Nervous System 1 Flashcards
What cellular changes are seen after acute neuronal injury (7)?
Within 12-24 hours:
- Cell body shrinks
- Pyknosis (condensation of chromatin)
- Nucleolus is lost
- Nissl substance is lost
- Intense cytoplasmic eosinophilia (RED NEURONS)
Later:
- Axons swell; axonal SPHEROIDS
- Intracellular inclusions: Lewy bodies (protein aggregates), viral inclusions, lipofuscin pigments
Does myelin stain with H&E?
Nope
What is hydrocephalus?
Accumulation of excessive CSF in the ventricular system in the brain.
Most cases of hydrocephalus are a consequence of impaired ______ or ______. Rarely, an overproduction of _____ from choroid plexus tumors can cause it.
impaired flow or resorption. Overproduction of CSF from choroid plexus tumors can cause it
Enlargement of the head from hydrocephalus occurs only if…?
if the cranial sutures (in infancy) have not closed yet
What happens in the case of hydrocephalus AFTER the cranial sutures have closed?
Ventricles expand –> increased intracranial pressure presses on the brain; no change in head circumference
What is the difference between non-communicating and communicating hydrocephalus?
Non-communicating is when there is an obstacle to the flow of CSF in the ventricular system - one portion of the ventricles will enlarge while other portions will not.
Communicating is due to reduced CSF resorption - the entire ventricular system will enlarge.
How is hydrocephalus treated?
A shunt is placed in the ventricles which drains CSF into the abdomen.
What are the five general causes of a CNS infarction?
- Thrombosis
- Embolism
- Vascular rupture
- Hypotension
- Hypertension
What are the three most common sites of CNS thrombosis?
- Carotid bifurcation
- Origin of the middle cerebral artery
- Either end of the basilar artery
What is the most common site of embolic occlusion that leads to CNS infarction?
Middle cerebral artery
Infarction via hypotension usually involves the ‘watershed’ areas and the deep layers of the cortex. What is a watershed area?
An area of tissue that lies at the far ends of arterial supply - usually in the area of an anastomosis of two arteries.
Are nonhemorrhagic infarcts and hemorrhagic infarcts treated the same way?
No, non-hemorrhagic infarcts are treated with thrombolytic therapies and hemorrhagic infarcts are not (it makes it worse)
Hemorrhagic CNS infarcts occur secondary to _______ of ischemic tissue, either through collaterals or after dissolution of intravascular occlusion.
reperfusion
Describe the timeline of morphological changes seen in a nonhemorrhagic infarct.
0-6 hours: no obvious signs.
By 48 hours: tissue is pale, soft, swollen.
2-10 days: brain is gelatinous and friable.
10 days - 3 weeks: tissue liquefies, fluid-filled cavity is lined by dark gray tissue.
What microscopic changes are seen in a nonhemorrhagic infarct (5)? What additional things are seen in a hemorrhagic infarct?
- Tissue is necrotic
- Phagocytosis
- Liquefactive process
- Revascularization/capillary growth
- After months: gliosis-lined cystic cavity
Hemorrhagic infarct adds blood extravasation and resorption.
What is an intracerebral hemorrhage aka primary brain parenchymal hemorrhage?
Bleeding into the brain
Is intracerebral hemorrhage aka primary brain parenchymal hemorrhage always caused by trauma?
No, spontaneous hemorrhages can occur; peak incidence of this is at age 60.
Most cases of intracerebral hemorrhage aka primary brain parenchymal hemorrhage are caused by rupture of a small _______ vessel.
intraparenchymal
_________ is the most common cause of intracerebral hemorrhage aka primary brain parenchymal hemorrhage, often complicated by minute dilations at small artery bifurcations (called _____-_____ aneurysms)
Hypertension is the most common cause. Minute dilations at small artery bifurcations are called Charcot-Bouchard aneurysms.
Specifically where in the brain does intracerebral hemorrhage aka primary brain parenchymal hemorrhage usually occur (5)?
- Basal ganglia
- Thalamus
- Pons
- Cerebellum
- Frontal lobe white matter
What morphological changes are seen in intracerebral hemorrhage aka primary brain parenchymal hemorrhage (4)?
- Extravasation of blood –> compression of adjacent parenchyma.
- Early lesions have a central core of clotted blood surrounded by a rim of brain tissue with anoxic neuronal and glial changes and edema.
- Old hemorrhages show a cavity of destruction with a rim of brown discoloration.
- Resolution of edema –> pigment and lipid-laden macrophages and reactive astrocytes appear.
A subarachnoid hemorrhage is characterized by bleeding into the _______ space.
subarachnoid
Subarachnoid hemorrhage is frequently associated with rupture of a _______ _________, especially in the circle of Willis. The initial rupture is ______ in 1/3 of patients.
rupture of a saccular (berry) aneurysm. Initial rupture is lethal in 1/3 of patients
Do patients that suffer from a subarachnoid hemorrhage often suffer from recurrent bleeding, with the prognosis worsening with each episode?
Yeah
Name four arteries where cerebral aneurysms most commonly occur.
- Anterior cerebral
- Internal carotid
- Middle cerebral
- Basilar
Describe the morphology of a saccular (berry) aneurysm. Where are they usually found?
Outpouching of an artery: the endothelium and intima punch through the muscular wall and internal elastic membrane and expand the adventitia on the outside.
85% are found in the anterior circulation (circle of Willis).
What usually causes an epidural hematoma? What artery is most often ruptured
Trauma. Middle meningeal artery is most often involved.
Once a vessel has been broken in the case of an epidural hematoma, accumulation of blood under arterial pressure can cause separation of the _____ from the inner surface of the skull.
dura separates from the inner surface of the skull
Describe how the clinical signs of an epidural hematoma progress.
Patients are ok for several hours after the traumatic event. If not treated, patients can die.
What does an epidural hematoma look like in a CT scan (2)?
- Fusiform (tapered at each end)
2. LENTICULAR (lens shaped)
What is Babinski’s sign? What does it tell you?
When poking the bottom of a person’s foot results in a big toe extension and abduction reflex rather than flexion. Indicative of pyramidal tract compression from an epidural hematoma.
If you punch or kick someone in the temporal region of the skull, you might damage the _______ ______ artery, resulting in an epidural hematoma.
middle meningeal artery
What is meningitis?
Inflammation of the leptomeninges (the pia and arachnoid mater) and CSF.
How is infectious meningitis classified?
- Acute pyogenic (bacterial)
- Aseptic (viral)
- Chronic (TB, spirochetal, or cryptococcal)
-classified on the basis of characteriestics of inflammatory exudate in the CSF and clinical signs
In what ages is acute pyogenic meningitis most often seen?
Highest incidence in children, second high incidence in elderly
What are the clinical features of acute pyogenic meningitis (7)?
- Fever
- Headache
- Photophobia
- Irritability
- Prostration
- Nuchal rigidity
- Increased CSF pressure
Easier: patients feel really crappy and have stiff neck with increased CSF pressure
Name some characteristics of the CSF from someone with acute pyogenic meningitis (4).
- Lots of neutrophils (purulent exudate)
- Elevated protein
- Reduced glucose (bacteria eat it up)
- Bacteria can be seen on a smear or can be cultured
Meningococcemia can also be associated with purpuric skin lesions and is sometimes complicated by Waterhouse-Friderichsen syndrome. What characterizes this syndrome (5)?
- Hemorrhagic destruction of the adrenal cortex
- Acute hypocorticism
- Circulatory collapse
- Disseminated intravascular coagulation
- Purpuric skin
Is bacterial meningitis associated with brain abscesses?
Yeah
Early treatment of bacterial meningitis can result in little evidence of the disease after ______.
resolution
How can bacteria invade the CNS?
Hematogenous, direct implantation, local extension, or via peripheral nerves
NOT lymphatics
What are the morphological differences between bacterial meningitis and aseptic (viral) meningitis?
Pyogenic (bacterial) will have a lot of neutrophils, fibrin, and engorged blood vessels in the subarachnoid space. Viral will have lymphocytes (not neutrophils) and fewer cells overall.
