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Clinical Neuroscience > 10.3.1 Subarachnoid Haemorrhages > Flashcards

10.3.1 Subarachnoid Haemorrhages Flashcards

1
Q

What two layers make up the dura mater?

A

Periosteal
Meningeal

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2
Q

Why can dementia increase the risk of chronic subdural haemorrhage?

A

Dementia causes brain atrophy, placing additional strains on bridging veins

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3
Q

What structures are within the arachnoid mater?

A

Arachnoid granulations- evaginations into dural venous sinuses to reabsorb CSF

Arachnoid trabeculae- pass through space and blend with pia

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4
Q

What are the 4 main dural septae?

A

Falx cerebri- between hemispheres
Falx cerebelli- between cerebellar hemispheres
Tentorium cerebelli
Diaphgrama sella

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5
Q

What are the two types of dural bleeds?

A

Extradural (epidural)
Between endosteal layer and skull
- Caused by trauma to MMA
- Lemon shaped

Subdural
Between meningeal layer and arachnoid
- Trauma to bridging veins
- Banana shaped

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6
Q

How do extradural haemorrhages present?

A

LOC
Lucid interval
Sudden decline, loss of consciousness

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7
Q

What are cisterns?

A

Enlarged regions where the brain moves away from the skull

Located in the subarachnoid space

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8
Q

What is present in the subarachnoid space?

A

CSF

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9
Q

What is the function of CSF?

A

Physical support of neural structures

Excretion of brain metabolites

Intracerebral transport (hormone releasing factors)

Control of chemical environment

Volume changes reciprocally with volume of intracranial contents

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10
Q

What forms CSF?

A

Choroid plexuses (and extra-choroidal structures)

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11
Q

Outline the flow of CSF

A

Choroid plexuses

Lateral ventricles
Interventricular foramen
3rd ventricle
Aqueduct of sylvius/ cerebral aqueduct of the midbrain
4th ventricle
Central canal, medial apeture and two lateral apetures
Subarachnoid space, small amount into spinal cord

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12
Q

What propels CSF through the ventricular system?

A

Newly formed fluid
Ciliary action of ventricular ependyma
Vascular pulsations

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13
Q

What causes subarachnoid haemorrhages?

A

Trauma
Spontaneous

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14
Q

Who is affected commonly by subarachnoid haemorrhages?

A

6% of all strokes
Females 1.6:1
More likely in black, Finnish and Japanese populations
50-55 years old

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15
Q

What does a subarachnoid haemorrhage present with?

A

Headache
Dizziness
Orbital pain
Diplopia
May have visual loss (due to anterior communicating artery aneurysm)

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16
Q

What can cause spontaneous subarachnoid haemorrhages?

A

Rupture of succular aneurysms (berry aneurysms)
80% of non-traumatic

Ruputure of arteriovenous malformations- 10%

17
Q

Label the image

A

ACA- may compress optic chiams and affect frontal lobe or pituitary gland

PCA- compresses oculomotor nerve, third nerve palsy

18
Q

What causes aneurysms to develop?

A

Pressures on the arterial wall (vessels in subarachnoid space)

Intracranial arteries lack external elastic lamina and have thin adventitia

Hypertension, smoking, alcohol, PCKD, Marfan’s, cocaine etc..

19
Q

Where do aneurysms tend to develop?

A

Usually at bifurcation points

Large cerebral arteries in anterior circle of Willis mostly affected

20
Q

What are the symptoms of a subarachnoid haemorrhage?

A

Worst headache of life
Nausea and vomiting
Loss of consciousness at onset, short

21
Q

What are the examination findings for subarachnoid haemorrhages?

A
  • Normal mental state
  • Meningism- stiff neck, photophobia
  • Third nerve palsy
  • No motor or sensory deficit
22
Q

What are sentinel headaches?

A

Bad headaches in the months preceding

Caused by minor leaks from aneurysm

23
Q

What happens after subarachnoid haemorrhages?

A
  • Microthrombi-can occlude smaller distal arteries
  • Vasoconstriction- CSF irritates cerebral arteries
  • Cerebral oedema- Response to hypoxia and extravasated blood
  • Sympathetic activation- early cushing response
  • Myocardial necrosis- due to sympathetic activation
  • Early rebleeding
  • Acute hydrocephalus -blood in subarachnoid space may block normal drainage of CSF
  • Global cerebral ischaemia
24
Q

What are the cellular changes in subarachnoid haemorrhages?

A

Oxidative stress
Release of inflammatory mediators- activation of microglia
Platelet activation

25
Q

What are the investigations for subarachnoid haemorrhages?

A

CT scan

Will detect 93% if within 24 hours of bleed

Small amounts of blood can be hard to see

26
Q

If there is a negative CT scan but a convincing history of SAH what should you do?

A

Lumbar Puncture

  • Wait at least 6 hours, 12+ is preferable
  • Need time for lysis of RBCs to take place to release bilirubin
  • CSF will have a yellow tinge after centrifuging, this can differentiate from a traumatic tap
  • Will cause Xanothchromia
27
Q

What is a traumatic tap?

A

Presence of blood in CSF due to damaged blood vessels as you enter into the subarachnoid space

28
Q

Describe the CSF in a SAH

A

Xanthochromia-yellow tinge
High protein- due to blood
WCC not raised
Normal glucose

29
Q

What is a star sign?

A

Accumulation of blood in the basal cisterns

30
Q

Once SAH has been confirmed what should be done?

A

CT angiography to confirm the location of the aneursym

31
Q

How are SAH treated?

A

ABC approach
- Support airway
- Give oxygen
- Support circulation, fluids
- CCB- Nimodipine to alleviate cerebral vasospasm

Neurological observations
- Look for tends suggesting raised ICP

Neurosurgery within 48 hours to prevent re-bleed
- Decompressive surgery- craniotomy
- Coiling- insertion of platinum wire into aneurysm sac, causes thrombosis of blood within aneurysm itself
- Clipping- open surgery, clamp the aneurysm neck with spring clip

32
Q

What is the prognosis of a SAH?

A

Very poor
10-15% die before hospital
25% die in 24 hours

Re-bleeding
Intravenitruclar haemorrhage
Delayed ischaemia from cerebral vasospasm, most common cause of death

33
Q

How do you carry out an LP?

A

Find the iliac crests, this identifies L4-5

Local anaesthetic

Insert LP needle, will feel a pop as you pass through ligamentum flavum and the dura

Collect the CSF, remove the needle and allow drip, do not aspirate

Clinical Neuroscience (45 decks)

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