Raised Intracranial Pressure

Question 1

What is meant by raised intracranial pressure?

Answer 1

“Idiopathic intracranial hypertension (IIH) - (pseudomotor cerebri) is a syndrome of reduced cerebrospinal fluid absorption. ”
- The volume inside the cranium is fixed so any increase in the contents can lead to raised ICP
- This can be mass effect, oedema or obstruction to fluid outflow
Normal ICP in adults in the supine position is <15mmHg

Question 2

What are the different risk factors for having raised ICP?

Answer 2

• female sex
• weight gain
• sleep apnoea
• using medications (e.g. Tetracyclines) or having a disease associated with idiopathic intracranial hypertension, SHHHIC:
  *Status epileptics
  *Head injury
  *Haemorrhage
  *Hydrocephalus (neurological disorder caused by an abnormal buildup of cerebrospinal fluid in the ventricles (cavities) deep within the brain)
  *Infection - meningitis, encephalitis, brain abscess
  *Cerebral oedema

Question 3

What are the presenting symptoms of raised ICP?

Answer 3

• Bilateral Headache → worse in mornings and when lying down due to effect of gravity (also worse when coughing/straining)
  Vomiting
  Altered GCS – drowsiness, irritability, coma
  History of trauma
  Poor vision

Question 4

What signs of raised ICP can be found on physical examination?

Answer 4

• Altered GCS
• Cushing Triad (reflects brainstem compression) → irregular breathing, widening pulse pressure and bradycardia
• Cheyne-Stokes respiration – progressively deeper and sometimes faster breathing followed by a gradual decrease that results in a temporary stop in breathing - cycle repeats
• Pupil changes – constriction first, later dilatation
• Reduced visual acuity
• Peripheral visual field loss
• Papilloedema:
  *swelling of optic disc (leads to blurring of optic disc margin on fundoscopy)
  *unreliable sign but venous pulsation at the disc may be absent
• Bilateral Visual Loss → increased ICP may cause compression of optic nerve

Question 5

What investigations are used to diagnose/ monitor a raised ICP?

Answer 5

• U&E, FBC, LFT, glucose, serum osmolality, clotting, blood culture
• Consider toxicology screen
• CXR – any source of infection may lead to abscess
• CT head
• Consider LP if safe – measure opening pressure
• Evidence of papilledema on fundoscopic eye exam
• Invasive ICP Monitoring → intraventricular catheter (monitoring device placed into the ventricles of the brain along with a CSF drainage system). Useful in conditions in which CSF drainage is required for both diagnostic and therapeutic purposes. Generally, ICP >20 mmHg indicates treatment is required.

Question 6

How is a raised ICP managed?

Answer 6

• Head elevation to 30°
• IV Mannitol (Osmotic Diuretic) → hyperosmolar solution, helping to draw water out of the brain, hence reducing ICP
• CSF Drainage
• Controlled Hyperventilation → hyperventilation = reduced pCO2 = vasoconstriction of the cerebral arteries = reduced ICP
• Glucocorticoids (Dexamethasone) → if elevated ICP is due to malignancy
• Emergency Surgery → resection of tumour, haematoma evacuation etc. (ie. treat underlying cause)

Question 7

What complications may arise from a raised ICP?

Answer 7

Cerebral oedema, decreased cerebral perfusion pressure, brain tissue herniation