Central Nervous System Flashcards
What are some characteristics of reversible injury in the CNS?
Decreased axonal trasnport (“spheroids” - swollen cells), swelling of soma, displacement of the Nissl substance (central chromatolysis) - possible axonal sprouting.
What is acute neuronal injury?
Irreversible injury
What is the cause of irreversible injury?
Result of an acute-hypoxic injury
What are some features of irreversible injury?
12-24 hours: soma shrinks, pyknosis, eosinophilia. - “red neurons” - (“red is dead”).
Cerebral edema, loss of Nissl body and nucleolus.
What role to astrocytes (astroglia) play in recovery from injury to the CNS?
Involved in the process of “gliosis” - CNS fibrosis.
What are some features of gliosis?
Injury -> hypertrophy & hyperplasia. Enlarged nucleus, eosinophilic (stain more pink). Gemistocytic astrocytes.
What are gemistocytic astrocytes?
An activated astrocyte, sprouting of glial filaments in the hypertrophy/hyperplasia response to CNS injury.
What CNS cells are most involved in acquired demyelinating disorders and leukodystrophies
Oligodendrocytes
What are some characterstics of demyelinating disorders and leukodystrophies?
White matter damage = nuclear swelling. Enlarged nucleus. May show viral inclusions.
What is the role of microglia?
Resident phagocytes of the CNS
What does injury, infxn, and trauma in the CNS do to microglia?
Cause them to proliferate and englarge (demyelination, infarctions, hemorrhage.
What is neuronophagia?
The phagocytoses of neurons and glial cells.
What are ependymal cells?
Make up the choroid plexus (produces CSF). Line the spinal cord and ventricles.
What infx especially affects ependymal cells?
CMV: Cytomegalovirus. Causes irregularities of ventricular surface (ependymal granulations), viral inclusions (evidences of infection).
If animals affected with rabies, what features characteristically appears?
Negri bodies
What characteristic histological features is found with CMV?
Owl’s eye
What inclusion is associated with Parkinson’s?
Lewy bodies
What kind of inclusions are associated with Alzheimer’s?
Neurofibrillary tangles, and beta-amyloid plaques (tau proteins, which are associated with degenerative, especially neurodegenerative, conditions).
What kind of inclusion is often noted in aging, lipid accumulating cells?
Lipofuscin
What is the primary issue, space wise, in the cranial vault, with edema.
Limited expansion, increased ICP (blood, pus, tumor, edema)
What are the 2 types of edema?
Vasogenic
Cytotoxic
What are some characteristics of vasogenic (blood-brain barrier disruption) edema?
Increased permeability leads to extracellular edema.
Localized: Tumors, infxn, inflammation
Generalized: Severe trauma
What are some characteristics of cytotoxic (neuronal/glial membrane injury) edema
Intracellular edema
Hypoxic-ischemic injury, toxic exposure.
What is hydrocephalus?
Increased CSF volume in ventricles (from overproducing, or under-resorbing).
What is the MC cause of hydrocephalus?
Disturbed flow/resorption.
T/F overproduction of CSF is rare?
True
What is the condition that would be most likely to lead to the overproduction of CSF?
Choroid plexus tumor
How is non-communicating hydrocephalus different from communicating hydrocephalus?
Some sort of mass is blocking flow with noncommunicating hydrocephalus.
What is an observable feature with hydrocephalus is those under 2 years old?
Cranial enlargement (sutures haven’t fused yet)
What are some general features of hydrocephalus in those greater than 2 years old?
Increased ICP, ventricular enlargement
What causes aquired hydrocephalus?
Unknown incidence. 50% idiopathic.
What can happen if hydrocephalus goes untreated?
Lethal tonsilar herniation. Increased ICP. Leads to respiratory arrest.
What is the tx for hydrocephalus?
Shunting (MC): ventriculo-atrial shunt (into abdominal cavity).
What is hydrocephalus ex vacuo?
Compensatory enlargement: infarct, neurodegeneration
Not so much a problem with CSF, but neurons lost that are then replaced by CSF
What are some of the hallmark signs of brain herniation?
Intracranial volume: Increased ICP (hemorrhage, edema, tumor, pus)
What will be noticed INITIALLY with brain still herniation?
Vessel compression and CSF displacement.
What changes in the cerebrum eventually happen with brain herniation?
Cerebrum shifts (herniation) across dura or through foramen magnum.
What structures become compromised (and in what way) with brain cerebral herniation?
Compression of neurons and vessels
What dangerous positive feedback loop is noticed with compression of vessels and neurons in brain herniation?
Decreased blood supply -> infarction. Injury -> swelling.
What is the MC type of brain herniation?
Subfalcine (cingulate): Displaced cingulate gyrus, under falx cerebri.
What physiological consequences are noted with subfalcine brain herniation?
Abnormal posturing (indicative of severe CNS damage), coma.
What is the second type of brain herniation?
Transtentorial (uncinate)
What is transtentorial (uncinate) brain herniation?
Displaced temporal lobe, under anterior tentorium.
What cranial nerve is especially affected by transtentorial herniation, and what abnormalities are noted?
C.N III (occulomotor).
“Blown pupil” (mydriasis) - dilated pupil found on the ipsilateral side of injury. Abnormal vision is also noted.
What are some more severe abnormalities associated with transtentorial herniation?
Hemiparesis, brain stem compression (with duret hemorrhage)
What is the 3rd type of brain herniation and what are it’s hallmark qualities?
Tonsillar herniation: displaced cerebellar tonsils (through FM). Cardiorespiratory arrest, hydrocephalus, headache.
What are some noticeable physical features of decorticate rigidity
Brachial rigidity
Extension/internal rotation of legs
Injury between the cortex/red nuclei (midbrain)
What are some noticeable physical feature of decerebrate rigidity?
Extension of all 4 limbs
Pronation of arms, plantar flexion
Injury to brainstem: Between red nuclei and vestibular nuclei (more life threatening)
What is a duret hemorrage?
Vessels that enter the pons are disrupted by herniation “flame-shaped hemorrhage”
What are the levels of severity of type I and II Arnold-Chiari malformations?
Type 1: MC, milder
Type 2: More severe
What are some features of Type 1 Chiari malformations?
Low-lying cerebellar tonsils,
Downward extension through FM (adults).
What are some features of Type 2 Chiari malformations?
Small posterior fossa,
Downward extention through FM (infants).
What are some possible pathological conditions associated with Chiari malformations?
Compress brainstem/medulla
CSF obstruction -> hydrocephalus
Headache (tell tale symptom), cervicalgia
What is the tx for chiari malformations
Neurosergical (decompression) therapy.
What is the 3rd leading cause of mortality in US?
Cerebrovascular disease
What is the MC cause of CVA?
neurologic morbidity