Intracranial pressure measurement

• Intracranial pressure (ICP) is defined as the pressure that is exerted between the skull and intracranial structures.
• Intracranial pressure measurement is an adjunct to the diagnosis and treatment of brain trauma Brain: trauma Head trauma: assessment of patient and disease potentially causing raised ICP.
• Intracranial pressure is thought to equilibrate equally within and among the intracranial contents, although, local increases in ICP have been noted.
• Measurement of ICP ipsilateral to a unilateral lesion most accurately reflects pathologically increased ICP.

Uses

• For a diagnostic and therapeutic aid in the management of brain trauma and disease potentially causing raised ICP.

Alternative techniques

• Attempts to measure ICP have, however, most commonly relied upon measurement of CSF pressure via needle puncture at either the cerebellomedullary cistern or the lumbar subarachnoid space.
• A manometer is attached to the needle hub and the pressures are recorded in centimetres of water.
• Unfortunately, this technique incorporating only a single time measurement is often of little diagnostic and therapeutic value as ICP changes are frequently episodic.
• This method also discounts compartmentalized ICP changes that can occur secondary to herniation.
• For more chronic measurement of ICP, a fiber-optic ICP monitoring system has been utilized in humans. This method of ICP measurement has now been adapted for use in dogs and cats. It involves placement of a pressure transducer approximately 3-5 mm into the brain parenchyma. Primary disadvantage in veterinary medicine is that they can become dislodged and the cables easily break if the patient is agitated.
• Transcranial Doppler is sometimes a non-invasive alternative which does not require anesthesia. However it is still experimental.