Session 10 L3: Intracranial pressure Flashcards
What is contained in the intracranial space?
- Neural tissue
- Blood
- CSF
What is the normal Intracranial pressure?
5-15 mmHg
How is intracranial pressure regulated?
In a healthy individual the blood low to the brain is regulated
Autoregulation
- Vasoconstriction
- Vasodilation
Chemo-regulation
-Vasodilation in response to low cerebral pH e.g. high pCO2
What is the pathophysiology of intracranial pressure?
- Reduction of blood supply to brain cells due to compression by intracranial tumour
- Leads to cell death as sodium potassium ATPase doesn’t work
- Cytotoxic cellular oedema occurs as sodium accumulates intracellularly
- This leads to further swelling and compression
Cycle keeps going on
What are the signs of raised Intracranial pressure?
- Headache
- Vomiting
- Visual disturbance
- Depression of conscious level
- Increasing head size in infants
Describe the headache experienced in raised ICP?
- Generalised Ache. May awaken patient from sleep.
- Worst on awakening in the morning. This is the result of hypoventilation during sleeping hours, so less CO2 is released from the system. Increased CO2 so the chemoregulation mechanism starts which leads to volume increasing in the head.
- Aggravated by bending, stooping, coughing or sneezing
- Severity gradually progresses
Describe the vomiting experienced in raised ICP.
Nausea and vomiting progresses so projectile vomiting
Describe the visual disturbance experienced in raised ICP.
- Blurring
- Obscuration so transient blindness upon bending or posture changes
- Papilloedema in some patients
- Retinal haemorrhages if the rise in ICP has been rapid
- CN6 palsy (false localising sign)
What are the types of herniation syndrome in the brain.
- Subfalcine
- Uncal
- Tonsillar
What is a subfalcine herniation?
- The Cingulate gyrus is displaced under the falx cerebri
- May be asymptomatic
- Symptoms can include headache and contralateral leg weakness if anterior cerebral artery affected
- Midline shift on CT
What is an uncle herniation and associated symptoms?
- The uncus, the medial part of the temporal lobe, is displaced across tentorial opening.
- As the herniation progresses the uncus puts pressure on the midbrain
- Ipsilateral oculomotor nerve causing ipsilateral dilated pupil
- Compression of cerebral peduncle causing contralateral leg weakness
- Above sign may be false localising if the midbrain is pushed against the opposite side of tentorium
- Decreased level of consciousness due to effects on arousal centre
What is a tonsillar herniation and associated symptoms?
Tonsillar Herniation
- Cerebellar tonsils herniate through the foramen magnum
- Compression of medulla and upper spinal cord
- Brainstem affected (cardiac and respiratory dysfunction)
- Decreased level of consciousness
What is the triad of symptoms of Cushing’s Reflex?
- High Blood Pressure
- Bradycardia
- Low respiratory rate
What is the hypothesis for Cushing’s Reflex?
- Ischaemia at medulla leading to sympathetic activation so rise in blood pressure + tachycardia. Baroreceptor react leading to bradycardia
- Ischaemia at pons/medulla at respiratory centres lead to low respiratory rate
- If untreated this leads to death
What are the causes of increased ICP?
- Increased cerebral blood volume
- Cerebral oedema
- Increased CSF
- Expanding mass other (space occupying lesions)
What are some causes of increased cerebral blood volume and treatments for it?
Venous outflow obstruction, Venous sinus thrombosis
- Anticoagulation
- Rarely, tenting of venous sinuses
What are some causes of increased cerebral volume and treatments for it?
Meningitis, Encephalitis, Diffuse head injury, Infarction
- Treat the cause
- Mannitol
- Hypertonic saline
What are some causes of increased CSF and treatments for it?
Impaired absorption (Hydrocephalus, Benign intracranial hypertension), Excessive secretion (Choroid plexus papilloma)
- Shunts
- Tumour resection
- Use furosemide whilst awaiting intervention e.g. furosemide, carbonic anhydrase inhibitors
What are some examples of expanding masses and treatments available?
-Abscess, Tumour, Haemorrhage/haematoma
- Surgical Resection e.g. craniotomy
- Steroids of high value for brain tumours
What leads to clinical suspicion of raised ICP?
- Traumatic brain injury by far the most common cause of raised ICP (Epidural, Subdural and subarachnoid haemorrhages, Any use of anticoagulants)
- Severe meningitis/encephalitis (Signs/Symptoms of meningitis, If severe can cause brain oedema acute and venous outflow obstruction long term, Immunosuppressed/TB exposure)
- Risk factors for cancer/sign and symptoms of cancer
- Cardiovascular risk factors
What is the pathway of CSF flow?
- Lateral ventricles CSF goes through interventricular foramina to the third ventricle
- CSF flows from third ventricle through cerebral aqueduct to fourth ventricle
- CSF flows from the fourth ventricle through lateral and median apertures to subarachnoid space
- CSF flows from subarachnoid space to the arachnoid villi of dural venous sinuses then to venous blood which goes back to heart and lungs
What is hydrocephalus?
Accumulation of CSF is thought to be due to an imbalance between production and absorption of CSF with subsequent enlargement of brain ventricles. 1 in 100 births
What are the common classifications of hydrocephalus?
- Non communication/obstructive
- Communication (communication between the ventricle and subarachnoid space)
What is a Non communication/obstructive hydrocephalus?
- CSF is obstructed within the ventricle or between the ventricle and subarachnoid space
- Most commonly due to aqueduct blockage
- Can be congenital or acquired
- Also can be due to tumours e.g. meningioma
What is a communication hydrocephalus?
- There is communication between the ventricle and subarachnoid space
- Problem is outside the ventricular system
- Due to reduced absorption or blockage of the venous drainage system. It may also be due to increased CSF reduction
What are the causes of communication hydrocephalus?
- Mostly to post-meningitis (Bacterial, fungal, TB)
- Subarachnoid haemorrhage
- Can be due to trauma + neoplastic infiltration
- Less common (Excess CSF production from choroid plexus papilloma)
What are common tumours within the brain in children?
- In children, brain tumour are the second most common childhood cancer after leukaemia. Most commonly astrocytomas and medulloblastomas (neuroectodermal)
- Tend to be midline or posterior region so raised ICP and Hydrocephalus
- Metastases from lung, breast and kidney
When do tumours of the brain commonly occur?
Age peaks in children and in late middle age
What are common tumours within the brain in adults?
- Gliomas and Meningiomas
- Metastases from lung, breast and kidney
What is idiopathic intracranial hypertension?
- Raised intracranial pressure without evidence of hydrocephalus or mass lesion
- Normal investigation including imaging of brain
- But signs of raised ICP
- Usually obese young women after weight gain
What are the treatment options of idiopathic intracranial hypertension?
Treatment options include weight loss, medical management such as using drugs such as carbonic anhydrase inhibitor, CSF drainage and Shunts
