CSF Flashcards
Where is CSF produced?
Studies of CSF production determined that 35% was derived from the third and lateral ventricles, 23% from the fourth ventricle, and 42% from the subarachnoid space
What is the Queckenstedt, or jugular compression, maneuver?
compression of the external jugular veins results in increased CSF pressure can be used when collecting CSF. In instances when CSF flows slowly, having an assistant carefully, without moving the patient, compress the external jugular veins may increase the flow of CSF, allowing for more rapid collection. : This extracranial venous compression causes an immediate increase in intracranial blood volume, which requires more space. CSF volume is compressed and displaced through the foramen magnum, causing an elevation in the pressure in the spinal cord subarachnoid space
Hypercapnia causes cerebral arterial vasodilatation or vasoconstriction?
Hypercapnia causes cerebral arterial vasodilation, which increases the volume of intracranial blood. Ensuring normal ventilation prevents dilation of cerebral blood vessels, which would contribute to an increase in ICP
How can hypocapnia be caused, by hiper- or hypoventilation? Does hypocapnia cause vasodilatation or vasocontriction?
hyperventilation will decrease carbon dioxide in blood (hypocapnia); this is a procedure that may be used during intracranial surgery to cause cerebral vasoconstriction.
What is the cerebral perfusion pressure?
mean arterial blood pressure minus ICP, it determines the oxygen and nutrient supply to the parenchyma.
Which cerebral gyrus is commonly displaced in subfalcine herniation (midline shift)?
the cingulate gyrus
Explain the miosis and mydriasis which occur due to a caudal transtentorial herniation.
patients initially often develop a constricted pupil followed by a widely dilated unresponsive pupil ipsilateral to the herniation, altered mentation, and gait deficits. The progressive increase in pressure initially causes pupillary constriction possibly because of disinhibition of oculomotor parasympathetic neurons from loss of the influence of prosencephalic upper motor neurons, whereas the subsequent pupillary dilation represents loss of function of these oculomotor neurons
Which cerebellar lobules usually herniate in a foramen magnum herniation?
Pyramis and uvula (caudoventral aspect of the vermis).
What is the major site of CSF absorption?
the arachnoid villi that are located in the venous sinuses or cerebral veins. Collection of these vili are known as arachnoid granulations.
What are other sites of CSF absorption besides the arachnoid vili?
the veins and lymphatics found around the spinal nerve roots and spinal nerves at the intervertebral foramina and associated with cranial nerves I, II, and VIII, where they pass through the skull bones. CSF passes through the cribriform lamina of the ethmoid bone, where it is absorbed or leaks into the nasal cavity, resulting in cerebrospinal rhinorrhea. The small amount of CSF in the interstitial spaces of the parenchyma may be absorbed into the parenchymal blood vessels. CSF is formed and absorbed throughout the ventricles and the subarachnoid space.
What is the role of the P-glycoprotein?
an adenosine triphosphate–dependent efflux pump expressed by brain capillaries that transports xenobiotics into the blood, thereby preventing accumulation in the brain parenchyma.
Name the gene which mutates, and typical breeds for defect coding of P-glycoprotein.
ABCB1 gene
- most common in collies but also occurs in Australian shepherds, border collies, and old English sheepdogs
What constitutes the blood-CSFD barrier and where is it found?
exists between plasma and CSF at the choroid plexus and consists of two cell layers separated by a thin basement membrane. The vascular endothelial layer and its basement membrane have fenestrations, and the cells lack tight junctions. The choroidal epithelium consists of large cuboidal cells with tight junctions at their ventricular surfaces. Fragments of meningeal cells are interspersed among these endothelial and epithelial cells
What is external hydrocephalus, and what internal hydrocephalus?
external - CSF accumulation in a dilated subarachnoid space. This is also referred to as hydrocephalus ex vacuo
internal - ventricular dilation with CSF accumulation.
What is compensatory hydrocephalus?
Hydrocephalus ex vacuo
a disease process has caused the loss of parenchyma and CSF volume has increased (hydrocephalus) to take up the space previously occupied by that portion of the lost parenchyma. CSF increases in volume to compensate for the loss of parenchyma.
Name the most important finding and most likely disease in this macro of a feline brain
lack of patency of the mesencephalic aqueduct (leading to obstructive hydrocephalus of the 3r and lat ventricles)
FIP
