Imaging of head trauma dr. Thanh Binh Nguyen
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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. 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 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 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 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: hemorrhages and tissue tears Axonal swellings Axonal bulbs 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: 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. 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. 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 Dostları ilə paylaş:
