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JC: Pneumomediastinum + Coronal Axis Measurement of ONSD

This weeks readings:

Saracino, C. and Tessaro M., Pneumomediastinum as a Sonographic Mimic of Pneumothorax. J Ultrasound Med 2015; 34:1515–1522 

Questions to Consider:

  1. Would you feel comfortable discharging a stable pneumomediastinum patient home after ultrasound diagnosis? What about if the clinical exam alone suggested pneumomediastinum?
  2. What patients would this exam be difficult on?
  3. What other body parts might show sonographic evidence of pneumomediastinum?
  4. What scenarios can mimic pneumomediastinum on x-ray? It’s kind of a trick question….

Amini et al—Coronal Axis Measurement of the Optic Nerve Sheath Diameter. Ultrasound Med 2015; 34:1607–1612 

Questions to Consider:

  1. What is the "cylinder tangent effect" as it pertains to ultrasound? Discuss how the visual axis approach and the infraorbital approach differ in their ability to ensure the cylinder of the optic nerve is in plane with the ultrasound beam.
  2. In this healthy volunteer study, the infraorbital approach produced measurements in agreement with the visual axis approach. Do you think this would also be true in patients with increased ONSD?
  3. What issues could arise in EM clinical practice regarding the head and eye positioning described for the infraorbital approach?
  4. What problem could exist in using the infraorbital technique serially (eg to assess response to therapy, or worsening ICP from baseline)?