The brain and spinal cord are surrounded by cerebrospinal fluid, or CSF, and are enclosed within bony skull and the spinal canal. CSF is made by specialized cells in the lateral and fourth ventricles, or brain chambers, which communicate with the spinal canal. Intracranial hypertension, or ICH, is an elevated CSF pressure within the skull, commonly measured by a catheter placed in one of the lateral ventricles. Intracranial pressure above or equal to 20 mmHg denotes ICH, which is caused by either brain swelling or increased CSF volume as a result of trauma, blood vessel disorders, tumors and infection.
Trauma
Brain swelling or bleeding may result in intracranial hypertension from a fractured skull, or brain-skull collision, as seen in shaken baby syndrome. The Centers for Disease Control and Prevention reports that falls are the leading cause of traumatic brain injury, followed by motor vehicle accidents.
Blood Vessel Anomalies
Arteriovenous malformation is an abnormal clumping of blood vessels with direct artery-to-vein connection. Such blood vessels can easily rupture, causing intracranial bleeding with a 13 percent death rate, according to Stroke. Intracranial aneurysm is focal ballooning of an artery as a result of smoking, high blood pressure, cholesterol deposits, head trauma or vessel anomaly present at birth. Upon rupture, and depending on its location, an intracranial aneurysm has a 12 to 45 percent risk of sudden death, reports Neurosurgery. Cerebral cavernous angioma is a collection of abnormal, enlarged capillaries, which are the smallest blood vessels, with very low risk of rupture. However, an enlarged collection of such blood vessels can obstruct the normal flow of CSF, causing hydrocephalus, or increased CSF volume in the ventricles.
Vasculitis
Vascultis is an inflammation of blood vessels during a normal body response to harmful substances, such as pathogens and illicit drugs, or in autoimmune disorders, in which the body's immune system works against itself. Inflamed blood vessels leak blood, causing brain edema and decreased oxygen supply, resulting in tissue death.
Intracranial Tumors
Intracranial tumors cause ICH by edema or obstruction of CSF flow by bleeding, compression or displacement of brain tissue. According to Neurosurgical Focus, bleeding can occur in up to 10 percent of all brain tumors. Examples include glioblastomas, tumors arising from glial cells rather than neurons and metastatic cancers, such as testicular and melanoma, a type of skin cancer.
Central Nervous System Infections
Most pathogens, such as bacteria and fungi, are too large to cross the tight blood-brain barrier and cause infection. Exceptions include: spirochetes, which cause syphilis and tick-borne Lyme disease; most viruses, such as herpes; prions, protein-based pathogens; and protozoa, which cause malaria. Infection can take the form of a brain abscess, encephalitis, or whole brain infection, and meningitis, an infection of membranes encasing the brain.
Other Causes
Chronic high blood pressure is the most common cause of spontaneous intracranial bleeding. Pseudotumor cerebri is a condition that mimics symptoms of a brain tumor and is commonly seen in obese women of childbearing age. Cerebral amyloid angiopathy is amyloid protein deposition in arteries, which results in bleeding, and most commonly affects the elderly.
References
- Centers for Disease Control & Prevention: Traumatic Brain Injury
- "Stroke"; A Population-Based Study of Brain Arteriovenous Malformation: Long-Term Treatment Outcomes; H.T. ApSimon et al.; Nov 2002
- "Neurosurgery"; The Probability of Sudden Death From Rupture of Intracranial Aneurysms: A Meta-analysis; J. Huang and J.M. van Gelder; 2002
- "Neurosurgical Focus"; Spontaneous Intracerebral Hemorrhage: A Review; M.E. Fewel et al.; October 2003
- "A Guide to the Primary Care of Neurological Disorders"; John Popp, M.D., and Eric Deshaies, M.D.; 2008
