Neuropathology: Circulatory Diseases Flashcards
What is the glymphatic system?
waste clearance system that utilises a unique system of perivascular channels formed by astroglial cells
What is the function of the glymphatic system?
- efficent elimination of soluble proteins and metabolites from the CNS
- Helps distribute non-waste compounds
may be supressed in certain diseases
What is vasogenic oedema?
Injury to the vascular endothelium -> breakdown of the blood-brain barrier -> permeability and leakage -> fluid spreads between cells
Name 5 causes of vasogenic oedema
- Inflammation
- Tumours
- Haemorrhage/ Contusions
- Infarcts
- Hypertension
What does intracellular cytotoxic oedema look like
hydropic degeneration
* astrocytes, neurons, endothelial cells, swelling of the cytoplasm
What causes cytotoxic intracellular oedema?
Cellular injury with disruption of the membrane- ATP-dependent NA+/ K+ pumps
What is cytotoxic oedema related to?
- decrease in energy supply
- Ischaemia
- Hypoxia
- Metabolic inhibitors
What is hydrostatic oedema?
Accumulation of fluid in the interstitial space
What is hypo-osmotic oedema?
- Over consumption of water leading to dilution of plasma
- Fluid moves to brain plasma causing salt poisioning
What is primary traumatic brain injury?
- Mechanical disruption of tissue
- Microvascular lesions
What is secondary traumatic brain injury?
- Occurs within hours to days after injury
- Changes lead to ischaemia
- Frequently fatal
What supplies oxygen to the brain?
O2 is supplied to the brain from the internal carotid and vertebral arteries which anastamose ventral to the brainstem and at the circle of willis
What is an ‘end-artery’ ?
an arterial branch that penetrates the brain
What is a cerebral infarction?
sudden occlusion of the arterial branch
What causes a cerebrovascular accident ‘stroke’?
Central haemorrhage or infarction
What is ischemic myelopathy?
herniation of the fibrocartilage from the intervertebral disc into the vasculature, forming occlusive emboli
What does cytotoxic oedema look like?
Sweling of the cytoplasm +/- the nucleus
related to a decrease in energy supply (ischaemia, hypoxia, decreased metabolic inhibitors)
What are the three sites where herniation occurs?
- Foramen magnum
- Falx cerebri
- Tentorium cerebelli
Give 4 possible causes of vasogenic oedema
- Oedema disease
- Focal symetrical encephalomalacia
- Mulberry heart disease
- Thiamine deficiency
Give two possible causes of cytotoxic oedema
- Early stages of hypoxic-ischaemic injury
- Ammonia toxicity in hepatic and renal encephalopathy
What cells in the brain are the most susceptible to injury?
- Neurones (high metabolic activity) and high energy use
- Endothelial cells are the least sensitive
What causes impaired cell utilisation of O2?
cyanide poisoning or fluroacetate
Where do small emboli tend to lodge in the brain?
tend to lodge close to the grey/ white matter junction
Where do the venous sinuses of the dura mater empty into?
Jugular veins and also communicate with the cranial bones
Give 4 causes of cerebral infarction
Thromboembolism
2. Feline cardiomyopathy
3. Septic thrombosis
4. Parasitic (dirofilaria immitis)
5. Fibrocartilaginous emboli
What does the consequence of vascular osbtrcution depend on?
- Type and size of the obstructed blood vessel
- Speed and onset
- Existence and capacity of the collateral circulation
What do CNS infarcts tend to undergo?
- Liquefactive necrosis
- Softening (malacia)
- Swelling
What colour do grey arterial infarcts tend to be?
red/ haemorrhagic
What colour do white arterial infarcts tend to be?
pale
What is fibrocartilaginous embolic myelopathy?
Herniation of fibrocartilage from the intervertebral disc into the vasculature, forming occlusive emboli
Trauma to the nucleus pulposus causes it to fragment and the pressure of the trauma forces small fragments into damaged veins, venous plexus or small arterioles
embolised fibrocart material resembels nucleus pulposus -> infarction
Where does water in the brain come from?
- Water comes from the blood and ultimately returns to it by re-entry at the venous ends of the capillaries
- little water passes through cerebrospinal fluid
What are dura mater lymphatics?
Network of lymphatics in the meninges running alongside the dural venous sinuses and extending upon the dura mater surrounding the brain
What are the three sites of herniation?
- Falx cerebri
- Tentorium cerebelli
- Foramen magnum
What is the pathophysiology of oedema?
- Compression and disrupted vessels go on to cause ischaemia
- excitatory neurtransmitters
- increased intracellular calcium
- proteloytic enzymes -> neuronal necrosis
- high levels of inflammatory mediators
- vasospasm
What are the 5 causes of hypoxic brain injury?
- Vascular obstruction
- Complete cessation of cerebral circulation
- Sustained hypotension
- Hypoxaemia
- Impaired cell utilisation of O2
What do abrupt changes in the calibre of the pia-arachnoid arterial vessels lead to?
large emboli to become trapped in leptomeningeal vessels
Why are strokes less common in dogs?
- Difference in arterial supply
- Decreased incidence of atherosclerosis
Name 4 causes of cerebral infarction
Thromboembolism
- Feline cardiomyopathy
- Septic thrombosis
- Parasitic
- Fibrocartilaginous emboli
