Raised Intracranial Pressure Flashcards
What is the intracranial and spinal vault enclosed by?
Dura mater and bone
What does the intracranial and spinal vault contain?
- Neural tissue (brain and spinal cord)
- Blood
- CSF
What is intracranial pressure?
The pressure within the intracranial space
What is the normal ICP?
5-15mmHg
What occupies the intracranial space?
- CSF
- Blood
- Brain
How is blood flow to the brain regulated in an healthy individual?
- Autoregulation
- Chemoregulation
How does autoregulation of blood flow to the brain occur?
- Vasoconstriction
- Vasodilation
How does chemoregulation of blood flow to the brain occur?
Vasodilation in response to a low cerebral pH
What is the result of adaptation of the brain, blood, and CSF?
It can maintain ICP to a degree, even in disease states
Describe the steps in the pathophysiology of a brain injury?
- Reduction in blood supply to brain cells, e.g. compression by intracranial tumour
- Cytotoxic cellular oedema
- Further swelling and compression, so further reduction in blood supply to brain cells
What are the signs and symptoms of raised ICP?
- Headache
- Vomiting
- Visual disturbances
- Depression of conscious level
What are the features of the headache caused by raised ICP?
- Generalised ache
- Worst on awakening in the morning
- May awaken patient from sleep
- Severity gradually progresses
Why is the headache from raised ICP worse in the morning?
As a result of hypoventilation during the sleeping hours
What factors aggregate the headache caused by raised ICP?
- Bending or snooping
- Coughing or sneezing
Describe the vomiting caused by raised ICP
Nausea and vomiting that progresses to projective vomiting
What visual disturbances might occur with raised ICP?
- Blurring
- Obscurations
- Papilloedema
- Retinal haemorrhages
What are obscurations?
Transient blindness upon bending or posture changes
When will raised ICP patients get retinal haemorrhages?
If the rise in ICP has been rapid
How might slowly increasing intracranial pressure present in infants?
As slowly increasing head size
What happens if raised ICP is not treated, and continues to rise?
You get herniation through the foramen magnum
What is the clinical relavance of herniation through the foramen magnum?
It is a poor prognostic sign
What is Cushing’s reflex?
A last effort to perfuse the brain, whereby there is;
- Increased blood pressure
- Irregular breathing
- Bradycardia
What causes the bradycardia in Cushing’s reflex?
Ischaemia at the medulla leads to sympathetic activation, which causes a rise in blood pressure and tachycardia. Baroreceptors react, causing bradycardia
What causes the low respiratory rate in the Cushing’s reflex?
Ischaemia at the respiratory centres in the pons/medulla
What are the categories of causes of raised intracranial pressure?
- Increased cerebral blood volume
- Cerebral oedema
- Increased CSF
- Space occupying lesion
What can cause an increased cerebral blood volume?
- Venous outflow obstruction
- Venous sinus thrombosis
What can cause increased CSF?
- Impaired absorption
- Excessive secretion
What can cause impaired absorption of CSF?
- Hydrocephalus
- Benign intracranial hypertension
What can cause excessive secretion of CSF?
Choroid plexus papilloma
What can cause cerebral oedema?
- Meningitis
- Encephalitis
- Diffuse head injury
- Infarction
What space occupying lesions can cause raised ICP?
- Abscess
- Tumour
- Haemorrhage/haemotoma
What is the most common cause of raised ICP?
Traumatic brain injury
What needs to be thought about in suspected raised ICP due to traumatic brain injury?
- Epidural, subdural, and subarachnoid harmorrhages
- Use of anticoagulants
What might suggest severe meningitis encephalitis as the cause of raised ICP?
- Signs/symptoms of meningitis
- Immunosupression
- Tb exposure
What can severe meningitis encephalitis cause in the short term?
Brain oedema
What can severe meningitis encephalitis cause in the long term?
Venous outflow obstruction
What colour is normal CSF?
Clear and colourless
Describe the composition of normal CSF
- Very little protein - 15 to 45mg/dL
- Little immunoglobulin
- 1-5 cells per ml
How are changes to CSF clinically important?
They are useful in diagnosis of a variety of disease processes
What is accumulation of CSF thought to be due to?
Imbalance between production and absorption of CSF with subsequent enlargement of brain ventricles
How common in hydrocephalus?
1 in 1000 births
What are the classifications of hydrocephalus?
- Non-communicating/obstructive
- Communicating
What is non-communicating/obstructive hydrocephalus?
CSF is obstructed within the ventricles, or between the ventricles and subarachnoid space
What is non-communicating/obstructive hydrocephalus most commonly due to?
Aqueduct blockage
Is non-communicating/obstructive hydrocephalus congential or acquired? her
Can be either
Give an example of an acquired cause of hydrocephalus
Tumours, e.g. meningiomas
What is communicating hydrocephalus?
When there is communication between the ventricles, or between the ventricles and subarachnoid space, and so the problem lies outside of the venticular system
What problems with CSF might cause communicating hydrocephalus?
- Reduced absorption or blockage of the venous drainage system
- Increased CSF production
What conditions might cause communicating hydrocephalus?
- Post-meningitis, bacterial, fungal, or TB
- Subarachnoid haemorrhage
- Trauma
- Neoplastic infiltration of subarachnoid space
- Choroid plexus papilloma
What is the incidence of brain tumours?
1 in 10,000
Where are the age peaks for brain tumours?
- Children
- Late middle age
How does the incidence of brain tumours in children differ to other childhood cancers?
Second most common childhood cancer after leukaemia
What are the most common forms of paediatric brain tumours?
- Astrocytomas from astrocytes
- Medulloblastomas from neuroectoderm cells
Where in the brain to brain tumours tend to effect?
Midline or posterior region
What are the most common types of brain tumours in adults?
- Gliomas
- Meningiomas
- Metastases from lung, breast, and kidney
What is idiopathic intracranial hypertension?
Raised intracranial pressure without evidence of hydrocephalus or mass lesion
What will be round on investigation with idiopathic intracranial hypertension?
- Normal investigations, including imaging of the brain
- Signs of raised ICP
Who is idiopathic intracranial hypertension most commonly found in?
Obese young women
What are the treatment options for idiopathic intracranial hypertension?
- Weight loss
- Medical management using drugs
- CSF drainage and shunts
Give an example of a drug that can be used to treat idiopathic intracranial hypertension
Carbonic anhydrase inhibitors
How is ICP caused by increased cerebral blood volume treated?
- Anticoagulation
- Rarely, tenting of venous sinuses
How is raised ICP caused by cerebral oedema treated?
- Treat the cause
- Mannitol
- Hypertonic saline
How is raised ICP caused by increased CSF treated?
- Shunts
- Tumour resection
- Diuretics whilst awaiting intervention, e.g. furosemide, carbonic anhydrase inhibitors
How is raised ICP caused by space occupying lesions treated?
- Surgical resection, e.g. craniotomy
- Steroids of high value for brain tumours
