Imaging of Traumatic Brain Injury: Pearls and Pitfalls

This was presented at the 51st Annual Scientific Meeting of the Royal College of Radiologists of Thailand.

Slideshow: Imaging of Facial Trauma

Metatarsal Stress Fracture

Oblique radiographic view of the foot shows transverse fracture lines of the proximal diaphyses of the forth and fifth metatarsals (arrows). Note sclerotic bone ends, periosteal reaction and minimal widening of the fracture gaps (degree of sclerosis is more on the forth digit)

Facts

• Spontaneous fractures of normal bone that result from summation of stresses
• Most common lower-extremity stress fracture
• Originally termed "march fracture" (seen in military recruits). Now seen in ballet, football, gymnastics and basketball
• Most common site = shaft (at diaphysis or neck)
• Increased incidence in pes cavus and pes planus foot

Radiography

• Often negative in early phase. May see thickening of cortex and small periosteal reaction
• Later, a fracture line with sclerotic bone ends, periosteal reaction, widening of fracture gap will be shown. 
• Late phase, the bone ends involved are entirely sclerotic 

References:

Schepsis AA, Busconi BD. Sports Medicine, 2006.

Baxter DE, Porter DA, Schon L. Baxter's the Foot and Ankle in Sport, 2008. 

Tibial Spine Fracture in Adults

A lateral knee radiograph of a 22-year-old man sustaining motor vehicle collision demonstrates an oval bone fragment (arrow) in the intercondylar region of the knee. There is complete separation between the fragment and the donor site with superior displacement of the fragment. Note hemarthrosis (asterisk).

Facts:

• Classically described in pediatric patients and considered the childhood equivalent of anterior cruciate ligament (ACL) ruptures in adults
• Forceful hyperextension of the knee resulting in avulsive force/tension on ACL, which inserts into the anterior tibial spine. Possibly with valgus stress or rotation. 
• In adults, most injuries occur in road-traffic accidents and are isolated
• Adults more likely to have associated tear of medial collateral ligament (MCL) or intra-articular fracture

Classification (Meyers and McKeever)

• Based on degree of displacement. Type II & III are most common
• Type I = incomplete avulsion of tibial spine without displacement
• Type II = incomplete avulsion with anterior elevation of the fragment
• Type IIIA = complete separation of fragment
• Type IIIB = rotated and comminuted fragment
• Generally, types I and II are managed conservatively while type III fractures are managed arthroscopically or with open reduction

References:

Kendall NS, et al. Fracture of the tibial spine in adults and children. J Bone J Surg [Br] 1992;74-B:848-52.

Rosen's Emergency Medicine - Concepts and Clinical Practice

Medial Epicondyle Fracture of the Humerus

AP views of both elbows of an 18-year-old boy who sustained an injury to the right elbow.  There is an avulsion fracture (arrow) of the medial epicondyle of the right humerus. Radiograph of the left side demonstrates different areas of distal humeral structures from medial to lateral: medial epicondyle, trochlea, capitellum and lateral epicondyle. 

Facts:

• Common pediatric elbow fracture (3rd common, after supracondylar and lateral condylar fractures)
• Valgus strain at elbow joint
• Two main types: simple avulsion (1/2) and fracture-dislocation (occurring with lateral elbow dislocation; 1/2)
• Indications for surgery include 1) displaced fragment trapped in joint preventing reduction, 2) ulnar neuropathy, 3) valgus instability, 4) open fracture

Imaging:

• Look for displaced fragment trapped in the joint and degree of displacement because they might indicate surgery
• In patients less than 8 years, trochlea may be non-ossified and this may be confused with fracture of medial condyle, which is rarer and could be more complicated
• Another imaging Ddx is osteochondrosis

References:

Wilson JN. The treatment of fractures of the medial epicondyle of the humerus. J Bone J Surg 1960;42:778.

Gottschalk HP, Eisner E, Hosalkar HS. Medial epicondyle fracture sin the pediatric population. J Am Acad Orthop Surgeons 2012; 20:223.

Wheeless' Textbook of Orthopedics link

Slideshow: Imaging of Thoracic Trauma

Imaging of Thoracic Trauma from Rathachai Kaewlai

Slideshow: Imaging of Abdominal Trauma

Imaging of Abdominal Trauma from Rathachai Kaewlai

Slideshow: Imaging of Traumatic Brain Injury

Imaging of Traumatic Brain Injury from Rathachai Kaewlai

Blunt Traumatic Colon Perforation

Axial non contrast CT image of the abdomen shows a localized collection of air and high-density fluid (C) medial to the ascending colon (AC) and the site of colonic wall discontinuity (between arrows). Note skin and subcutaneous swelling/contusion of the right flank. 

Sagittal-reformatted CT image shows similar findings as  on the axial imaging. The entire length of the ascending colon (AC) is better appreciated and the collection (C) is located posteromedial to the colon within the retroperitoneal space. Colonic perforation was confirmed at surgery. 

Facts:

• Uncommon injury in blunt trauma
• Severe direct force is usually required to produce this injury, mostly from motor vehicle collision
• Often associated with other injuries, both intra- (liver, spleen, small bowel mesentery) and extra-abdominal (skeletal, facial, neurologic)
• CT may not be 100% sensitive. Findings could be overlooked in multiply-injured patients, large patients or if metallic monitoring/support devices are obscuring the area.
• "Normal" CT could be misleading when other factors such as physical examination is not taken into account. Re-review of images to look for subtle free fluid/air is essential in these cases.

CT Findings:

• Discontinuity of bowel wall
• Extraluminal contrast leakage
• Extraluminal air either intra- or retroperitoneal (nonspecific, can be seen after DPL, mechanical ventilation, barotrauma, etc)
• Intramural air
• Bowel wall thickening
• Bowel wall enhancement
• Mesenteric fat stranding
• Intraperitoneal and retroperitoneal fluid

References:

1. Barden BE et al. Perforation of the colon after blunt trauma. South Med J 2000;93(1)
2. Brody JM, et al. CT of blunt trauma bowel and mesenteric injury: typical findings and pitfalls in diagnosis. RadioGraphics 2000;20: 1525

Criteria and Consensus Method for Blunt Cervical Vascular Injury (BCVI) Screening with Imaging

According to the updated Guidelines for the Management of Acute Cervical Spine and Spinal Cord Injuries (published on March 2013, Neurosurgery 2013;72), 

• Computed tomography is the imaging study of choice for obtunded or un-evaluable patients with potential cervical spine injuries. (Level I)
• Computed tomographic angiography is recommended to assess for vertebral artery injury in selected patients who meet the modified Denver Screening Criteria after blunt cervical trauma. (Level I)

Currently accepted standard used for BCVI screening is that of Modified Denver Criteria applying to acute trauma patients suffering blunt cervical vascular injury with details listed below. In this post, they have been rearranged from the original description.

Injury Mechanisms/Patterns

• High-energy mechanism causing 1) displaced Le Fort II or III, or 2) complex mandible fracture
• Cervical hyperextension/rotation/flexion injury with 1) midface fracture, 2) complex mandible fracture or 3) closed-head injury and diffuse axonal injury

Symptoms

• Massive epistaxis
• Central or lateralizing neurologic deficit that is unexplained or incongruent with CT
• Transient ischemic attack or stroke after blunt neck trauma

Signs

• Expanding neck hematoma
• Honor syndrome
• Cervical vascular bruit in a patient less than 50 years old with blunt neck trauma
• Seat belt abrasion, hanging bruise, or unexplained contusion or hematoma of neck, resulting in significant cervical swelling or altered mental status

Findings on C-spine NCCT

• Upper cervical vertebral fracture (C1-C3)
• Cervical vertebral fracture extending through the transverse foramen
• Cervical vertebral subluxation
• Cervical spine fracture with cervical hyperextension/rotation/flexion injury

Findings on head NCCT

• Acute or subacute cerebral infarction
• Skull base fracture involving foramen lacerum, sphenoid, mastoid, or petrous bones

References: 

1. Biffl WL, Moore EE, Offner PJ, et al. Optimizing screening for blunt cerebrovascular injuries. Am J Surg 1999;178:517–22; 
2. Cothren CC, Moore EE, Biffl WL, et al. Cervical spine fracture patterns predictive of blunt vertebral artery injury. J Trauma 2003;55:811–3.
3. Neurosurgery 2013;72 Supplement 2. Full-text access is FREE

Maisonneuve Fracture

Figure 1: AP and lateral ankle radiographs demonstrate a vertical fracture of the medial/posterior malleolus of the distal tibia without a fibular fracture.  

Figure 2: Full-length AP fibular radiograph shows a mildly displaced fracture of the fibular shaft at the junction between the proximal 1/3 and middle 1/3. 

Facts: Rotational Ankle Fractures

• Rotational ankle fractures are classified according to force direction applied to the foot, while the injured foot can be in a different position (supination/pronation, adduction/external rotation)
• AO/Weber classification: A, B, C fractures are differentiated by location of fibular fractures. 
• Fibular fracture below the syndesmosis = AO/Weber A (usually supination-adduction)
• Fibular fracture at the syndesmosis = AO/Weber B (~ supination and external rotation)
• Fibular fracture above the syndesmosis = AO/Weber C (~ pronation external rotation)

Facts: Maisonneuve Fractures

• High fibular fracture above the syndesmosis resulting from external rotation
• Often, there is injury to the medial ankle either a tranverse medial malleolar fracture, posterior malleolar fracture or disruption of the deltoid ligament
• Disruption of the syndesmosis and interosseous ligament up to the fibular fracture site
• Suspicious for this fracture if you see a 1) transverse medial malleolar fracture or 2) posterior malleolar fracture but no fibular fracture on the ankle radiographic series. In these situation, a full-length fibular radiograph should be taken

Reference:

Sakthivel-Wainford K. Self-assessment in limb x-ray interpretation, 2006

Rockwood CA, Green DP. Rockwood and Green's fractures in adults, 2005

Avulsion of the Anterior Superior Iliac Spine

A pelvic radiograph demonstrates an avulsion fracture (arrows) of the right anterior superior iliac spine (ASIS) in a 14-year-old boy. 

Facts: Pelvic Avulsions

• Avulsion of pelvic bones usually found in young, skeletally immature athletes.
• Forceful contraction of the attached muscle while the athlete actively engages in kicking, running or jumping.
• Three major locations: ASIS (sartorius attachment), anterior inferior iliac spine (AIIS, rectus femoral attachment) and ischial tuberosity (hamstrings and adductor attachment).
• 50% of cases at ischial tuberosity, 23% ASIS, 22% AIIS (of all pelvic avulsions).
• Localized swelling and tenderness at the site of avulsion fracture. Limited motion from pain.

Imaging

• Plain radiography usually sufficient for diagnosis. 
• Comparison view helpful to ensure that abnormality is not a secondary center of ossification.
• Pitfalls: secondary ossification center, osseous mass seen as a delayed presentation mimicking neoplasm.

References

Davies AM, Johnson KJ, Whitehouse RW. Imaging of the hip & bony pelvis: techniques and applications. 

Beaty JH, Rockwood CA, Kasser R. Rockwood and Wilkins' fractures in children. 

Acute Isodense Subdural Hematoma

Plain and contrast-enhanced axial CT images of the brain show an isodense subdural hematoma (SDH, arrows) in the left cerebral convexity, much better appreciated on post-contrast image. There is also a thinner right frontal convexity SDH. 

Facts: Isodense Subdural Hematoma (SDH)

• Subdural blood collection that has similar attenuation with the gray matter
• Acute SDH appears as a high density collection with declining density with time. It passes "isodense" state mostly in subacute phase (2-6 weeks after initial trauma)
• Isodense SDH poses diagnostic dilemma because it is not apparently seen on CT
• In acute setting this can be seen in anemic patients (acute isodense SDH). Experimental data showed that Hb 8-10 g/dl will be isodense to the adjacent brain

Reference:

Smith, Jr., WP, Batnitzky S, Rengachary SS. Acute isodense subdural hematomas: a problem in anemic patients. AJR 1981; 136:543-546. 

ACR Appropriateness Criteria for Suspected Aortic Injury

Axial contrast-enhanced CT image shows a pseudoaneurysm (arrow), intimal flap and periaortic hematoma of the proximal descending thoracic aorta in a patient experienced severe blunt chest trauma.

A newly revised American College of Radiology (ACR)'s Appropriateness Criteria for blunt chest trauma - suspected aortic injury has been published in March 2012 in the journal Emergency Radiology, summary and useful points are provided below

• Chest x-ray remains an initial screening examination in patients who has sustained blunt chest trauma
• In the appropriate clinical setting and with a CXR demonstrating mediastinal widening or other signs of mediastinal hemorrhage, thoracic aortography or helical chest CT is indicated
• CTA is emerging as a very sensitive and specific examination for aortic injury and has replaced aortography in many trauma centers

Useful Points

• Mediastinal widening has been defined as a transverse diameter of 8 cm from the left side of aortic arch to the right margin of the mediastinum (even on AP portable CXR)
• Mediastinal widening is 90% sensitive but 10% specific for aortic injury
• Approx 7% of patients with aortic injury have normal initial CXR
• If no mediastinal hematoma seen on CT, probability of significant aortic injury is very low

Reference

Demehri S, et al. ACR Appropriateness Criteria blunt chest trauma--suspected aortic injury. Emerg Radiol 2012 (published online: 18 Mar 2012)

Triquetral Fracture

A lateral wrist radiograph shows a small bone fragment (arrow) dorsum to the wrist with overlying soft tissue swelling.

Facts:

• Second most common carpal bone fracture
• Two main types: dorsal chip fracture and body fracture
• Dorsal chip fracture (like in our case ) believed to be due to forceful impingement of the triquetrum during wrist hyperextension
• Body fracture frequently associated with perilunate dislocation (direct blow)
• Pain and swelling localized at the dorsum of the wrist where triquetrum is located
• Complication: motor branch of ulnar nerve injury

Imaging

• Chip fracture best seen on lateral radiograph with hand in flexion
• Body fracture best seen on AP and oblique radiographs
• Fractures are possibly underreported. CT can help in suspected cases.

Reference:

Simon RR, Koenigsknecht SJ. Emergency orthopedics: the extremities, 2001.

Fracture of the Lateral Process of Talus

AP view of the foot shows a small avulsion fracture (arrow) of the lateral process of the talus.

Facts: Lateral Process of Talus

• Lateral process is a broad-based, wedge-shaped prominence of the lateral talar body that articulates with the fibula and posterior facet of talus
• Anchor point for lateral talocalcaneal, anterior and posterior talofibular ligaments

Facts: Fracture of the Lateral Process of Talus

• Axial loading with elements of dorsiflexion and eversion or external rotation
• High incidence among snowboarders, sometimes called "snowboarder fracture"
• Can be difficult to diagnose clinically, easily confused with ankle sprain
• Pain localized anteroinferior to the distal end of fibula

Imaging

• Important to look specifically at this area in patients presenting with lateral ankle pain following trauma
• Small, nondisplaced fracture can be overlooked. CT may be warranted if suspicion persists in a normal-looking x-ray series
• Hawkins classified this fracture into 3 types: 1) large single fragment, 2) large comminuted fragment, 3) small, extra-articular fragment

Reference:

Browner BD, Levine AM, Jupiter JB, et al. Skeletal Trauma: Basic Science, Management, and Reconstruction, 2009.

Predictors of Cervical Spine Fractures and Fracture Risk

Flow diagram (originally published by Blackmore CC, et al, Radiology 1999) demonstrating a prediction rule for determination of risk of cervical spine fracture in blunt trauma patients. Percentages indicate the risk of fracture for each group with 95% CIs. Area under the ROC curve = 0.87

Facts:

• Three common options exist to "clear" cervical spine in trauma patients: clinical evaluation, radiography or CT
• Canadian C-spine Rule (CCR) or NEXUS criteria are generally used by emergency physicians and trauma surgeons to determine which patients require imaging clearance
• Among patients who, based on CCR or NEXUS, need imaging clearance: an issue exists whether to choose x-ray vs. CT
• In general, CT is preferred for patients with moderate or high likelihood of having C-spine injury given its higher accuracy, cost-effectiveness and ease of performance. However, C-spine CT has not been tested as cost-effective among patients with low likelihood of C-spine injury - practice has been different from one place to another

According to Blackmore CC, et al

• We can stratify patients into groups of different fracture probabilities by using 4 predictors: severe head injury, high-energy cause, age and focal neurologic deficit
• Definition of severe head injury = intracranial hematoma, brain contusion, skull fracture or unconsciousness
• Definition of high-energy cause = high-speed MVC (greater than 30 mph), pedestrian struck by car
• Definition of moderate-energy cause = low-speed MVC, MVC at unknown speed, bicycle accident, motorcycle accident or fall
• Definition of focal deficit = those that could be in a spinal cord or spinal nerve distribution

Reference:

Blackmore CC, Emerson SS, Mann FA, Koepsell TD. Cervical spine imaging in patients with trauma: determination of fracture risk to optimize use. Radiology 1999; 211:759-765.

Tibial Plateau Fracture

An AP knee radiograph shows a fracture of the lateral tibial plateau (arrows) in an osteopenic patient who had a recent trauma.

Facts

• Fractures involving the articular surface of the proximal tibia. This is a diverse group of fractures, a spectrum of different severity of injuries
• Most common mechanism of injury is fall with knee forced into valgus or varus
• Imaging performed to locate the fracture, identify fracture pattern and degrees of displacement
• Most common location = lateral tibial plateau
• Aim of surgical treatment is to restore or preserve limb alignment

Imaging

• Usually AP and lateral views of the knee show the fracture but bilateral oblique views are also recommended since many subtle joint impaction or fracture lines are not visible on the two views.
• CT with reformations is a study of choice to delineate the extent, orientation of condyle, location and depth of articular comminution and impaction
• Schatzker classification divides tibial plateau fractures into 6 types: lateral plateau without depression, lateral plateau with depression, lateral or central plateau compression, medial plateau, bicondylar plateau, plateau fracture with diaphyseal discontinuity.
• Based on the classification, the management is different. The first three: repair the articular cartilage. The latter three: treatment depends on location of soft tissue injury.

Reference:

Markhardt BK, Gross JM, Monu J. Schatzer classification of tibial plateau fractures: use of CT and MR imaging improves assessment. RadioGraphics 2009

Hangman's Fracture

A lateral cervical spine radiograph shows grade I anterolisthesis of C2 on C3 (arrow) with fractures of the C2 pars interarticulares (arrowheads).

Facts:

• Traumatic spondylolisthesis of C2
• Combination of soft tissue and bony injuries believed to start from anterior longitudinal ligament (ALL) tear, avulsion of C2/3 disc from either inferior or superior endplate - then bony malignment and posterior element fractures.
• Posterior element fractures are often extra-articular, involving the pars interarticulares (pedicles)
• Named "hangman" because of mechanism of injuries mimic that of hanging (neck hyperextension with compression of posterior elements)
• Displaced fractures often are associated with neurologic injuries (apnea, complete paralysis, sensory loss distal to lesion)

Reference:

Mandavia DP, Newton EJ, Demetriades D. Color Atlas of Emergency Trauma, 2003.

The Fat Pad Sign

A lateral radiograph of the elbow shows a posterior fat pad sign (arrows) and elevation of the anterior fat pad (arrowheads) in a patient with a radial neck fracture (seen anteriorly on this image).

Facts

• Normal: elbow fat pads are intracapsular but extrasynovial, they are visible anteriorly to the elbow joint but not posteriorly.
• Effusion: elevation of both anterior and posterior fat pads are seen on lateral x-ray
• In an acute injury to the elbow, elevated posterior fat pad suggests the possibility of an intracapsular fracture
• Most common causes in children are supracondylar fracture, lateral epicondyle and separation of medial epicondylar ossification center
• Most common causes in adults are radial head or neck fractures, olecranon fractures, dislocations and fracture/dislocations
• Value of the posterior fat pad sign depends on its ability to predict an occult fracture in the absence of a radiographically visible fracture
• False-negative fat pad sign may occur if there is poor radiographic positioning, extracapsular abnormality or capsular rupture
• False-positive fat pad sign can be seen when the elbow is extended

References:

1. Goswami GK. The fat pad sign. Radiology 2002;222:419-420.

2. Skaggs DL, Mirzayan R. The posterior fat pad sign in association with occult fracture of the elbow in children. J Bone J Surg 1999;81:1429-1433.