raised intracranial pressure

Question 1

what is it?

Answer 1

Normal intracranial pressure (ICP) is approximately 9-20cmH20 when measured on lumbar puncture (5-15mmHg). This can be increased by a number of pathologies in the brain, ranging from chronic causes such as a growing benign tumour to acute traumatic brain injuries causing haemorrhage and cerebral oedema.
Because the skull vault has a fixed volume, expansion of the brain, cerebrospinal fluid or blood within the skull can only be compensated for minimally (via a decrease in the volume of the other components) before ICP starts to rise rapidly.

Question 2

what is the aetiology?

Answer 2

Space-occupying lesions which may be benign or malignant, including cerebral abscesses, vascular lesions and tuberculomas
Haemorrhage which may be extradural, subdural or intracerebral
Cerebral oedema which can be secondary to trauma, infarction or reactive (e.g. around a malignant deposit)
Hydrocephalus where there is an abnormal accumulation of cerebrospinal fluid in the ventricles
Inflammation e.g. secondary to meningitis or encephalitis
Idiopathic intracranial hypertension where ICP is raised without a clear cause
Cerebral venous thrombosis

Question 3

what are the features?

Answer 3

Headache, often worse on waking, lying down, or when coughing/straining
Nausea and vomiting
Altered mental state e.g. lethargy or irritability
Diplopia due to cranial nerve palsies
Seizures

Cushing’s reflex - hypertension, bradycardia and irregular breathing
Cranial nerve palsies, especially the oculomotor and abducens nerves
Decreased level of consciousness
Focal neurological deficits e.g. hemiparesis
On fundoscopy: blurring of the disc margins, loss of venous pulsations, retinal haemorrhages

Question 4

what re the ix?

Answer 4

CT ideally (MRI later or less acutely)
LP in IIH

Question 5

what is mx?

Answer 5

elevate head of bed to 30 degrees
Patients with seizures or reduced levels of consciousness may require intubation and ventilation - In intubated patients, hyperventilation may be used to lower CO2 levels which in turn reduces ICP

CSF drainage, manage seizures, monitor ICP
analgesia, sedation and antiemetics
IV mannitol or hypertonic saline can be used to reduce ICP

Surgical options (e.g. decompressive craniectomy) can be used for severe cases of raised ICP for a number of causes

Question 6

what are the complications?

Answer 6

Coma and death
Status epilepticus
Permanent neurological deficits including loss of vision
Tonsillar herniation (“coning”)