1. Approach to the Mediastinum in Trauma:
Density vs. Width
Tammy Washut MS4

2. Traumatic Injuries to Worry About
Mediastinal hematoma
Aorta/great vessel injury
Spinal hematoma

3. Mechanism Rapid deceleration injury Blunt chest trauma- MVA, falls
The sudden stop
causes the blood
filled descending
aorta to “snap”.
The aortic arch is
fixed in position by
branches from the
arch.
Mechanism
Rapid deceleration injury
Blunt chest trauma- MVA, falls
Sudden
deceleration
as sternum
hits steering
wheel.
As the aortic tube
“snaps”, the intima
is torn just distal
to left sub-
clavian artery.

4. External signs
“Seat belt sign”
Chest ecchymosis
Sternal/Rib fractures

5. Chest X-ray Classically taught to look for widened mediastinum
Wide mediastinum = 8 cm
What is the problem with this???
Wide mediastinum has a broader differential than paratracheal density

6. Causes of Wide Mediastinum
Magnification
Rotation
Mediastinal hematoma
Spinal hematoma
Lymphadenopathy
Long intravascular volume
Obese patients

7. Magnification

8. Magnification Film placed directly behind the patient
Initially used to determine the 8 cm criteria for wide mediastinum

9. Magnification
Film placed under the backboard
17% enlargement

10. Magnification
Film placed in trauma bed
25% enlargement

11. Rotation 4 cm 7 cm Rotated Right Rotated Left
For example, when the patient is rotated to the right, the mediastinum is artificially widened by laterally displacing the SVC and aorta. When rotated to the left, the mediastinum is artifically narrrowed by overlapping the SVC and aorta.
Rotated Right
Rotated Left

12. Intravascular Volume 7 cm 4 cm Pre-Dialysis Post-Dialysis
Intravascular volume status can also affect the width of the mediastinum as shown in this dialysis patient pre and post dialysis
Pre-Dialysis
Post-Dialysis

13. Lymphadenopathy
Lymphadenopathy can widen the mediastinum as demonstrated in this patient with sarcoidosis

14. Right Paratracheal Density
Composed of azygous vein and SVC
Density normally less than aortic arch
Increased = hematoma
Why?
Not affected by technical factors
Simple
Right paratracheal region composed of the azygos vein and SVC
--Right paratracheal region should be less dense than the aortic arch
--As density of right paratracheal region equals or exceeds that of the aortic arch – increased suspicion for mediastinal hematoma
--This sign is different than the previously published signs as…Density is not affected as much by technical factors and we felt it was a simple and reproducible sign

15. Right Paratracheal Density
This example demonstrates what the right paratracheal region looks like in a patient with a normal PT density and in a patient with increased PT density and proven mediastinal hematoma…
Normal
Increased Density

16. Mediastinal Hematoma Other Signs: PT stripe Apical cap Aortic Arch
NG deviation
Tracheal deviation
--Additional signs that have been utilized for detection of mediastinal hematoma include…all of which are present in this patient…

17. Mediastinal Hematoma Other Signs: PT stripe Apical cap Aortic Arch
NG deviation
Tracheal deviation

18. Mediastinal Hematoma Other Signs: PT stripe Apical cap Aortic Arch
NG deviation
Tracheal deviation

19. Mediastinal Hematoma Other Signs: PT stripe Apical cap Aortic Arch
NG deviation
Tracheal deviation

20. Mediastinal Hematoma Other Signs: PT stripe Apical cap Aortic Arch
NG deviation
Tracheal deviation

21. OHSU DATA
Hypothesis:
Right paratracheal density is discriminatory sign in trauma patients with widened mediastinum
So, our hypothesis was that the R PT density is a discriminatory sign for the presence of mediastinal hematoma in trauma patients with widened mediastinum…

22. Methods 122 Trauma patients (2001-2003)
Screening Trauma chest radiograph
Mediastinal width > 8.0 cm
CT Chest w/contrast within 24 hours
Four readers of different levels of training
R paratracheal region evaluated
We evaluated 122 trauma patients presenting to OHSU ED from 2001 to 2003 whom underwent screening chest radiograph, found to have a mediastinal width > 8.0 cm and whom underwent CT chest within 24 hours of presentation…
--Four readers of different training levels evaluated the R PT density as being normal or increased (defined as equal or greater than density of aortic arch)

23. Methods Patients categorized by ISS AIS by body region Chest: 1-6
Low risk: 0-2 (80 patients)
High risk: >2 (42 patients)
Patients were divided into low and high risk categories based on their Chest ISS

24. Results 19 mediastinal hematomas (15.6%) 5 aortic injuries (4.1%)
13 high-risk
6 low-risk
5 aortic injuries (4.1%)
4 deceased (3.3%)
There were…

25. Results

26. Results

27. Results

28. Results
Interestingly, the mediastinal width was greater in those without hematoma than those with, again demonstrating the inconsistency of this commonly used sign…

29. Results
The overall average of all 4 readers seen herre demonstrates very high sensitivity, NPV, and quite high specificity in the low-risk population

30. Results
Compared to the other commonly used signs for detecting mediastinal hematoma, the sensitivity of the R PT density sign is significantly better
Sensitivity

31. Limitations Single institution
Presented to readers in artificial setting
Relatively few hematomas
AIS/ISS scoring not useful as triage tool

32. Strengths Trauma patients with widened mediastinum
Confirmed by CT w/in 24 hours
Blinded analysis
Clinical information available on all patients

33. Conclusions
Screening chest radiograph valuable in low/moderate risk trauma patients
Right paratracheal density valuable
Avoid CT in low-risk patients
7.3% normal mediastinum
High risk patients should have CT
--It is important to remember, however, that many high risk chest trauma patients will have a normal mediastinum on chest radiograph and therefore, high risk patients should have CT regardless of the chest radiograph findings

34. Recommendations
Low risk patients with or without a wide mediastinum but no paratracheal density do not need to have CT of the chest
High risk patients with mechanism of injury (i.e. seatbelt sign) should go to CT regardless
Paratracheal density, not width, should direct further management

35. Examples

36. Possible Hematoma? Yes- aortic rupture
Paratracheal density on right and loss of aortic arch definition

37. Possible Hematoma?
Yes, but in this case it is lymphadenopathy in a high risk trauma patient
This patient should get a chest CT

38. Possible Hematoma?
No- mediastinum is wide, but no paratracheal density
Patient is rotated to right

39. Examples

40. Examples

41. Examples

42. References Melton SM et al., J Trauma 2004; 56:243-250
Mirvis SE et al., Radiology 1987; 13:
Baker SP et al., J Trauma 1974; 14:
Woodring JH et al., Radiology 1984; 151:15-21
Parmley LF et al., Circulation 1953; 17:
Woodring JH et al., J Emerg Med 1990; 8:
Woodring D et al., Ann Thor Surg 1984; 37:
Blackmore CC et al., Emerg Radiology 2000; 7:
Patel NH et al., Radiology 1998; 209:
Milne EN et al., Radiology 1984; 153:25-31
Demetriades D et al., Arch Surg 1998; 133:
O’Connor CE et al., Emerg Med J 2004; 21:
Special thanks to Dr. Marc Gosselin and Dr Peter Verhey for references,
images and study data and slides.