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Head and Neck Trauma: An Overview of Radiologic Findings

Overview of the CT and MR findings of various neurologic emergencies

Justin Skweres

on 11 May 2014

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Transcript of Head and Neck Trauma: An Overview of Radiologic Findings

Head and Neck Trauma An Overview of Radiologic Findings in Cranial and Spinal Trauma Imaging In Head Trauma Learning Objectives To describe the typical radiologic findings in head and neck trauma
To provide an overview of the epidemiology of and the mechanism involved in the various conditions described
To present relevant guidelines and recommendations relating to appropriate imaging and management CT is the indisputable modality of choice and compliments what may be difficult physical exam due to altered consciousness

Noncontrast CT often the first choice to evaluate for hemorrhage

MR may be helpful in situations where clinical findings exceed expectations - to check for DAI or cerebral contusions Classifying the Mechanisms of Head Trauma Type of Injury Blunt Penetrating Most damage due to change in brain shape +/-deformation of the skull without a change in volume
MECHANISMS - (1) Direct Blow, (2) Acceleration
Superficial injuries are most common and result in CEREBRAL CONTUSIONS - often associated with skull fractures
Coup vs Coutrecoup Projectile (bullet) vs nonprojectile (knife)
For projectiles - a cavity is created, often with missile and other foreign contents, shockwave damages surrounding tissues
superficial, tangential, penetrating (still in calvarium), perforating (exits calvarium)
Velocity - high vs low velocity
low velocity (non military) projectiles exhibit fragmentation because they are not usually jacketed
Penetrating injuries - infections, CSF leaks, delayed hemorrhage, migration of bullets Head Trauma Imaging Modalities CT - better in the acute setting to detect
treatable conditions before secondary neurologic
damage occurs MR - longer exams, issues with life support
equipment, inferior bone detail; best in subacute
to chronic traumatic injuries, better predictor
of prognosis Mechanics of Neuronal Injury Experiments in primate models have shown all forms of major intra-axial head injuries and subdural hematomas can be produced by purely rotational acceleration (no head impact

Only epidural hematomas and skull fractures require impact! Calvarial Fractures Intra-axial injuries Non-displaced, linear most common Extra-Axial
(SDH) CT imaging of choice - bone algorithm Treatment required with depressed
or complex fractures Longitudinal Temporal Bone Fracture (red arrow) Extra-axial Injuries Epidural Hematoma Subdural Hematoma Subarachnoid hemorrhage Intraventricular hemorrhage Diffuse Axonal Injury Cerebral contusions Fracture of skullbase (A) with cisternogram (B) showing small encephalocele and CSF leak Diastasis of the right lambdoid suture
(white circle) Contrast administered via lumbar puncture Encephalocele and CSF leak Underlying injuries Cortical contusions, or thrombosis/infarction tearing of dural sinuses, cortical veins, and arteries - classically the middle meningeal extra-axial hemorrhage intra-axial injury Overall, trauma most common cause of SAH; incidence reported to be 33-60% Acute bleed in sulci bilaterally Characteristic CT appearance -
hyperattenuating sulci / cisterns Blood along tentorium - SDH vs SAH?
if extension into the sulci, there
is subarachnoid involvement FLAIR images show
hyperintense signal MR imaging shows hyperintensity on FLAIR sequences Postcontrast FLAIR has even higher sensitivity for acute SAH Warning: Limited evaluation of posterior fossa due to flow artifacts Complications of SAH - Communicating hydrocephalus Vasospasm and infarction Right occipital bone fracture at area of impact and resulting countre-coup injury of with hemorrhagic contusions of left frontal lobe with associated extra-axial hemorrhage Vascular Injuries Primary Injuries Primary vs Secondary Extra-axial vs Intra-axial Secondary Injuries Two axial CTs with SAH T2*GRE image Other Examples SAH Subdural vs Epidural Epidural - above periosteum - does not cross the cranial sutures Subdural - potential space between dura and arachnoid, freely crosses sutures convex inward Crescent-shaped Overview Spinal Trauma Stability vs Instability Arterial laceration along the inner table of the skull Generally do not cross the tough attachments of dura at cranial sutures EXCEPTION - arterial EDH can cross the sagittal suture at the vertex, dura less well attached here 90% associated with calvarial fractures - classically middle meningeal Complications - increased ICP --> herniation Mixed hyper/hypoattenuation - sign of active bleed (A) shows small mixed
attenuation bleed of the middle cranial fossa. (B) CT a few
hours later shows marked increase in size. EDH, right middle cranial fossa Venous Epidural Hematoma Slower bleeding from lacerations of the dural venous sinuses. Notice extension of EDH from supra- to infratentorial regions suggesting laceration of the venous sinus as the cause Due to rupture of the bridging cortical veins Predisposed - brain atrophy (age, alcoholism), anticoagulated patients, rapid decompression/shunting of hydrocephalus Often contrecoup Acute SDH in patient stabbed with knife Classically crescent shaped, crosses suture lines, tracks along dural reflections May be delayed, as in this patient s/p fall on Coumadin therapy Acute Vs. Chronic SDH Imaging Characteristics These findings CANNOT be reliably extrapolated to extraaxial blood! Possibly increased time of evolution due to higher oxygen tension, dependent on hematocrit and field strength Chronic SDH at CT septation SDH is hypodense, but remains hyperdense to CSF Normal CSF Same patient's MR... Axial T2 FLAIR T2*GRE Note the signal of the fluid DOES NOT suppress and the varying intensities of the areas withing the SDH Treatment may require decompression if impending herniation Higher risk in anticoagulated patients, suspect delayed hemorrhage Acute on Chronic SDH - Acute blood seen as hyperdensity in hypodense chronic subdural hematoma. Notice the HEMATOCRIT EFFECT! Hematocrit effect Axial CT and T2 weighted images showing hematocrit effect in two different patients Usually associated with other types of intra or extra-axial hemorrhage

Usually seen as blood pooling in the dependent portions of the lateral ventricles At risk for obstructive hydrocephalus

Check the occipital horns! Associated with tearing of subependymal veins Hemorrhage in the occipital horns of the lateral ventricles Hemorrhagic
Contusions Is My Patient Going to Die? Justin Skweres, MD Maxillofacial Injury Injuries to the capillaries and associated edema Anterior and inferior surfaces of the frontal lobes and occipital and temporal poles Often contrecoup More likely to be hemorrhagic than DAI Subsequent imaging shows enlarging or new hemorrhage Contusion Progression and Prognosis Hemorrhagic contusions represent areas of focal ischemia Larger contusions --> increased chance of enlargement on subsequent imaging Size of contusion and associated SDH (burst lobe phenomenon) were predictive of hemorrhage progression The Burst Lobe Burst lobe phenomenon - related to rupture of a large contusion into the subdural space This is a poor prognostic sign Large contusions, associated SDH, low GCS - associated with delayed clinical deterioration "Spot sign" - sign of active bleeding and was predictive in a study of nontraumatic patients of continuing hemorrhage Due to differential acceleration of parenchyma of varying density (ie grey white junction) Can occur without direct blow to the head Often less hemorrhagic than more superficial cortical contusions Occurs most often in the grey-white matter junction, next most common deep white matter DAI Grading Based on Location Grade 1 - lesions in the grey-white matter junction or deep white matter Grade 2 - lesions in the corpus callosum, most often the splenium Grade 3 - lesions in the dorsolateral midbrain and upper pons Hemorrhagic grade I DAI of the grey-white matter junction seen due to signal loss on T2*GRE MR is superior to CT to demonstrate extent of DAI CT is relatively insensitive for DAI when the lesions are non-hemorrhagic One study found that only 19% of DAI lesions were hemorrhagic - many missed at initial NCCT MR is very sensitive for DAI lesions, hemorrhagic or non-hemorrhagic, particularly with newer sequences DAI findings at MR Blood-sensitive sequences are particularly useful - T2*GRE, susceptibility-weighted imaging Diffusion weighted imaging and apparent diffusion coefficient mapping DWI and ADC map showing DAI of the splenium of the corpus callosum (grade II DAI). One small retrospective study showed DWI to be more sensitive than T2/FLAIR or T2*GRE for DAI lesions Restricted Diffusion Axial T2*GRE image showing signal loss due to susceptibility effect T2*GRE (left) and SWI (right) images. Notice the more conspicous lesions on the SWI sequence Findings at CT CT less sensitive and only useful for visualizing hemorrhagic lesions Axial CT images showing hemorrhagic DAI - Grade II lesions involving deep white matter and splenium of corpus callosum Chronic DAI findings persist as hemosiderin deposits Chronic DAI seen as T2 hypointensity corpus callosum and upper midbrain CTA after nail to the head! Vascular Injury Mechanisms Subintimal versus Subadventitial Dissection Subintimal dissection Results in the narrowing of the true lumen and eventually OCCLUSION resulting in downstream ischemia T1 hyperintensity representing intramural hematoma Subadventitial dissection Results in pseudoaneurysm formation and possibly traumatic arterovenous fistula Carotid-cavernous fistula Dissection of right ICA Resulting from head trauma (or ruptured aneurysm - symptoms include chemosis and pulsating exophthalmos Subintimal dissection can lead to occlusion, thrombosis and embolization, and downstream ischemia Delayed Contusions and DAI are always possible... Always need short term follow up! Secondary vascular injuries Can result from damage to adjacent vascular structures during calvarial fracture Thrombosis of the right internal jugular vein due to right temporal bone fracture Entrapment of the basilar artery due to fracture of the clivus Secondary / Delayed Injuries and Long Term Sequelae Herniation Syndromes Subfalcine Herniation Seen as shift of the midline indicating herniation of the cingulate gyrus under the falx to the contralateral side Many secondary injuries are preventable with apporpriate intervention Uncal Herniation Herniation of the medial-most temporal lobe inferiorly through the incisura. Note compression of left PCA and peduncle, compression of left ambient cistern, and dilated lateral ventricles indicating obstructive hydrocephalus Cerebral Edema Blunting of the sulci bilaterally Decreased attenuation of the cerebrum and loss of grey-white matter differentiation Sparing of the infratentorial structures (cerebellum) in this case make them appear relatively hyperintense Note SDH of the tentorium Axial CT image of infant following strangulation Tonsilar Herniation Herniation of the cerebellar tonsils inferiorly with compression of the cervical spine Spinal injury distribution - 55% cervical, 15% thoracic, 15% lumbar, and 15% lumbosacral (systematic review by Sekhon and Fehlings); HOWEVER - spinal fractures more common in thoracic/lumbar Risk of spinal cord injury is much higher in the cervical spine than thoracic or lumbar Cervical spine fractures - mostly in upper and lower ends (C1, C2 and C6, C7) - C2 fractures are more common in elderly Most thoracolumbar fractures occur in the lower thoracic and upper lumbar spine - and the majority of these do not have spinal cord injury Indications for Imaging NEXUS High NEGATIVE PREDICTIVE VALUE for abscence of a cervical spine fracture (sensitivity 99.6% reported) If all of the following are ABSENT, imaging is not indicated: 1. No midline cervical tenderness on exam

2. No focal neurologic deficit

3. No alteration in consciousness

4. No intoxication

5. No painful, distracting injuries Canadian Cervical Spine Group Low risk of cervical spine fracture when the following criteria are met: Sensitivity 100% reported and specificity of 42.5% - also a high NPV 1. Normal GCS of 15

3. Presence of low risk factors ** 2. Absence of high risk factors *

4. The ability to actively rotate the neck 45 degrees left and right *High Risk Factors: age >65 years, high risk mechanism (fall >3m or 5 stairs, high speed MVC, axial loading, bicycle or motorcycle crash, parasthesias in extremities) **Low Risk Factors simple MVC, sitting position in ER, ambulatory at any time, no midline tenderness Both the NEXUS and CCSG studies showed a high NPV for cervical fracture, neither shown to be superior to the other These guidelines are for adults and cannot be extrapolated to children Use the "Three Column Theory" of Denis Line 1 - The soft tissues posterior to the airway Line 2 - The line connecting anterior aspect of vertebral bodies Line 3 - The line connecting the posterior aspect of the vertebral bodies Line 4 - Spinolaminar line Normal distance of dens to anterior arch is <2.5mm in adults; if more, suspect rupture of transverse ligament C1-C2 dislocation with rupture of the transverse ligament Jefferson fracture on radiography (A) and at CT (B). Notice the displaced lateral bodies of C1 on dens in the open-mouth view and the asymmetry of the two sides "Hangman's fracture" - hyperflexion/distraction injury of C2 (ie. head vs. dashboard). Notice the SPINOLAMINAR LINE is displaced posteriorly at C2 Two or more columns involved = UNSTABLE Stable vs Unstable Radiologic Signs of Mechanical Instability 1. Displacement/Translation > 2mm (ligamentous disruption

2. Widening of interpedicular distance, the facet joints, or the interspinous spaces

3. Disruption of the posterior vertebral body line

4. Loss of height of vertebral body > 50%

5. Kyphosis > 20 degrees Increased basion to dens distance indicating atlanto-occipital dislocation. There is increased lateral distance from lateral masses of C1 to occipital condyles seen on coronal view Fracture through the anterior arch bilaterally of C1 at junction of arch and lateral masses. Mechanism - axial loading Classic Jefferson Fracture Atlanto-Occipital Dislocation Atypical Jefferson Fracture (A) Lateral radiograph, no evidence of fracture
(B) Open mouth view and (C) axial CT show unilateral fracture through the anterior arch of C1. NOTE: can be difficult to distinguish from congenital nonunion Hangman's Fracture Internal Carotid Artery Injury Seen best at CTA of the head At left, there is a traumatic pseudoaneurysm of the left ICA with an associated fracture of the left sphenoid sinus wall One small series found carotid canal fractures identified at CT had sensitivity/specificity of 60%/67% for ICA injury Sphenoid sinus air/fluid level had a higher sensitivity (98%), but low specificity for ICA injury Pseudoaneurysms are prone to rupture and can cause local compression Spinal Trauma Cervical Spine Trauma Plain Radiography Evaluation of the cervical spine should always begin by inspecting alignment as follows Think Mechanism! Found One Lesion, Intensify the Search For Another, Don't Relax! Results from a noose, or the dashboard (sudden deceleration, hyperextension/distraction injury to the pars interarticularis) Fracture is through the weakest part of the axis - the articular portions of the pedicles (PARS INTERARTICULARIS) This results in traumatic spondylolisthesis Unstable lesions are more likely to progress to neurologic injury, major deformaty, or incapacitating pain Hyperflexion Hyperextension Axial loading Lateral Flexion (Atlantoaxial dissociation, flexion teardrop) (Hangman fxr, Extension teardrop) (Burst fxr, Jefferson fxr) (Occipital condyle, transverse process fxr) 70-90% are "longitudinal," or parallel to the long axis of the petrous bone, the remainder are "transverse" or "mixed" Temporal Bone Fracture Results from blow to side of head - generally less severe, may have facial palsy Blow to occiput or frontal region and is generally more severe. May have hearing loss, facial palsy, carotid canal or jugular foramen fxr Longitudinal vs Transverse Classification CSF Leak Due to Skullbase FXR Otic Capsule Classification Otic Capsule Sparing: Anterolateral to the otic capsule, less risk of complications Otic Capsule Violating: Involvement of the cochlea or semicircular canals - higher risk of CSF leaks, hearing loss, and facial nerve injury

MORE LIKELY TO HAVE OTHER INJURIES! Longitudinal: Transverse: Depressed Fractures Occipital Condyle Fractures Three types - Type I is a comminuted fracture of the condyle (uncommon) due to axial loading, Type II is fracture extending into condyle, Type III (most common and most severe) is avulsion of inferomedial fragment into foramen magnum (unstable) Posterior
Displacement Odontoid Injuries Type I injuries involve avulsion of the tip, which must be differentiated from os odontoideum - a well corticated ossification center above a rudimentary dens Type II is a transverse fracture at the base of the dens - this is the MOST COMMON and MOST LIKELY TO GO ON TO NONHEALING Type III is a fracture that extends into the lateral body of the axis and must be distinguished from isolated lateral body fracture (rare) Type II fracture of the dens with posterior displacement T2, T1, and STIR images showing type II fracture with intact posterior longitudinal ligament and no cord damage C2 Fractures and The Elderly Type II fracture of the dens in an elderly patient. C2 Fractures are more common in elderly patients due to osteopenia and degenerative changes Type III axis injury. Plain radiograph demonstrates mild subluxation of C2 on C3 only. CT shows C2 body fracture extending into the dens Type II Type III The Cervicocranium Subaxial Injury Lumber Bullet Gunshot Wounds Bullet path can be seen as a hemorrhage streak on CT. Bullets that cross the midline or those that fragment have the worst prognosis Beveled appearance is characteristic of the entry site. Bone and scalp debris also forced into lesion results in increased risk of infection Depressed skull fracture With associated epidural hematoma Regular Old MR in Acute DAI Proton density (left) and T2-weighted (right) images of acute DAI are HYPERINTENSE Within 3-4 hours - short term follow up needed! Sagittal T1 image showing contusions of the frontal and temporal lobes Clay Shoveler Fracture Historically heavy lifting, now often with trauma. This is a STABLE fracture of the spinous process of C6-T1 due to avulsion during hyperflexion Anterior Subluxation (A) Lateral radiograph shows anterior subluxation of C4 on C5. (B,C) Flexion/extension images do not show increased subluxation or kyphosis. Anterior subluxation involves damage to the posterior longitudinal ligament with a normal anterior longitudinal ligament - IMPORTANT to recognize as FAILED LIGAMENTOUS HEALING can lead to INSTABILITY Bilateral Interfacetal Dislocation Laceration
Dissection/Occlusion Pseudoaneurysm
AV Fistula Flexion Teardrop Fracture The most severe of flexion injuries - most often in the lower C-spine (C5). Disruption of ALL, IVD, and PLL. Retropulsed fragments lead to anterior cord syndrome. UNSTABLE! teardrop retropulsion A more severe hyperflexion injury in which the facet joints dislocate - often associated with anterior compression fractures, UNSTABLE Double Vertebral Body Sign HYPERFLEXION HYPEREXTENSION Predisposed to Ext Injuries: Ankylosing Spondylitis
Diffuse Idiopathic Skeletal Hyperostosis
Acquired or congenital spinal stenosis WORSENING INJURY Articular Pillar Fracture Extension/rotation injury involving the lateral masses and often extending into the transverse process - these are usually STABLE (posterior column only) Extension Dislocation Distraction of Ant & Mid Columns Hyperextension Fracture / Dislocation Note the calcification of the anterior and posterior longitudinal ligaments and syndesmophytes in this patient with ankylosing spondylitis AS patients are predisposed to hyperext/fracture - here there is fracture of the calcified ant longitudinal ligament and widening of C5-C6 disk space Bamboo Spine Extension Teardrop Fracture Commonly involves the C2 vertebral body. Usually only involves the anterior column and are thus STABLE IN FLEXION, UNSTABLE IN EXT. Mechanism - avulsion due to hyperextension Cervical Burst Fractures While normally seen in the thoracolumbar spine, burst fractures can occur in the C-spine with significant axial loading - UNSTABLE, RETROPULSION! Anatomy of the Viscerocranium Buttresses of the Face The face is divided into 5 anatomic regions:
(1) Nasal
(2) Orbital
(3) Zygomatic
(4) Maxillary
(5) Mandibular Forces delivered to the face are transmitted through the natural buttresses - thus, typical fracture patterns arise A Tour of Facial Trauma Nasal and NOE Fractures NOE = Naso-orbital-ethmoid complex - includes the nasal bone, the ethmoid bone, and the medial orbital rim and medial canthal tendon Isolated Nasal Fractures - MOST COMMON Comminuted bilateral nasal fracture Right Maxillary fracture Vomer Fracture Type III Nasal Fracture Large central fragment that contains the attachment of the MCT Comminuted central fragment, but MCT attaches at a piece large enough for stabilization Severely comminuted NOE fracture that extends beneath MCT insertion - repair required Bilateral NOEC Fxr comminuted nasal fracture Ethmoid sinus fractures and fracture of the lamina papyracea (medial orbital lamina) Orbital Fractures NOEC Fxrs are associated with increased Interpupillary distance, flattening of nasal dorsum, and telescoping! Subacute SDH Can Hide on CT Isodense to brain in the subacute phase, can be difficult to see. Look for the THICK GREY MATTER MANTLE and DISTORTION OF THE VENTRICLES Subacute SDH Can't Hide on MR HYPERINTENSE signal on T1 weighted imaging due to the presence of methemoglobin Intracerebral Hematoma Isolated hemorrage in the parenchyma without associated cortical contusion Shear stress injury resulting in tearing of small parenchymal vessels Less common Biconvex Bleed Midline Shift Assoc Hemorrhagic Contusions Epidural Hematoma Depressed?
Check underneath! (Methemaglobin again) Brain Stem Injuries Primary - Secondary - Most common DAI, dorsolateral midbrain Herniation; classically Duret Hemorrhage from DESCENDING TRANSTENTORIAL herniation Brainstem DAI at CT (left) and T2W MR (right) typically involves the dorsolateral aspect of the midbrain/upper pons Central hemorrhage in the pons classically seen with descending transtenorial herniation thought to be due to stretching of penetrating arteries as brainstem is displaced Encephalomalacia CSF Leaks Leptomeningeal Cysts Admission 2 Weeks 6 Weeks Chronic (seen previously) Classified the same as extracranial arterial injury - subintimal and subadventitial dissection Subadventitial dissection causes pseudoaneurysm and arteriovenous fistulas Blow-In Fractures Result from fracture of the superior orbital rim from direct trauma, or fracture of the frontal bone only from transmitted force. Both result in DOWNWARD displacement and DECREASE in orbital volume Complex Supraorbital fracture involving the sphenoid bone. Involvement of the APEX of the orbital space by fragments can damage nerves (II, III, IV, V1, VI) and vessels Fragments involving orbital apex Fragment in Optic Canal Blow-Out Fractures IMPORTANT - No fracture of the infraorbital rim! Medial Blow-Out Fracture of the right orbit. Involve the ORBITAL FLOOR (MOST COMMON) or MEDIAL wall. Herniated medial rectus Inferior Blow-Outs Most Common Worry about inferior rectus entrapment! Enophthalmos and Entrapment - repair If extends into posterior maxillary sinus wall --> difficult repair Inferior Orbital Blowout Inferior Orbital Rim Fracture must be noted as it has implications for surgery (Different from Blow-Out)

If you find an isolated orbital rim fracture - look for other injuries Blood (yellow)
Intraorbital fat (white)
Fragment (short white) Inferior Rectus Zygoma Fractures Direct blow to lateral midface May involve orbital floor through zygomaticomaxillary connection Fracture of arch may compress temporalis tendon --> trismus Arch fracture, compression of temporalis Indications for operation - important to note: Significant displacement Trismus Orbital entrapment Orbital apex involvement (from zygoma-sphenoid connection) V2 (infraorbital nerve) parasthesia Classification Zygoma Complex Fracture Zygo-Temporal Zygo-Frontal suture diastasis; orbital floor fxr Zygo-maxillary suture fxr Maxillary Fractures Common feature - all involve pterygoid plates Lefort I - Lefort II - Lefort III - Fracture through the alveolar processes of the maxilla; the maxilla and hard palate are distinctly mobile The pyramidal fracture - from pterygoid plates to inferior and medial orbital walls and terminates in nasal fracture or nasofrontal diastasis; mobile maxilla/nasal region "Craniofacial disjunction" - pterygoids to zygoma to lateral and medial orbital wall to nasal bone; midface mobile relative to supraorbital regions Lefort I Fracture of pterygoids and maxilla just above the alveolar process Lefort II Fxr both infraorbital rims and just above the nasofrontal suture Midface Smash Severe comminution of the midface that does not conform to any one pattern Pay attention to soft tissue structures! Mandibular Fractures coup-contre coup injuries are common Right parasymphyseal and left ramus fracture Another Example CSF Leak
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