The ventricles of the brain are a interacting network of caries filled with cerebrospinal fluid (CSF) and located within the mind parenchyma. The ventricular system is created of 2 lateral ventricles, the 3rd ventricle, the cerebral aqueduct, and also the fourth ventricle (see the images below). The choroid plexuses arelocated in the ventricles create CSF, which fills the ventricles and also subarachnoid space, adhering to a bike of continuous production and 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 at an early stage in the advance of the neural tube. The 3 brain vesicles (prosencephalon or forebrain, mesencephalon or midbrain, and rhombencephalon or hindbrain) form around the finish of the very first gestational month. The neural canal dilates within the prosencephalon, bring about the formation of the lateral ventricles and 3rd ventricle. The cavity of the mesencephalon creates the cerebral aqueduct. The dilation of the neural canal within the rhombencephalon creates the fourth ventricle.


The lateral ventricles connect with the third ventricle v interventricular foramens, and also the third ventricle communicates v the fourth ventricle v the cerebral aqueduct (see the photo below). <1> during early development, the septum pellucidum is developed 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 mechanism of the human being brain.

Tufts of capillaries invaginate the roofs of prosencephalon and also rhombencephalon, forming the choroid plexuses the the ventricles. Cerebrospinal liquid (CSF) is secreted by the choroid plexuses, filling the ventricular system. CSF flows the end of the 4th ventricle with the 3 apertures formed at the roof that the fourth ventricle through 12 weeks" gestation. <1>


Lateral ventricles

The biggest cavities of the ventricular system are the lateral ventricles. Every lateral ventricle is split into a central portion, developed by the body and atrium (or trigone), and also 3 lateral extensions or horns the the ventricles. <1, 2> The central portion or the human body of the ventricle is situated within the parietal lobe. The roof is formed by the corpus 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 caudate nucleus, kind the floor that the lateral ventricle. <2> view the photo below.


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Ventricles and the borders of major adjacent anatomy.

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


The anterior or frontal horn is located anterior to the interventricular foramen. The floor and the lateral wall are developed by the head the 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 situated within the occipital lobe. The yarn of the corpus callosum and the splenium type the roof. The forceps major is located on the medial side and also forms the bulb of the occipital horn. <1, 2>


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


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


The choroid plexus that the lateral ventricle is connected with the choroid plexus of the contralateral ventricle and the third ventricle v the interventricular foramen. The anterior choroidal arteries (branch of internal carotid artery) and also lateral posterior choroidal arteries (branch of the posterior cerebral artery) type the choroid plexus. Venous supply from the choroidal veins drain into the cerebral veins. <2>


Third ventricle

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


Fourth ventricle

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


Inferiorly, it extends into the central canal of medulla. The fourth ventricle communicates with the subarachnoid an are through the lateral foramen of Luschka, located near the flocculus the the cerebellum, and also through the average foramen the Magendie, situated in the roof the the ventricle. Most of the CSF outflow passes v the medial foramen. The cerebral aqueduct includes no choroid plexus. The tela choroidea that the fourth ventricle, i beg your pardon is supplied by branches of the posterior worse cerebellar arteries, is situated in the posterior medullary velum. <1, 2>


Cerebrospinal fluid

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


CSF operation from the lateral ventricles, through the interventricular foramens, and into the 3rd ventricle, cerebral aqueduct, and the fourth ventricle. Only a very small amount start the main canal of the spinal cord. CSF flow is the an outcome of a mix of factors, which encompass the hydrostatic push generated throughout CSF manufacturing (known as mass flow), arterial pulsations that the big arteries, and also directional beating that the ependymal cilia. Hydrostatic pressure has a predominant function in the CSF flow within the larger ventricles, whereas cilia donate the motion of the CSF in the narrow regions of the ventricular system, such as the cerebral aqueduct. Immotile cilia syndrome is a rare reason of hydrocephalus in children. <4>


The ventricles constitute the internal part of a interacting system containing CSF. The external part of the mechanism is developed by the subarachnoid room and cisterns. The communication between the 2 parts occurs at the level of fourth ventricle with the median foramen of Magendie (into the cistern magna) and the 2 lateral foramina that Luschka (into the spaces roughly the brainstem cerebellopontine angles and also prepontine cisterns). The CSF is took in from the subarachnoid an are into the venous blood (of the sinuses or veins) by the tiny arachnoid villi, which space clusters of cell projecting native subarachnoid room into a venous sinus, and the bigger arachnoid granulations. <4, 5>


The total CSF volume consisted of within the communicating system in adults is around 150 mL, with approximately 25% filling the ventricular system. CSF is developed at a price of around 20 mL/h, and also an approximated 400-500 mL the CSF is developed and absorbed daily.


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


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


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Microscopic Anatomy


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


The choroid plexus forms early in development, soon after the closing of the neural tube. The ependymal cell coming in call with the nearby mesodermally acquired tissue form pseudorosettes, which protrude in ~ the neural pipe at the sites of ventricular system formation. The differentiation of this cells v resulting development of the choroid plexus is mostly completed by 22 weeks" gestation. <4>


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


In the blood, the CSF barrier and epithelial cells of the plexus are associated by tight junctions, developing a constant layer the permits the passage of selected substances. The capillaries that the choroid plexuses have much more fenestration 보다 the brain capillaries. The choroid plexus capillaries space separated native the choroidal cell by a basement membrane and a class of connective tissue. The ependymal cell type the lining that the ventricles and also are constant with the epithelium that the choroid plexus.


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


The main features of the blood-brain obstacle are to protect against the entry of perhaps harmful substances into the CNS, to preserve ion and volume regulation, and also to maintain metabolic as well as immunologic function. A dysfunction or disruption in the blood-brain barrier may be encountered in many disease states, such as infection, inflammation, existence of tumors, and hypoxic-ischemic events with potential significant neurologic sequelae. <4>


The blood-brain barrier is missing in several dedicated areas the the brain, recognized as circumventricular organs. These room the area postrema of the 4th ventricle, the average eminence, basal hypothalamus/neurohypophysis, the pineal gland, subfornical and subcommissural organs, and also lamina terminalis. In these regions, the ependymal lining has discontinuous void junctions and few tight junctions, and the fenestrated capillaries are very permeable. These locations have details secretory role (neurohypophysis) or surveillance function (eg, area postrema). <4>


CSF is an ultrafiltrate of plasma. Salt is secreted into the CSF through the sodium-potassium ATPase pump, followed by the passive move of water molecules. Intracellular carbonic anhydrase generates bicarbonate and hydrogen ions. Many proteins space excluded from the CSF by the blood-brain barrier. <4>


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Pathophysiologic Variants


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


An rise in CSF pressure happens as a result of rise in the intracranial volume (eg, tumors), blood volume (with hemorrhages), or CSF volume (eg, hydrocephalus). Impede the circulation the the CSF leads to dilatation of the ventricular system upstream to the level of obstruction, identified as hydrocephalus.


Hydrocephalus

The old classification divides hydrocephalus right into 2 types: noncommunicating and communicating. In noncommunicating or obstructive hydrocephalus, the CSF accumulates within the ventricles as a result of an obstruction in ~ the ventricular device (most typically at the level that cerebral aqueduct). In interacting hydrocephalus, the CSF flows freely through the outflow foramens of the fourth ventricles right into the arachnoid space.


Current imaging techniques, consisting of CTscanning and also MRI (see the picture below), do inferences around the level of obstruction, depending upon the visibility or lack of ventriculomegaly, especially fourth ventricle dilatation. 4th ventricle dilatation suggests obstruction distally, typically at the level of the subarachnoid space. A tiny fourth ventricle suggests obstruction proximal come the fourth ventricle. <2, 3>


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

Current hatchet classifies all varieties of hydrocephalus as obstructive at some level, except for the rare reason of CSF overproduction associated with choroid plexus papilloma. <6, 7>


Intraventricular obstructive hydrocephalus refers to hydrocephalus result from one obstruction within the ventricular device (eg, aqueductal stenosis). The continuous production that the CSF leads to dilatation of one or much more ventricles, depending upon the website of obstruction. In the acute obstruction phase, transependymal circulation of CSF might occur. The gyri room flattened against the skull. If the skull sutures room not calcified, such as in children younger than period 2 years, the head may enlarge.


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


Hydrocephalus reasons symptoms mainly because of increased intracranial pressure. The symptoms and also findings vary with age. Clinical features of hydrocephalus in infants encompass irritability, lethargy, poor feeding, vomiting, and also failure to thrive. In enlarge children and also adults, morning headache linked with vomiting, diplopia, gait dysfunction together a result of extending of the paracentral corticospinal fibers, coordination problems, and impairment in the higher functions room seen.


Macrocephalus, cracked pot sound through percussion, separation the sutures, frontal bossing, or occipital importance is normally seen in youngsters with hydrocephalus that occurred before the closing of the cranial vault. Papilledema, exudates or hemorrhages, and optic atrophy may be watched upon funduscopic check in children or adults. Enlargement of the remote spot is also noted.


Diplopia is usually caused by bilateral 6th nerve palsy due to increased intracranial pressure. A paralysis the the upgaze or partial Parinaud syndrome (setting sun sign) is seen as a an outcome of pressure on the exceptional colliculus or tectum. Other findings encompass hormonal alters as a result of third ventricle dilatation and pressure ~ above the hypothalamic-pituitary structures, cognitive dysfunction, changes in personality might be seen, and, occasionally, seizures. Posterior fossa tumors may cause transforaminal herniation the the cerebellar tonsils with neck stiffness. <3>


The etiologies and also pathogenesis that hydrocephalus include overproduction, blockage, or reduced absorption. The only known etiology that excess manufacturing is choroid plexus papilloma, which accounts for much less than 2% the childhood tumors.

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Etiologies of hydrocephalus an additional to blockage or diminished absorption encompass 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, huge hypothalamic-optic or thalamic glioma, or suprasellar mass


Obstruction in ~ the level of fourth ventricle might be led to by posterior fossa tumors, hemorrhage, or ventriculitis


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


Obstruction at the level the subarachnoid space is usually resulted in by hemorrhage (subarachnoid or subdural), meningitis, and, rarely, by Chiari malformation


Congenital hydrocephalus has actually an incidence the 0.4-0.8 every 1000 live births and stillbirths; noncommunicating hydrocephalus is the many common type of hydrocephalus in fetuses. Aqueductal stenosis is the many common reason of congenital hydrocephalus, whereas fixed lesions room the most common reason of aqueductal obstruction throughout childhood. <3> Other causes of congenital noncommunicating hydrocephalus encompass the following:


Chiari malformation


Vein that Galen malformation


Hydrancephaly, porencephaly, and schizencephaly


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


Porencephaly describes hemispheric cysts result from the devastation of immature mind parenchyma, which might or might not interact with the lateral ventricle and also subarachnoid space.


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


The uniformly dilatated ventricles through normal CSF pressure are classified as normal push hydrocephalus (NPH). Arrested hydrocephalus may represent a form of normal press hydrocephalus. Normal push hydrocephalus may be accompanied by gait disorder, incontinence, and dementia in yonsi patients. The etiology is presumed to it is in idiopathic, result in boosted resistance to CSF absorption across the arachnoid villi. A remote history of trauma, infection, or subarachnoid hemorrhage may be elicited occasionally. CT scanning or MRI reveals uniform ventricular dilatation the end of proportion come the cortical atrophy, with periventricular lucencies. <4>


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


Management

Treatment of hydrocephalus is an extremely diverse, including conservative and also surgical approaches, depending upon the underlying abnormality and also the site of obstruction. <3, 7>


In patients v normal press hydrocephalus, large-volume lumbar puncture with removal that 40-50 mL that CSF is adhered to by clinical improvement and high convexity tightness, as watched on CT scan or MRI, suggest a potential benefit with shunting procedures. <10> Isotope cisternography and perfusion tests are additional tests offered in selecting surgical candidates. <11>


For idiopathic intracranial hypertension, the treatment is directed at lowering CSF pressure and also volume. The mainstays of clinical treatment incorporate weight reduction, low salt diet, and diuretics (acetazolamide). <9, 12> A surgical technique is encourage in the setup of fail of standard clinical treatment, including shunting, optic nerve fenestration, and, much more recently, venous sinus stenting. <13, 14> In obese patients through idiopathic intracranial hypertension, there have been reports that suggest a potential benefit in resolution of symptoms after bariatric surgery. <15>


CSF leak and low pressure may happen after lumbar puncture, dural operation procedures, or as a spontaneous thecal tear. A headache that intensifies 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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