Raised intracranial pressure (N) Flashcards
What is raised intracranial pressure, and how does it come about?
- increased pressure in the cranium
- as the brain and ventricles are enclosed by a rigid skull, they have a limited ability to accommodate additional volume
- additional volume –> rise in ICP
What is normal ICP in adults in the supine position?
</=15mmHg
What are some causes of raised intracranial pressure? (6)
- idiopathic intracranial hypertension
- CNS infection - meningitis, encephalitis, brain abscess
- space occupying lesions - haemorrhage, aneurysm, tumours
- increased CSF i.e. hydrocephalus
- cerebral oedema
- increased BP (malignant hypertension)
What is idiopathic intracranial hypertension?
AKA pseudotumour cerebri, a disorder of increased ICP of unknown cause
What demographic does idiopathic intracranial hypertension classically happen in?
Young, overweight females
What are the clinical features of idiopathic intracranial hypertension? (4)
- headache
- blurred vision
- papilloedema on fundoscopy
- CN VI palsy
What does CT show in idiopathic intracranial hypertension?
Enlarged arachnoid outpouchings and prominent perivascular spaces
What drug can increase the risk of developing idiopathic intracranial hypertension?
Tetracyclines e.g. doxycycline
How do we manage idiopathic intracranial hypertension? (2)
- weight loss (low-sodium weight-reduction diet)
- acetazolamide (carbonic anhydrase inhibitor)
What are some examples of CNS infections that can cause raised ICP?
Meningitis, encephalitis, brain abscess
What are some examples of space-occupying lesions (raised ICP)? (3)
- haemorrhage
- aneurysm
- tumours
What is it called when a patient has increased CSF (raised ICP)?
Hydrocephalus
What are the clinical features of raised ICP? (4)
- bilateral headache
- vomiting
- reduced level of consciousness
- bilateral visual field loss (raised ICP may compress optic nerve)
What is seen on examination in raised ICP? (5)
- Cushing Triad - reflects brainstem compression (irregular breathing, widening PP, bradycardia)
- fundoscopy - papilloedema (swelling of optic disc)
- altered GCS
- Cheyne-Stokes respiration - progressively deeper and sometimes faster breathing followed by gradual decrease that results in temporary stop in breathing + cycle repeats
- CN palsies - III, IV, VI, RAPD
When is the bilateral headache in raised ICP worse? (2)
- in morning and lying down due to gravity
- when coughing/straining - if patient presents with headache upon straining, non-contrast CT head must be done
Why is there bilateral visual loss in raised ICP?
Raised ICP may compress optic nerve
What is the Cushing Triad (raised ICP)?
Reflects brainstem compression
- irregular breathing
- widened pulse pressure (hypertension)
- bradycardia
What does papilloedema look like on fundoscopy (raised ICP)?
Blurring of optic disc margin
What is Cheyne-Stokes respiration (raised ICP)?
Progressively deeper and sometimes faster breathing followed by gradual decrease that results in temporary stop in breathing + cycle repeats
What are some clinical features that are more specific to idiopathic intracranial hypertension (raised ICP)? (3)
- pulse-synchronous tinnitus (unilateral)
- photophobia
- retrobulbar pain
How does obstructive hydrocephalus present (raised ICP)?
Acute drop in conscious level, diplopia
How does normal pressure hydrocephalus present (raised ICP)? (3)
Triad of:
- dementia/cognitive impairment
- gait disturbances (apraxia/shuffling)
- urinary incontinence
Wacky, wobbly, wet
What is a risk factor for idiopathic intracranial hypertension (raised ICP)?
Tetracyclines e.g. doxycycline
What are the first-line investigations for idiopathic intracranial hypertension (raised ICP)? (4)
- dilated fundoscopy
- visual field testing (perimetry)
- visual acuity
- MRI of brain +/- contrast
What investigation can help us understand the underlying cause of raised ICP?
Neuroimaging - CT/MRI head
What other main investigation is there for raised ICP, apart from CT/MRI?
Invasive ICP monitoring - intraventricular catheter –> monitoring device placed into ventricles of brain along with CSF drainage system
Useful in conditions where CSF drainage is required for both diagnostic and therapeutic purposes e.g. hydrocephalus
What ICP level on invasive ICP monitoring would indicate treatment is needed?
> 20mmHg
What do we measure in lumbar puncture (L3/4) in raised ICP?
Measure opening pressure (definite: >250mmHg, intermediate: 200-250mmHg)
What are some differential diagnoses for raised ICP?
THIN BB
- Trauma
- Hydrocephalus / haemorrhage
- Infection
- Neoplasm
- Bleeding
- Benign intracranial hypertension
What is the diagnostic criteria for idiopathic intracranial hypertension? (5)
- Sx of raised ICP
- absence of localised findings on neurological examination
- absence of deformity, displacement, or obstruction of the ventricular system
- patient alert and awake
- no other causes
How do we manage idiopathic intracranial hypertension? (2)
- weight loss if obese: low-sodium weight-reduction diet
- acetazolamide (carbonic anhydrase inhibitor)
- (discontinue tetracyclines, retinoids and excessive vitamin A)
What is a simple 1st step to management of raised ICP?
Head elevation to 30 degrees
What drug can be given to reduce ICP?
IV mannitol (osmotic diuretic) - hyperosmolar solution that helps drain water out of brain, reducing ICP
(Used in patients with raised ICP secondary to traumatic brain injury)
What can we do if the underlying cause of raised ICP is hydrocephalus (excess CSF)?
CSF drainage (via external ventricular drain)
What must be done before CSF drainage (if required) in raised ICP?
IV mannitol must be given first
What can we give for raised ICP due to CNS infection or inflammation (or cancer)?
Glucocorticoid - dexamethasone
What breathing strategies can help reduce ICP?
Controlled hyperventilation –> reduced pCO2 –> vasoconstriction of cerebral arteries –> reduced ICP
When might emergency surgery be required for raised ICP? (2)
- presence of tumour –> resection
- haematoma –> evacuation
What are some complications of raised ICP? (4)
- cerebral oedema
- decreased cerebral perfusion pressure
- brain tissue herniation
- severe irreversible visual loss
