Imaging of head trauma dr. Thanh Binh Nguyen



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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




CANADIAN CT HEAD RULE

  • Minor head injury: patients with witnessed loss of consciousness, amnesia or disorientation and a Glasgow coma Scale(GCS) of 13-15.

  • Prospective study of 3121 patients who presented with a GCS of 13-15 (Stiell et al, Lancet 2001; 357:1391-96)



CANADIAN CT HEAD RULE

  • CT is required for patients with minor head injury and any one of the following:

  • High risk (for neurological intervention)

    • GCS score<15 at 2h after injury
    • Suspected open or depressed skull fracture
    • Any sign of basal skull fracture (hemotympanum, ‘racoon’ eyes, CSF otorrhoea…)
    • Vomiting  2 episodes
    • Age  65 years.
  • Sensitivity of these rules (100%), specificity (69%), CT ordering proportion (32%)



CANADIAN CT HEAD RULE

  • Medium risk (for brain injury on CT)

    • Amnesia after impact > 30 min
    • Dangerous mechanism (pedestrian struck by motor vehicle, occupant ejected from motor vehicle, fall from height > 3 feet or five stairs)
  • Sensitivity of these rules (98%), specificity (50%), CT ordering proportion (54%)



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)













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





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:

  • Days/weeks: clusters of microglia and macrophages, astrocytosis

  • Months/years: Wallerian degeneration







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.



ANATOMY



BASE OF SKULL ANATOMY



BASE OF SKULL ANATOMY



BASE OF SKULL ANATOMY



BASE OF SKULL ANATOMY



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







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