patho exam 3
cranial compartments contains ... *** brain tissue (80%), CSF (10%), and blood volume (10%)
what is the monroe-kellie hypothesis *** concept of maintaining normal pressure within the cranium
describe monroe-kellie hypothesis *** -brain tissue, CSF, and blood volume maintain normal intracranial
pressure (ICP)
- To maintain normal ICP, any increase in a components must be compensated for by a decrease in
another.
- if compensatory mechanisms are overcome, point of "decompensation" occurs = steep rise is ICP =
herniation
ex: as a brain tumor increases the volume of brain tissue, the CSF production is slowed to maintain
normal ICP. Once the volume of the brain tumor exceeds the volume of the CSF reduction, ICP increases.
ICP rises until compensatory mechanisms are overcome. The point of decompensation is reached when
further expansion of the brain mass causes a steep rise in ICP. The final result is herniation of the brain.
4 mechanisms of TBI *** Blunt trauma
Acceleration-deceleration
penetrating injury
blast injury
blunt trauma *** object hits the skull forcefully.
EX: struck in the head with a baseball or head hits the dashboard
Acceleration-deceleration *** the skull stops abruptly and the brain continues to move forward,
rotating within the skull and causing shearing of brain and stretching of neural axons.
,Causes coup-contrecoup injury, when the brain bounces off the skull and moves in the opposite
direction of the first impact, then brain strikes the skull in the opposite area.
penetrating injury *** When a foreign object penetrates the skull and brain, the skull is fractured and
brain tissue is injured.
causes: an increase risk of infection as the foreign body disrupts the meningeal layers and carries
external debris, such as gunpowder and pieces of skull and hair, into the brain.
blast injury *** Primary injury: detonation of explosives. pressure wave created by the explosion can be
especially harmful to parts of the body filled with air (lungs, ears, and skull).
Secondary injury: This occurs from flying debris, like pieces of the bomb or shrapnel, which can
penetrate or strike the body.
Tertiary injury: when the explosion throws a person through the air, causing blunt trauma (broken bones
or internal injurie)
quaternary injury: related to burns, inhalation of gases, and angina that result from the experience.
most common cause of increased ICP *** cerebral edema
Causes of cerebral edema *** Trauma
Tumor
Hemorrhage
Inflammatory condition of the brain
Ischemia
, how does trauma cause cerebral edema *** stress on the brain that leads to vasogenic cerebral edema-
in which the pores of the brain's capillaries open wide, allowing proteins and fluids to leak from the
blood into the brain tissues -> excess fluids -> cerebral edema
how does hemorrhage cause cerebral edema *** ruptured cerebral vessel creates a pool of blood that
forms a space-occupying lesion within the closed cranium. The collection of blood is toxic to brain cells
and places pressure on brain tissue, which rapidly increases ICP
how does a brain tumor cause cerebral edema *** Brain tumor -> compresses blood vessels -> venous
congestion -> increased hydrostatic pressure -> resulting in cerebral edema.
how does inflammatory condition cause cerebral edema *** inflammatory condition in the brain ->
increases permeability of capillary membranes (leaky blood vessels) -> cerebral edema
what is cytotoxic cerebral edema *** a type of brain swelling that occurs with cerebral ischemia or
hypoxia
describe cytotoxic cerebral edema *** -Ischemia -> failure of ion pumps -> cellular swelling -> increases
the volume of brain tissue -> increases ICP
low oxygen/high CO2 levels in the brain -> reflexive cerebral vasodilation -> increases the brain's blood
volume -> increased ICP
CM of ICP *** headache and vomiting (due to compressed tissue)
decreased LOC
altered pupil response to light, and pupil size (due to pressure on cranial nerve 3 by uncal herniation)
Cushing's Triad: hypertension, bradycardia, bradypnea
common causes of decreased ICP *** draining CSF
cranial compartments contains ... *** brain tissue (80%), CSF (10%), and blood volume (10%)
what is the monroe-kellie hypothesis *** concept of maintaining normal pressure within the cranium
describe monroe-kellie hypothesis *** -brain tissue, CSF, and blood volume maintain normal intracranial
pressure (ICP)
- To maintain normal ICP, any increase in a components must be compensated for by a decrease in
another.
- if compensatory mechanisms are overcome, point of "decompensation" occurs = steep rise is ICP =
herniation
ex: as a brain tumor increases the volume of brain tissue, the CSF production is slowed to maintain
normal ICP. Once the volume of the brain tumor exceeds the volume of the CSF reduction, ICP increases.
ICP rises until compensatory mechanisms are overcome. The point of decompensation is reached when
further expansion of the brain mass causes a steep rise in ICP. The final result is herniation of the brain.
4 mechanisms of TBI *** Blunt trauma
Acceleration-deceleration
penetrating injury
blast injury
blunt trauma *** object hits the skull forcefully.
EX: struck in the head with a baseball or head hits the dashboard
Acceleration-deceleration *** the skull stops abruptly and the brain continues to move forward,
rotating within the skull and causing shearing of brain and stretching of neural axons.
,Causes coup-contrecoup injury, when the brain bounces off the skull and moves in the opposite
direction of the first impact, then brain strikes the skull in the opposite area.
penetrating injury *** When a foreign object penetrates the skull and brain, the skull is fractured and
brain tissue is injured.
causes: an increase risk of infection as the foreign body disrupts the meningeal layers and carries
external debris, such as gunpowder and pieces of skull and hair, into the brain.
blast injury *** Primary injury: detonation of explosives. pressure wave created by the explosion can be
especially harmful to parts of the body filled with air (lungs, ears, and skull).
Secondary injury: This occurs from flying debris, like pieces of the bomb or shrapnel, which can
penetrate or strike the body.
Tertiary injury: when the explosion throws a person through the air, causing blunt trauma (broken bones
or internal injurie)
quaternary injury: related to burns, inhalation of gases, and angina that result from the experience.
most common cause of increased ICP *** cerebral edema
Causes of cerebral edema *** Trauma
Tumor
Hemorrhage
Inflammatory condition of the brain
Ischemia
, how does trauma cause cerebral edema *** stress on the brain that leads to vasogenic cerebral edema-
in which the pores of the brain's capillaries open wide, allowing proteins and fluids to leak from the
blood into the brain tissues -> excess fluids -> cerebral edema
how does hemorrhage cause cerebral edema *** ruptured cerebral vessel creates a pool of blood that
forms a space-occupying lesion within the closed cranium. The collection of blood is toxic to brain cells
and places pressure on brain tissue, which rapidly increases ICP
how does a brain tumor cause cerebral edema *** Brain tumor -> compresses blood vessels -> venous
congestion -> increased hydrostatic pressure -> resulting in cerebral edema.
how does inflammatory condition cause cerebral edema *** inflammatory condition in the brain ->
increases permeability of capillary membranes (leaky blood vessels) -> cerebral edema
what is cytotoxic cerebral edema *** a type of brain swelling that occurs with cerebral ischemia or
hypoxia
describe cytotoxic cerebral edema *** -Ischemia -> failure of ion pumps -> cellular swelling -> increases
the volume of brain tissue -> increases ICP
low oxygen/high CO2 levels in the brain -> reflexive cerebral vasodilation -> increases the brain's blood
volume -> increased ICP
CM of ICP *** headache and vomiting (due to compressed tissue)
decreased LOC
altered pupil response to light, and pupil size (due to pressure on cranial nerve 3 by uncal herniation)
Cushing's Triad: hypertension, bradycardia, bradypnea
common causes of decreased ICP *** draining CSF
