ONSD and Idiopathic Intracranial Hypertension

27F no PMH presenting with a nontraumatic headache and with normal vitals

1. What are the normal values for the ONSD?

Measured from the inner-edge to inner-edge, 3 mm posterior to the retina, for the upper limit of normal of the ONSD is:
– up to 4 mm in infants
– up to 4.5 mm in children
– up to 5 mm in adults
Measurements above 5 mm (bilaterally) classically correspond with elevations in intracranial pressure above 20 mmHg


2. What is visualized in picture B?

Crescent Sign – The separation of the optic nerve sheath from the nerve due to increased subarachnoid fluid
Nipple Sign – Protrusion of the ONSD into the vitreous chamber, >0.6 mm correlates with papilledema
Differentiation between acute and chronic elevations in ICP may be aided by the crescent sign, the sonographic correlate of papilledema

Correlation signs of papilledema

3. What is the significance of the ONSD:ETD Ratio?

While taking multiple measurements and averaging them is useful for accuracy, studies have shown upper limit ONSD ranges from 4.8 to 6.2mm.
There has been increasing evidence that the ONSD:ETD Ratio is more accurate.
One study in patients with TBI was able to predict intracranial hypertension with a threshold ratio value of 0.25 with a sensitivity of 90% and a specificity of 82.3%.


In our patient’s case, the ONSD:ETD Ratio is 0.318. Confirmatory LP was performed and found to be elevated confirming her diagnosis of Idiopathic Intracranial Hypertension.


We are bringing back Image of the Week! However we renamed it the Sono of the Century. We hope you enjoy!

38 y/o F p/w sublingual pain and swelling
The sublingual space was evaluated with the endocavitary transducer

Purulence was expressed

Q) What is the treatment for acute suppurative sialadenitis?
A) Antibiotics (e.g. clindamycin, amoxicillin/clavulanic acid), salivary massage, hydration, sialogogues (e.g. lemon drops, sour lozenges).

IOTW 5/03/21

27 y/o F p/w right flank pain

  1. What is the finding labeled “A”?
    • These adjacent hyperechoic structures with shadowing are representative of intrarenal calculi. CT demonstrated that this was actually a partial staghorn calculus.
  2. How would you describe the structure labeled “B” in sonographic terms? What do you think this is?
    • This is a hypoechoic complex round mass with posterior acoustic enhancement containing internal debris consistent with perinephric abscess.
  3. How would you grade the hydronephrosis on image “C”?
    • Notice that the dilated calyces are beginning to form the “bear paw” sign. This suggests that this is at least high-grade mild hydronephrosis.

IOTW 3/02/21

64 y/o M p/w dyspnea

  1. What are labels A and B referring to?
    • These are clots in transit. They are occasionally seen in the setting of pulmonary embolism (4-18% of cases). In this case they were visualized traversing the tricuspid valve from right atrium to right ventricle.
  2. How does this finding affect prognosis?
    • This is a poor prognostic factor. The mortality of patients with PE without RV thrombus ranges between 11-16% whereas the presence of clot in transit raises mortality to at least 44%.
  3. Name 2 other signs of RV strain seen in the images above.
    • Dilated RV. Note the RV:LV ratio even in this parasternal short axis view is >1:1.
    • Interventricular septal dependence. In the parasternal short axis view, this is also called the “D sign” where the left ventricle forms the shape of the letter “D” due to elevated right ventricle pressures combined with lower left ventricle pressures due to the obstructive physiology proximal to the pulmonary arteries.
  4. What are some treatment options available other than anticoagulation or systemic thrombolysis?
    • Although more research is needed in regards to treatments such as endovascular therapy, options include: catheter-directed thrombolysis, surgical embolectomy, mechanical thrombectomy, suction thrombectomy, and IVC filter.
  5. How would you dose alteplase in the setting of massive pulmonary embolism? What about in the setting of cardiac arrest?
    • Numerous dosing regimens have been implemented. The most common method is Alteplase 100 mg (full dose) or 50 mg (half dose) IV administered over 2 hours. In cardiac arrest, you can give Alteplase 50 mg IV administered over 60 seconds. It is recommended to continue CPR for at least another 15 minutes if not longer (some guidelines suggest 30-60 minutes) to allow thrombolysis time to work. Be sure to familiarize yourself with the thrombolytic contraindications.