IMAGING OF HEAD TRAUMA

1. IMAGING OF HEAD TRAUMA Dr. Thanh Binh Nguyen University of Ottawa, Canada July 2009

2. OUTLINE • Clinical indications for imaging • Imaging technique • Extraaxial hemorrhage • Intraaxial injury • Brain herniations • Skull fractures

3. 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

4. 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

6. 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

7. 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)

8. 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

9. 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)

17. SCALP INJURY

18. 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.

19. Extraaxial fluid collections • Subarachnoid hemorrhage(SAH) • Subdural hematoma(SDH) • Epidural hematoma • Subdural hygroma • Intraventricular hemorrhage

21. 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

26. 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)

28. W=33 L=41

32. 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.

33. 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)

36. 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

37. 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

41. INTRA-AXIAL INJURY • Surface contusion/laceration • Intraparenchymal hematoma • White matter shearing injury/diffuse axonal injury • Post-traumatic infarction • Brainstem injury

42. 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

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

44. 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

45. DIFFUSE AXONAL INJURY • Rarely detected on CT ( 20% of DAI lesions are hemorrhagic) • MRI: T1, T2, T2 GRE, SWI

46. 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

47. DAI • Hours: • hemorrhages and tissue tears • Axonal swellings • Axonal bulbs • Days/weeks: clusters of microglia and macrophages, astrocytosis • Months/years: Wallerian degeneration

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

50. Sagittal T1-W images