traumatic brain injury
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DESCRIPTIONTraumatic Brain Injury. The effects of trauma to the skull and brain, during closed head injury depend upon a number of factors: (a) the shape of the objects causing the trauma, (b) the force of the impact, (c) whether the head is in motion at the time of impact. - PowerPoint PPT Presentation
Traumatic Brain Injury
The effects of trauma to the skull and brain, during closed head injury depend upon a number of factors: (a) the shape of the objects causing the trauma,(b) the force of the impact,(c) whether the head is in motion at the time of impact.
Traumatic brain injury (TBI)An external mechanical force, possibly leading to permanent or temporary impairments of :cognitive, physical, psychosocial functions with an associated diminished or altered state of consciousness.
Young people Low-income individuals Unmarried individuals Men (2:1 vs. women)Individuals with previous history of substance abuse Individuals with previous TBIHigh Risk Populations
Brain injury results from:
Direct injury to brain tissue
External forces applied to outside of skull transmitted to the brain
Movement of brain inside skullTraumatic Brain Injury (TBI)
Thus the mechanisms of closed head injury are either due to contact phenomena (usually resulting in focal lesions) or acceleration/deceleration phenomena (principally causing diffuse axonal injury (DAI). It is important to realize that severe brain damage can occur in the absence of easily visible external injury and vice versa, and that focal and diffuse lesions may occur in isolation or be combined.
HEAD INJURIES / BRAIN INJURIESCONCUSSIONDIFFUSE AXONAL INJURYEPIDURALSUBDURALSUBARACHNOIDPARENCHYMALCOUP/CONTRE COUPFOCAL/MULTIFOCALINTRAVENTRICULAR
CONTACT PHENOMENA &/OR ACC/DEC INJURYPRIMARY DAMAGEFOCALDIFFUSEFRACTURESCONTUSIONSLACERATIONSHEMORRHAGESDIFFUSE AXONAL INJURY(DIFFUSE BRAIN INJURY)EPIDURALSUBDURALSUBARACHNOIDPARENCHYMALCOUP/CONTRE COUPFOCAL/MULTIFOCALINTRAVENTRICULARHEMATOMAS
ConcussionConcussion is caused by deformity of the deep structures of the brain, leading to widespread neurologic dysfunction that can result in impaired consciousness or coma.Concussion is considered a mild form of diffuse axonal injury.
DIFFUSE AXONAL INJURY (DAI)
Diffuse axonal injuryDiffuse axonal injury is characterized by extensive generalized damage to the white matter of the brain.Strains during high-speed acceleration/deceleration produced in lateral motions of the head may cause the injuries. Diffuse axonal injury also could occur as a result of ischemia.
Diffuse axonal injury, in its mildest form is probably responsible for concussion, but if severe is associated with prolonged unconsciousness from the moment of injury. The mechanism is one of widespread tearing of axons due to shearing forces during acceleration/deceleration of brain. While focal injuries such as contusions, lacerations and intracranial hematomas, are usually readily apparent radiologically, DAI is more subtle.
CONSCIOUSNESS DISTURBANCEIN DIFFUSE BRAIN INJURYMild concussion : LOC - transient Cerebral concussion : LOC 24 hrsSevere DAI : days-weeksLOC:Loss of ConsciousnessDAI: Diffuse axonal injury
PATHOMORPHOLOGY OF DAICorpus callosum & brainstem most commonly affectedSpheroids appear when coma exceeds 6 hrsOnly detectable at LM level after 24 hoursEvanescent - days to weeksINVISIBLE ON CT/MR SCAN
Morphology of DAIAxonal spheroids
A. Dural associated hematomas Epidural HematomaSubdural Hematoma
Epidural HematomaNormally the dura is fused with the periosteum on the internal surface of the skull. Dural arteries, most importantly the middle meningeal artery, are vulnerable to injury, particularly with temporal skull fractures in which the fracture lines cross the course of the vessel. In children, in whom the skull is deformable, a temporary displacement of the skull bones leading to laceration of a vessel can occur in the absence of a skull fracture.
Epidural HematomaThe extravasation of blood under arterial pressure can cause the dura to separate from the inner surface of the skull . The expanding hematoma has a smooth inner contour that compresses the brain surface. When blood accumulates slowly patients may be lucid for several hours before the onset of neurologic signs. An epidural hematoma may expand rapidly and is a neurosurgical emergency requiring prompt drainage.
Epidural HematomaMore often, a tear in the middle meningeal artery causes this type of hematoma. When hematoma occurs from laceration of an artery, blood collection can cause rapid neurologic deterioration.
Two-thirds of epidural hematomas are in the temporo-parietal region and they usually have a biconvex or lentiform configuration. Epidurals are limited by the firmer attachment of the dura at the suture margins, but they may cross the midline.
Subdural hematomaSubdural hematoma tends to occur in patients with injuries to the dural (cortical) veins or pial artery in severe TBI.The associated mortality rate is high, approximately 60-80%.They occur most frequently over the convexities, covering the entire hemisphere and are manifested clinically by fluctuating levels of consciousness.
Subdural hematomas, both acute and chronic, are most often caused by bleeding from torn bridging dural veins. Subdural hematomas are less frequently associated with skull fractures, but more frequently associated with parenchymal brain damage. The subdural space is a more freely communicating space and the hematomas form a crescentic shaped layer over the brain surface.
Instead, they extend along the dura of the falx into the interhemispheric fissure and onto the tentorium, which epidurals cannot do. Both epidural and subdural hemorrhages occur within the confined space of the bony calvarium and compress the adjacent brain, often requiring emergency evacuation.
In alcoholic or elderly patients with cerebral atrophy, SDH's are often bilateral and may occur after insignificant or even unnoticed trauma.
bridging veins are more susceptible to tearing when there is cortical atrophy
Chronic subdural hematomas are usually related to a slower venous bleed without accompanying cerebral parenchymal injury.
These collections are more often biconvex, rather than the crescentic shape of acute subdural hematomas.
Subdural hygromas or effusions consist of collections of CSF in the subdural spaces, presumably due to a traumatic arachnoid tear or they may also develop following ventricular shunting. They may accumulate slowly during the first few days following head trauma, especially in the pediatric population.
Contusions & Lacerations Contusions are focal areas of cortical hemorrhagic necrosis occurring at the crest of a gyrus and are said to be the hallmark of closed head injury; they may occur : at the site of impact (coup lesions), or at a point opposite (contrecoup lesions).
Contusion/laceration of the brain may be accompanied by pure intracerebral hematoma, often multiple, mainly involving temporal and frontal regions. A distinction is made between contusions and lacerations: Contusions (contusio cerebri) : the pia is intact, Lacerations (laceratio cerebri) : the pia-arachnoid and underlying brain tissue are torn.
Coup-Contrecoup ContusionsA combination of vascular and tissue damage leads to cerebral contusion.
Coup contusions occur at the area of direct impact to the skull and occur because of the creation of negative pressure when the skull, distorted at the site of impact, returns to its normal shape.
Contrecoup contusions are similar to coup contusions but are located opposite the site of direct impact.
Most of the energy of impact from a small hard object tends to dissipate at the impact site, leading to a coup contusion.
On the contrary, impact from a larger object causes less injury at the impact site since energy is dissipated at the beginning or end of the head motion, leading to a contrecoup contusion.
Coup contracoup injury
Traumatic intracerebral / intraventricular hemorrhagesProbably they result from tearing of the vessels themselves by mechanical forces.
VASCULAR INJURIESTraumatic carotid cavernous fistulas can result from an injury to the carotid artery at the level of the cavernous sinus. This causes a high flow arterial venous shunt and often results in painful unilateral pulsating exopthalmos as a result of increased flow in a retrograde direction in the superior opthalmic vein (v. ophthalmica superior). This can lead to visual loss.
Traumatic dissections of the carotid or vertebral arteries in the neck can cause stroke. This can be due to strangulation or whiplash mechanisms which may tear the intima. Typically the carotid is dissected usually just proximal to entering the petrous bone at about the C1-C2 level.
Post-traumatic pseudoaneurysms can occur as a result of vascular injuries intracranially. Vascular spasm can occur as a result of subarachnoid hemorrhage.
CEREBROVASCULAR DISEASE (CVD)CVD REFERS TO ANY ABNORMALITY OF THE BRAIN RESULTING FROM A PATHOLOGICAL PROCESS INVOLVING BLOOD VESSELS, CAUSING INADEQUATE OXYGENATION OF BRAIN TISSUE
CLASSIFICATIONHYPOXIC ENCEPHALOPATHYan overall (GLOBAL) reduction in blood flow to the brainSTROKE (focal lesion)sudden onsetrapid evolutionfocal neurologic deficit
STROKEThe typical clinical features include a sudden onset and rapid evolution (minutes/hours) of a focal neurological deficit (indicative of focal damage to the brain).
STROKE: CLASSIFICATIONISCHEMIC STROKEHEMORRHAGIC STROKEorBRAIN INFARCTIONorINTRACEREBRAL BLEEDINGTHE CLINICIAN MUST MAKE THIS DISTINCTION IN ORDER TO TREATCT/MR SCAN A