Topic 112-115: CNS bleeds, hypoxia, malformations Flashcards
Increased intracranial pressure has consequences for acute or slower onset of inc intracranial pressure. what are the consequences?
- acute = herniation
- slower onset - cerebral edema or hydrocephalus
what is the difference between cerebral edema and hydrocephalus?
Cerebral edema is excess fluid in the brain parenchyma
hydrocephalus is increased CSF volume
What Are the two mechanisms that cause cerebral edema?
- vasogenic edema: bbb is disrupted and there is inc fluid in IC space of the brain. Localized due to local inflammation or generalized due to water toxicity, etc
- cytotoxic edema: Inc in fluid due to cytotoxic injury such as following a stroke
herniation is due to what?what are the three types?
acute swelling and rise of intracranial pressure
- subfalcine
- transtentorial
- tonsillar
what anatomical location is the three herniations?
subfalcine herniation - cingualate gyrus is displaced under the falx cerebri. causes anterior ischemia
transtentorial - medial temporal lobe is compressed against the tentorium cerebelli. CN III compromised –> big ass pupils
tonsillar herniation - tonsils through foramen magnum. compresses vital respiratory and cardiac centers.
hydrocephalus is what? what are the three mechanisms?
increase in csf due to either increased production or decreased absorption.
- communicating - decreased absorption
- noncommunicating - obstruction of CSF flow (ex. tumor) also leads to ventricular dilation
- hydrocephalus ex vacuo - when the brain atrophies and the ventricles dilate, there is compensatory inc in CSF
what are the 4 types of congenital CNS malformations?
- Neural tube defects
- forebrain malformations
- posterior fossa anomalies
- spinal cord anomalies
what are the 5 neural tube closure problems?
- spina bifida occulta: posterior end abnormalities. may be asymptomatic
- meningocele: posterior end abnormality with a flattened segment of the spinal cord and a meningeal outpouching
- myelomeningocele: defect in vertebral column leads to extension of the CNS tissue through this defect. leads to sensory defects
- anencephaly: anterior tube closure issue leads to absence of top of skull and brain
- encephalocele: cranial defect wit diverticulated CNS tissue extending out
What are the 4 forebrain malformations?
- mega and microcephaly: volume of the brain is too large or small. associated with chromosomal problems, congenital HIV or fetal alcohol syndrome
- lissencephaly or pachygyria:total or patchy brain smoothness (agyria)
- polymicrogyria: increased number irreg gyria leading to cobblestone or bumpy surface
- holoprosencephaly:disruption of brain patterning with missing features (olfactory bulbs) or even lack of hemisphere divisions
think brain size, gyri, and patterns
4 posterior fossa abnormalities?
- most common is absence of cerebellum
- chiari I - low lying Tonsils project through the F. magnum (T = I)
- Chiari II - small posterior fossa, vermis projects through F. magnum (V = two fingers, II)
- Dandy walker - large posterior fossa
spinal cord malformations
Hydromyelia: an abnormal widening of the central canal of the spinal cord that creates a cavity in which cerebrospinal fluid can accumulate
syrinx or syringomyelia: fluid-filled neuroglial cavity within the spinal cord
Cerebrovascular disease is how common? what are the basic processes at play? ischemia can be classified into several categories
It is the #3 cause of death in the US after cancer and heart disease
- thrombotic occlusion
- embolic occlusion
- vascular rupture
ischemia can be generalized or localized, hemorrhagic or ischemic.
generalized ischemia and hypoxia of the brain is due to what? what are some consequences?
- reduction in cerebral perfusion (shock, cardiac arrest)
- decreased oxygen saturation
- mild hypoxia- confusion state
- severe ischemia - widespread neuronal death (impaired neurologically or vegetative)
- severe hypoxia - borderzone infarct - hemorrhagic infarct in areas farthest from cerebral arteries
infarcts can be placed in two categories. w
- ischemic - due to occlusion
- hemorrhagic - reperfusion, obstruction of a vein, borderzone infarct
What are the main causes of cerebral infarcts?
- embolism
- atherosclerosis - causes occlusion. common in basilar and origin of middle cerebral
- vasculitis - symptoms and morphology depend on the type of vasculitis, but inflammation can lead to arterial narrowing
- lacunar infarcts due to hypertension - hyaline arteriolar sclerosis leading to ischemic strokes
- charcot bouchard aneurysms are hemorrhagic basal ganglia bleeds due to hypertension
NOTE: The Charcot-Bouchard aneurysms are due to intraparenchymal hypertension in the basal ganglia. The lacunar infarcts are ischemic strokes, not hemorrhagic strokes. They are lacunar because of the liquefactive necrosis pools they leave behind.
