Neuroscience 1A 1.14 Ventricular System PDF

UNIVERSITY OF NORTHERN PHILIPPINES NEUROSCIENCE 1A LC14 VENTRICULAR SYSTEM...

UNIVERSITY OF NORTHERN PHILIPPINES NEUROSCIENCE 1A LC14 VENTRICULAR SYSTEM COLLEGE OF MEDICINE, BATCH 2026 Transcribers & Editors: Dr. Vida Margarette D. Andal | Dec. 2022 Octaviano, Paringit, Patao, Patricio, Pigar, Quiambao OUTLINE o It can serve as a marker for disease. o If neurons are diseased, you can expect toxic metabolites in the I. INTRODUCTION CSF. II. CEREBROSPINAL FLUID Carries secretions from the pineal gland to the pituitary gland III. CHOROID PLEXUS o It carries hormones and other molecules. IV. VENTRICLES Formed mainly in the choroid plexuses of the lateral, third, and fourth V. CSF FLOW ventricles VI. BLOOD-BRAIN BARRIER Also produced by the ependymal cells that line the ventricles and form VII. BLOOD-CSF BARRIER brain substance through the perivascular spaces. VIII. CLINICAL IMPLICATIONS o It is mostly produced in the choroid plexuses of the lateral, third, IX. TEST YOURSELF and fourth ventricles. I. THE VENTRICULAR SYSTEM It is a series of interconnected canals that contain the cerebrospinal fluid. II. CEREBROSPINAL FLUID (CSF) Clear, colorless fluid found in the ventricles of the brain and in the subarachnoid space around the brain and the spinal cord. Contains: Figure 1. Choroid plexus and ependymal cells. o Glucose (half that of blood, 50-85 mg/100ml) ▪ When you harvest CSF, you always compare it with the real time glucose of the patient so you can know if it is abnormal or not. ▪ If the patient is in a fasting state, you will expect that the glucose is low. ▪ It depends on the serum glucose of the patient. o Protein (15- 45 mg/100 ml) ▪ It is constant. o Inorganic salts (chloride 720- 750 mg/100ml) o Few cells (0-3 leukocytes per mm3) ▪ Normally tolerated at around 5. Total volume (at any time): 150 ml o Anything in excess is hydrocephalus. Rate of production: 0.5 ml/minute (constant) o In abnormal states such as in choroid plexus papilloma, you will expect an increase in production. Figure 2. Choroid plexus supply, epithelial layer and function in CSF secretion in Rate of absorption: varies terms of Na +-K + pump o CSF is like a cushion. o When you have high pressure in your brain, instead of sacrificing blood, the brain will sacrifice CSF. ▪ The brain will not compromise its nourishment, which is in the blood. ▪ It would rather absorb more CSF to make way for a constant supply of blood in the head. Turnover rate: 5 hours o Turnaround time is the time it takes for the brain to produce CSF, have it circulate around the ventricles, and absorb it. The approximate time for the CSF to go through this once is 5 hours. Constant pressure (60- 150 mm water in lateral recumbent position), may be raised by straining, coughing or compressing the internal jugular vein. o Anything above 60-150 mmH2O, there will be increased intracranial pressure. Serves as a cushion between the CNS and the surrounding bones to protect it from mechanical trauma. o Functions as a reservoir and assist in the regulation of the contents of the skull. o If brain volume or blood volume increases, CSF volume Figure 3. Location of ependymal cells in the lateral ventricle. The mass seen in decreases. the image is the choroid plexus. Plays a part in the nourishment of nervous tissue Assists in removal of products of neuronal metabolism Page 1 of 10 [NEUROSCIENCE 1A] 01.14 VENTRICULAR SYSTEM – Dr. Vida Margarette Andal Figure 4. Microscopic view of the choroid plexus and the ependymal cells. Figure 6. Ependymal cells secrete and maintain homeostasis via aquaporins. III. CHOROID PLEXUS IV. VENTRICLES Grossly, they are seaweed-like and flows inside the canals. “cavity”; four cavities in the brain that are filled with CSF lined by Complex network of capillaries lined by ependymal cells ependymal cells Functions: 2 lateral ventricles o Produce CSF ↓2 foramen of Monro/interventricular foramen o Maintaining the blood-CSF barrier One third ventricle ▪ It is so the CSF will not mix with arterial blood. ↓ one aqueduct of Sylvius/Cerebral aqueduct ▪ It will mix with venous blood eventually but you don’t One fourth ventricle want it mixing with arterial blood. ↓ Two foramen of Luschka and one foramen of Magendie o Secretes various growth factors that maintain the stem cell pool Subarachnoid space (in the convexity or go down the spinal cord) in the subventricular zone You can harvest CSF through the spinal cord, in between the vertebra ▪ There are stem cells in the brain but it is very minor. (subarachnoid space). Ependymal Cells o If the CSF does not exit the foramen of Luschka and Magendie, o They have a lot of channels where ions can move freely in they will go to the central canal of the spinal cord. exchange with other intraventricular ions. ▪ They are also maintaining homeostasis within the CSF. o Cuboidal, ciliated o Oscillates 200 times per minute o Secrete, circulate and maintain homeostasis of the CSF (via aquaporins) ▪ Aquaporins- water channels o Facilitates flow of CSF by wafting of the cilia ▪ Flow of CSF is from the lateral ventricles→ foramen of Monro→ third ventricle→ aqueduct of Sylvius→ foramen of Luschka and Magendie→ spinal cord ▪ In order to facilitate the traffic of the CSF, the cilia will oscillate. o Lack tight junctions in between them ▪ Free exchange between the extracellular space and CSF ▪ There are tight junctions but not as tight as what you can see in the blood brain barrier. ▪ The tight junctions somehow allow an exchange between CSF and extracellular space. Figure 6. Ventricles of the brain. The flow of CSF is from the temporal horn, up to the occipital horn, to the frontal horn, and to the 2 lateral foramen of Monro → single 3rd ventral (found medial to the thalamus) → single aqueduct of Sylvius → single fourth ventricle → 3 exits (2 lateral foramen of Luschka, and one foramen Figure 5. Ependymal cells in the ventricles. of Magendie at the midline) Page 2 of 10 [NEUROSCIENCE 1A] 01.14 VENTRICULAR SYSTEM – Dr. Vida Margarette Andal Figure 10. MRI: Empty spaces in black depicting the ventricles. Figure 7. Observable structures of the brain ventricles: frontal horn, occipital horn, and temporal horn. Figure 8. Ventricles and foramen. Figure 11. Cast of the ventricular cavities of the brain. (A) Lateral view. (B) Anterior view. Figure 9. Fourth ventricle. Page 3 of 10 [NEUROSCIENCE 1A] 01.14 VENTRICULAR SYSTEM – Dr. Vida Margarette Andal Figure 12. Lateral ventricles. Figure 14. Fourth Ventricle in close association with the cerebellum. Figure 15. Coronal sections of the brain passing through the anterior horn of the lateral ventricle. Figure 13. Third ventricle in close association with the pineal gland. The pineal gland can send hormones to the pituitary via the CSF because it is close to the 3rd ventricle. Figure 16. Coronal sections of the brain passing through the body of the lateral ventricle. Page 4 of 10 [NEUROSCIENCE 1A] 01.14 VENTRICULAR SYSTEM – Dr. Vida Margarette Andal Figure 19. Flow of CSF in the optic nerve. CSF is found in the subarachnoid space in the optic nerve. It circulates around the eye but does not go into the eyeball. o When you have increased intracranial pressure, the cushion (CSF) will compress the optic nerve so you can end up with papilledema (bulging in the path of the optic nerve). Figure 17. Coronal sections of the brain passing through the posterior horn of the lateral ventricle. V. CSF FLOW Figure 20. Flow of CSF in the spinal nerve. CSF can extend up to the dorsal root ganglion of the spinal nerves but will not join the ganglion itself. CSF Absorption o Arachnoid villi that project into the dural venous sinuses, especially in the superior sagittal sinus. ▪ Projections that absorb the CSF. o Occurs when CSF pressure exceed venous pressure in the sinus ▪ If venous pressure increases, compression of the tips of the villi closes the tubules and prevents reflux of blood into the subarachnoid space → arachnoid villi prevent reflux of blood from the venous space to the subarachnoid space. - Venous sinus pressure is always higher which will compress the villi, rendering it unable to do its job. - This is a good thing because you don’t want a lot of blood to reflux into the subarachnoid space Figure 18. Circulation of the cerebrospinal fluid. The dashed line indicates the because you don’t want mixing when it is not course taken by fluid within the cavities of the central nervous system inside the sinus. o Because rate of production of CSF is constant, the rate of CSF CSF Flow- Extensions absorption controls CSF pressure. o CSF can also extend into small areas in the brain and surrounding organs such as the eyes. o A sleeve of subarachnoid space extends around the optic nerve to the back of the eyeball. At this point, arachnoids and pia mater fuse with the sclera o Around other cranial nerves and spinal nerves Page 5 of 10 [NEUROSCIENCE 1A] 01.14 VENTRICULAR SYSTEM – Dr. Vida Margarette Andal BBB is absent in areas of the brain where the capillary endothelium, contains fenestration across which proteins and small organic molecules may pass from the blood to nervous tissue: o Area postrema of the floor of the fourth ventricle ▪ Triggering or irritation of the area postrema will produce vomiting. o Hypothalamus o Pineal gland o Posterior lobe of the pituitary gland o The BBB is absent because you would want a free exchange of molecules and hormones Figure 22. The components of the Blood-Brain barrier. VII. BLOOD – CSF BARRIER Facilitates secretion of hormones Composed of: o Fenestrated endothelial cells o Basement membrane Figure 21. (A) Coronal section of the superior sagittal sinus showing an o Scattered pale cells with flattened process (as compared to the arachnoid granulation. (B) Magnified view of an arachnoid granulation showing foot processes of the astrocytes) the path taken by the CSF into the venous system. o Choroid plexus epithelial cells You want CSF to go out to the sinuses so it can drain out to the internal jugular vein where they can mix with the blood. VI. BLOOD – BRAIN BARRIER Tightly regulates the movement of ions, molecules and cells between the cells of the blood and the brain. Protects the neural tissue from toxins and pathogens that may be carried by blood o Even if you have infection in the body, there will be no meningitis because the body has a mechanism to protect the brain from the toxins in the blood. Composed of: o Capillary endothelial cells ▪ They overlap to form tight junctions. o Basement membrane surrounding the capillary ▪ Found between the capillary endothelial cells and the astrocytes. o Foot processes of astrocytes Figure 23. The components of the Blood-CSF barrier. ▪ They have an endothelium and foot processes which are normally tight. Cells involved in the BBB are lipophilic so lipophilic molecules can readily diffuse through the BBB, whereas hydrophilic molecules are excluded. VIII. CLINICAL CORRELATIONS Newborn BBB is more permeable to certain substances than it is in adults. o This is why there are more cases of neonatal meningitis. A. PAPILLEDEMA o You should be aggressive when it comes to infection of the o Edema of the optic disc newborn, because their BBB is not very well- developed yet. o Due to rise of the CSF pressure o Also compresses the thin walls of the retinal veins (resulting in congestion), bulging forward of the optic disc and papilledema Page 6 of 10 [NEUROSCIENCE 1A] 01.14 VENTRICULAR SYSTEM – Dr. Vida Margarette Andal o May result to optic atrophy and blindness - Causes can be choroid plexus papilloma; you can expect a communicating hydrocephalus. - It is the 3rd most common congenital brain tumor. You can expect increased head circumference in children because their fontanelles have not yet closed (which is why you measure the head circumference in neonates). - Altered mental status because of the compression of the thalamus. - In adults, signs of intracranial pressure are papilledema, headache, vomiting, decreased sensorium, etc. ▪ Atrophy of brain substance HYDROCEPHALUS CAUSES Figure 24. Papilledema 1. Choroid Plexus Papilloma (WHO Grade I) o More common in infants (third most common congenital brain o When there is increased pressure in the subarachnoid space, it tumor) compresses the structures inside, including the central retinal o Pediatric: present with increasing head circumference or altered artery and vein. mental status ▪ When you compress it, you will have congestion. o Adult: signs of increased intracranial pressure o When you view the retina through an ophthalmoscope, you o Surgical: tumor evacuation and cauterization might see exudation of blood, and bulging forward of the nerve. o Cannot be cured by medications o It is an ophthalmologic emergency. o You have to remove the tumor or cauterize the choroid plexus. o You have to relieve the pressure either by decreasing intracranial pressure or relieving CSF pressure because prolonged compression will result to death of optic nerve and irreversible blindness. B. HYDROCEPHALUS o Abnormal increase in the volume of the CSF within the skull o Causes: ▪ Abnormal increase in the formation of CSF (Choroid plexus papilloma, etc.) - In abnormal conditions like choroid plexus papilloma, you will have so much ependymal cells Figure 25. (A) Soft, globular, friable pink mass with irregular projections and high producing the CSF so you can expect increased vascularity (from capillaries). (B) Microscopy: papillary frond lined by columnar formation of CSF. epithelium. No mitotic activity, nuclear polymorphism and necrosis which is seen ▪ Blockage of the circulation of fluid (mass effect: tumor, in atypical and carcinomatous papilloma (WHO Gr II, III) abscess, blood) - When you block the circulation of fluid such as in Choroid Plexus Papilloma (WHO Grade I) the third ventricle, you can expect backflow in your o Communicating lateral ventricles. - Regular mast inside the ventricle ▪ Diminished absorption of fluid (meningitis, etc.) - In adult: CPP gets so big it can become non- - It can also occur with decreased absorption of communicating (there’s no flow of CSF, completely fluids such as in meningitis. obstructed). o Varieties: ▪ Noncommunicating - The ventricles are not connected to each other. - You can have hydrocephalus in the lateral ventricle but your 3rd and 4th ventricles are okay. ▪ Communicating - Can occur in cases of meningitis where you can expect a backflow to your ventricles. - Dilated lateral, 3rd and 4th ventricles. - There is no area of blockage between the ventricles. o Complications ▪ Compression or even herniation of brain matter - You don’t want your thalamus to be compressed since it can lead to a big 3rd ventricle and you can Figure 26. (Left) CPP in child at Lateral ventricle. (Right) CPP in adult patient at 4th end up with a comatose patient (compression of ventricle. intermedullary nuclei and reticular formation). ▪ Hypoplasia of brain substance 2. Compression of one lateral ventricle - Especially in kids o Non-communicating - If you don’t relieve the pressure of hydrocephalus - Can be non-communicating, especially if in kids, it will impede the growth of the gyri which completely operculated on one ventricle can lead to hypoplasia or atrophy (worst case) of brain substance. Page 7 of 10 [NEUROSCIENCE 1A] 01.14 VENTRICULAR SYSTEM – Dr. Vida Margarette Andal 6. Obstruction of cerebral aqueduct / aqueduct of Sylvius o Non-communicating Figure 31. Obstruction of cerebral aqueduct / aqueduct of Sylvius Figure 27. Compression of one lateral ventricle 7. Obstruction of the fourth ventricle 3. Obstruction of the interventricular foramen /foramen of Monro o Non-communicating o Non-communicating - Cerebellar stroke compressing the fourth ventricle - There’s blood inside Figure 32. Obstruction of the fourth ventricle Figure 28. Obstruction of the interventricular foramen /foramen of Monro Fourth Ventricle Outlet Obstruction (FVOO) o Congenital (in infants) or acquired (in adults); presence of 4. Obstruction of the third ventricle membranous structures obstructing the foramen of Magendie, o Non-communicating the only exit is Foramen of Luschka o Dandy-Walker, Arnold Chiari, Bourneville disease Figure 29. Obstruction of the third ventricle. (A,B,C) Papilloma, Craniopharyngioma 5. Obstruction of the third ventricle o Non-communicating - There’s no flow of CSF on each side Figure 33. Fourth Ventricle Outlet Obstruction (FVOO) - Blood is thicker than water; impedes CSF flow Dandy-Walker Malformation - Agenesis or hypoplasia of the vermis and failure of fourth ventricle foramina fenestration resulting to cystic enlargement of the fourth ventricle causing upward displacement of tentorium - Presents with bulging mast; macrocephaly during 1st month of life - Tx: ventriculoperitoneal shunt (VPS) insertion - Luschka and Magendie have no proper fenestration, upward displacement of the Tentorium Cerebelli. Figure 30. Obstruction of the third ventricle. Page 8 of 10 [NEUROSCIENCE 1A] 01.14 VENTRICULAR SYSTEM – Dr. Vida Margarette Andal 3. Chiari III o Herniation of the hindbrain into a low occipital or high cervical meningoencephalocele Figure 34. Dandy-Walker Malformation Figure 37. Chiari Malformation III C. ARNOLD-CHIARI MALFORMATION o Group of deformities of the posterior fossa and hindbrain 4. Chiari IV (cerebellum, pons, medulla) o Now obsolete o Severe cerebellar hypoplasia that is similar to primary cerebellar MALFORMATION TYPES agenesis 1. Chari I o There’s no cerebellum. o Least severe o One or both cerebellar tonsils project 5mm below the foramen magnum o There’s downward herniation of cerebellar tonsil Figure 38. Chiari Malformation IV Figure 35. Chiari I Malformation LUMBAR TAP / LUMBAR PUNCTURE Acquisition of CSF from the subarachnoid space in the lumbar space to be 2. Chiari II used for diagnostic purposes. o brainstem herniation and a towering cerebellum, in addition to Puncturing the lumbar area herniated cerebellar tonsils and vermis due to open distal spinal dysraphism/myelomeningocele. o Myelomeningocele in lumbar spine o Downward displacement of many things (tonsils, cerebellum, 4th o ventricle, tectum; downward suction) Figure 39. Lumbar Puncture In doing your lumbar tap, you must know your Anatomy! In adult, spinal cord ends at L1 (therefore make a puncture below L2 or at the level of the iliac crest). Figure 36. Chiari Malformation II Page 9 of 10 [NEUROSCIENCE 1A] 01.14 VENTRICULAR SYSTEM – Dr. Vida Margarette Andal IX. TEST YOURSELF 1. They are seaweed-like structures that flow inside the ventricular canals. a. Choroid plexus c. Ependymal cells b. Aquaporins d. Arachnoid granulation 2. The following statements concern the ventricular system: a. The fourth ventricle has a rectangular-shaped floor. b. The pineal body is suspended from the roof of the fourth ventricle. c. The nerve centers controlling the heart rate and blood pressure lie beneath the floor of the third ventricle. d. The choroid plexus of the lateral ventricle projects into the cavity on Figure 40. Anatomy of the spinal cord for lumbar puncture. its medial side through the choroidal fissure. e. The foramen of Magendie is an aperture in the roof of the third After lumbar puncture, a lot of patients will complain about headache ventricle due to spinal compliance Develops after 24 hours, usually last and resolve on its own after 10 days. 3. Ependymal cells maintain homeostasis of the CSF via: a. Aqueduct c. Aquaporins Indications b. Tight junctions d. Microvilli To exclude subarachnoid hemorrhage in acute severe headache, especially when neuroimaging is normal/inconclusive. 4. The following statements concern the third ventricle EXCEPT: To investigate meningitis: bacterial, viral, tuberculous, cryptococcal, a. It is situated between the thalami. chemical, carcinomatous (patient with fever, rigid neck, seizures, b. It communicates with the lateral ventricles through the infection) interventricular foramina. To investigate neurological disorders: multiple sclerosis, sarcoidosis, GBS, c. It is continuous with the fourth ventricle through the cerebral CIDP, mitochondrial disorders, leukoencephalopathies, paraneoplastic aqueduct. syndromes, autoimmune encephalitis d. The choroid plexus is situated in the floor. To demonstrate and manage disorders of ICP: idiopathic intracranial e. The choroid plexus receives its arterial supply from the internal carotid hypertension, normal pressure hydrocephalus and basilar arteries To administer therapeutic or diagnostic tests: spinal anesthesia, intrathecal chemotherapy, intrathecal antibiotics, intrathecal baclofen, 5. What structures absorb CSF? contrast media in myelography or cisternography a. Cisterna magna c. Choroid plexus b. Ependymal cells d. Arachnoid villi Contraindications Infected skin over the puncture site (otherwise you will introduce 6. Why is the brain free of infections even if the rest of the body is infected? bacteria to the sub arachnoid space) a. Because of the blood-CSF barrier Increased intracranial pressure from any space-occupying lesion (mass, b. Because of the blood-brain barrier abscess). c. Because the brain has resident microglia and non-parenchymal Trauma or mass to lumbar vertebrae macrophages ready to kill the pathogens. Severe thrombocytopenia, bleeding diathesis, anticoagulant therapy d. Because it has choroid plexus to trap pathogens from entering the (invasive procedure). substance of the brain May be done if platelet is ≥ 50 x 109/L Safe to do in patients on aspirin. No data on clopidogrel 7. Triggering of this area will induce vomiting. Warfarin must be stopped 5-7 days in advance, INR < 1.2 a. Area postrema c. Dura mater Heparin must be stopped 24h prior b. Foramen of Luschka d. Subarachnoid space 8. What are the arteries of the brain? Layers for Lumbar Puncture a. One internal carotid artery b. Two vertebral arteries c. Two internal carotid arteries d. B and C 9. Agenesis or hypoplasia of the vermis and failure of fourth ventricle foramina fenestration resulting to cystic enlargement of the fourth ventricle causing upward displacement of tentorium a. Dandy-Walker Malformation b. Choroid Plexus Papilloma (WHO Grade I) c. Arnold Chiari Malformation d. Hydrocephalus 10. The rate of CSF production is constant, and the rate of CSF absorption controls CSF pressure. Figure 41. Anatomy of the spinal cord for lumbar puncture. In doing a lumbar tap even the depth of the needle is appropriate, CSF can be contaminated with blood, especially in epidural space which means you're too shallow to extract CSF. In case of a bloody extract, one must replace the needle then use this until it reaches the subarachnoid space. Answers: 1. A 2. D 3. C 4. D 5. D. 6. B 7. A 8. D 9. A 10. TRUE Page 10 of 10