16. Raised Intracranial Pressure Flashcards
What is normal ICP?
5-15mmHg.
What is contained within the cranium?
CSF + blood + brain.
How is intracranial pressure regulated?
Autoregulation (vasoconstriction and vasodilation), chemo-reulation (vasodilation in response to low cerebral pH).
What happens to CSF and venous volume of the brain if there is a mass in the cranium?
CSF drains and veins are compressed.
What is the pathophysiology of brain injury and swelling?
Reduced blood supply to brain cells from compression by e.g. tumour, so less O2 delivered, therefore no ATP so NaKATPase fails and Na builds up in cell so water follows in causing more swelling and compression.
What are the general signs and symptoms of raised intracranial pressure?
Headache, vomiting, visual disturbances, depression of conscious level.
What are the features of headache in RICP?
Generalised headache, worse in mornings and worsened by coughing/sneezing/bending/stooping, severity gradually progresses.
What are the features of visual disturbance in RICP?
Blurring, obscurations, papilloedema, retinal haemorrhages, CNVI palsy.
What is Cushing’s reflex in RICP?
Herniation through foramen magnum as last effort to perfuse brain.
What is the triad in Cushing’s reflex in RICP?
High BP, bradycardia, low RR.
How does RICP cause bradycardia?
Ischaemia at medulla -> SANS -> rise in BP and tachycardia -> detected by baroreceptors -> bradycardia.
How does RICP cause low respiratory rate?
Ischaemia at pons/medulla at respiratory centres -> low respiratory rate.
What are the causes of RICP linked with increased cerebral blood volume?
Venous outflow obstruction and venous sinus thrombosis.
What are the causes of RICP linked with cerebral oedema?
Meningitis, encephalitis, diffuse head injury, infarction.
What are the causes of RICP linked with increased CSF?
Impaired absorption from hydrocephalus or benign intracranial hypertension or excessive secretion by choroid plexus papilloma.
What are the causes of RICP linked with expanding mass?
Abscess, tumour, haemorrhage/haematoma.
What is the pathway of CSF from synthesis to out of the brain?
Synthesised in the choroid plexus cells -> lateral ventricle -> 3rd ventricle (cerebral aqueduct) -> 4th ventricle -> medial or lateral apperture -> subarachnoid space -> SC.
What is hydrocephalus?
Accumulation of CSF due to imbalance between production and absorption of CSF with enlargement of brain ventricles.
What are the two types of hydrocephalus?
Non-communicating/obstructive, and communicating.
What is non-communicating/ obstructive hydrocephalus?
CSF obstructed within ventricles or between ventricles and subarachnoid space.
What is communicating hydrocephalus?
Communication between ventricles and subarachnoid space, problem is outside of ventricular system - reduced absorption or blockage of venous drainage system or increased CSF production.
What is the main cause of obstructive hydrocephalus?
Aqueduct blockade.
What is the main cause of communicating hydrocephalus?
Post-meningitis.
What are the most common brain tumours in children?
Astrocytomas (astrocytes), medulloblastomas (neuroectodermal cells).
