raised intercranial pressure Flashcards
1
Q
define
A
Raised intracranial pressure is caused by intracranial lesions causing an increased volume of blood, CSF or parenchymal tissue.
Vol inside cranium is fixed containing brain, blood and CSF so any increase in contents can lead to raised ICP.
This can be mass effect, oedema or obstruction to fluid outflow.
Normally ICP in adults is <15mmHg.
2
Q
causes
A
expanding mass:
- tumour
- haemorrhage
- abscess
increased cerebral blood volume:vasodilation:
- hypercapnia
- venous outflow obstruction
- venous sinus thrombosis
increased CSF:impaired absorption:
- hydrocephalus
- benign intracranial hypertension
excessive secretion:
- choroid plexus papilloma
cerebral oedema:
- chronic meningitis
- hypertensive encephalopathy
head injury
3
Q
s/s
A
- Headache -worse on coughing, leaning fwd
- N&V
- Altered GCS – drowsiness, listlessness, irritability, coma
- History of trauma
- Cushing’s response – (due to medullary involvement) increased BP and decreased HR, irregular breathing
- Cheyne – stokes respiration (abnormal pattern of breathing, characterised by progressively deeper, sometimes faster breathing followed by gradual decrease resulting in apnea – pattern repeats) NB: it is a poor prognostic sign.
- Pupil changes – (constrict first – later dilatation)
- Reduced visual acuity- peripheral visual field loss.
- Papilloedema- usually present if raised pressure is long standing. – but venous pulsation at disc may be absent (NB: absent in approx. 50% norm, but loss = useful sign)
- 6th CN palsy – common false localising sign due to compression of 6th CN as it passes over the petrous ridge.
- 3rd CN palsy– in temporal lobe herniation
- Failure of upgaze– due to midbrain compression
4
Q
Investigations
A
- Bloods; FBC, U&E, LFT, glucose, serum osmolality, clotting, blood culture.
- Consider toxicology screen
- CXR – any source of infection that may indicate abscess?
- CT head
- Consider LP if safe
5
Q
Mx
A
- Goal is to decrease ICP and avert secondary injury. Urgent neurosurgery is required for the definitive txt of increased ICP from focal causes (e.g. haematomas) – achieved via a craniotomy or burr hole.
- ICP monitor may be placed to monitor pressure.
- Surgery generally not helpful following ischaemic or anoxic injury.
6
Q
Immediate management plan for raised ICP, is as follows;
A
- ABC
- Correct hypotension, maintain MAP >90mmHg and treat seizures
- Brief examination; history if available:
- Any clues, e.g meningococcal rash, previous carcinoma
- Elevate head of bed to 30-40 degrees
- If intubated, hyperventilate to decrease PaCO2 (aim 4-4.5kpa)
- This causes cerebral vasoconstriction and reduces ICP almost immediately. Maintain PaO2 >12kPa
- Osmotic agents (e.g. mannitol) can be useful pro tem but may lead to rebound increased ICP after prolonged use (approx. 12-24hrs)
- Give 20% solution 0.25 – 0.5g/kg IV over 10 -20 mins(e.g. 5ml/kg) Effect is seen after approx. 20 mins and lasts for 2-6 hrs. follow serum osmolality – aim for about 300mosmol/ kg but don’t exceed 310.
- Corticosteroids are NOT effective in reducing ICP except for oedema surrounding tumours e.g. dexamethasone 10mg IV and follow with 4mg/6h IV/PO
- Restrict fluid to <1.5L/d
- Monitor pt closely; consider monitoring ICP
- Aim to make a diagnosis
- Treat cause or exacerbating factors, e.g hyperglycaemia, hyponatraemia
- Definitive treatment if possible
7
Q
what types of herniation syndromes are there
A
Transtentorial/ Uncal herniation
Tonsilar (coning) herniation
Subfalcian (cingulate) herniation
8
Q
Transtentorial/ Uncal herniation
A
- Lateral supratentorial mass – pushes the ipsilateral inferomedial temporal lobe (uncus) through the temporal incisura and against midbrain.
- CN3 compression, causing dilated ipsilateral pupil, then opthalmoplegia (fixed pupil ) down and out
- Ipsilateral corticospinal tract; contralateral hemiparesis
- May be followed by contralateral hemiparesis (pressure on cerebral peduncle) and coma from pressure on ascending reticular activating system (ARAS) in the midbrain.
9
Q
Tonsilar (coning) herniation
A
- Increased pressure in posterior fossa – displacement of cerebellar tonsils through foramen magnum
- Ataxia, CN6 palsies and upgoing plantar reflexes occur first – then LOC, irregular breathing, and apnoea. – syndrome may proceed rapidly due to small size and poor compliance in posterior fossa.
10
Q
Subfalcian (cingulate) herniation
A
- Due to frontal mass
- Displacement of cingulate gyrus (medial frontal lobe) under falx cerebri
- May be silent unless ACA (anterior cerebral artery) is compressed and causes a stroke – e.g. contralateral leg weakness +/- Abulia( lack of decision making)
11
Q
different ct scans
A
