18) Raised ICP Flashcards
What is a normal ICP?
5-15mmHg
What is in the intracranial space?
Brain, blood and CSF
What are the 3 steps in the pathophysiological cycle of brain injury?
Reduction of blood supply to brain -> cytotoxic cellular oedema -> further swelling and compression -> repeat
What are some signs and symptoms of raised ICP?
Headache
Vomiting
Visual disturbances
Depression of conscious level
Describe the typical headache in raised ICP:
Generalised, worse in morning due to hypoventilation (more CO2 = dilation), aggravated by bending and coughing
How can the cranial nerves be affected in raised ICP?
Optic nerve has meningeal covering so is surrounded by CSF
CN6 palsy due to compression of pons on temporal bone (false localising sign)
What are the triad of symptoms in Cushing’s reflex?
High BP, bradycardia, low RR
Explain why you get the triad of symptoms in raised ICP:
Ischemia at medulla -> sympathetic activation -> rise in BP and HR -> baroreceptors react -> bradycardia
Ischemia at pons/medulla resp centres causes low RR
What are some causes of raised ICP?
Increase in cerebral blood volume - venous outflow obstruction, venous sinus thrombosis
Cerebral oedema - infection or infarction
Increased CSF
Expanding mass - abscess, tumour, haemorrhage
When is there impaired absorption of CSF?
Hydrocephalus, benign intracranial hypertension
When can there be excessive secretion of CSF?
Choroid plexus papilloma
Describe the features of normal CSF:
Clear and colourless
Contains very little protein, immunoglobulins or leucocytes
Hypertonic compared to plasma
Describe the path of CSF from its production onwards:
CP cells in ventricles produce CSF and enters subarachnoid space by apertures in 4th ventricle. Into venous blood by arachnoid villi in dural venous sinus
What is hydrocephalus?
Accumulation of CSF due to imbalance between production and absorption
What is non-communicating hydrocephalus?
CSF is obstructed within the ventricles or between the ventricles and sub-arachnoid space
