Cerebrovascular issues

Question 1

What is intracranial pressure?

Answer 1

-The pressure exerted within the rigid skull and meninges by the brain matter (80%), cerebral spinal fluid (10%), and the amount of cerebral blood flow (10%)

-normal range for adults is 0-15mmHg

Question 2

What is the mono-kellie hypothesis?

Answer 2

-the volume of the brain, CSF, and intravascular blood remains nearly constant in a state of dynamic equilibrium

-if any one compartment increases in overall volume, another compartment must decrease for the overall volume and dynamic equilibrium to remain constant, otherwise inter cranial pressure will rise

Question 3

What are the 4 compensatory mechanisms for ICP?

Answer 3

-increased CSF absoprtion
-decreased CSF production
-shunting of CSF to the spinal space
-vasoconstriction, reducing cerebral blood volume

Question 4

What is cerebral blood flow?

Answer 4

-essential for the supply of oxygen, glucose and nutrients to the cerebral tissues

-a critical relationship exists between CBF and ICP- CBF being disadvantaged in the presence of raised ICP

Question 5

What is cerebral perfusion pressure? and how is it calculated?

Answer 5

-the pressure required to maintain an adequate cerebral blood flow

-calculated by Mean Arterial Blood Pressure (MAP) - ICP

-acceptable CPP is 50-70mmHg

Question 6

List the signs and symptoms of raised ICP

Answer 6

-disorientation
-irritation
-decrease in conscious level
-headache
-pupillary abnormalities
-visual disturbances
-aphasia
-seizures
-motor dysfunction
-nausea and vomiting
-changes in respiratory pattern
-changes in vital signs

Question 7

what is the crushing’s Triad?

Answer 7

a set of signs that indicate increased ICP in the brain

-increased blood pressure
-decreased heart rate
-decreased respiratory rate and change in respiratory pattern

Question 8

How is raised ICP managed?

Answer 8

-maintaining optimum cerebral perfusion pressure
-maintain ICP below 20mmHg
-provide oxygen and glucose
-maintain cardiorespiratory stability

Question 9

What is the circle of Willis?

Answer 9

-a blood ‘roundabout’ in the brain, with many arteries branching off, including the posterior cerebral artery, middle cerebral artery, and the anterior cerebral artery
-important because if there is damage in one part of the brain, blood can still get to this area
-AVMs may occur in children, blood is shunted straight from arteries to veins, and the high arterial pressure causes veins to burst

Question 9

What are venous sinuses?

Answer 9

a network of blood channels that drain deoxygenated blood from the brain to the heart

Question 10

What is autoregulation?

Answer 10

the ability of an organ to maintain a constant blood flow rate despite changes in arterial pressure

Question 11

What is an inter cranial haemorrhage, and what are the 2 main types?

Answer 11

-a brain bleed
-can either be extra-axial= occurring outside of the brain tissue
-or intra-axial= occurring within the brain tissue

Question 12

What is an epidural extra-axial haemorrhage?

Answer 12

-bleed occurs between the skull and the dural membrane
-results from head trauma e.g car accident
-clinical manifestation= altered consciousness, headache, vomiting, confusion, seizures, aphasia

Question 13

What is a subdural extra-axial haemorrhage?

Answer 13

-bleed occurs between the dura matter and the arachnoid membrane
-results from head trauma
-clinical manifestation= 50% have a coma

Question 14

What is a subarachnoid extra-axial haemorrhage?

Answer 14

-bleed occurs in subarachnoid space
-results from cerebral artery aneurism
-clinical manifestation= severe, sudden headache, loss of consciousness, nausea, vomiting, seizures

Question 15

What is an intracerebral intra-axial haemorrhage?

Answer 15

-second most common cause of strokes
-results from hypertension, embolism, brain tumour, bleeding disorders, drug use
-clinical manifestations= neurological signs, headaches, nausea, vomiting, decreased consciousness

Question 16

What is an intraventricular intra-axial haemorrhage?

Answer 16

-bleeding occurs within ventricle system in brain
-most often occurs as a secondary phenomenon to other inter cranial haemorrhage

Question 17

What is a brain herniation and what is the cause?

Answer 17

-when brain tissue moves outside of the skull, or moves into a structure within the skull
-typically occurs in response to increased intracranial pressure (above 15mmHg)

Question 18

What is a mass effect and how does this relate to ICP and brain herniation?

Answer 18

-a mass effect increases intracranial pressure, so less CSF is produced and more is reabsorbed, = brain herniation

-can be focal mass effect e.g intracranial bleeds, tumours causing local oedema
-or diffuse mass effect e.g generalised cerebral oedema, cryogenic oedema (within cells= retention of sodium and water)

Question 19

What is a supratentorial herniation? What are the 4 types

Answer 19

-displacement of the cerebrum
1. uncal herniation
2. central herniation
3. singular herniation
4. transcalvarial herniation

Question 20

What is an infratentorial herniation? What are the 2 types

Answer 20

-displacement of the cerebellum
1. upward herniation (displacement of cerebellum upwards)
2. tonsillar herniation (cerebellar tonsils slip down through foramen magnum)

Question 21

What is hydrocephalus?

Answer 21

a condition that involves the build up of cerebrospinal fluid (CSF) produced in the ventricles, which can be congenital or acquired

Question 22

What are the 3 ways a build of CSF can occur?

Answer 22

1. excess production of CSF
2. impaired reabsorption of CSF
3. blockage in ventricular system

Question 23

What is the difference between communicating and non-communicating hydrocephalus?

Answer 23

communicating= no blockage in ventricular system
non-communicating= blockage in ventricular system (the most common)

Question 24

What is a major difference in children and adults with hydrocephalus?

Answer 24

-in infants, the skull is more capable of expanding so head is enlarged, but there is more time before the onset of other symptoms
-in adults, the skull isn’t able to expand and symptoms may appear more quickly

Question 25

How can hydrocephalus be treated?

Answer 25

attempt to drain the excess CSF, done using a shunt (a plastic tube connected to a catheter) where CSF is diverted to abdominal cavity where it can safely drain