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

Arachnoid Cyst

Axial T1W MR image shows a large T1 hypointense extra axial lesion in the left parietal region (arrow). 

Coronal T2GRE and T2W images demonstrate homogeneous T2 hyperintensity of the mass that follows CSF signal. There is compression of the adjacent gyri.  

Facts: Arachnoid Cyst

• Congenital lesion arising during development from splitting of arachnoid membrane
• Contains fluid usually identical to CSF
• Do not communicate with ventricles or subarachnoid space
• Lined with meningothelial cells 
• Incidence: 5 in 1,000 autopsies. 1% of intracranial masses
• Predominant male
• Mostly asymptomatic

Imaging:

• Extraaxial cystic mass with pressure effect to underlying brain
• Signal intensity follows CSF in all sequences
• No restricted diffusion
• Most common location (from highest to lowest frequency: Sylvian fissure (almost 50%), cerebellopontine angle, supracollicular, vermin, sella/suprasella

Reference:

Greenberg MS. Handbook of Neurosurgery, 7th edition. 2010

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