AP: Raised Intracranial Pressure Flashcards
What are the ranges of ICP?
Normal: 7-15mmHg in adults lying supine
Abnormal: >15mmHg
Pathological: >20mmHg
What are the 3 main causes of raised intracranial pressure?
- Space-occupying lesions
- CSF flow obstruction (hydrocephalus)
- Cerebral oedema
What are the most common space-occupying lesions?
- Tumour
- Abscess
- Intracranial haemorrhage:
- epidural hematoma
- subdural hematoma
- intraparenchymal hematoma
What is the normal flow of CSF?
Produced by choroid plexus –> lateral ventricles –> 3rd ventricle –> Aqueduct of Sylvus –> 4th ventricle –> spinal column or subarachnoid space –> Arachnoid villi
Is it safe to perform a lumbar puncture when a patient has hydrocephalus?
It depends:
- Commucating hydrocephalus: YES
- caused by defective absorption of CSF (most often), overproduction CSF (rare), venous drainage insufficiency (sometimes)
- Non-communicating hydrocephalus: NO
- caused by obstruction CSF flow within ventricular system or outlets to arachnoid space
What are some causes of cerebral oedema resulting in raised ICP?
- Traumatic brain injury
- Ischemic stroke
- Hypoxic or ischemic encephalopathy
- Postoperative edema
What are some other causes of raised ICP?
- Metabolic disorders:
- hyponatremia - sodium important - controls water content in brain. Low Na = hydrocephaly
- hypo-osmolality
- Increase in venous pressure
- cerebral venous sinus thrombosis
- heart feailure
- Increased CSF flow production
- choroid plexus tumour
- Idiopathic intracranial hypertension
- Pseudo tumour cerebri
What are the pathophysiological consequences of raised ICP?
Herniation syndromes:
- subfalcine (side to side)
- uncal (transtentorial)
- central herniation
- tonsillar herniation
- upward herniation
What are the consequences of subfalcine herniation?
- Anterior cerebral artery compression (contralateral leg paresis)
- Somnolence
What are the consequences of uncal (transtentorial) herniation?
- Anisocoria (uneven pupils)
- Midbrain and posterior cerebral artery compression
- somnolence
- contralateral hemiparesis, occipital infarct
- Decerebrate posturing (extensor - arms like e’s)
What is central herniation and what are its consequences?
Downward shift of the brainstem and diencephalon due to supratentorial lesion
- somnolence/coma
- bilaterally “blown” pupils
- decorticate/decrebrate posturing
- bilateral midbrain, posterior communicating artery compression
- Cheyne-Stokes respirations with pinpoint nonreactive pupils
What are the consequences of tonsillar herniation?
- Somnolence
- Quariparesis
- Cardiac arrythmias
- Respiratory failure
This is a premorbid event
What are the consequences of (uncommon) upward herniation?
- Posterior fossa swelling
- excessive ventricular drainage
- bilateral fixed mid position
What are the typical clinical presentations of intracranial pressure?
- Headache
- worse in morning/coughing
- relieved by vomiting
- Nausea/vomiting
- Drowsiness/fatigue
- Focal deficits
- VI nerve palsy
- failure of upward gaze
How is the Glascow Coma Scale scored?
Eye Opening (E)
- spontaneously (4)
- to speech (3)
- to pain (2)
- no response (1)
Best Verbal Response (V)
- orientated (5)
- confused (4)
- inappropriate words (3)
- incomprehensible sounds (2)
- no response (1)
Best Motor Response (M)
- obeys commands (6)
- localises to pain (5)
- withdraws (4)
- abnormal flexion (3)
- extension (2)
- no response (1)
