Session 9 - Raised Intracranial Pressure Flashcards
What is the range for normal intracranial pressure?
5-15 mm Hg
How is blood flow to the brain regulated in healthy individuals?
Autoregulation:
- vasoconstriction
- vasodilation
Chemo-regulation:
- vasodilation in response to low cerebral pH e.g. high pCO2
These can maintain ICP to a degree even in diseased states
What are the signs and symptoms of raised intracranial pressure?
Headache Vomiting CN VI palsy Visual disturbances Depression of conscious level In infants, slowly increasing intracranial pressure may present as a slowly increasing head size.
Describe the headache experienced by patients with raised intracranial pressure.
Generalised headache Worst on awakening in the morning (result of hypoventilation during sleep and increased venous pressure in the head when lying down) May awaken patient from sleep Aggravated by bending, stooping Aggravated by coughing or sneezing Severity gradually progresses
The nausea and vomiting experienced by patients with raised intracranial pressure will eventually progress to what?
Projectile vomiting
What visual disturbances are experienced by patients with raised intracranial pressure?
Blurring
Obscurations - transient blindness upon bending or posture changes
Papilloedema in some patients
Retinal haemorrhages if the rise in ICP has been rapid
Why do patients with raised intracranial pressure experience depression of conscious level?
Ischaemia of the reticular formation
What are the three kinds of brain herniation?
Subfalcine herniation
Uncal herniation
Tonsillar herniation
Which kind of brain herniation is the most common?
Subfalcine herniation
What are the symptoms of a subfalcine herniation?
May be asymptomatic
Symptoms can include headache and contralateral leg weakness if anterior cerebral artery affected.
Midline shift on CT
How is the brain displaced in an uncal herniation?
The uncut (medial part of the temporal lobe) is displaced across the tentorial opening.
What are the symptoms of uncal herniation?
As the herniation progresses, the uncus puts pressure on the midbrain. This leads to
Ipsilateral oculomotor nerve (parasympathetic fibres) - ipsilateral dilated pupil
Compression of cerebral peduncle - contralateral leg weakness
Above signs may be false localising if the midbrain is pushed against the opposite side of the tentorium.
Decreased level of consciousness.
What is a tonsillar herniation?
The cerebellar tonsils herniate through the foramen magnum.
What are the symptoms of a tonsillar herniation?
Compression of medulla and upper spinal cord.
Brainstem affected - cardiac and respiratory dysfunction
Decreased level of consciousness
What is Cushing’s reflex?
If raised ICP is untreated and continues to rise you get a triad of:
High BP
Bradycardia
Low respiratory rate - altered breathing pattern
Poor prognostic sign. If left untreated - death.
Explain why Cushing’s reflex occurs.
Ischaemia at the medulla —> sympathetic activation —> rise in blood pressure and tachycardia —> baroreceptors react —> bradycardia
Ischaemia at pons/medulla at respiratory centres —> low respiratory rate
What are the causes of raised intracranial pressure?
Increased cerebral blood volume
Cerebral oedema
Increased CSF
Expanding mass/space occupying lesion
What are the possible causes of increased cerebral blood volume?
Venous outflow obstruction
Venous sinus thrombosis
What are the possible causes of cerebral oedema?
Meningitis
Encephalitis
Diffuse head injury
Infarction
What are the possibel causes of increased cerebrospinal fluid?
Impaired absorption of CSF: - hydrocephalus - benign intracranial hypertension Excessive secretion of CSF: - choroid plexus papilloma
What are the possible causes of space occupying lesions?
Abscess
Tumour
Haemorrhage/haematoma
What is the most common cause of raised intracranial pressure?
Traumatic brain injury leading to epidural, subdural or subarachnoid haemorrhages
(Can also be caused by anticoagulants)
How does severe meningitis encephalitis lead to raised intracranial pressure?
Can cause brain oedema acutely and venous outflow obstruction long term
Describe the contents of normal cerebrospinal fluid.
Contains very little protein
Little immunoglobulin
Only one to five cells (leukocytes) per ml
Is clear and colourless
Where is CSF produced?
Choroid plexus cell of the ventricles
Describe the route CSF takes from the lateral ventricle’s choroid plexuses to the venous circulation.
Lateral ventricle’s choroid plexus —> lateral ventricles —> through interventricular foramina —> third ventricle —> through cerebral aqueduct —> fourth ventricle —> through lateral and median apertures —> subarachnoid space —> arachnoid villi of venous sinuses —> venous blood —> heart and lungs
What is hydrocephalus?
Accumulation of CSF thought to be due to an imbalance between production and absorption of CSF with subsequent enlargement of brain ventricles.
Affects 1 in 1000 births
What is the difference between non-communicating/obstructive and communicating hydrocephalus?
Non-communicating/obstructive - CSF is obstructed within the ventricles or between the ventricles and the subarachnoid space
Communicating - there is communication between the ventricles and the subarachnoid space. (Problem lies outside of the ventricular system)
What are the causes of non-communicating hydrocephalus?
Most commonly due to aqueduct blockage.
Can be congenital or acquired.
Also due to tumours e.g. meningioma
What are the causes of communicating hydrocephalus?
Due to reduced absorption of blockage of the venous drainage system.
It may also be due to increased CSF production (e.g. choroid plexus papilloma)
Mostly post-meningitis - bacterial, fungal, TB
Subarachnoid haemorrhage
Trauma
Neoplastic infiltration of subarachnoid space
What are the most common brain tumours in children?
Astrocytoma
Medulloblastoma
Tend to be found in the midline or posterior regions
What are the most common brain tumours in adults?
Glioma
Meningioma
Metastases (from lung, breast, kidney)
What is idiopathic intracranial hypertension?
Raised intracranial pressure without evidence of hydrocephalus or mass lesion.
Investigations come back normal including imaging of the Brian.
But patient has signs of raised ICP.
Who is most commonly affected by idiopathic intracranial hypertension?
Usually affects obese young women after weight gain.
What are treatment options for idiopathic intracranial hypertension?
Weight loss
Medical management using drugs e.g. carbonic anhydrase inhibitors
CSF drainage and shunts
What treatment is used in raised ICP due to expanding mass?
Surgical resection e.g. craniotomy
Steroids of high value for brain tumours
What treatment is used in raised ICP due to cerebral oedema?
Treat the cause
Mannitol
Hypertonic saline
What treatment is used in raised ICP due to increased cerebral blood volume?
Anticoagulation
Rarely use stunting of venous sinuses
What treatment is used to treat raised ICP due to increased CSF?
Shunts
Tumour resection
Use diuretics whilst awaiting intervention e.g. furosemide, carbonic anhydrase inhibitors
