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What is cerebral edema?
An increase in the fluid content of the brain which increases intracranial pressure.
Flattened gyri and narrowed sulci.
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What are the 3 intracranial tissue compartments?
Brain %80
Blood supply 10%
CSF 10%
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What tissue compartment is most likely to compensate in the event of increased intracranial pressure?
CSF compartment
Compensation occurs because there's no extra room in the skull so edema takes up room from other compartments.
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How do you calculate cerebral perfusion pressure?
Mean arterial pressure - intracranial pressure (ICP)
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What happens if intracranial pressure becomes close to or exceeds mean a. pressure?
Decreased tissue perfusion which leads to hypoxia, cell injury and/or death
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What can severe increased intracranial pressure?
Herniation
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When can increased intracranial pressure lead to death?
If vital brain centers are compressed
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What is herniation?
Displacement of tissue from one cavity to another.
With increased ICP, the pressure is uneven and brain tissue shifts from areas of high pressure to low.
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Herniation and the increased pressure leads to _____ displacement of the brain.
Downward
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Hernation of the medulla oblangata into the ______ ______ may result from increased ICP.
Foramen magnum
Immediate death occurs if cardio-resp. centers in medulla are compressed.
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Where is CSF formed?
Choroid plexus
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Describe the flow of CSF
Choroid plexus - lateral vents - 3rd vent - cerebral aqueduct - 4th vent - central canal - aperatures - subarachnoid space - arachnoid villi - dural sinuses
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What is hydrocephalus?
Abnormal increase in CSF in the ventricular system
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What are different causes for hydrocephalus?
Congenital abnormalities
Tumor obstruction
Inflammation
Obstructed villi
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What is hydrocephalus ex vacuo?
Secondary to brain atrophy, happens before an increase in CSF
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Does congenital hydrocephalus affect ICP?
Nope
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What is congenital hydrocephalus?
Seperation of cranial sutures leading to bulging of fontanels.
Risk of development disorders
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What are the 2 distinct components of normal consciousness?
Arousal (wakefulness)
Content of thought (awareness)
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What defines unconsciousness?
State of being insensible, or without conscious experience
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What is physiological unconsciousness?
Sleepzzzz
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_____ is profound unconsciousness.
Coma
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What are the decreasing levels of consciousness?
Confusion - disorientation - lethargy - stupor - coma
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What is a seizure?
Excessive or abnormal, high frequency electrical discharge of cerebral neruons
Symptom not disease
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Seizure threshold is ______ variable.
Genetically
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What is a convulsion?
Jerky, rapid, contract-relax movement seen with some seizures
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What are the 3 phases of a seizure?
Aura 5-15sec
Ictal 2-3min (actual seizure)
Post-ictal
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What are generalized seizures?
Involves neurons bilaterally; consciousness is always lost
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What are partial seizures?
Involves neurons unilaterally; relatively harmless
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What is a secondary generalization seizure?
Starts as partial but becomes generalized
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What are cluster seizures?
Onset of subsequent seizure before the patient has fully recovered from previous seizure.
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What is status epilepticus?
Patient remains in the seizure; can be fatal without treatment
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What is epilepsy?
Term for a primary condition that causes seizures
Could be due to metabolic defects, genetcic predisposition, or congenital malformation
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What are 3 common causes for secondary seizures?
Cerebral lesions
Metabolic disorders
Cerebral trauma
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What are the 3 mechanisms for head trauma?
Primary injury caused by the insult
Secondary injury which could include cerebral edema, hemorrhage, increased ICP, and hypoxia from cerebral ischemia
Tertiary injury which is seen in other parts of the body as a result of the injury
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What is a concussion?
Functional disturbance without significant macroscopic changes
Debateble whether or not there are lasting effects after recovery
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What are the symptoms of post-concussion syndrome?
Headache, irritability, insomnia, poor memory/concentration
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What characterizes mild concussions? (grades I-III)
Diffuse brain injury
Confusion and disorientation with brief amnesia without loss of consciousness
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What characterizes a classic concussion? (grade IV)
Immediate loss of consciousness with amnesia
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What are contusions?
Bruise (to cortical surface of brain in this case); the focal injury due to blunt trauma
Can lead to hematomas
High fatality rate
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What is a coup lesion?
Lesion located at site of impact due to the direct force
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What is a countercoup lesion?
Located at opposite side of brain due to hitting that side of the skull
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Intracranial hemorrhage and hematomas _____ the underlying brain tissue.
Compress
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What can cause intracranial hemorrhage and hematoma?
Trauma, rupture of congentially abnrml or hyptertensive vessels, aneurysm rupture, or bleeding disorders
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Where do traumatic brain hemorrhages and hematomas usually occur?
Epidural or subdural spaces
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What causes intracerebral and subarachnoid hemorrhage?
Cerebrovascular disease
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How many mL of fluid in the cranium can cause coma and death?
50 cc
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What is a epidural hematoma?
Rupture of meningeal a., usually associated with skull fracture.
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Where is the most common site for epidural hematomas?
Middle meningeal a.
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How can epidural hematomas progress if they aren't drained?
They can herniate. You'll die.
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Epidural hematomas have arterial bleeding so they expand _____.
Rapidly
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What is a subdural hematoma?
Disruption of bridging veins that extend from the surface of the brain to the dural sinuses.
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What causes acute subdural hematomas?
Caused by any condition associated with rapid changes in head velocity
Can progress into chronic subdural hematoma
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What are chronic subdural hematomas?
Develop over period of weeks to months, often associated with brain atrophy.
Formation of neomembrane
Slowly evolving symptoms can be confused with dementia
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What are some cerebrovascular disorders?
Subarachnoid hemorrhage, CVA/stroke, aneurysm, arteriovenous malformation
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What is subarachnoid hemorrhage?
Blood escapes from a defect into the subarachnoid space, traps CSF
Can result from braineurysm, arteriovenous malformations, HTN
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What's the most common underlying cause of brain hemorrhage?
Hypertension
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Coagulation disorders, open heart surgery, neoplasms, aneurysms, and vascular malformations are examples of what?
Intracerebral hemorrhage
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What is common evidence in increased ICP?
Severe headache, vomiting, and loss of consciousness
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For intracranial hemorrhages, if it's bleeding slowly, there is (more/less) time for collateral circulation.
More
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____ account for 80% of all cerebrovascular accidents.
Infarcts
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What is the most common cause of brain infarcts?
Cerebral atherosclerosis
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What are secondary risk factors for CVAs/stroke?
HTN, diabetes mellitus, smoking
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What are ischemic strokes?
Account for 80% of strokes, similar to MI.
- Thrombotic: from clot in the head
- Embolic: elsewhere
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What is a hemorrhagic stroke?
Account for 20%; most frequently fatal stroke, shouldn't treat with a clot buster
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What do the clinical signs of CVA depend on?
Location of lesion, time it took to develop, collateral circulation
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Describe the normal blood supply of the heart. Quickly.
- Vertebral a.
- Basilar a.
- Circle of Willis
- Internal carotid a.
- Anterior cerbral a.
- Middle cerebral a.
- Posterior cerebral a.
- Superior cerebellar a.
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CVA of the middle cerebral a. causes contralateral _______ and ______.
Hemiparesis and spasticity
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CVA of which artery causes loss of sensation on side of the body opposite the infarct, visual field abnormalities, and speech abnormalities?
CVA of the middle cerebral a.
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Why are CVA of the internal carotid a. less serious in most cases?
The Circle of WIllis supplies internal carotid area so deficits are diminished
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What happens in extreme cases of CVA of the internal carotid a.?
Massive infarction of cerebrum with blindness in one eye.
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What are TIAs?
Ischemia without infarction
Often epreced CVAs
Can last minutes up to several hours
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1/3 of patients with TIAs will have a significant infarct within ___ years.
5
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What's the most common cause of spontaneous subarachnoid hemorrhage?
Rupture of a saccular aneurysm
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What are different types of cerebral aneurysms?
- Saccular
- Fusiform dialtions
- Infectious mycotic aneurysms
- Dissecting aneurysms
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Where do most (80%) saccular aneurysms occur?
Bifurcations
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Saccular aneurysms are ____-occupying lesions that increase _ _ _.
Space-occupying
ICP
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What is associated with abrupt onset of saccular aneurysm?
Sever headache, vomiting, and loss of consciousness
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50% of patients with abrupt _____ aneurysms die within several days.
Saccular
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What are common complications that occur with saccular aneurysms?
- Cerebral infarcts
- Acute hydrocephalus
- Herniation
- Chronic hydrocephalus
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What are arteriovenous malformations?
Abnormalities in angiogenesis producing a mass of tortuous vessels; usually congenital
Range from small to large lesions associated with variable neurologic deficits and massive hemorrhage
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Is there a capillary bed with arteriovenous malformations?
Nope
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Small arteries have a _____ tunica media.
Deficient.
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With arteriovenous malformation, the vessel is predisposed to _____ and ______ .
rupture and hemorrhage
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