Focal and diffuse brain injury

Focal and diffuse brain injury
Classification and external resources
Epidural hematoma, an example of a focal injury
ICD-10	S06.2, S06.3
MeSH	D001930

Focal and diffuse brain injury are ways to classify brain injury: focal injury occurs in a specific location, while diffuse injury occurs over a more widespread area. It is common for both focal and diffuse damage to occur as the result of the same event; many traumatic brain injuries have aspects of both focal and diffuse injury.^[1] Focal injuries are commonly associated with an injury in which the head strikes or is struck by an object; diffuse injuries are more often found in acceleration/deceleration injuries, in which the head does not necessarily contact anything, but brain tissue is damaged because tissue types with varying densities accelerate at different rates.^[2] In addition to physical trauma, other types of brain injury, such as stroke, can also produce focal and diffuse injuries.^[1] There may be primary and secondary brain injury processes.

Focal

A focal traumatic injury results from direct mechanical forces (such as occur when the head strikes a windshield in a vehicle accident) and is usually associated with brain tissue damage visible to the naked eye.^[3] A common cause of focal injury is penetrating head injury, in which the skull is perforated, as frequently occurs in auto accidents, blows, and gunshot wounds.^[3] Focal injuries typically have symptoms that are related to the damaged area of the brain.^[3] Stroke can produce focal damage that is associated with signs and symptoms that correspond to the part of the brain that was damaged.^[1] For example, if a speech center of the brain such as Broca's area is damaged, problems with speech are common.

Focal injuries include the following:

• Cerebral contusion is a bruise of brain tissue that commonly results from contact of the brain with the inside of the skull.^[4]
• Cerebral laceration is a brain injury in which the pia-arachnoid is torn.^[4]
• Epidural hemorrhage is bleeding between the dura mater and the skull.^[4] It is commonly associated with damage to the middle meningeal artery, often resulting from a skull fracture.
• Subdural hemorrhage is bleeding between the dura mater and the arachnoid.^[4]
• Intracerebral hemorrhage is bleeding within the brain tissue itself.^[4]
• Intraventricular hemorrhage is bleeding within the ventricles of the brain.^[4]

Diffuse

Diffuse injuries, also called multifocal injuries, include brain injury due to hypoxia, meningitis, and damage to blood vessels.^[2] Unlike focal injuries, which are usually easy to detect using imaging, diffuse injuries may be difficult to detect and define; often, much of the damage is microscopic.^[4] Diffuse injuries can result from acceleration/deceleration injuries.^[2] Rotational forces are a common cause of diffuse injuries;^[5] these forces are common in diffuse injuries such as concussion and diffuse axonal injury. The term "diffuse" has been called a misnomer, since injury is often actually multifocal, with multiple locations of injury.^[2]

Diffuse injuries include the following:

• Diffuse axonal injury is widespread damage to the white matter of the brain that usually results from acceleration/deceleration types of injury.^[4]
• Ischemic brain injury resulting from an insufficient blood supply to the brain, is one of the leading causes of secondary brain damage after head trauma.^[4]
• Vascular injury usually causes death shortly after an injury.^[4] Although it is diffuse type of brain injury itself, diffuse vascular injury is generally more likely to be caused by focal than diffuse injury.^[4]
• Swelling, commonly seen after TBI, can lead to dangerous increases in intracranial pressure.^[4] Though swelling itself is a diffuse type of injury, it can result from either focal or diffuse injury.^[4]

See also

• Focal neurologic deficit

References

1. ^ ^{a b c} Lovell MK, Franzen MD (1994). "Neuropsychological assessment". In Silver JM, Yudofsky SC, Hales RE. Neuropsychiatry of Traumatic Brain Injury. Washington, DC: American Psychiatric Press. pp. 152–3. ISBN 0-88048-538-8. http://books.google.com/books?id=wugk-4Io1XAC&printsec=frontcover&dq=Neuropsychiatry+of+Traumatic+Brain+Injury&client=firefox-a&sig=ACfU3U3BufR_kC8UZWZYw_-hEUfRgZPGLA#PPA152,M1. Retrieved 2008-06-17. "Although brain injuries are often described as diffuse or focal in nature, in reality many traumatic brain injuries have both focal and diffuse components." 
2. ^ ^{a b c d} Gennarelli GA, Graham DI (2005). "Neuropathology". In Silver JM, McAllister TW, Yudofsky SC. Textbook Of Traumatic Brain Injury. Washington, DC: American Psychiatric Association. pp. 27–34. ISBN 1-58562-105-6. http://books.google.com/books?id=3CuM6MviwMAC&pg=PA47&dq=neurotrauma&lr=&client=firefox-a&sig=7kXGu4v_cHPiZRFPwo2j7uIT-og#PPA27,M1. Retrieved 2008-06-10. 
3. ^ ^{a b c} LaPlaca MC, Simon CM, Prado GR, Cullen DR. "CNS injury biomechanics and experimental models". In Weber JT. Neurotrauma: New Insights Into Pathology and Treatment. pp. 16. ISBN 0444530177. http://books.google.com/books?id=FyzEQPKUuPcC&pg=PP1&dq=neurotrauma&client=firefox-a&sig=rMCcbEcUwojhorMEC3D9Bd4eqUo#PPA14,M1. Retrieved 2008-06-10. 
4. ^ ^{a b c d e f g h i j k l m} Granacher RP (2007). Traumatic Brain Injury: Methods for Clinical & Forensic Neuropsychiatric Assessment, Second Edition. Boca Raton: CRC. pp. 26–33. ISBN 0-8493-8138-X. http://books.google.com/books?id=xt1YFydzXKQC&pg=PA32&lpg=PA32&dq=focal+diffuse+brain+injury+&source=web&ots=w7wP6GHZlC&sig=QTuqyJSaHrbwZvlVFClvDtEpEQk&hl=en&sa=X&oi=book_result&resnum=9&ct=result#PPA26,M1. Retrieved 2008-07-06. 
5. ^ Hammeke TA, Gennarelli TA (2003). "Traumatic brain injury". In Schiffer RB, Rao SM, Fogel BS. Neuropsychiatry. Hagerstown, MD: Lippincott Williams & Wilkins. pp. 1150. ISBN 0-7817-2655-7. http://books.google.com/books?id=I2N9COt-4C0C&pg=PA1150&dq=%22focal+brain+injury%22&client=firefox-a&sig=GQeYrowTYcfxgUqLxnnYjEbs9YE. Retrieved 2008-06-16.