Term
| What are the primary functions of CSF? |
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Definition
1) Keeping brain and chord aloft and cushioning it during movement/trauma
2) Removal of metabolites from brain to venous system.
3) Osmotic and ionic balance of extracellular fluid
4) Intracranial pressure |
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Term
| Where and how is CSF produced? |
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Definition
Produced at 500ml/day for rapid turnover.
Extracellular fluid and CSF readily diffuse between ependymal lining of ventricles (maintain ionic concentration of membranes)
**Ependymal lining separates blood from brain
1) 70% from choroids plexus (ciliated cuboidal epithelial cells that face into ventricles and sit on vascularized stroma) in walls of Lateral and 3rd ventricles and roof of 4th ventricles
2) 30% produced as ultra filtrate of capillary blood or fluid from neuronal metabolism |
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Term
| How does the ionic composition of CSF differ from serum? |
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Definition
1) Active transport into epithelial cells of choroid plexus via Na/K+ pumps maintains differential
1) K and Ca, as well as protein are lower in CSF, but Mg and Cl are higher |
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Term
| Explain how CSF is circulated and absorbed. |
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Definition
- Moves unidirectionally from paired lateral ventricles through Foraminae of Monroe, into 3rd ventricle, then through Cerebral Aqueduct into 4th ventricle.
- CSF then exits the ventricles via Foraminae of Magendie and Luschka and enters subarachnoid space at Cisterna Magna, and then flows into the spinal chord and brain across the pia mater.
- Most CSF absorned via arachnoid granulations (one-way valves driven by CSF pressure differential with venous pressure) into superior saggital sinus |
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Term
| What 3 factors drive CSF circulation? |
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Definition
1) Constant CSF production increases hydrostatic pressure
2) Beating of ciliated epithelia lining ventricles and spinal chord
3) Pulsatile changes in volume that accompany cardiac systole |
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Term
| How is intracranial pressure (ICP) determined? |
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Definition
1) ICP is Vbrain +V blood + Vcsf (normally 2-5mmHg).
- If one component is enlarged, abnormal ICP can cause compression of brain and vessels (Monro-Kellie hypothesis) |
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Term
| What are the cardinal signs of abnormal ICP? |
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Definition
1) Severe headache (compressed vessels and expansion of dura stimulate pain receptors)
2) Nausea and vomiting (pressure on medullary centers receiving GI signals and controlling emesis
3) Papilloedema (pressure-induced swelling of optic nerve) |
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Term
| What are the 2 major types of pathology associated with the CSF system? |
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Definition
1) Obstructions to flow such as intraventricular tumors that lead to CSF buildup, increased ICP with ventricular enlargement, and brain damage (non-communicating hydrocephalus)
- Congenital NCH is Arnold-Chiari Malformation from Spina Bifida, where vertebral canal fails to close completely during development, and compression on foramen of Magendie and Lushka block CSF outflow
- Communicating Hyrocephallus arises when CSF absorption at arachnoid granulation is prevented, or when CSF is overproduced by choroids plexus (normal ventricular-extraventricular communication)
2) Altered composition of CSF that affect meninges and neuronal function.
- Meningitis caused by Staph or TB that enter CSF and cause inflammation presenting with stiff neck and headache because of irritation of motor nerves of cervical chord and cranial nerve XI. |
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Term
| What is the difference between Communicating and Non-communicating Hydrocephalus? |
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Definition
1) NCH is from obstruction to flow that prevents exchange between extra-ventricular and ventricular systems (blockage of foramen)
- Congenital NCH is Arnold-Chiari Malformation from Spina Bifida, where vertebral canal fails to close completely during development
2) Communicating Hydrocephallus arises when there is normal communication, but ICP results from decreased absorption or overproduction
- arises when CSF absorption at arachnoid granulation is prevented, or hen CSF is overproduced by choroids plexus |
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Term
| What is the course of CSF flow from the cerebral aqueduct to the extra-ventricular environment. |
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Definition
1) Flows from laterally ventricle (telencephalic), through foramen of monroe, on to the 3rd ventricle (diencephalic)
2) Flows from 3rd ventricle through the Cerebral aqueduct (mesencephalic) and into the 4th ventricle (Myelencephalic and Metencephalic)
3) Flows from 4th ventricle through left and right foramina of Lushka and central foramen of Magendie into the sub-arachnoid space
4) Flow on to the pia and the brain/spinal chord, before draining through Arachnoid granulations into the superior sagittal sinus and back through the venous system. |
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