Neuro 1 Flashcards
Meninges surround the brain and spinal cord. What are these 3 layers called?
Dura mater
Arachnoid
Pia mater
What is cerebral spinal fluid, and what does it do?
It is a clear lymph-like fluid, produced by ultra filtration of blood plasma.
It bathes and protects the brain, circulating in sub-arachnoid space.
What does the blood brain barrier do?
Allows entry to lipid-soluble substances.
- facilitated diffusion of nutrients.
- alcohol, anaesthetics, and some antibiotics can enter.
The blood brain barrier has tightly packed endothelial cells of blood vessels which provide a ……. ……..
Tight junction
Astrocytes which help remove waste from the brain are known as ……… ……..
Glial cells
The brain requires a …….. supply of blood which is rich in ……..
Constant
Glucose
Neurons cannot adapt to ischaemia. If blood flow stops for just a few seconds, …………… occurs.
Unconsciousness
Components of the cranium are
1.
2.
3.
Brain tissue
Blood
CSF
The cranium allows for increases in expansion.
True or false?
False. There is no room for expansion.
Increased volume in one component of the brain must be balanced by a decrease in another (compensation). When small increases in volume occur, the other two compartments compensate and inter-cranial pressure (ICP) does not change.
What is this phenomenon known as?
Monro-Kellie hypothesis
What happens when large increases in volume occur in one compartment of the brain?
Cannot be adequately compensated by the other two compartments of the brain, which results in increased ICP and decompensation
Space occupying lesions (SOLs), can cause raised ICP.
Explain SOLs
Generalised brain swelling due to cerebral oedema, or vasodilation due to hypercapnia or hypoxia.
Focal brain swelling due to intracranial tumour, abscess or haematoma.
List the clinical features of increased ICP during the stages of compensation……….
Headache, confusion
Blurred vision
Nausea/vomiting
List the clinical features of increased ICP during decompensation………..
Irregular pattern of breathing Pupillary changes Changes in BP and pulse Abnormal flexor and extensor responses Coma Herniation and death
What is brain herniation?
When compensation is no longer adequate, brain is forced down into the brain stem, causing death.
Interstitial or intracellular fluid accumulation causes……… ……..
Cerebral oedema
Causes of cerebral oedema include………
Brain and vascular injury due to trauma, cerebral infarction, infection, haemorrhage or tumour.
Brain injury can result in……..
Increased permeability of cerebral capillaries (BBB is disrupted).
This causes oedema, proteins and fluid leak into extra cellular space.
Which causes increased ICP and further damage to surrounding tissues.
Cerebral oedema development operates in a cycle. The following flow chart will explain it simply.
Damage to capillaries Leakage Oedema Increased pressure Compressed blood vessels Reduced blood flow Vasodilation to compensate for reduced blood flow Cell Death Contents of cells leak out More fluid in area Further oedema
Put simply, oedema creates more oedema!
Treatment of cerebral oedema should commence with treating the underlying cause.
Treatments include………
Elevate head to promote venous drainage. (Mechanical ventilation can exacerbate ICP!!!) Drain CSF Administer mannitol/hypertonic saline Hyperventilation (with caution) Surgery Administer steroids
Mechanical ventilation can exacerbate ICP……
How does this occur?
Positive pressure ventilation
Increased thoracic pressure
Impaired cranial venous drainage
Increased intracranial pressure
What can be placed in the ventricle of the brain to drain CSF?
Catheter
How does mannitol (IV) or hypertonic saline work to reduce cerebral oedema?
Rapid diuresis
Decreased plasma volume
Decreased ECF in brain.
How does hyperventilation work in the treatment of cerebral oedema?
Lowers arterial CO2 to 25-30mmHg
Immediate vasoconstriction
Reduces cerebral blood volume
