Traumatic Brain Injury

• Epidural hematoma

• Subdural hematoma

• Acute contusion and laceration

Material to read later-Layers of the Meninges

Traumatic Vascular InjuryTraumatic Vascular Injury

• Vascular injury is a frequent component of CNS trauma and results from direct trauma and disruption of the vessel wall, leading to hemorrhage

• Hemorrhage will occur in any of several compartments (sometimes in combination): epidural, subdural, subarachnoid, and intraparenchymal

• Vascular injury is a frequent component of CNS trauma and results from direct trauma and disruption of the vessel wall, leading to hemorrhage

• Hemorrhage will occur in any of several compartments (sometimes in combination): epidural, subdural, subarachnoid, and intraparenchymal

EPIDURAL HEMATOMA

Epidural Hematoma: in which rupture of meningeal artery, usually associated with a skull fracture, leads to accumulation of arterial blood between the dura and the skull. This blood clot can cause fast changes in the pressure inside the brain. Emergency surgery may be needed. The size of the clot will determine if surgery is needed.

Traumatic Vascular InjuryTraumatic Vascular Injury• Epidural Hematoma

•Vessels that course within the dura, most importantly the middle meningeal artery, are vulnerable to injury, particularly with skull fractures

•The expanding hematoma has a smooth inner contour that compresses the brain surface

•Clinically, patients can be lucid for several hours between the moment of trauma and the development of neurologic signs

•EDH is considered to be the most serious complication of head injury, requiring immediate diagnosis and surgical intervention (mortality rate associated with epidural hematoma has been estimated to be 5-50%

• Epidural Hematoma•Vessels that course within the dura, most

importantly the middle meningeal artery, are vulnerable to injury, particularly with skull fractures

•The expanding hematoma has a smooth inner contour that compresses the brain surface

•Clinically, patients can be lucid for several hours between the moment of trauma and the development of neurologic signs

•EDH is considered to be the most serious complication of head injury, requiring immediate diagnosis and surgical intervention (mortality rate associated with epidural hematoma has been estimated to be 5-50%

PathophysiologyUsually results from a brief linear contact

force to the calvaria that causes separation of the periosteal dura from bone and disruption of interposed vessels due to shearing stress

Skull fractures occur in 85-95% of adult cases Extension of the hematoma usually is limited

by suture lines owing to the tight attachment of the dura at these locations.

The temporoparietal region and the middle meningeal artery are involved most commonly (66%)

FrequencyEpidural hematoma complicates 2% of cases of head trauma

(approximately 40,000 cases per year)Alcohol and other forms of intoxication have been associated

with a higher incidence of epidural hematomaSex

more frequent in men, with a male-to-female ratio of 4:1Age

rare in individuals younger than 2 years rare in individuals older than 60 years because the dura is tightly

adherent to the calvaria

HistoryHead traumaLucid interval between the initial loss of

consciousness at the time of impact and a delayed decline in mental status (10-33% of cases)

HeadacheNausea/vomitingSeizuresFocal neurological deficits (eg, visual field cuts,

aphasia, weakness, numbness)

Diagnostic ImagingNoncontrast CT scanning of the head (imaging study

of choice for intracranial EDH) not only visualizes skull fractures, but also directly images an epidural hematoma

• It appears as a hyperdense biconvex or lenticular-shaped mass situated between the brain and the skull, though regions of hypodensity may be seen with serum or fresh blood. Adjacent skull fracture, cerebral edema, midline deviation    

MRI also demonstrates the evolution of an epidural hematoma, though this imaging modality may not be appropriate for patients in unstable condition

Diagnostic ImagingCT of the head obtained without intravenous contrast enhancement shows

a biconvex high-attenuation epidural hematoma adjacent to the right frontal lobe (arrows). The lesion extends superiorly to the level of the body of the lateral ventricle (arrow)

SUBDURAL HEMATOMA In a subdural hematoma

(right), damage to bridging veins between the brain and the superior sagittal sinus leads to the accumulation of blood between the dura and the arachnoid. If this bleeding occurs quickly it is called an acute subdural hematoma. If it occurs slowly over several weeks, it is called a chronic subdural hematoma. The clot may cause increased pressure and may need to be removed surgically.

Subdural HematomaRapidly clotting blood collection below the inner

layer of the dura but external to the brain and arachnoid membrane

Typically, low-pressure venous bleeding of bridging veins (between the cortex and venous sinuses) dissects the arachnoid away from the dura and layers out along the cerebral convexity

It conforms to the shape of the brain and the cranial vault, exhibiting concave inner margins and convex outer margins (crescent shape)

Frequency is related directly to the incidence of blunt head trauma

It’s the most common type of intracranial mass lesion, occurring in about a third of those with severe head injuries

ACUTE AND SUBACUTE SUBDURAL HEMATOMA

ACUTE

Associated with major head injury involving contussion and lacerations

SUBACUTE

Are the result of less severe contussions and head trauma.

CHRONIC SUBDURAL HEMATOMACan develop seemingly

minor head injury.Commonly in elderly.Resembles other

conditions.May be mistaken as

strokes.

Bleeding is less profuse.Compressions of the

intracranial contents.

Mortality/AgeMortality

Simple SDH (no parenchymal injury) is associated with a mortality rate of about 20%

Complicated SDH (parenchymal injury) is associated with a mortality rate of about 50%

AgeIt’s associated with age factors related to the risk of blunt

head traumaMore common in people older than 60 years (bridging

veins are more easily damaged/falls are more common)Bilateral SDHs are more common in infants since adhesions

existing in the subdural space are absent at birthInterhemispheric SDHs are often associate with child abuse

HistoryUsually involves moderately severe to severe blunt head

trauma Subdural hematomas most often become manifest within the

first 48 hours after injuryAcute deceleration injury from a fall or motor vehicle

accident, but rarely associated with skull fractureGenerally loss of consciousnessAny degree or type of coagulopathy should heighten suspicion

of SDHCommonly seen in alcoholics because they’re prone to

thrombocytopenia, prolonged bleeding times, and blunt head trauma

Patients on anticoagulants can develop SDH with minimal trauma and warrant a lowered threshold for obtaining a head CT scan

Diagnostic ImagingMRI is superior for demonstrating the size of an acute SDH

and its effect on the brain, however noncontrast head CT is the primary means of making a diagnosis and suffice for immediate management purposes

Noncontrast head CT scan (imaging study of choice for acute SDH) The SDH appears as a hyperdense (white) crescentic mass along the

inner table of the skull, most commonly over the cerebral convexity in the parietal region. The second most common area is above the tentorium cerebelli

Contrast-enhanced CT or MRI is widely recommended for imaging 48-72 hours after head injury because the lesion becomes isodense in the subacute phase

In the chronic phase, the lesion becomes hypodense and is easy to appreciate on a noncontrast head CT scan

Diagnostic ImagingAxial CT images of the brain show a large isodense right-sided subdural

hematoma (short arrows) extending from the high convexities to the low frontal lobe. It is producing extensive right to left midline shift with subfalcine (arrow)

SummaryEpidural HematomaPotential space between the

dura in the inner table of the skull

Can’t cross suturesSkull fractures in

temporoparietal regionMiddle meningeal arteryLenticular or biconvex shapeLucid intervalCommon in alcoholicsMedical emergencyCT without contrastEvacuate via burr holes

Subdural HematomaBetween the dura mater and

the arachnoid materCan cross suturesCortical bridging veinsCrescent shapeLoss of consciousnessCommon in elderlyCommon in alcoholicsMedical emergencyCT without contrastEvacuate via burr holes

Epidural hematoma (left) in which rupture of meningeal artery, usually associated with a skull fracture, leads to accumulation of arterial blood between the dura and the skull. In a subdural hematoma (right), damage to bridging veins between the brain and the superior sagittal sinus leads to the accumulation of blood between the dura and the arachnoid.

Epidural hematoma (left) in which rupture of meningeal artery, usually associated with a skull fracture, leads to accumulation of arterial blood between the dura and the skull. In a subdural hematoma (right), damage to bridging veins between the brain and the superior sagittal sinus leads to the accumulation of blood between the dura and the arachnoid.

Summary

CONTUSSIONCerebral contusion, latin contusio cerebri, a form of traumatic brain injury,

is a bruise of the brain tissue. Like bruises in other tissues, cerebral contusion can be caused by multiple microhemorrhages, small blood vessel leaks into brain tissue. Head CT scans of unconscious patients reveal that 20% have hemorrhagic contusion.

Damage occurs at (and sometimes opposite) the point of impact—the contact part of the gyri with the skull

Parenchymal Injuries

CONTUSSION

Acute cerebral contusion, there are low-density edema with flake high-density shadow(Asterisk), accompanied with subarachnoid hemorrhage in the suprasellar pool, sylvian cistern and around the right falx cerebri(black arrow). The gas in the suprasellar pool indicates basal skull fractures(black arrowhead).

CEREBRAL LACERATIONSCerebral lacerations, related

to contusions, occur when the piamater or arachnoid membranes are cut or torn.

Acute contusion and laceration of brain•Pathology: regional cerebral edema, necrosis,

liquefying, bleeding foci•Clinical symptoms: headache, nausea, vomiting,

disturbance of consciousness

Parenchymal Injuries: ConcussionParenchymal Injuries: Concussion•Concussion is a clinical syndrome of

alteration of consciousness secondary to head injury typically brought about by a change in the momentum of the head (movement of the head arrested by a rigid surface)

•There is instantaneous onset of transient neurologic dysfunction, including loss of consciousness, temporary respiratory arrest, and loss of reflexes

•Although neurologic recovery is complete, amnesia for the event persists

•Concussion is a clinical syndrome of alteration of consciousness secondary to head injury typically brought about by a change in the momentum of the head (movement of the head arrested by a rigid surface)

•There is instantaneous onset of transient neurologic dysfunction, including loss of consciousness, temporary respiratory arrest, and loss of reflexes

•Although neurologic recovery is complete, amnesia for the event persists

DIFFUSE AXONAL INJURY (DAI) Diffuse axonal injury (DAI) is one of the most common and devastating types of

traumatic brain injury, meaning that damage occurs over a more widespread area than in focal brain injury. DAI, which refers to extensive lesions in white matter tracts, is one of the major causes of unconsciousness and persistent vegetative state after head trauma. It occurs in about half of all cases of severe head trauma and also occurs in moderate and mild brain injury. The outcome is frequently coma, with over 90% of patients with severe DAI never regaining consciousness. Those who do wake up often remain significantly impaired. Mechanism: shearing force during brain injury.

INTRACEREBRAL HEMORRHAGE

Intracerebral Hemorrhage: A blood clot deep in the middle of the brain that is hard to remove. Pressure from this clot may cause damage to the brain. Surgery may be needed to relieve the pressure.

Exam prep-what to know!

• Recognize the clinical neuroimaging examples from this lecture

• Recall the different forms of traumatic brain injury and their radiographic presentation.

• Recognize anatomical regions of the brain on CT/MRI-re-visit normal anatomy of the brain notes at the end of this lecture as you learn from the practical and weekly anatomy lectures.

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