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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)
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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
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where does temporal lobe sit?
inferior to the lateral fissure (Fissure of sylvius) and extends posteriorly to parietal and temporal lobes
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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
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where is the occipital lobe located? what does it contain?
begins at parietooccipital sulcus and extends posteriorly to tentorium cerebelli. Contains the visual cortex.
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what does the most medial portion of the temporal lobe contain?
olfactory cortex
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what is normal CMRO2? where is oxygen consumption the greatest?
- 3-3.5 ml/100gm/min 50ml/min
- In gray matter
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what percent of oxygen does the brain normally consume?
20 %
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what is the average CBF?
in gray matter?
in white matter?
- 50 ml/100g/min
- 80 ml/100g/min
- 20 ml/100g/min
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What is the total CBF in adults? what percent of cardiac output does it make up?
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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
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where does the vertebral artery branch off from?
the subclavian artery, ascends through foramen magnum and divides into 2 posterior cerebral arteries
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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
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what supplies a large area of frontal, parietal and temporal lobes?
middle cerebral artery
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what happens from occlusion of middle cerebral artery?
dysfunction of cortical area innervating face and upper extremity, also involves language and speech
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what does posterior cerebral artery supply? what happens if its occluded?
- supplies occipital lobe.
- occlusion leads to dysfunction of vision
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whats the equation for CPP? what is normal? below normal causes? above normal causes?
- MAP-ICP=CPP
- normal 50-150 mmHg
- below 50 mmHG ischemia
- above 150 mmHG hyperemia
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what is pressure auto regulation?
arterioles dilate or constrict in response to changes in BP and ICP in order to maintain a constant CBF
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what factors can impair autoregulation?
head injury, hypercapnea, htn, hypoxia/ischemia, hypothermia, intracranial tumors, SAH, I.A
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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
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what is vasogenic edema?
cytotoxic edema?
interstitial?
hyperemic?
- 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
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what does hypoperfusion lead to?
- cerebral ischemia
- complete vs incomplete depends on degree of blood flow reduction and its duration
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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
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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
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what factors increase CSF production?
- hyperthermia
- cervical sympathectomy
- decrease serum osmolality
- halothane
- growing tumors
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what factors increase CSF production?
- hypothermia
- diamox
- high osmolarity
- increase ICP
- steroids
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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
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what are the early warning signs for increased ICP?
- decreased LOC
- pupillary dysfunction
- changes in vision
- deterioration of motor function
- headache
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late signs of increased ICP?
- further decrease in LOC
- dilated pupils
- hemiplegia
- vomiting
- papilledema
- htn
- bradycardia
- irregular respiration
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what is cushings triad?
htn, bradycardia, irreg. respirations
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what are the 4 indications for ICP monitoring?
- increased volume of brain
- increased vol of blood
- increased vol of CSF
- lesions
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what are the ICP monitoring devices?
- catheters (can drain fluid, must be placed in O.R)
- bolts (fastest but cannot drain fluid)
- screws
- fiberoptic cables
- microchip pressure transducers
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where are the sites for ICP monitoring?
- ventricular
- parenchymal
- epidural
- subdural
- subarachnoid
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what are the 3 herniation syndromes?
- transcalvarial
- subfalcine- hemispheres herniate under the falx
- transtentorial- the supratentorial content herniates through the tentorial notch.
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what are the 4 types of transtentorial herniations?
uncal, upward, tonsillar, cenal
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