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[AMS] Clinical Neuroscience > S10) Pathophysiology and Management of Raised Intracranial Pressure > Flashcards

S10) Pathophysiology and Management of Raised Intracranial Pressure Flashcards

1
Q

What is normal intracranial pressure?

A

Normal ICP = 5–15 mm Hg (7–20 cm H2O)

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2
Q

What are the occupants of intracranial space?

A
  • CSF
  • Blood
  • Neural tissue (brain + spinal cord)
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3
Q

In a healthy individual, the blood flow to the brain is regulated.

Explain how this occurs by autoregulation and chemo-regulation?

A
  • Autoregulation – vasoconstriction, vasodilation
  • Chemo-regulation – vasodilation in response to low cerebral pH e.g. high pCO2
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4
Q

Illustrate the intracranial compensation for an expanding mass

A
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5
Q

In four steps, illustrate the pathophysiology of a brain injury

A
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6
Q

Identify four signs of symptoms of raised intracranial pressure

A
  • Headache
  • Vomiting
  • Visual disturbances
  • Depression of conscious level
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7
Q

Describe five characteristics of a headache due to raised ICP

A
  • Generalised ache
  • Worst on awakening in the morning
  • May awaken patient from sleep (due to hypoventilation in sleep)
  • Aggravated by bending, stooping, coughing or sneezing
  • Severity gradually progresses
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8
Q

Describe four characteristics of visual disturbances due to raised ICP

A
  • Blurring
  • Obscurations – transient blindness upon bending or posture changes
  • Papilloedema (some patients)
  • Retinal haemorrhages (if rapid ICP rise)
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9
Q

Identify two red flag signs of raised ICP

A
  • Papilloedema
  • CN VI palsy – false localising sign
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10
Q

Describe the occurrence and presentation of a subfalcine herniation

A
  • Most common
  • May be asymptomatic
  • Symptoms incl. headache, contralateral leg weakness (if, ACA affected)
  • Midline shift on CT
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11
Q

What is an uncal herniation?

A

An uncal herniation is when the uncus, the medial part of the temporal lobe, is displaced across the tentorial opening

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12
Q

As the herniation progresses, the uncus puts pressure on the midbrain.

Describe the different possible presentations of uncal herniations

A
  • Decreased level of consciousness
  • Compressed ipsilateral oculomotor nerve – ipsilateral dilated pupil
  • Compressed cerebral peduncle – contralateral leg weakness
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13
Q

What is a tonsillar herniation?

A

A tonsillar herniation is when the cerebellar tonsils herniate through the foramen magnum

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14
Q

Explain the presentations of tonsillar herniations?

A

Compression of medulla and upper spinal cord:

  • Brainstem affected – cardiac and respiratory dysfunction
  • Decreased level of consciousness
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15
Q

What is Cushing’s reflex?

A

- Cushing reflex is a physiological nervous system response to untreated raised ICP

  • It is a poor prognostic sign consisting of the following triad: high BP, bradycardia, low RR
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16
Q

In five steps, explain how bradycardia and hypertension occur due to raised ICP

A

⇒ Ischaemia at medulla

⇒ Sympathetic activation

⇒ Rise in blood pressure & tachycardia

⇒ Baroreceptors react

⇒ Bradycardia

17
Q

In two steps, explain how hypoventilation occur due to raised ICP

A

⇒ Ischaemia at pons/medulla at respiratory centres

⇒ Low respiratory rate

18
Q

Identify and describe the four causes of raised intracranial pressure

A
  • Increased cerebral blood volume – venous outflow obstruction, venous sinus thrombosis
  • Cerebral oedema – meningitis, encephalitis, diffuse head injury, infarction
  • Increased CSF – impaired absorption (hydrocephalus), excessive secretion (choroid plexus papilloma)
  • Expanding mass / SOL – abscess, tumour, haematoma
19
Q

What leads to the clinical suspicion of raised ICP?

A
  • Traumatic brain injury (haemorrhages, anticoagulants)
  • Severe meningitis encephalitis
  • Risk factors, signs and symptoms of cancer
  • CVS risk factors
20
Q

Describe the composition and appearance of cerebrospinal fluid

A
  • Normal CSF is clear and colourless
  • It contains very little protein (15 to 45 mg/dL), little immunoglobulin, and only 1-5 cells (leukocytes) per ml
  • It is hyperosmolar compared to plasma
21
Q

Where is CSF produced?

A

The choroid plexus

22
Q

Briefly describe the pathway of CSF flow

A
23
Q

What is hydrocephalus?

A

Hydrocephalus is the accumulation of CSF due to an imbalance between the production and absorption of CSF with subsequent enlargement of brain ventricles

24
Q

Identify and describe the two types of hydrocephalus

A
  • Non-communicating/obstructive – CSF is obstructed within the ventricles or between the ventricles
  • Communicating – there is communication between the ventricles and the subarachnoid space
25
Q

A communicating hydrocephalus occurs when there is communication between the ventricles and the subarachnoid space.

Discuss the possible causes

A

Problem lies outside of the ventricular system:

  • Due to reduced absorption or blockage of the venous drainage system
  • May also be due to increased CSF production the subarachnoid space
  • Mostly due to post-meningitis (bacterial, fungal, TB)
  • Also due to trauma + neoplastic infiltration of subarachnoid space
26
Q

A non-communicating/obstructive hydrocephalus occurs when the CSF is obstructed within the ventricles or between the ventricles and the subarachnoid space.

Discuss its possible causes

A
  • Most commonly due to aqueduct blockade
  • Can be congenital or acquired
  • May be due to tumours e.g. meningioma
27
Q

What are the two age peaks for brain tumours?

A
  • In children
  • In late middle age
28
Q

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

A
  • Astrocytomas from astrocytes
  • Medulloblastomas from neuroectodermal cells
29
Q

What are the most common types of brain tumours for adults?

A
  • Gliomas
  • Meningiomas
  • Metastases from lung, breast and kidneys
30
Q

What is idiopathic intracranial hypertension?

A
  • Idiopathic intracranial hypertension is raised intracranial pressure without evidence of hydrocephalus or mass lesion
  • This usually occurs in obese young women after weight gain
31
Q

What are the treatment options for idiopathic intracranial hypertension?

A
  • Weight loss
  • Drugs e.g. carbonic anhydrase inhibitors, CSF drainage and shunts
32
Q

What are the principles of management of raised ICP due to increased cerebral blood volume?

A

Varies:

  • Anticoagulation
  • Rarely, tenting of venous sinuses
33
Q

What are the principles of management of raised ICP due to cerebral oedema?

A

Treat the cause:

  • Mannitol
  • Hypertonic saline
34
Q

What are the principles of management of raised ICP due to increased CSF?

A
  • Shunts
  • Tumour resection
  • Use diuretics whilst awaiting intervention e.g. furosemide, carbonic anhydrase inhibitors
35
Q

What are the principles of management of raised ICP due to space occupying lesions?

A
  • Surgical resection e.g. craniotomy
  • Steroids of high value of brain tumours

[AMS] Clinical Neuroscience (21 decks)

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