Brain

Meninges

• dura mater
  • holds in the CSF in which the hemispheres and brainstem float
  • leathery, hide-like texture
• arachnoid mater
  • thin membrane
  • subarachnoid space where CSF circulates: combined w/membrane creates spongy cushion
  • arteries and veins enter and exit space
• pia mater
  • thin, filmy membrane
  • adheres closely to cortical surface

Potential Space

• no measurable volume until something causes them to expand and create a “real” space
• often referenced when bleeding occurs in one of the spaces between the layers of the protective coverings
• collection of blood within the meningeal spaces can exert pressure on brain tissues and cause loss of function, including speech and lang
• epidural space: between skull and dura mater
• subdural space: between dura and arachnoid mater
• subdural hematoma: pooled blood in the space between the the dura and arachnoid mater

Ventricles

• lateral ventricles (paired)

• third ventricle

• cerebral ventricle

• fourth ventricle

  

• function of ventricles

  • to produce CSF
  • protects/gives nutrients to brain
  • makes brain float within the skull
  • Continuous with the central canal of the spinal cord
  • CSF is found between the pia mater and arachnoid mater

Circulation

• Anterior circulation: derived from internal carotid artery via aortic arch

  • pathway
  • aorta → common carotid artery (left & right)
  • common carotid artery → internal carotid artery and external carotid artery
  • internal carotid artery → anterior cerebral artery & middle cerebral artery
  • Aorta: Largest artery; feeds the left and right common carotid arteries
  • Left common carotid artery: supplies the left side of the face and hemisphere of brain
  • External carotid artery: provides blood to the pharynx, tongue, face and eyes
  • Internal carotid artery: main source of blood supply to the brain
  • Anterior cerebral artery: supplies blood to medial portions of the frontal and parietal lobes, corpus callosum, and basal ganglia
  • Middle cerebral artery: important in speech, language and hearing function

• posterior circulation: derived from basilar artery via subclavian artery

• circle of willis

  • located on base of brain
  • circular pattern of blood flow has capability of compensating for loss of blood flow from one of the main blood supplies in the brain
  • locating damage to site is important to diagnostics
  • Vertebral artery (VA)
  • Basilar artery (BA)
  • Posterior cerebral artery (PCA)
  • Posterior communicating artery (PComm)
  • Middle cerebral artery (MCA)
  • Internal carotid artery (IC)
  • Anterior cerebral artery (ACA)
  • Anterior communicating artery (AComm)

  

• Middle cerebral artery

  • MCA upper and lower branches provide blood supply to lateral hemisphere surfaces
  • affects Broca’s area, primary auditory cortex, most of primary motor and somatosensory cortex, Wernicke’s area, angular and supramarginal gyri, and arcuate fasciculus
  • MCA includes branches that supply blood to the frontal, parietal, and temporal lobes
  • infarct at junction between ICA and MCA interrupts blood flow to all perisylvian speech and language areas
  • deeper infarcts (further into cerebral hemispheres) may produce more localized deficits

Stroke/Cerebrovascular Accident (CVA)

• brain requires a constant supply of oxygen and glucose, and is intolerant of sudden decreases in oxygen, which are often signaled by a rapid decrease in cognitive functioning
• acute events and processes
  • sudden onset - embolism
• insidious events and processes
  • gradual onset - thrombosis
• CVA is sudden death of some brain cells due to lack of oxygen when the blood flow to the brain is impaired by blockage or rupture of an artery to the brain
• Necrosis
  • death of tissue
  • w/out oxygen, brain tissue can become necrotic in 3-5 min
• infarct
  • necrosis of brain tissue caused by lack of oxygen (sometimes used to refer to specific type of stroke)
• CVA Facts
  • more than 795,000 in US have a stroke per year, 610,000 are first time
  • someone in US has stroke every 40 sec
  • leading cause of serious long term disability
  • there are nearly 7 million stroke survivors in the US
  • stroke is 5th leading cause of death in US
• types of CVAs
  • ischemic (80%) - occlusion within an artery causing decreased overall blood flow, artery walls stay intact
  • thrombosis - gradual (insidious) occlusion of artery, usually by plaque or fatty buildup in areas of slowed blood flow or bifurcation
  • embolism - (acute) artery is occluded by a mass flowing in the bloodstream, often a disturbed piece of plaque or fatty buildup
  • TIA (transient ischemic attack) - temporary stroke, often a warning sign of ischemic stroke, 80% chance of having stroke within 6 months of TIA
  • Hemorrhagic (20%) - decreased overall blood flow caused by a rupture in the vessel wall
  • intracerebral - often in region of brainstem
    • aneurysm - ballooning or weakness in vessel wall, usually genetically determined
    • hypertension - heightened blood pressure, most common modifiable risk factor for stroke
    • AVM (ateriovenous malformation) - malformed or tangled mass of arteries/veins, usually genetically determined
  • extracerebral - bleeding into the spaces between the meninges, often caused by TBI
    • epidural hematoma - bleeding between dura mater and skull
    • subdural hematoma - bleeding between dura mater and arachnoid membrane

Traumatic Brain Injury (TBI)

• TBI Facts

  • TBI is caused by bump, blow, or jolt to the head, disrupts the normal function of the brain. Not all blows result in TBI
  • severity ranges from mild-severe, most are mild concussions
  • 2.8 million TBI - related emergency department visits, hospitalizations, and deaths occurred in the U.S.
  • TBI contributed to the deaths of nearly 50,000 people
  • those who survive TBI can face effects that last a few days, or the rest of their lives

• top 4 leading causes for TBI-related ER visits, hospitalizations, death

  • falls (47%)
  • more than half (54%) among children
  • 79% in adults aged 65+
  • being struck by object (15%)
  • motor vehicle crashes (14%)
  • intentional self-harm (33%)

• leading cause of TBI deaths by age

  • 65+ : falls
  • 64-25: intentional self-harm, vehicle accidents
  • 24-15: car crashes
  • 14-5: sports, road accidents
  • 4-0: assaults

• risk factors

  • alcohol/drugs

• high risk sports for TBI

  • boxing
  • motorcycling
  • bicycling
  • horse-riding
  • ice hockey
  • football
  • rock-climbing

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