Chapter 2: Primary Effects of CNS trauma (Paranchymal and Miscellaneous Injuries)

Question 1

Cortical contusions and lacerations, diffuse axonal injury (DAI), subcortical injuries, and intraventricular hemorrhages are what kind of injuries?

Answer 1

Intraaxial traumatic injuries

Question 2

Most common of the intraaxial injuries.

Answer 2

Cerebral contusions

Question 3

Basically “brain bruises”

Answer 3

Cerebral contusions

Question 4

Most commonly affected areas in cebral contusions?

Answer 4

Temporal tips, as well as the lateral and inferior surfaces and the perisylvian gyri, are most commonly affected.

The inferior (orbital) surfaces of the frontal lobes are also frequently affected.

Question 5

Contusions that occur at 180 degree opposite the site of direct impact (the “coup”) are common.

They are called what?

Answer 5

“contre-coup” lesions.

Question 6

Most frequent CT scan abnormality in cerebral contusions.

Answer 6

Presence of petechial hemorrhages along gyral crests immediately adjacent to the calvaria.

A mixture of petechial hemorrhages surrounded by patchy ill-defined hypodense areas of edema is common.

Question 7

Lesions “blooming” over time is frequent and is seen with progressive increase in hemorrhage, edema, and mass effect.

Small lesions may coalesce, forming larger focal hematomas. Devolopment of new lesions that were not present on initial imaging is also common.

This is seen on what parenchymal injury?

Answer 7

Cerebral contusions

Question 8

What is more sensitive in detecting cerebral contusion?

A. CT scan
B. MRI

Answer 8

MR is much more sensitive than CT in detecting cerebral contusions but is rarely obtained in the acute stage of traumatic brain injury.

Question 9

T1 and T2 findings of cerebral contusion.

Answer 9

T1 scans may show only mild inhomogeneous isointensities and mass effect.

T2 scans show patchy hyperintense areas (edema) surrounding hypointense foci of hemorrhage.

Question 10

Most sensitive MR sequence for detecting cortical edema associated tSAH?

Answer 10

FLAIR

Both of which appear as hyperintense foci on FLAIR.

Question 11

Most sensitive sequence for imaging parenchymal hemorrhages?

Answer 11

T2* (GRE, SWI)

Significant “blooming” is typical in acute lesions.

Question 12

Atrophy, demyelination, and microglial scarring are seen on what sequences?

Answer 12

FLAIR and T2WI

Parenchymal volume loss with ventricular enlargement and sulcal prominence is common.

Question 13

DWI in patients with cortical contusion shows what?

Answer 13

Diffusion restriction in areas of cell death.

Question 14

Regarding cerebral contusion. What is the role of DTI?

Answer 14

DTI may discolse coexisting white matter damage in minor head trauma even when standard MR sequences are normal.

Question 15

What is the major differential diagnosis of cortical contusion?

Answer 15

Diffuse axonal injury.

Both cerebral contusions and DAI are often present in patients who have sustained moderate to severe head injury.

Question 16

Difference of cerebral contusion and diffuse axonal injury.

Answer 16

Contusions tend to be superficial, located along gyral crests.

DAI is most commonly found in the corona radiata and along compact white matter tracts such as the internal capsule and corpus callosum.

Question 17

This occurs when severe trauma disrupts the pia and literally tears the underlying brain apart.

Answer 17

Brain laceration

Severe cortical contusion with confluent hematomas may be difficult to distinguish from brain laceration on imaging.

Question 18

This is the most severe manifestation of frank brain laceration.

Answer 18

“Burst lobe”

Here the affected lobe is grossly disrupted, with large hematoma formation and adjacent tSAH.

Question 19

The second most common parenchymal lesion seen in traumatic brain injury.

Answer 19

Diffuse axonal injury

Question 20

Also known as traumatic axonal stretch injury

Answer 20

Diffuse axonal injury

Question 21

True or false.

Direct head impact is required to produce diffuse axonal injury.

Answer 21

False.

Direct head impact is NOT required to produce DAI.

Most DAIs are not associated with skull fracture.

Question 22

Most of diffuse axonal injuries are cause by what?

Answer 22

Cause by high-velocity motor vehicle collisions (MVCs) and are dynamic, deformative, nonimpact injuries resulting from the inertial forces of rotation generated by sudden changes in acceleration/deceleration.

This results in AXONAL STRETCHING, especially where brain tissues are different density intersect, i.e., the gray-white matter interface.

Question 23

Pathophysiologic change of diffuse axonal injury (specific).

Answer 23

Rapid deformation of white matter at the instant of trauma can lead to mechanical failure.

A cascade of adverse events occurs, including calcium-dependent proteolysis of the axonal cystoskelton in association with axonal transport interruption.

Traumatic axonal stretching also causes depolarization , ion fluxes, and spreading depression.

Amyloid precursor protein, excitatory amino acies, and proteolytic fragments of neurofilaments may be released.

Cellular swelling and cytotoxic edema ensues, altering brain anistrophy.

Significant and widespread alterations in brain perfusion may also occur as a result of TBI.

Question 24

Most commonly affected areas of diffuse axonal injuries.

Answer 24

The cortex is typically spared;

It is the SUBCORTICAL AND DEEP WHITE MATTER that is MOST COMMONLY AFFECTED.

Lesions in compact white matter tracts such as the corpus callosum, especially the genu and splenium, fornix, and internal capsule, are frequent.

The midbrain and pons are less common sites.

Question 25

True or False.

The vast majority of diffuse axonal injuries are microscopic and nonhemorrhagic.

Answer 25

True.

Tears penetrating vessels (diffuse vascular injury) may cause small round to ovoid linear hemorrhages that sometimes are the only gross indications of underlying axonal injury.

These visible lesions are truely just the “tip of the iceberg.”

Question 26

Which causes more significant neurological impairment:

Diffuse axonal injury, extracerebral hematomas, or cortical contusions?

Answer 26

Diffuse axonal injury.

It often causes immediated loss of consciousness which may be transient (mild) or progress to coma (moderate to severe injury).

Question 27

The most serious issue in managing DAI?

Answer 27

Intracranial pressure.

In some cases with impending herniation, craniectomy may be a last resort.

Question 28

Initial CT findings in diffuse axonal injury.

Answer 28

Often normal or minimally abnormal (?).

Question 29

Other CT findings of diffuse axonal injury.

Answer 29

Gross hemorrhages are uncommon immediately following injury.

A few small round or ovoid subcortical hemorrhages may be visible, but the underlying damage is typically much more diffuse and much more severe than these relatively modest abnormalities would indicate.

Question 30

MR findings of DAI

Answer 30

As most DAIs are nonhemorrhage, T1 scans are often normal, especially in the early stages of TBI.

T2WI and FLAIR may show hyperintense foci in the subcortical white matter and corpus callosum.

Multiple lesions are the rule, and a combination of DAI and contusions or hematomas are very common.

T2* scans are very sensitive to the microbleeds of DAI and typically show multifocal ovoid and linear hypointensities.

SWI sequences typically demonstrate more lesions than GRE. Residual from DAI may persist for years following traumatic episodes.

DWI may show restricted diffusion, particularly within the corpus callosum.

Question 31

This injury probably represents the extreme end of the diffuse axonal injury continuum.

Answer 31

Diffuse vascular injury (DVI).

Question 32

Etiology:

Diffuse vascular injury is caused by what?

Answer 32

Similar to DAI.

Caused by the extreme acceleration/rotational forces that are incurred in high-velocity motor vehicle collision.

The brain microvasculature, particularly long penetrating subcortical and deep perforating vessels, is disrupted by high tensile forces.

The result is numerous small punctate and linear parenchymal hemorrhages.

Question 33

True or False.

Many patients with DVI do not survive long enough for imaging.

Answer 33

True.

Question 34

CT findings of diffuse vascular injury.

Answer 34

NECT scans may show only diffuse brain swelling with effaced superficial sulci and small ventricles.

A few small foci of hemorrhage in the white matter and basal ganglia can sometimes be identified.

Bone CT shows multuple skull fractures in unrestrained passengers, but fractures are absent in one-third of individual wearing seat belts.

Question 35

MR Findings of DVI

Answer 35

T1W1 shows only mild brain swelling. T2WI and FLAIR scans may demonstrate a few foci of hyperintensity in the white matter. Occasionally, scattered hypointensities can be identified iwthin the hyperintesities, suggesting the presence of hemorrhage.

T2* scans, especially susceptibility-weighted sequences, are striking.

Punctate and linear “blooming” hypointensities are seen oriented perpendicularly to the ventricles, predominantly in the subcortical and deep white matter, especially the corpus callosum.

Additional lesions in the basal ganglia, thalami, brainstem, and cerebellum are often present.

DWI may demonstrate a few foci of restricted diffusion consistent with ischemia caused by the vascular injuries.

Question 36

What distinguishes diffuse vascular injury from diffuse axonal injury?

Answer 36

It is the number, severity, and extent of the hemorrhages that distinguishes DVI from DAI.

Question 37

This injuries are traumatic lesions of deep brain structures such as the brainstem, basal ganglia, thalami, and ventricles.

Answer 37

Subcortical (Deep Brain) injury

Most represent severe shear-strain injuries that disrupts axons, tear penetrating blood vessels, and damage that choroid plexus of the lateral ventricles.

Question 38

Differential diagnosis for sucbortical injury.

Answer 38

Secondary midbrain (“Duret”) hemorrhage - may occur with severe descending transtentorial herniation.

These hemorrhages are typically centrally located within the midbrain, whereas contusional SCI are dorsolateral.

Question 39

This means the presence of gas or air within the intracranial cavity.

Answer 39

Pneumocephalus.

Intracranial air does not exist under normal conditions.

Question 40

This is a collection of intracranial air that is under pressure that causes mass effect on the brain and results in neurologic deterioration.

Answer 40

Tension pneumocephalus.

Intracerebral pneumatocele or “aerocele” is a less commonly used term and refers specifically to a focal gas collection within the brain parenchyma.

Question 41

Most common cause of pneumocephalus

Answer 41

Trauma/Surgery (page 49)

Question 42

Most frequent/common site of intracranial air.

Answer 42

Subdural space, frontal.

Question 43

In pneumocephalus:

What intracranial compartment in which air is typically unilateral, solitary, and biconvex in configuration and does not move with changes in head position?

Answer 43

Epidural air

Question 44

What intracranial compartment in which air is confluent, cresentic, and often bilateral, frequently contains air-fluid levels, moves with changes in head position?

Answer 44

Subdural air

It surrounds cortical veins that cross the subdural space.

Question 45

Intracranial compartment in which air is typically seen as multifocal small “dots” or “droplets” of air within and around cerebral sulci.

Answer 45

Subarachnoid air

Question 46

Another term for intraparenchymal air collection.

Answer 46

Pneumatocele

Question 47

Intracranial compartment in which air form air-fluid levels.

Answer 47

Intraventricular air

Most often in the frontal horns of the lateral ventricles.

Question 48

What are other causes of pneumocephalus besides surgery/trauma?

Answer 48

Spontaneous pneumocephalus

• can occur with primary defects in the temporal bone (“otogenic pneumocephalus”).
• Rare, defects in or rupture of an enlarged paranasal sinus air cell (“pneumosinus dilatans”) resultas in intracranial air.

Question 49

Most common clinical presentation of pneumocephalus?

Answer 49

Nonspecific headache.

Question 50

This is a sign of tension pneumocephalus seen as a bilateral subdural air collections that seperate and compress the frontal lobes, widening the interhemispheric fissure.

Answer 50

“Mount Fuji” sign