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where is the frontal lobe located? what does it contain?
- largest lobe
- extends posteriorly to central sulcus,
- contains motor cortex( pre central gyrus) and Brocas speech area (motor component of speech)
Where is parietal lobe located?
- extends from central sulcus to parieto occipital sulcus.
- Sensory cortex of brain that integrates sensory input to allow discriminiation of shape, texture size and weight
where does temporal lobe sit?
inferior to the lateral fissure (Fissure of sylvius) and extends posteriorly to parietal and temporal lobes
what is the temporal lobe of the dominant hemisphere responsible for?
language. wernikes speech area located at junction of parietal and temporal lobes is responsible for language input
where is the occipital lobe located? what does it contain?
begins at parietooccipital sulcus and extends posteriorly to tentorium cerebelli. Contains the visual cortex.
what does the most medial portion of the temporal lobe contain?
what is normal CMRO2? where is oxygen consumption the greatest?
- 3-3.5 ml/100gm/min 50ml/min
- In gray matter
what percent of oxygen does the brain normally consume?
what is the average CBF?
in gray matter?
in white matter?
- 50 ml/100g/min
- 80 ml/100g/min
- 20 ml/100g/min
What is the total CBF in adults? what percent of cardiac output does it make up?
where does the internal carotid arise from?
the common carotid, runs through the base of the skull and branches into anterior and middle cerebral arteries
where does the vertebral artery branch off from?
the subclavian artery, ascends through foramen magnum and divides into 2 posterior cerebral arteries
what does the anterior cerebral artery do? what does occlusion of this artery result in?
- supplies the medial portion of the frontal and parietal lobes.
- dysfunction of the cortical area supplying primarily lower extremities
what supplies a large area of frontal, parietal and temporal lobes?
middle cerebral artery
what happens from occlusion of middle cerebral artery?
dysfunction of cortical area innervating face and upper extremity, also involves language and speech
what does posterior cerebral artery supply? what happens if its occluded?
- supplies occipital lobe.
- occlusion leads to dysfunction of vision
whats the equation for CPP? what is normal? below normal causes? above normal causes?
- normal 50-150 mmHg
- below 50 mmHG ischemia
- above 150 mmHG hyperemia
what is pressure auto regulation?
arterioles dilate or constrict in response to changes in BP and ICP in order to maintain a constant CBF
what factors can impair autoregulation?
head injury, hypercapnea, htn, hypoxia/ischemia, hypothermia, intracranial tumors, SAH, I.A
what is hyperperfusion?
- "right sided" autoreg failure.
- CPP exceeds the upper limit of autoregulation, flow initially increases with a fixed maximal arterial resistance. the arterial bed dilates under increasing pressure, and resistance falls
what is vasogenic edema?
- shift of fluid from intravascular to extracellular space
- shift of fluid from extracellular to intracellular space
- shift of CSF into extracellular space
- increase in intravascular volume
what does hypoperfusion lead to?
- cerebral ischemia
- complete vs incomplete depends on degree of blood flow reduction and its duration
what is cerebral steal? inverse steal?
- decrease flow to ischemic areas caused by blood vessel dilatation in non ischemic areas
- can redistribute CBF to ischemic areas
where is CSF made? how much is made per hour? day?
- produced in choroid plexus of lateral 3 and 4 ventricle. Small amts produced in ependymal cell lining
- 21 ml/hr
- 500 cc/day
what factors increase CSF production?
- cervical sympathectomy
- decrease serum osmolality
- growing tumors
what factors increase CSF production?
- high osmolarity
- increase ICP
what is in the cranial vault?
- brain 80%, blood 12% CSF 8%
- increase in any of the components will result in decrease in the other
what are the early warning signs for increased ICP?
- decreased LOC
- pupillary dysfunction
- changes in vision
- deterioration of motor function
late signs of increased ICP?
- further decrease in LOC
- dilated pupils
- irregular respiration
what is cushings triad?
htn, bradycardia, irreg. respirations
what are the 4 indications for ICP monitoring?
- increased volume of brain
- increased vol of blood
- increased vol of CSF
what are the ICP monitoring devices?
- catheters (can drain fluid, must be placed in O.R)
- bolts (fastest but cannot drain fluid)
- fiberoptic cables
- microchip pressure transducers
where are the sites for ICP monitoring?
what are the 3 herniation syndromes?
- subfalcine- hemispheres herniate under the falx
- transtentorial- the supratentorial content herniates through the tentorial notch.
what are the 4 types of transtentorial herniations?
uncal, upward, tonsillar, cenal