October 1, 2013
INCREASED INTRACRANIAL PRESSURE
Concept of Mass Lesions
Hydrocephalus: too much csf within ventricles, blood vessels dilate, abscess (infection), speed at which this happens is important! If it increases slowly, there can be compensations. If it occurs too fast, there are complications
My head is too small for my brain
Too much volume in the skull and it’s not big enough for brain, blood, csf
Complications of increased IP
Herniation: displacement of tissue that extends from an area it’s not supposed to be
Too much csf inside the ventricles mean it starts to enlarge creating another mass
Herniations
Reflection that separates brain stem from cerebellum
1. Subfalx hernation: parts of the hemisphere goes to the other side, doesn’t really create many problems
2. Uncal: a portion starts to squeeze on the midbrain: respiration, circulation, level of consciousness is affected
3. Tonsillar: inferior portion of the brain goes into the spinal canal. Contains neurons responsible for respiration, so stop breathing
Uncal or Transtentorial Herniation
Uncus squeezes on 3rd cranial nerve which paralyzes nerve fibers that normally constrict: “blown pupil” – indication that there is an uncal herniation
Black and white drawing of brain
Uncus squeezes upper brainstem and could also lacerate and cause a hemorrhage if gets worse
Picture of brain with Kernohan’s Notch
Tentorium: extension of dura mater
Incisura: cuts part of the brain stem
Lesion on the right you’d think that it would cause paralysis on the left, but you have paralysis on the same side. Called kernohan’s notch
Aquaduct: connects 3rd ventricle with 4th ventricle
When you squeeze the midbrain, you end up with another lesion called hydrocephalus causing fluid to build up in the ventricle
Brain with duret hemorrhages
Duret Hemorrhages: the whole process generates hemorrhages
Brain edema
Most common cause of increase intracranial picture
Normal brain picture
Spaces on the sides between gyrus and sulci
As you look at the cortex, you can see its rounded
Edematous brain
Third ventricle is squeeze, great volumes of mass, no roundness – flat
Normal white matter
Edema: too much water in the brain. Could be extracellular or intracellular
Spaces where water has accumulated gives rise to the edema
Types of Brain Edema
Vasogenic: associated with breakdown of BBB and extracellular accumulation of fluid
Cytotoxic: some kind of noxious event that has interfered with the brain to be