CSF and ICP Flashcards
What pathologies can cause raised ICP?
Haemorrhage e.g. due to trauma Vasogenic oedema Cytotoxic oedema Influx of inflammatory mediators Space occupying lesion
What is the cellular effect of raised ICP?
Decreased cerebral perfusion: ischaemia, leading to infarction
What is the anatomical effect of raised ICP?
Herniation syndromes
- subfalcine herniation (affects medial motor cortex)
- uncal herniation (affects CrN III)
- foramen magnum herniation (affects brain stem)
What is the total volume of CSF in the body?
150ml (half intracranial, half in spinal cord)
Describe the functions of CSF
Buoyancy; reduced the net weight of the brain Protection from trauma; shock absorption Regulation of ICP Homeostasis e.g. pH Waste removal
Describe the normal composition of CSF
No RBCs A few WBCs Glucose (40-80mg/100ml) Protein (15-45mg/100ml) Chloride Sodium
Where does CSF drain back into the venous circulation?
Arachnoid granulations
Where is the choroid plexus located and what is its function?
Floor of the lateral ventricles and the roofs of the third and fourth ventricles
Produces CSF
Define the two types of hydrocephalus
Obstructive: blockage of outflow from ventricles
Communicating: blockage at the level of the arachnoid granules, causing a mismatch between production and absorption of CSF
What investigations should be carried out when hydrocephalus is suspected?
Fundoscopy (look for papilloedema secondary to raised ICP) Head CT (look for reduced clarity of ulci and gyri, and dilated ventricles)
What is the significance of normal pressure hydrocephalus?
It is a potentially reversible dementia
Describe the classical triad of symptoms of normal pressure hydrocephalus
Dementia (confusion)
Gait disturbance (magnetic gait)
Urinary incontinence
How is hydrocephalus treated?
Surgical insertion of a CSF shunt to create a drainage route for CSF that is alternative to the arachnoid granules
- works because NPH is a communicating hydrocephalus
What is normal pressure hydrocephalus?
The condition of ventricular dilatation in the absence of raised CSF pressure on lumbar puncture
How is hydrocephalus treated in emergency situations?
CSF drainage
What is the medical treatment for hydrocephalus? Is this long term or short term?
Carbonic anhydrase inhibitor such as acetazolamide
- reduces CSF production from choroid plexus
- short term measure
Describe the potential complications of shunts
Over-drainage; risk of low pressure headaches or
subdural haematoma
Under-drainage
Blockage
Infection; often caused by skin flora and hard to treat
Disconnection
Seizures
Distal end problems; abdominal hernias, cardiac
arrhythmias
What is xanthochromic CSF?
CSF is yellow due to presence of blood breakdown products (bilirubin)
Most commonly seen in SAH (12 hours after onset)
What checks should be carried out before performing a lumbar puncture?
Patient should be conscious
No focal neurological deficit (LP dangerous if patient has raised ICP)
CT/MRI to rule out intracranial mass lesion (again due to risks associated with raised ICP)
No infection at the site of needle insertion
Ensure that the patient is not on anticoagulants
Must get verbal consent from the patient
