Interventricular foramina (neuroanatomy)

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Interventricular foramina
Interventricularforamina.jpg
The lateral ventricles connected to the third ventricle by the interventricular foramina.
Blausen 0216 CerebrospinalSystem.png
Cerebrospinal fluid is present in spaces in and around the brain.
Details
Part of Ventricular system
Identifiers
Latin foramen interventriculare,
foramen Monroi
NeuroNames 447
TA98 A14.1.08.411
TA2 5641
FMA 75351
Anatomical terms of neuroanatomy

In the brain, the interventricular foramina (foramina of Monro) are channels that connect the paired lateral ventricles with the third ventricle at the midline of the brain. As channels, they allow cerebrospinal fluid (CSF) produced in the lateral ventricles to reach the third ventricle and then the rest of the brain's ventricular system. The walls of the interventricular foramina also contain choroid plexus, a specialized CSF-producing structure, that is continuous with that of the lateral and third ventricles above and below it.

Contents

Structure

The interventricular foramina are two holes (Latin : foramen, pl. foramina) that connect the left and the right lateral ventricles to the third ventricle. [1] They are located on the underside near the midline of the lateral ventricles, [2] and join the third ventricle where its roof meets its anterior surface. [3] In front of the foramen is the fornix and behind is the thalamus. [3] The foramen is normally crescent-shaped, but rounds and increases in size depending on the size of the lateral ventricles. [3]

Development

The development and shape of the ventricular system relates to the differential development of different parts of the brain, with the ventricular system ultimately arising from the neural tube. [3] The lateral ventricles remain connected to the third ventricle throughout development, themselves developing as outpouchings from the third ventricle. [3] The foramina develop slowly in a forward and outward direction as the fornix grows in size. [3] [4]

Function

The interventricular foramina connect the lateral ventricles to the third ventricle. This allows cerebrospinal fluid produced in the lateral ventricles to reach the third ventricle and then the rest of the brain's ventricular system. [1]

The walls of the interventricular foramina contain choroid plexus, a specialized structure that produces cerebrospinal fluid. The choroid plexus of the third ventricles continues through the foramina into the lateral ventricles. [5]

End branches of the medial posterior choroidal arteries, superior thalamostriate, superior choroid veins and septal veins also pass through the foramen. [3]

Clinical significance

The interventricular foramina give rise to disease when they are narrowed or blocked. [3] Narrowing of the foramen is more common in children [6] and linked to: inflammation and scarring from congenital infections, particularly TORCH infections; developmental abnormalities, including of the basilar artery and choroid plexus; and abnormal surrounding tissue growths, such as colloid cysts, subependymal giant-cell tumours, nodules and harmatomas. [3] [6]

The most common symptom of blockage is headache; [6] other symptoms include fainting, dementia, and coma, all of which are associated with obstructive hydrocephalus of the affected side or sides. [3] [6] Hydrocephalus can be identified by a CT scan or MRI scan of the brain, [6] and treatment involves a neurosurgical operation in which an endoscope (i.e., a tiny camera and tools) is used to widen the foramen or create a new opening through the septum pellucidum between the lateral ventricles. [3] If an obstructing mass is too large or too difficult to remove endoscopically, an open operation or the insertion of an artificial path between the ventricles and peritoneum may be required. [3] [6] Because of the intimate nature of pathways within the brain, such operations may result in damage to nearby structures, with complications including anterograde amnesia, inability to move half the body, akinetic mutism and disconnection syndromes. [3]

History

The foramina were named after the Scottish physician and University of Edinburgh graduate Alexander Monro, who first described an enlarged foramen in the context of hydrocephalus in a presentation to the Philosophical Society of Edinburgh in 1764, [7] and subsequently in his 1783 publication, Observations on the Structure and Functions of the Nervous System. [3]

In this publication, Monro notes that the ventricular system has been noted to be connected, implying the presence of the foramen, since the time of the physician anatomist Galen. [3] Monro described it as:

... an oval hole, large enough to admit a goose quill, under forepart of the fornix. From this hole, a probe can be readily passed into the other lateral ventricle, shewing [sic], in the first place that the two lateral ventricles communicate with each other [8]

Monro's original description, of two lateral ventricles joined by a foramen that then joined the third ventricle, is in fact incorrect. [7] [8] As noted by Monro himself, previous authors have also described the ventricles as having connections; consequently, the eponym of "Monro" has been disputed. [8]

Related Research Articles

<span class="mw-page-title-main">Cerebrospinal fluid</span> Clear, colorless bodily fluid found in the brain and spinal cord

Cerebrospinal fluid (CSF) is a clear, colorless body fluid found within the tissue that surrounds the brain and spinal cord of all vertebrates.

<span class="mw-page-title-main">Hydrocephalus</span> Abnormal increase in cerebrospinal fluid in the ventricles of the brain

Hydrocephalus is a condition in which an accumulation of cerebrospinal fluid (CSF) occurs within the brain. This typically causes increased pressure inside the skull. Older people may have headaches, double vision, poor balance, urinary incontinence, personality changes, or mental impairment. In babies, it may be seen as a rapid increase in head size. Other symptoms may include vomiting, sleepiness, seizures, and downward pointing of the eyes.

<span class="mw-page-title-main">Ventricular system</span> Set of structures containing cerebrospinal fluid in the brain

In neuroanatomy, the ventricular system is a set of four interconnected cavities known as cerebral ventricles in the brain. Within each ventricle is a region of choroid plexus which produces the circulating cerebrospinal fluid (CSF). The ventricular system is continuous with the central canal of the spinal cord from the fourth ventricle, allowing for the flow of CSF to circulate.

<span class="mw-page-title-main">Pia mater</span> Delicate innermost layer of the meninges, the membranes surrounding the brain and spinal cord

Pia mater, often referred to as simply the pia, is the delicate innermost layer of the meninges, the membranes surrounding the brain and spinal cord. Pia mater is medieval Latin meaning "tender mother". The other two meningeal membranes are the dura mater and the arachnoid mater. Both the pia and arachnoid mater are derivatives of the neural crest while the dura is derived from embryonic mesoderm. The pia mater is a thin fibrous tissue that is permeable to water and small solutes. The pia mater allows blood vessels to pass through and nourish the brain. The perivascular space between blood vessels and pia mater is proposed to be part of a pseudolymphatic system for the brain. When the pia mater becomes irritated and inflamed the result is meningitis.

<span class="mw-page-title-main">Third ventricle</span> Ventricle of the brain located between the two thalami

The third ventricle is one of the four connected ventricles of the ventricular system within the mammalian brain. It is a slit-like cavity formed in the diencephalon between the two thalami, in the midline between the right and left lateral ventricles, and is filled with cerebrospinal fluid (CSF).

<span class="mw-page-title-main">Choroid plexus</span> Structure in the ventricles of the brain

The choroid plexus, or plica choroidea, is a plexus of cells that arises from the tela choroidea in each of the ventricles of the brain. Regions of the choroid plexus produce and secrete most of the cerebrospinal fluid (CSF) of the central nervous system. The choroid plexus consists of modified ependymal cells surrounding a core of capillaries and loose connective tissue. Multiple cilia on the ependymal cells move to circulate the cerebrospinal fluid.

<span class="mw-page-title-main">Cerebral aqueduct</span> Conduit for CSF to the brain

The cerebral aqueduct is a narrow 15 mm conduit for cerebrospinal fluid (CSF) that connects the third ventricle to the fourth ventricle of the ventricular system of the brain. It is located in the midbrain dorsal to the pons and ventral to the cerebellum. The cerebral aqueduct is surrounded by an enclosing area of gray matter called the periaqueductal gray, or central gray. It was first named after Franciscus Sylvius.

<span class="mw-page-title-main">Fourth ventricle</span> Ventricle in front of the cerebellum

The fourth ventricle is one of the four connected fluid-filled cavities within the human brain. These cavities, known collectively as the ventricular system, consist of the left and right lateral ventricles, the third ventricle, and the fourth ventricle. The fourth ventricle extends from the cerebral aqueduct to the obex, and is filled with cerebrospinal fluid (CSF).

<span class="mw-page-title-main">Ependyma</span>

The ependyma is the thin neuroepithelial lining of the ventricular system of the brain and the central canal of the spinal cord. The ependyma is one of the four types of neuroglia in the central nervous system (CNS). It is involved in the production of cerebrospinal fluid (CSF), and is shown to serve as a reservoir for neuroregeneration.

<span class="mw-page-title-main">Choroid plexus cyst</span> Medical condition

Choroid plexus cysts (CPCs) are cysts that occur within choroid plexus of the brain. They are the most common type of intraventricular cyst, occurring in 1% of all pregnancies.

<span class="mw-page-title-main">Median aperture</span>

The median aperture is an opening of the fourth ventricle at the caudal portion of the roof of the fourth ventricle. It allows flow of cerebrospinal fluid (CSF) from the fourth ventricle into the cisterna magna. The other two openings of the fourth ventricle are the lateral apertures - one on either side. Nonetheless, the median aperture accounts for most of the outflow of CSF out of the fourth ventricle. The median aperture varies in size.

<span class="mw-page-title-main">Lateral ventricles</span> Two largest ventricles in each cerebral hemisphere

The lateral ventricles are the two largest ventricles of the brain and contain cerebrospinal fluid (CSF). Each cerebral hemisphere contains a lateral ventricle, known as the left or right lateral ventricle, respectively.

<span class="mw-page-title-main">Tela choroidea</span>

The tela choroidea is a region of meningeal pia mater that adheres to the underlying ependyma, and gives rise to the choroid plexus in each of the brain’s four ventricles. Tela is Latin for woven and is used to describe a web-like membrane or layer. The tela choroidea is a very thin part of the loose connective tissue of pia mater overlying and closely adhering to the ependyma. It has a rich blood supply. The ependyma and vascular pia mater – the tela choroidea, form regions of minute projections known as a choroid plexus that projects into each ventricle. The choroid plexus produces most of the cerebrospinal fluid of the central nervous system that circulates through the ventricles of the brain, the central canal of the spinal cord, and the subarachnoid space. The tela choroidea in the ventricles forms from different parts of the roof plate in the development of the embryo.

<span class="mw-page-title-main">Superior medullary velum</span> Thin layer between the superior cerebellar peduncles

The superior medullary velum is a thin, transparent lamina of white matter which - together with the inferior medullary velum - forms the roof of the fourth ventricle. It extends between the two superior cerebellar peduncles. The lingula of cerebellum covers - and adheres to - its dorsal surface.

Ventriculostomy is a neurosurgical procedure that involves creating a hole (stoma) within a cerebral ventricle for drainage. It is most commonly performed on those with hydrocephalus. It is done by surgically penetrating the skull, dura mater, and brain such that the ventricular system ventricle of the brain is accessed. When catheter drainage is temporary, it is commonly referred to as an external ventricular drain (EVD). When catheter drainage is permanent, it is usually referred to as a shunt. There are many catheter-based ventricular shunts that are named for where they terminate, for example, a ventriculi-peritoneal shunt terminates in the peritoneal cavity, a ventriculoarterial shunt terminates within the atrium of the heart, etc. The most common entry point on the skull is called Kocher's point, which is measured 11 cm posterior to the nasion and 3 cm lateral to midline. EVD ventriculostomy is done primarily to monitor the intracranial pressure as well as to drain cerebrospinal fluid (CSF), primarily, or blood to relieve pressure from the central nervous system (CNS).

<span class="mw-page-title-main">Intraventricular hemorrhage</span> Medical condition

Intraventricular hemorrhage (IVH), also known as intraventricular bleeding, is a bleeding into the brain's ventricular system, where the cerebrospinal fluid is produced and circulates through towards the subarachnoid space. It can result from physical trauma or from hemorrhagic stroke.

Endoscopic third ventriculostomy (ETV) is a surgical procedure for treatment of hydrocephalus in which an opening is created in the floor of the third ventricle using an endoscope placed within the ventricular system through a burr hole. This allows the cerebrospinal fluid to flow directly to the basal cisterns, bypassing the obstruction. Specifically, the opening is created in the translucent tuber cinereum on the third ventricular floor.

<span class="mw-page-title-main">Choroid plexus carcinoma</span> Medical condition

A choroid plexus carcinoma is a type of choroid plexus tumor that affects the choroid plexus of the brain. It is considered the worst of the three grades of chord plexus tumors, having a much poorer prognosis than choroid atypical plexus papilloma and choroid plexus papilloma. The disease creates lesions in the brain and increases cerebrospinal fluid volume, resulting in hydrocephalus.

Bobble-head doll syndrome is a rare neurological movement disorder in which patients, usually children around age 3, begin to bob their head and shoulders forward and back, or sometimes side-to-side, involuntarily, in a manner reminiscent of a bobblehead doll. The syndrome is related to cystic lesions and swelling of the third ventricle in the brain.

References

  1. 1 2 Gray's Anatomy 2008, p. 237.
  2. ↑ Gray's Anatomy 2008, p. 287.
  3. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 Tubbs, R. Shane; Oakes, Peter; Maran, Ilavarasy S.; Salib, Christian; Loukas, Marios (31 July 2014). "The foramen of Monro: a review of its anatomy, history, pathology, and surgery". Child's Nervous System. 30 (10): 1645–1649. doi: 10.1007/s00381-014-2512-6 . PMID   25079886.
  4. ↑ Gray's Anatomy 2008, p. 383.
  5. ↑ Gray's Anatomy 2008, p. 242.
  6. 1 2 3 4 5 6 Martínez-Berganza, Maria Teresa Escolar; Bergua, Beatriz Sierra; del Río Pérez, Clara; Ballarín, Susana Monzón (May 2011). "Biventricular Hydrocephalus Due to Idiopatic Occlussion of Foramina of Monro". The Neurologist. 17 (3): 154–156. doi:10.1097/NRL.0b013e31821733af. PMID   21532385.
  7. 1 2 Wu, Osmond C.; Manjila, Sunil; Malakooti, Nima; Cohen, Alan R. (June 2012). "The remarkable medical lineage of the Monro family: contributions of Alexander and". Journal of Neurosurgery. 116 (6): 1337–1346. doi:10.3171/2012.2.JNS111366. PMID   22482794.
  8. 1 2 3 Sharp, JA (1961). "Alexander Monro Secundus and the interventricular foramen". Medical History. 5 (1): 83–89. doi:10.1017/S0025727300025941. PMC   1034587 . PMID   16562219.
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