Increased Intracranial Pressure (ICP)
Intracranial pressure or ICP is the pressure or force exerted
on the skull by the brain and fluid inside the skull cavity. These
include:
- 80% brain tissue and water
- 10% blood
- 10% cerebrospinal fluid (CSF)
Causes
Increase in intracranial pressure can be due to increase in cerebrospinal
fluid pressure, brain lesion, or swelling of the brain. The following
conditions can lead to increased ICP:
- Severe head injury
- Subdural hematoma
A hematoma or localized swelling filled with blood that occurs
in the dura matter and the arachnoid membrane of the brain.
- Hydrocephalus
Abnormal accumulation of fluid in cerebral ventricles
- Brain
tumor
- Brain hemorrhage
Bleeding in the brain
- Meningitis
Inflammation of the meninges (membrane that covers the brain)
due to bacterial or viral infection.
- Encephalitis or cephalitis
Inflammation of the brain
- Aneurysm
Localized dilation of a blood vessel
- Status epilepticus
Rapid and successive attacks of epilepsy
- Stroke
Rupture or a blood vessel in the brain
Symptoms
Symptoms of increased ICP in infants include:
- Bulging fontanelle or soft spot
Infants have soft, membranous gaps between the incompletely
formed bones of the skull called fontanelle or soft spot. Increased
ICP can show up as bulging fontanelle.
- Lethargy
- Vomiting
Symptoms of increased ICP in older children and adults include:
- Vomiting
- Headache
- Blurred vision
- Seizure
- Changes in behavior
- Loss of consciousness
- Lethargy
- Neurological symptoms
Diagnosis
Increased ICP is diagnosed by:
- Computed tomography (CT) scan or magnetic resonance imaging
(MRI)
- Measuring intracranial pressure through a spinal tap or lumbar
puncture, by drilling through the skull to measure pressure
on the surface of the brain, and by inserting a catheter to
measure the pressure inside the brain
Compensatory Mechanism
The skull is rigid and does not allow much expansion of the brain,
so increases in ICP is a critical medical condition that can lead
to brain damage. To compensate for increased ICP, the brain will
reduce the volume of fluid inside the skull cavity by:
- Limiting blood flow to the head
- Moving the cerebrospinal fluid into the spinal canal
- Increasing the absorption of CSF
- Decreasing the production of CSF
With large ICP, however, these compensatory measures can be overwhelmed
and small changes in fluid volumes can lead to large changes in
pressure inside the skull.
Left untreated, ICP can lead to:
- Brain hypoxia
Lack of blood flow to the brain can lead to deficiency in oxygen
reaching the brain tissues.
- Brain herniation
Increased pressure causes displacement of the brain tissue,
CSF, and blood vessels outside its normal space in the head.
This displacement (called herniation) can occur through a natural
opening at the base of the skull or formen occipitalis, or between
compartments inside the skull through the rigid tentorium membrane.
- Brain death
Treatment
Immediate medical attention is necessary to decrease the swelling
and improve drainage of the cerebrospinal fluid to lower the pressure
in the brain. If the condition is due to tumor or hemorrhage,
then the root cause of increased ICP needs to be treated.
Prognosis
Increased ICP is a critical medical condition and can lead to
disability, permanent neurological deficit and even fatality if
not treated immediately.
Reference
