery liquid that filling the ventricles that the mind and the subarachnoid space around the brain and spinal cord. CSF isprimarilyproduced through the choroid plexus that the ventricles (≤70% that the volume); many of the is developed by the choroid plexus that the lateral ventricles. The remainder of the CSF manufacturing is the an outcome of transependymal flow from the brain to the ventricles. <3>


CSF flows from the lateral ventricles, with the interventricular foramens, and also into the third ventricle, cerebral aqueduct, and also the 4th ventricle. Just a very little amount enters the main canal the the spinal cord. CSF circulation is the an outcome of a mix of factors, which encompass the hydrostatic push generated during CSF manufacturing (known as mass flow), arterial pulsations of the big arteries, and also directional beating the the ependymal cilia. Hydrostatic pressure has a predominant role in the CSF flow within the larger ventricles, whereas cilia favor the motion of the CSF in the narrow regions of the ventricular system, such together the cerebral aqueduct. Immotile cilia syndrome is a rare reason of hydrocephalus in children. <4>


The ventricles constitute the internal component of a connecting system containing CSF. The external part of the system is formed by the subarachnoid space and cisterns. The communication between the 2 components occurs in ~ the level of 4th ventricle v the average foramen of Magendie (into the cistern magna) and also the 2 lateral foramina of Luschka (into the spaces around the brainstem cerebellopontine angles and also prepontine cisterns). The CSF is absorbed from the subarachnoid an are into the venous blood (of the sinuses or veins) by the little arachnoid villi, which space clusters of cell projecting native subarachnoid an are into a venous sinus, and the larger arachnoid granulations. <4, 5>


The full CSF volume contained within the connecting system in adults is around 150 mL, with around 25% filling the ventricular system. CSF is developed at a rate of about 20 mL/h, and an approximated 400-500 mL of CSF is developed and absorbed daily.


CSF absorption volume is normally about 2-4 times the price of production. The typical CSF press is in between 5-15 mm Hg (65-195 mm H2 O) in adults. In youngsters younger than 6 years, regular CSF press ranges in between 10-100 mm H2 O. <4, 5>


CSF plays crucial role in sustaining the mind growth during evolution, protecting against external trauma, removal of metabolites developed by neuronal and glial cell activity, and transport of biologically active substances (like hormones and also neuropeptides) transparent the brain. <4>


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Microscopic Anatomy


The ventricles space lined by a single layer that ciliated squamous or columnar ependymal cells. The ependymal cells construct from tanycytes, types of transitional cells v radially extending processes, i m sorry come in call with the blood vessels, neurons, and glia.


The choroid plexus forms at an early stage in development, soon after the closing of the neural tube. The ependymal cells coming in contact with the adjacent mesodermally obtained tissue form pseudorosettes, i beg your pardon protrude within the neural tube at the sites of ventricular device formation. The differentiation of these cells through resulting development of the choroid plexus is largely completed through 22 weeks" gestation. <4>


The blood-brain obstacle is created by capillary endothelial cells, pluripotent pericytes, a dense basement membrane, and also perivascular end-feet the astrocytes. The vascular endothelial barrier is developed by chop junctions and adherence junctions between endothelial cells. Cerebral capillary endothelial cells absence fenestrations, have fewer pinocytic vesicles, have actually an increased number of mitochondria, and also have a more thick basement membrane (30-40 mm thick) and nearby astrocytic end-feet loved one to the systemic endothelial cells. A single cell typically spans the whole circumference that a cerebral capillary lumen.


In the blood, the CSF barrier and also epithelial cells of the plexus are connected by chop junctions, developing a constant layer the permits the i of selected substances. The capillaries that the choroid plexuses have much more fenestration 보다 the mind capillaries. The choroid plexus capillaries are separated indigenous the choroidal cells by a basement membrane and also a class of connective tissue. The ependymal cell kind the lining of the ventricles and are constant with the epithelium of the choroid plexus.


The arachnoid obstacle is developed by the external layer of the cell of the arachnoid, which room joined by tight junctions and have similar permeability to those of the mind blood vessels. <2, 4>


The main attributes of the blood-brain barrier are to prevent the entrance of perhaps harmful substances right into the CNS, to keep ion and also volume regulation, and also to preserve metabolic and immunologic function. A dysfunction or disruption in the blood-brain barrier may it is in encountered in many disease states, such as infection, inflammation, visibility of tumors, and hypoxic-ischemic occasions with potential significant neurologic sequelae. <4>


The blood-brain barrier is missing in several dedicated areas that the brain, known as circumventricular organs. These room the area postrema of the 4th ventricle, the typical eminence, basal hypothalamus/neurohypophysis, the pineal gland, subfornical and subcommissural organs, and also lamina terminalis. In these regions, the ependymal lining has actually discontinuous gap junctions and couple of tight junctions, and the fenestrated capillaries are highly permeable. These locations have certain secretory duty (neurohypophysis) or surveillance duty (eg, area postrema). <4>


CSF is one ultrafiltrate that plasma. Salt is secreted right into the CSF by the sodium-potassium ATPase pump, complied with by the passive transport of water molecules. Intracellular carbonic anhydrase generates bicarbonate and also hydrogen ions. Many proteins space excluded indigenous the CSF by the blood-brain barrier. <4>


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Pathophysiologic Variants


Intracranial pressure is the press within the closed craniospinal compartment, which includes 3 key components: brain parenchyma, intracranial cerebrospinal liquid (CSF), and also cerebral blood volume.


An rise in CSF push happens together a an outcome of boost in the intracranial volume (eg, tumors), blood volume (with hemorrhages), or CSF volume (eg, hydrocephalus). Impede the circulation that the CSF leader to dilatation of the ventricular system upstream to the level the obstruction, characterized as hydrocephalus.


Hydrocephalus

The old group divides hydrocephalus into 2 types: noncommunicating and also communicating. In noncommunicating or obstructive hydrocephalus, the CSF accumulates within the ventricles together a an outcome of an obstruction in ~ the ventricular device (most commonly at the level of cerebral aqueduct). In communicating hydrocephalus, the CSF flows easily through the outflow foramens that the fourth ventricles right into the arachnoid space.


Current imaging techniques, including CTscanning and MRI (see the picture below), do inferences around the level of obstruction, depending on the visibility or absence of ventriculomegaly, especially fourth ventricle dilatation. Fourth ventricle dilatation means obstruction distally, typically at the level the the subarachnoid space. A little fourth ventricle says obstruction proximal to the fourth ventricle. <2, 3>


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Coronal magnetic resonance image shows a colloid cyst (arrow) in the roof of the third ventricle. The patient has mild hydrocephalus.

Current terminology classifies all species of hydrocephalus together obstructive at part level, except for the rare reason of CSF overproduction linked with choroid plexus papilloma. <6, 7>


Intraventricular obstructive hydrocephalus refers to hydrocephalus result from one obstruction in ~ the ventricular system (eg, aqueductal stenosis). The constant production that the CSF leads to dilatation the one or more ventricles, depending on the website of obstruction. In the acute obstruction phase, transependymal circulation of CSF may occur. The gyri room flattened against the skull. If the skull sutures space not calcified, such together in kids younger than age 2 years, the head may enlarge.


Extraventricular obstructive hydrocephalus shows an obstruction outside the ventricles (eg, at the level of arachnoid villi, together a an outcome of ahead bleeding, infection, or inflammation, which results in thickening the the arachnoid and also decreased absorb of the CSF). <3, 7>


Hydrocephalus reasons symptoms mainly due to increased intracranial pressure. The symptoms and also findings vary with age. Clinical features of hydrocephalus in infants encompass irritability, lethargy, bad feeding, vomiting, and also failure to thrive. In enlarge children and adults, morning headache connected with vomiting, diplopia, gait dysfunction together a an outcome of stretching of the paracentral corticospinal fibers, coordination problems, and impairment in the greater functions are seen.


Macrocephalus, cracked pot sound with percussion, separation the sutures, frontal bossing, or occipital importance is commonly seen in youngsters with hydrocephalus that arisen before the close up door of the cranial vault. Papilledema, exudates or hemorrhages, and optic atrophy might be seen upon funduscopic check in youngsters or adults. Enlargement that the remote spot is likewise noted.


Diplopia is usually led to by bilateral 6th nerve palsy as result of increased intracranial pressure. A paralysis that the upgaze or partial Parinaud syndrome (setting sun sign) is viewed as a result of press on the superior colliculus or tectum. Various other findings encompass hormonal alters as a result of third ventricle dilatation and pressure on the hypothalamic-pituitary structures, cognitive dysfunction, transforms in personality might be seen, and, occasionally, seizures. Posterior fossa tumors may cause transforaminal herniation that the cerebellar tonsils through neck stiffness. <3>


The etiologies and also pathogenesis of hydrocephalus include overproduction, blockage, or decreased absorption. The only known etiology of excess production is choroid plexus papilloma, which account for much less than 2% the childhood tumors.

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Etiologies that hydrocephalus secondary to blockage or lessened absorption include developmental abnormalities, trauma, tumors, infectious, inflammatory, and also idiopathic. Solid tumors develop hydrocephalus through obstruction the the ventricles, whereas nonsolid tumors (eg, leukemia, carcinomatous infiltration) impair CSF absorption in ~ the subarachnoid space. <3, 7>


Third ventricle obstruction may an outcome from a colloid cyst, large hypothalamic-optic or thalamic glioma, or suprasellar mass


Obstruction at the level of fourth ventricle might be resulted in by posterior fossa tumors, hemorrhage, or ventriculitis


Obstruction of the 4th ventricle foramina the Luschka and also Magendie may be due to a Dandy-Walker malformation, arachnoid cyst, epidemic (eg, ventriculitis, meningitis), or cerebellar tumors


Obstruction in ~ the level that subarachnoid an are is usually led to by hemorrhage (subarachnoid or subdural), meningitis, and, rarely, by Chiari malformation


Congenital hydrocephalus has an incidence that 0.4-0.8 every 1000 live births and also stillbirths; noncommunicating hydrocephalus is the many common form of hydrocephalus in fetuses. Aqueductal stenosis is the many common cause of congenital hydrocephalus, whereas mass lesions are the many common reason of aqueductal obstruction during childhood. <3> Other reasons of congenital noncommunicating hydrocephalus include the following:


Chiari malformation


Vein the Galen malformation


Hydrancephaly, porencephaly, and also schizencephaly


Hydranencephaly outcomes from instead of of the mind parenchyma by the CSF. Causes include a failure in normal brain development, intrauterine condition destroying the normal mind tissue, or untreated steady obstructive hydrocephalus. <3>


Porencephaly refers to hemispheric cysts resulting from the devastation of immature brain parenchyma, which might or may not interact with the lateral ventricle and subarachnoid space.


Schizencephaly is the term supplied for a slot in the brain parenchyma that is lined through dysplastic gray matter, extending from the ventricles come the cortex. <3, 8>


The uniformly dilatated ventricles with normal CSF push are classified together normal push hydrocephalus (NPH). Arrested hydrocephalus may represent a kind of normal push hydrocephalus. Normal push hydrocephalus may be attach by gait disorder, incontinence, and also dementia in yonsi patients. The etiology is presumed to it is in idiopathic, resulting in increased resistance to CSF absorption throughout the arachnoid villi. A remote background of trauma, infection, or subarachnoid hemorrhage may be elicited occasionally. CT scanning or MRI expose uniform ventricular dilatation out of proportion come the cortical atrophy, v periventricular lucencies. <4>


Idiopathic intracranial hypertension (IIH) (also known as pseudotumor cerebri) is a diagnosis that exclusion. Predominantly seen in young, obese ladies (age 20-40 y; female-to-male ratio, 3:1), it manifests v headaches and also visual disturbances; in the many severe cases, intuitive loss might result. The eye examination result are related to boosted intracranial pressure and also include papilledema, retinal hemorrhages, exudates, enlargement of the blind spot, and sixth cranial nerve palsies. Top top CT scan or MRI, the ventricular system shows up normal. North sella may be checked out in a tiny percentile that patients. Lumbar puncture reveals elevated CSF pressure greater than 250 mm H2 O, through normal CSF composition. <9>


Management

Treatment that hydrocephalus is very diverse, consisting of conservative and also surgical approaches, depending upon the underlying abnormality and also the site of obstruction. <3, 7>


In patients v normal pressure hydrocephalus, large-volume lumbar puncture through removal the 40-50 mL the CSF is complied with by clinical improvement and high convexity tightness, as viewed on CT scan or MRI, suggest a potential advantage with shunting procedures. <10> Isotope cisternography and perfusion test are additional tests offered in picking surgical candidates. <11>


For idiopathic intracranial hypertension, the therapy is directed at lowering CSF pressure and also volume. The mainstays of medical treatment incorporate weight reduction, low sodium diet, and also diuretics (acetazolamide). <9, 12> A surgical approach is recommended in the setup of failure of standard medical treatment, consisting of shunting, optic nerve fenestration, and, much more recently, venous sinus stenting. <13, 14> In obese patients with idiopathic intracranial hypertension, there have been reports that imply a potential benefit in resolution of symptoms after bariatric surgery. <15>


CSF leak and also low push may occur after lumbar puncture, dural surgical procedures, or as a voluntarily thecal tear. A headache that worsens in the upright position is the clinical hallmark of CSF leaks. Treatment depends on the etiology and also includes bedrest, hydration, and an autologous blood patch. <16>


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Irani DN, ed. Cerebrospinal liquid in Clinical Practice. Philadelphia, Pa: Saunders; 2009.

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