IMAGING OF HEAD TRAUMA

Dr. Thanh Binh Nguyen

University of Ottawa, Canada

July 2009

OUTLINE

Clinical indications for imaging Imaging technique Extraaxial hemorrhage Intraaxial injury Brain herniations Skull fractures

INTRODUCTION

Head trauma is the leading cause of death in people under the age of 30.

Males have 2-3 x frequency of brain injury than females

Due mainly to motor vehicle accidents and assaults

Classification of TBI

Primary Injury to scalp, skull fracture Surface contusion/laceration Intracranial hematoma Diffuse axonal injury, diffuse vascular injury

Secondary Hypoxia-ischemia, swelling/edema, raised

intracranial pressure Meningitis/abscess

IMAGING TECHNIQUE

The presence of a skull fracture increases the risk of having a posttraumatic intracranial lesion.

However, the absence of a skull fracture does not exclude a brain injury, which is particularly true in pediatric patients due to the capacity of the skull to bend.

NO ROLE FOR PLAIN FILMS IN ACUTE HEAD TRAUMA

IMAGING TECHNIQUE

CT without contrast is the modality of choice in acute trauma (fast, available, sensitive to acute subarachnoid hemorrhage and skull fractures)

MRI is useful in non-acute head trauma (higher sensitivity than CT for cortical contusions, diffuse axonal injury, posterior fossa abnormalities)

OUR CT PROTOCOLS

“ROUTINE”: posterior fossa and supratentorial region (slice thickness = 5mm)

“TRAUMA”: posterior fossa (2.5mm), supratentorial region (5mm)

“TEMPORAL BONE”: <1mm in axial or coronal plane

“ORBITS/FACIAL BONES”: 1.25 mm axial/coronal orbits

APPROACH TO CT BRAIN

Look at the scout film: ? Fracture of upper cervical spine or skull

Look for brain asymmetry Look at sulci, Sylvian fissure and cisterns to

exclude subarachnoid hemorrhage Change windows to look for subdural collection Look at bone windows to see fractures Determine if mass is intraaxial (in the brain) or

extraaxial (outside)

SCALP INJURY

SCALP INJURY

Cephalohematoma: blood between the bone and periosteum. Cannot cross the suture lines.

Subgaleal hematoma: blood between the periosteum and aponeurosis. Can cross the suture lines.

Caput Succ: swelling across the midline with scalp moulding. Resolves spontaneously.

Extraaxial fluid collections

Subarachnoid hemorrhage(SAH) Subdural hematoma(SDH) Epidural hematoma Subdural hygroma Intraventricular hemorrhage

Subarachnoid hemorrage

Can originate from direct vessel injury, contused cortex or intraventricular hemorrhage.

Look in the interpeduncular cistern and Sylvian fissure

Usually focal (but diffuse from aneurysm)

Can lead to communicating hydrocephalus

SUBDURAL HEMATOMA

Occurs between the dura and arachnoid Can cross the sutures but not the dural

reflections Due to disruption of the bridging cortical

veins Hypodense(hyperacute, chronic),

isodense(subacute), hyperdense(acute)

W=33 L=41

MANAGEMENT OF aSDH

Acute SDH with thickness > 10 mm or midline shift > 5mm should be evacuated

Patient in coma with a decrease in GCS by >2 points with a SDH should undergo surgical evacuation.

EPIDURAL HEMATOMA

Located between the skull and periosteum

Due to laceration of the middle meningeal artery or dural veins

Can cross dural reflections but is limited by suture lines

Lentiform shape (but concave shape in SDH)

MANAGEMENT OF aEDH

EDH > 30 cm3 should be evacuated.

EDH < 30 cm3 and <15 mm thickness and < 5 mm midline shift and GCS >8 may be managed nonoperatively with serial CT

Intraventricular hemorrhage

Most commonly due to rupture of subependymal vessels

Can occur from reflux of SAH or contiguous extension of an intracerebral hemorrhage

Look for blood-cerebrospinal fluid level in occipital horns

INTRA-AXIAL INJURY

Surface contusion/laceration Intraparenchymal hematoma White matter shearing injury/diffuse

axonal injury Post-traumatic infarction Brainstem injury

CONTUSION/LACERATIONS

Most common source of traumatic SAH Contusion: must involve the superficial gray

matter Laceration: contusion + tear of pia-arachnoid Affects the crests of gyri Hemorrhage present ½ cases and occur at

right angles to the cortical surface Located near the irregular bony contours:

poles of frontal lobes, temporal lobes, inferior cerebellar hemispheres

From http://neuropathology.neoucom.edu/Dr.Agamanolis

Intraparenchymal hematoma

Focal collections of blood that most commonly arise from shear-strain injury to intraparenchymal vessels.

Usually located in the frontotemporal white matter or basal ganglia

Hematoma within normal brain DDx: DAI, hemorrhagic contusion

DIFFUSE AXONAL INJURY

Rarely detected on CT ( 20% of DAI lesions are hemorrhagic)

MRI: T1, T2, T2 GRE, SWI

DAI

Due to acceleration/deceleration to whtie matter + hypoxia

Patients have severe LOC at impact Grade 1: axonal damage in WM only -

67% Grade 2: WM + corpus callosum

(posterior > anterior) – 21% Grade 3: WM + CC + brainstem

DAI

Hours: hemorrhages and tissue tears Axonal swellings Axonal bulbs

Days/weeks: clusters of microglia and macrophages, astrocytosis

Months/years: Wallerian degeneration

From http://neuropathology.neoucom.edu/Dr.Agamanolis

Sagittal T1-W images

Axial FLAIR images

AXIAL FLAIR

AXIAL T2 GRADIENT-ECHO

BRAINSTEM INJURY

By direct or indirect forces Most commonly associated with DAI Involves the dorsolateral midbrain and upper

pons and is usually hemorrhagic Duret hemorrhage is an example of indirect

damage: tearing of the pontine perforators leading to hemorrhage in the setting transtentorial herniation

<20% of brainstem lesions are seen on CT

18 biker hit by a car

BRAIN HERNIATIONS

SUBFALCIAL HERNIATION

Subfalcial: displacement of the cingulate gyrus under the free edge of the falx along with the pericallosal arteries.

Can lead to anterior cerebral artery infarction

UNCAL HERNIATION Displacement of the medial temporal lobe

through the tentorial notch Displacement of the midbrain Effacement of the suprasellar cistern Displacement of the contralateral cerebral

peduncle against the tentorium Widening of the ipsilateral cerebello pontine

angle Compression of the posterior cerebral artery

DOWNWARD HERNIATION Caudal displacement of the thalamus

and midbrain Effacement of the perimensencephalic

cistern and 4th ventricle. Can cause a 3rd nerve palsy and disrupt

pontine vessels leading to brainstem hemorrhage

UPWARD HERNIATION

Due to posterior fossa mass causing superior displacement of the vermis through the tentorial incisura

Compression of the 4th ventricle and effacement of the quadrigeminal plate cistern.

Compression of the superior cerebellar artery

TONSILLAR HERNIATION

Inferior displacement of the cerebellar tonsils through the foramen magnum

Can lead to posterior cerebellar artery infarction

EXTERNAL HERNIATION

Due to a defect in the skull in combination with elevated ICP

Venous obstruction can occur at the margins of the defect.

SIGNIFICANT SKULL FRACTURES “Depressed”: inner table is depressed

by the thickness of the skull. Overlie major venous sinus, motor

cortex, middle meningeal artery Pass through sinuses Look for sutural diastasis (lambdoid)

TEMPORAL BONE FRACTURES Look for opacification of the mastoid Longitudinal: 70%, parallel to long axis

of petrous bone, conductive hearing loss (from ossicular dislocation), facial nerve paralysis (20%)

Transverse: 20%, sensorineural hearing loss, facial nerve paralysis (50%)

Complex Complications: meningitis, abscess

POST TRAUMATIC SEQUELAE Carotid-cavernous fistula(CCF) Dissection/pseudoaneurysm Infarction Atrophy/encephalomalacia Infection Leptomeningeal cyst