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Sem 4 - Nervous System > Raised Intracranial Pressure > Flashcards

Raised Intracranial Pressure Flashcards

1
Q

What is contained in the intracranial space?

A

Brain

Dura mater

Blood

CSF

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2
Q

Is there more arterial blood or venous blood in the intracranial space?

A

Venous blood

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3
Q

What is intracranial pressure?

A

Refers to pressure within the intracranial space

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4
Q

What is normal intracranial pressure?

A

5-15 mmHg

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5
Q

How is intracranial pressure measured?

A

Lumbar puncture with a manometer, this is a tube which CSF runs up in, measure its height

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6
Q

How is intracranial pressure regulated?

A

Regulation of blood flow to the brain by

  • autoregulation
  • chemoregulation
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7
Q

What is autoregulation in terms of regulating intracranial pressure?

A

Vasoconstriction and vasodilation

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8
Q

What is chemoregulation in terms of regulating intracranial pressure?

A

Vasodilation in response to low cerebral pH, high pCO2

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9
Q

How is increasing intracranial pressure regulated?

A

Vasoconstriction to reduce venous blood volume

Reduced volume of CSF

Eventually cannot do this any further

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10
Q

How does brain injury cause raised intracranial pressure?

A

Reduced arterial blood supply to brain cells
Reduced delivery of oxygen to brain cells
Reduced aerobic metabolism
Reduced ATP
Reduced function of Na+ K+ ATPase
Increased concentration of sodium ions in the brain cells
Water moves into the brain cells by osmosis
Oedema of brain cells
Further compression of arteries supplying the brain

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11
Q

What are the signs and symptoms of raised intracranial pressure?

A

Headache

Vomiting

Visual disturbances, CN6 palsy

Depression of conscious level

In infants, may present as slowly increasing head size

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12
Q

What are the characteristics of the headache with raised intracranial pressure?

A

Generalised ache

May wake the patient up from sleep

Worst when wake up in the morning
Aggravated by bending, stooping
Aggravated by coughing, sneezing

Severity gradually progresses

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13
Q

Why do the aggravating factors of a headache with raised intracranial pressure make it worse?

A

Increased venous blood volume in the intracranial space, further raising the intracranial pressure

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14
Q

Why is there vomiting with raised intracranial pressure?

A

Ischaemia and hypoxia of vomiting centre in the brain

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15
Q

How does the vomiting change with the duration of the raised intracranial pressure?

A

Starts off as nausea, progresses to vomiting, then to projectile vomiting

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16
Q

What are the visual disturbances with raised intracranial pressure?

A

Blurring

Obscurations

Papilloedema

Retinal haemorrhages

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17
Q

What causes the visual disturbances with raised intracranial pressure?

A

Compression of the CN2 optic nerve

Because it is an extension of the brain so it surrounded by dura and CSF

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18
Q

What does the optic disc look like on fundoscopy with raised intracranial pressure?

A

Enlarged

Blurred outline

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19
Q

What does the retina look like on fundoscopy with raised intracranial pressure?

A

Cannot see blood vessels on retina

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20
Q

Retinal haemorrhages tend to occur with raised intracranial pressure that happened…

A

Rapidly

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21
Q

Why does a CN6 abducens nerve palsy occur with raised intracranial pressure?

A

CN6 abducens nerve runs closely to the pons and the skull, easily compressed by raised intracranial pressure

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22
Q

What are the signs and symptoms of a CN6 abducens nerve palsy?

A

Patient’s eye is adducted due to unopposed pull of the medial rectus muscle

Patient cannot abduct their eye due to loss of innervation to lateral rectus muscle

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23
Q

Why is there a depression in consciousness level with raised intracranial pressure?

A

Due to effects of ischaemia on raised intracranial pressure

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24
Q

What are the complications of raised intracranial pressure?

A

Herniation syndromes

Cushing’s reflex

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25
Q

What are the different types of herniation syndromes? Which is the most common?

A

Subfalcine herniation - most common

Uncal herniation

Tonsillar herniation

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26
Q

What is a subfalcine herniation?

A

Refers to the herniation of the brain under the falx cerebri

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27
Q

What are the signs and symptoms of a subfalcine herniation?

A

Asymptomatic

Contralateral leg weakness if anterior cerebral artery is compressed

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28
Q

What does a subfalcine herniation look like on a CT head scan?

A

Midline shift

29
Q

What is an uncal herniation?

A

Uncus of temporal lobe herniates through the opening of the tentorium cerebelli
Uncus compresses the midbrain

30
Q

What are the signs or symptoms of uncal herniation?

A

Dilated pupil

Contralateral weakness

Decreased level of consciousness

31
Q

Why does uncal herniation cause a dilated pupil?

A

Compression of CN3 oculomotor nerve

Loss of parasympathetic innervation to the constrictor pupillae muscle on same side

32
Q

Why does uncal herniation cause contralateral weakness?

A

Compression of cerebral peduncles

Which contain sensory and motor fibres running between the cerebral hemispheres and the pons

33
Q

Why does uncal herniation cause decreases level of consciousness?

A

Compression of reticular formation

34
Q

What is a tonsillar herniation?

A

Cerebellar tonsils herniates through the foramen magnum

35
Q

What are the signs and symptoms of a tonsillar herniation?

A

Decreased level of consciousness

Cardiovascular and respiratory dysfunction

36
Q

Why does a tonsillar herniation cause decreased level of consciousness?

A

Compresses the reticular formation

37
Q

Why does a tonsillar herniation cause cardiovascular and respiratory dysfunction?

A

Compresses the medulla which contains the cardiovascular and respiratory control centres

38
Q

What is Cushing’s reflex?

A

Physiological nervous system response to continuous raised intracranial pressure

  • high blood pressure
  • bradycardia
  • low respiratory rate
39
Q

What causes high blood pressure and bradycardia in Cushing’s reflex?

A

Ischaemia of medulla results in activation of sympathetic nervous system
Which increases blood pressure and causes tachycardia
Baroreceptors react to this and stimulate bradycardia

40
Q

What causes low respiratory rate in Cushing’s reflex?

A

Ischaemia of pons and medulla, which contain the respiratory centres, gives low respiratory rate

41
Q

What are the causes of raised intracranial pressure?

A

Cerebral oedema

Increased cerebral blood volume

Increased CSF

Expanding mass

42
Q

What are the causes of cerebral oedema?

A

Ischaemic stroke

Meningitis

Encephalitis

Diffuse head injury

43
Q

What are the causes of increased cerebral blood volume?

A

Venous outflow obstruction

-venous sinus thrombosis

44
Q

What are the causes of increased CSF?

A

Impaired absorption

  • hydrocephalus
  • benign intracranial hypertension

Excessive secretion
-choroid plexus papilloma

45
Q

What are the causes of an expanding mass in the intracranial space?

A

Abscess

Tumour

Haemorrhage, haematoma

46
Q

What is hydrocephalus?

A

Accumulation of CSF

47
Q

What causes hydrocephalus?

A

Imbalance between production and absorption of CSF

More production or less absorption

48
Q

What are the types of hydrocephalus?

A

Non-communicating

Communicating

49
Q

What is non-communicating hydrocephalus?

A

CSF is obstructed within the ventricles

Or between the ventricles and the sub-arachnoid space

50
Q

What are the causes of non-communicating hydrocephalus? Which is the most common cause?

A

Blockage of aqueduct
Can be congenital or acquired
Most common cause

Tumours compressing the ventricular system

51
Q

What does non-communicating hydrocephalus look like on a CT scan?

A

Large third ventricle, small fourth ventricle

52
Q

What is communicating hydrocephalus?

A

Communication between the ventricles and the subarachnoid space

53
Q

What are the causes of communicating hydrocephalus? Which is the most common

A

Choroid plexus papilloma

Post-meningitis - most common
Sub-arachnoid haemorrhage
Trauma
Neoplastic infiltration of subarachnoid space
-all give blockage of arachnoid granulation

54
Q

What does non-communicating hydrocephalus look like on a CT scan?

A

Whole ventricular system is enlarged

55
Q

What are the most common ages with brain tumours?

A

Children

Late middle age

56
Q

What are the most common types of brain tumours in children?

A

Astrocytomas

Medullablastomas

57
Q

What parts of the brain are brain tumours in children most common in?

A

Midline

Posterior region

58
Q

What are the most common types of brain tumours in middle-aged people?

A

Metastases from other types of tumours e.g. breast, lung, kidney cancer

59
Q

What are the most common types of primary brain tumours in middle-aged people?

A

Gliomas

Meningiomas

60
Q

What is idiopathic intracranial hypertension?

A

Raised intracranial pressure but no pathology

61
Q

What group of patients most commonly have idiopathic intracranial hypertension?

A

Obese women after weight gain

62
Q

How is idiopathic intracranial hypertension treated?

A

Weight loss

Carbonic anhydrase inhibitor diuretics

CSF drainage

63
Q

How can CSF be drained to treat idiopathic intracranial hypertension?

A

Therapeutic lumbar puncture

Shunts

64
Q

How is raised intracranial pressure due to cerebral oedema treated?

A

Treat the underlying cause

Give mannitol or hypertonic saline

65
Q

Why is mannitol or hypertonic saline given to treat raised intracranial pressure due to cerebral oedema?

A

Makes the plasma hyper-osmotic to CSF
So water moves from the CSF to the plasma
Reducing the volume of CSF

66
Q

How is raised intracranial pressure due to increased cerebral blood volume treated?

A

Anticoagulation for venous sinus thrombosis

Or stunting of venous sinuses

67
Q

How is raised intracranial pressure due to increased CSF treated?

A

Shunts from the ventricles to the peritoneum

Tumour resection

Diuretics while waiting for other treatments e.g. carbonic anhydrase inhibitors

68
Q

How is raised intracranial pressure due to an expanding mass treated?

A

Surgical resection

Draining abscess

Craniotomy, surgically removing part of skull to relieve pressure

Sem 4 - Nervous System (25 decks)

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