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CT and MRI are most commonly used to observe the brain for cerebral atrophy. A CT scan takes cross sectional images of the brain using X-rays, while an MRI uses a magnetic field. With both measures, multiple images can be compared to see if there is a loss in brain volume over time. [20]
Micrograph showing gliosis in the cerebellum. Reactive astrocytes on the left display severe proliferation and domain overlap. Reactive astrogliosis is the most common form of gliosis and involves the proliferation of astrocytes, a type of glial cell responsible for maintaining extracellular ion and neurotransmitter concentrations, modulating synapse function, and forming the blood–brain ...
Hydrocephalus ex vacuo is a condition in which there is ventriculomegaly due to loss of brain volume which then results in a subsequent increase in CSF. [19] This is most commonly seen in patients with neurodegenerative disorders such as Alzheimer's disease (due to hippocampal atrophy specifically). [20]
Hypovolemia, also known as volume depletion or volume contraction, is a state of abnormally low extracellular fluid in the body. [1] This may be due to either a loss of both salt and water or a decrease in blood volume. [2] [3] Hypovolemia refers to the loss of extracellular fluid and should not be confused with dehydration. [4]
Overall there is more water than sodium in the body. The intravascular volume is low because the water will move through a process called osmosis out of the vasculature into the cells (intracellularly). The danger is tissue swelling (edema) the most important being brain edema which in turn will cause more vomiting.
The body compensates for volume loss by increasing heart rate and contractility, followed by baroreceptor activation resulting in sympathetic nervous system activation and peripheral vasoconstriction. Typically, there is a slight increase in the diastolic blood pressure with narrowing of the pulse pressure.
The typical brain sample is a surgical specimen, a brain sample obtained during epilepsy surgery. [1] The International League Against Epilepsy (ILAE) defines 3 hippocampal sclerosis (HS) types: predominant neuronal cell loss in subfields CA1 and CA4 (HS ILAE type 1), subfield CA1 (HS ILAE type 2) or subfield CA4 (HS ILAE type 3).
The pressure–volume relationship between ICP, volume of CSF, blood, and brain tissue, and cerebral perfusion pressure (CPP) is known as the Monro–Kellie doctrine or hypothesis. [22] [23] [24] The Monro–Kellie hypothesis states that the cranial compartment is inelastic and that the volume inside the cranium is fixed.