Section 1: Trauma

Question 1

Types of Skull Fractures

Answer 1

• Linear
  
  • Sharp lucent line
  • Can be extensive and widespread
• Depressed
  
  • Focal
  • Inwardly displaced fragments
  • Often lacerates dura-arachnoid
• Elevated
  
  • Rare
  • Fragmented rotated outward
• Diastatic
  
  • Typically associated with severe trauma
  • Usually caused by linear fracture that extends into suture
  • Widens, spreads apart suture or synchondrosis
• ”Growing”
  
  • Rare
  • Usually in young children
  • Fracture lacerates dura-arachnoid
  • Brain/arachnoid herniates through torn dura
  • Trapped tissue prevents bone healing
  • CT: Rounded edges, scalloped margins of skull
  • MR: CSF ± brain

Question 2

Types of Scalp Lacerations

Answer 2

• Lacerations
  
  • ± Foreign bodies
• Cephalohematoma
  
  • Usually infants
  • Subperiosteal
  • Small, unilateral (limited by sutures)
• Subgaleal hematoma
  
  • Between galea, periosteum of skull
  • Circumferential, not limited by sutures
  • Can be very large, life-threatening

Question 3

Classic Acute Epidural Hematoma

• Terminology
• Etiology
• Pathology
• Clinical
• Imaging

Answer 3

• Terminology
  
  • EDH = blood between skull, dura
• Etiology
  
  • Associated skull fracture in 90-95%
  • Arterial 90%
    
    • Most often middle meningeal artery
  • Venous 10%
• Pathology
  
  • Unilateral, supratentorial (> 90%)
  • Dura stripped away from skull → biconvex hematoma
  • Usually does not cross sutures (exception = children, 10%)
  • Does cross sites of dural attachment
• Clinical
  
  • Rare (1-4% of head trauma)
  • Older children, and young adults most common
  • M:F = 4:1
  • Classic “lucid interval” in only 50%
  • Delayed deterioration common
  • Low mortality if recognized, treated
  • Small EDHs
    
    • If minimal mass, no “swirl sign” is often managed conservatively
• Imaging
  
  • Hyperdense lens-shaped
  • “Swirl sign” (hypodensity) = rapid bleeding

Question 4

Venous Epidural Hematomas

Tell me a little about them?

Subtypes?

Answer 4

• Not all EDHs are the same!
  
  • Different etiologies in different anatomic locations
  • Prognosis and treatment vary.
• Venous EDHs = 10% of all EDHs
  
  • Skull fracture crosses dural venous sinus
    
    • Can cross sutures, dural attachments
• Often subtle, easily overlooked
  
  • Coronal, sagittal reformatted images key to diagnosis
• Subtypes
  
  • Vertex EDH
  • Anterior temporal EDH
  • Clival EDH

Question 5

Vertex EDH

Answer 5

• Venous epidural hematoma subtype
• Skull fracture crosses superior sagittal sinus (SSS)
• SSS can be lacerated, compressed, thrombosed
• Hematoma under low pressure develops gradually
• Slow onset of symptoms
• May become large, cause significant mass effect

Question 6

Anterior Temporal EDH

Answer 6

• Venous epidural hematoma subtype
• Sphenoid wing or zygomaticomaxillary fracture
• Injures sphenoparietal venous sinus
• Hematoma accumulates at anterior tip of middle cranial fossa
• Limited anatomically (laterally by sphenotemporal suture, medially by orbital fissure)
• Benign clinical course

Question 7

Clival EDH

Answer 7

• Venous epidural hematoma subtype
• Most common = child with neck injury
• May cause multiple cranial neuropathies (CN VI most common)
• Hyperdense collection under clival dura
• Limited by tight attachment of dura to basisphenoid, tectorial membrane
• Usually benign course, resolves spontaneously

Question 8

Acute SDH (aSDH)

Answer 8

• Second most common traumatic extraaxial hemorrhage
  
  • Acute SDH > > epidural hematoma
• Crescentic collection of blood between dura, arachnoid
  
  • Supratentorial (95%), bilateral (15%)
  • SDHs cross sutures
  • SDHs do not cross dural attachments
• CT
  
  • Hyperdense (60%) 
  • Mixed (40%)
  • Isodense acute SDH rare (anemia, coagulopathy, CSF mixture)

Question 9

Subacute SDH (sSDH)

Answer 9

• Clot organizes, lysis, forms “neomembranes”
• CT
  
  • Density decreases 1-2 HU/day
  • Isodense with cortex in 7-10 days
  • Look for displaced “dots” of CSF under SDH
  • Gray-white interface “buckled” inward
  • Displaced cortical veins seen on CECT
• MR
  
  • Signal varies with clot age
  • T2* (GRE, SWI) shows “blooming” 
  • T1 C+ shows clot inside enhancing membranes

Question 10

Chronic/Mixed SDH (s/mSDH)

Answer 10

• Serosanguineous fluid
  
  • Hypodense on NECT
  • Rehemorrhage (5-10%)
  • Loculated blood “pockets” with fluid-fluid levels common
• Differential diagnosis of uncomplicated cSDH
  
  • Subdural hygroma (arachnoid tear → subdural CSF)
  • Subdural effusion (clear fluid accumulates after meningitis)
  • Subdural empyema (pus)

Question 11

Traumatic Subarachnoid Hemorrhage (tSAH)

Answer 11

• Most common traumatic extraaxial hemorrhage
• tSAH >> aneurysmal SAH
• Adjacent to cortic contusions
• Superficial sulci > basal cisters

Question 12

Cerebral Contusions

Answer 12

• Most common intraaxial injury
  
  • Brain impacts skull and/or dura
  • Causes “brain bruises” in gyral crests
  • Usually multiple, often bilateral
  • Anteroinferior frontal, temporal lobes most common sites
• Imaging
  
  • Superficial petechial, focal hemorrhage
  • Edema, hemorrhage more apparent with time
  • T2* (GRE, SWI) most sensitive imaging

Question 13

Diffuse Axonal Injury (DAI)

Answer 13

• Second most common intraaxial injury
  
  • Spares cortex, involves subcortical/deep WM
• Imaging
  
  • GCS low; initial imaging often minimally abnormal
  • Subcortical, deep petechial hemorrhages (“tip of the iceberg”)
  • T2* (GRE, SWI) most sensitive technique

Question 14

Diffuse Vascular Injury

Answer 14

• Rare, usually fatal
• High-speed, high-impact MVCs
• May represent extreme end of DAI spectrum
• Imaging
  
  • CT shows diffuse brain swelling
  • T2 and FLAIR show a few scattered hyperintensities
  • SWI shows innumerable linear hypointensities

Question 15

Subcortical Injury

Answer 15

• Basically really bad shear-strain injuries
• “The deeper the injury, the worse it is”
• Basal ganglia, thalami, midbrain, pons
  
  • Hemorrhages, axonal injury, brain tears
  • Gross intraventricular hemorrhage common

Question 16

Subfalcine Herniation

• Etiology and Pathology
• Epidemiology
• Imaging
• Complications

Answer 16

• Etiology and Pathology
  
  • U/L hemispheric mass effect
  • Brain shifts across midline under falx cerebri
• Epidemiology
  
  • Most common brain herniation
• Imaging
  
  • Cingulate gyrus, ACA, internal cerebral veins displaced accross midline
  • Foramen of monroe kinked/obstructed
  • I/L small ventricle, C/L enlarged
• Complications
  
  • Obstructive hydrocephalus
  • 2/2 ACA infarction (severe cases)

Question 17

Descending Transtentorial Herniation

• Terminology and Pathology
• Epidemiology
• Imaging
• Complications

 

Answer 17

• Terminology and Pathology
  
  • Unilateral DTH
    
    • Temporal lobe (uncus, hippocampus) pushed over tentorial incisura
  • Severe bilateral DTH = “complete” or “central” herniation
    
    • Hypothalamus, chiasm flattened against sella
• Epidemiology
  
  • 2nd MC cerebral herniation
• Imaging
  
  • Unilateral DTH
    
    • Suprasellar cistern encroached, then obliterated
    • Herniating temporal lobe pushes midbrain to the opposite side
  • Bilateral DTH
    
    • Basal cisterns completely effaced
    • Midbrain pushed down, compressed on both sides
• Complications
  
  • CNIII compression = pupil-involving 3rd nerve palsy
  • 2/2 occipital PCA +/- hypothalamus, basal infarcts
  • Compression of C/L cerebral peduncle (“Kernohan’s Notch”)
    
    • Midbrain “Durret” hemorrhage

Question 18

TONSILLAR HERNIATION

• Etiology and Pathology
• Imaging Findings
• Complications

Answer 18

• Etiology and Pathology
  
  • Most common posterior fossa herniation
  • Can be congenital (Chiari I) or acquired.
  • Acquired
    
    • Most common = secondary to posterior fossa mass effect
    • Less common = intracranial hypotension
    • Rare = severe central DTH, brain death
• Imaging Findings
  
  • 1 or both tonsils > 5 mm below the foramen magnum
  • CSF in foramen magnum effaced
  • Foramen magnum appears tissue-filled on axial NECT, T2WI
  • Inferior “pointing” or peg-like configuration of cerebellar tonsils on sagg
• Complications
  
  • Obstructive hydrocephalus
  • Tonsilar necrosis

Question 19

ASCENDING TRANSTENTORIAL HERNIATION

• Epidemiology
• Imaging Findings
• Complications

Answer 19

• Relatively Rare
  
  • Caused by expanding posterior fossa mass
  • Neoplasm > Trauma
  • Cerebellum pushed upward through the incisura
  • Compresses deforms midbrain
• Imaging Findings
  
  • Incusura filled with tissue, CSF spaces obliterated
  • Quadrigeminal cistern, tectal plate compressed/flattened
    
    • Eventually appear obliterated
• Complications
  
  • Hydrocephalus (2/2 to aqueductal stenosis)

Question 20

What other less common herniation patterns?

Answer 20

Ascending transalar herniation

Descending transalar herniation

Transcranial/transdural herniation

Question 21

Ascending Transalar Herniation

Answer 21

• Most common transalar herniation
• Caused my middle cranial fossa mass
• Sagittal imaging (best appreciated on off-midline images)
  
  • Sylvian fissure, MCA displaced up/over greater sphenoid ala
• Axial imaging
  
  • Sylvian fissue/MCA bowed forward
  • Temporal lobe bulges into anterior fossa

Question 22

Descending Transalar Herniation

Answer 22

• Caused by anterior fossa mass
• Sagittal imaging
  
  • Sylvian fissure, MCA displaced posteroinferiorly
  • Frontal lobe pushed backward over greater sphenoid ala 
• Axial imaging
  
  • Gyrus rectus pushed posteriorly
  • MCA curved backward

Question 23

Transcranial/Transdural Herniation

Answer 23

• Increased ICP + Skull defect + arachnoid tear
• Caused by:
  
  • Comminuted, often depressed skull fracture
  • Craniectomy
• Brain extruded through skull, under scalp aponeurosis
• Best appreciated on axial T2WI