Papilledema and the Crescent Sign

 

What’s abnormal in this image?

 

Screen shot 2012 08 09 at 6.27.44 PM1 230x300 Papilledema and the Crescent Sign

Here’s a hint.  Here is an example of normal.

 

Screen shot 2012 08 09 at 6.18.41 PM1 256x300 Papilledema and the Crescent Sign

When evaluating for possible elevation in intracranial pressure, it has been shown that optic nerve sheath diameter (ONSD) measurements correlate with elevated intracranial pressures.(1,2)  The optic nerve attaches to the globe posteriorly and is wrapped in a sheath that contains cerebral spinal fluid.  The optic nerve sheath is contiguous with the dura mater and has a trabeculated arachnoid space through which cerebrospinal fluid slowly percolates.

Eye Sono 261x300 Papilledema and the Crescent Sign

ONSD Normal Ranges

Normal Adults < 5 mm
Children >1 yr < 4.5 mm
Infants < 1 yr <4 mm

 

The ONSD is measured 3 mm posterior to the globe for both eyes.  A position of 3 mm behind the globe is recommended because the ultrasound contrast is greatest.  It is best to average two measurements of each eye.  An average ONSD greater than 5 mm is considered abnormal and elevated intracranial pressure should be suspected.

 

ONSD large Papilledema and the Crescent Sign

ONSD Measurement

 

Crescent Sign

In severe cases of elevated ICP, one can see an echolucent circle within the optic nerve sheath separating the sheath from the nerve due to increased subarachnoid fluid surrounding the optic nerve.  Ophthalmologists refer to this as the crescent sign.

 crescent 2 Papilledema and the Crescent Sign

 

 The Case

40 yo female patient presents with several months of frontal headache associated with photophobia and blurry vision.  Symptoms have gotten much worse over the last few days and she has had difficulty reading and watching TV because of her visual symptoms.  She denies fevers, chills, nausea, vomiting, or focal weakness.   Pt is hypertensive 170/100.  Her vital signs are otherwise normal.

  • Visual acuity - 20/30 OD, 20/70 OS
  • CT head is normal
  • Bedside point of care ultrasound

papilledema cropped from Sinai EM Ultrasound on Vimeo.

Papilledema 2 cropped from Sinai EM Ultrasound on Vimeo.

This patient had enlarged ONSD (measurements were 6 mm bilaterally) as well as papilledema(arrow).

 

Papilledema arrow Papilledema and the Crescent Sign

Arrow notes papilledema

 

Lumbar puncture was performed.  Opening pressure was 44.  30 cc’s of CSF was drained and the closing pressure was 11.  The patient’s headache and visual symptoms improved .  She was started on acetazolamide and admitted to the neurology service.  MRI brain prior to lumbar puncture showed posterior scleral flattening bilaterally with protrusion of the optic nerve in the the globes bilaterally consistent with increased ICP.

This patient’s papilledema and increased ONSD correlated with a markedly increased opening pressure during lumbar puncture and suggests that ocular ultrasound may play a role in the ED management of patients with suspected pseudotumor cerebri.

Pseudotumor cerebri

Elevated intracranial pressure in the abscence of intracranial mass lesion.  Most common in young, over weight women. If the diagnosis is missed, persistently elevated intracranial pressure can lead to optic atrophy and blindness.

Treatment

  • Lumbar puncture to drain CSF to a normal opening pressure.
  • Medical:  Diomox (acetazolamide), high dose steroids
  • Surgical : Optic nerve sheath fenestration, VP shunt

Summary

The ability to diagnose papilledema using bedside sonography is useful to emergency physicians, as many non-ophthalmologist clinicians do not feel confident in their ability to perform an accurate nondilated fundoscopic examination. (3)  Ultrasound provides a useful alternative means of determining the presence or absence of papilledema in a patient in whom fundoscopy cannot be adequately performed.

 

 

[1] Geeraerts T, Launey Y, Martin L, et al. Ultrasonography of the optic nerve sheath may be useful for detecting raised intracranial pressure after severe brain injury. Intensive Care Med 2007;33(10):1704-11 [electronic publication 2007 Aug 1]. PMID: 17668184

 

[2] Kimberly HH, Shah S, Marill K, Noble V. Correlation of optic nerve sheath diameter with direct measurement of intracranial pressure. Acad Emerg Med 2008;15(2):201-4. PMID: 18275454

 

[3] Wu EH, Fagan MJ, Reinert SE, Diaz JA. Self-confidence in and perceived utility of the physical examination: a comparison of medical students, residents, and faculty internists. J Gen Intern Med 2007;22 (12):1725-30 [electronic publication 2007 Oct 6].  PMID: 17922165

 

Jim Tsung publishes groundbreaking pneumonia POCUS study.

Screen Shot 2012 12 11 at 6.53.54 PM 300x123 Jim Tsung publishes groundbreaking pneumonia POCUS study.It truly is the year of ultrasound — and it isn’t even 2013 yet.  Groundbreaking article on lung ultrasound by our Jim Tsung who found point of care ultrasound to be 86% sensitive and 89% specific in detecting pneumonia up to age 21.  ePub is available ahead of print in JAMA’s Archives of Pediatric and Adolescent Medicine.  Time to say goodbye to ionizing radiation!

 

 

JimTsung 300x221 Jim Tsung publishes groundbreaking pneumonia POCUS study.Prospective Evaluation of Point-of-Care Ultrasonography for the Diagnosis of Pneumonia in Children and Young Adults

Vaishali P. Shah, MD; Michael G. Tunik, MD; James W. Tsung, MD, MPH
Arch Pediatr Adolesc Med. 2012;():1-7. doi:10.1001/2013.jamapediatrics.107.

Core-Renal Ultrasound

kidney beans 300x300 Core Renal UltrasoundThis core didactic session recap is devoted to renal ultrasound. Point-of-care ultrasound uses focused clinical questions to guide management, and our didactic session use focused clinical questions to guide discussions of key literature.

Discussants Vincent Roddy and Phillip Andrus led our group through a series of questions which bring the relevance of renal sonography home.

1. Can the degree of hydronephrosis predict stone size?

In an word, yes. In a retrospective study of 177 patients with documented stones on CT scans, ultrasonographers blinded to the CT results were able to predict stone size (>5mm or <5mm) based on the degree of hydronephrosis observed (1).

Hydronephrosis was defined as mild, moderate, severe

  1. Mild: Enlargement of calices with preservation of renal papillae
  2. Moderate: Rounding of calices with obliteration of renal papillae
  3. Severe: Caliceal ballooning with cortical thinning

Results:

Increasing degree of hydro associated with increasing proportion of ureteral calculi > 5mm (p < 0.001)
Take-home points:

  • Stone size is an important predictor of stone passage and clinical outcome; < 5mm likely to pass regardless of location
  • Current guidelines recommend triage of “medical expulsion therapy” for calculi between 5 and 10 mm; > 10mm often require surgical removal
  • Ultrasound sensitivity for detection of stones greater than 5mm is poor. With severe hydro over one-third had stones over 5mm and one third of THAT group had caliculi larger than 10mm (2)

References:

  1. Goertz JK, Lotterman S. Can the degree od hydronephrosis on US predict kidney stone size? Am J Emerg Med 2010; 28:813-6.
  2. Preminger GM, Tiselius HG, Assimos DG, et al. 2007 guideline for the mgmt of ureteral calcul. J Urol 2007; 178:2418-34.

2. Should the bladder be included in the renal scan?

Yes – rapid ED renal ultrasound including images of the bladder might exclude distal obstruction and allows clinicians to focus on other diagnoses (1).

Ultrasound of the bladder also allows for the evaluation of the presence of “ureteral jets.”  Although clinically utility is debatable, a unilaterally abnormal ureteral jet can be suggestive of high-grade obstruction on the ipsilateral body side.  Ultrasound is useful in making this determination, though it is limited in its ability to determine stone location.  It is important to note that  normal ureteral jets cannot be used to exclude a diagnosis of renal colic.  (2).

References:

  1. Wakins S, Bowra J. Validation of EP Ultrasound in Diagnosing hydronephrosis in ureteric colic. Emergency Medicine Australasia (2007) 19, 188-195.
  2. Sheafor D, Hertzberg B, et al. Nonenchanced Helical CT and US in the Emergency Evaluation of Patients with Renal Colic.

 

3. Can Emergency Physicians accurately diagnosis hydroneprhosis on bedside ultrasonography?

Yes, numerous studies have documented that ultrasound can accurately predict the degree of hydronephrosis as compared to that on CT scans (1-2) and that the degree of hydronephrosis is related to stone size (3).

References:

  1. Gaspari RJ, Horst K. Emergency Ultrasound and urinalysis in the evaluation of flank pain. Acad Emer Med 2005; 12:1180-4.
  2.  Watkins S, Bowra J, Sharma P, Holdgate A, et el. Validation of EP ultrasound in diagnosing hydronephrosis in ureteric colic. Emerg Med Australas 2007; 19:188-95.
  3. Goertz JK, Lotterman S. Can the degree od hydronephrosis on US predict kidney stone size? Am J Emerg Med 2010; 28:813-6.

NYC Resuscitative Ultrasound Rounds

Ultrasound e1355006243756 NYC Resuscitative Ultrasound Rounds

Were looking forward to the first citywide critical care ultrasound meeting. The idea for this gathering grew out of discussions between ED and ICU folks interested in critical care ultrasound who wanted to share experiences, interesting cases and ongoing research that would benefit from multicenter study.

Date: January 3, 2013
Time: 5pm
Location: 3 E 101st Street, Second Floor Emergency Medicine Conference Room New York, NY

Bubble test

bubbles 300x225 Bubble testWe already know it is helpful to use ultrasound to guide placement of central venous catheters.

How can we use ultrasound to help confirm proper placement of an internal jugular catheter?

There are several methods which have been described:

  • Visualize the needle entering the vein (optimally in the long axis)
  • Visualize the guide wire in the vein
  • Visualize the tip of the triple lumen catheter in the right atrium, then pull back 2 cm
  • Bubble test (more on this below)

In addition there are non-ultrasound-related methods to confirm placement (but who cares about those?):

  • Chest x-ray
  • Blood gas drawn through central venous catheter port
  • Pressure transduction (quantitative- manometry)
  • Pressure transduction (qualitative- attach IV tubing and check height of blood column)

So let’s get back to that bubble test. In order to confirm that the catheter has been placed in the superior vena cava, inject 5-10 cc normal saline through the catheter while visualizing the right heart on a subxiphoid 4-chamber view.  When done right should look something like this :

Saline flush right heart from Sinai EM Ultrasound on Vimeo.

So this is a neat trick after the catheter is in, but the horse is out of the barn at that point. Ideally you should confirm proper venous placement prior to dilating the vessel and placing the central line. You could do this while the needle is in the vessel, but that’s a bit unstable. Instead consider using the long angiocatheter found in most central line kits to puncture the internal jugular vein.

After the flash (and ultrasound confirmation of venous puncture) advance the catheter and remove the needle. You then have an angiocatheter in the central venous system, which can be used for manometry, blood gas analysis, or the saline push necessary for the bubble test. Some people have used this angiocatheter during ACLS situations to administer a few doses of code medications in a shorter time than it would take to complete a “full” central line.

Once proper venous placement is confirmed, you can advance the guide wire through the angiocatheter and continue the procedure as normal.

For a great overview of central venous catheterization, check out this post by Haru Okuda and Scott Weingart at EMCrit.org.

Further Reading

Prekker ME, Chang R, Cole JB, Reardon R.  “Rapid confirmation of central venous catheter placement using an ultrasonographic “Bubble Test.” Acad Emerg Med 2010;17(7):e85-6. (PMID: 20653578)

Angles for Doppler

A prior post discussed the optimal imaging angle for 2D scanning.

Quick quiz: what is that angle?
45 degrees
90 degrees
180 degrees
360 degrees

In this post we’ll illustrate the optimal imaging angle for Doppler evaluation. Let’s start with basic Doppler physics.
Where to police officers situate themselves to aim a radar gun at speeding cars?

radar 500x334 Angles for Doppler

The maximal Doppler shift will be seen at 180 degrees. In fact at the instant the car passes the officer, (90 degrees) there will be zero Doppler shift. At that instant there is no movement between the object and the listener. So they aim the gun directly at the oncoming traffic, so the direction of their beam is parallel to the direction of [traffic] flow.

The image below illustrates Doppler shift of ultrasound reflected off a red blood cell:

  1. Top: A normal ultrasound wave
  2. Middle: Doppler shift reflected off the RBC moving toward the transducer (thus increasing the frequency of the returning wave)
  3. Bottom: Doppler shift reflected off the RBC moving away from the transducer (thus decreasing the frequency of the returning wave).

to away composite 500x273 Angles for Doppler

Thanks to equipmentexplained.com for the image. Imaging at 180 degrees is impractical for diagnostic ultrasound, since the optimal B-mode imaging angle is 90 degrees. Therefore, most authorities recommend an imaging angle between 45-60 degrees for Doppler ultrasound imaging . If you are imaging a vascular structure at 90 degrees and getting no Doppler signal, try lowering your angle.

Physical exam

Is ultrasound the stethoscope of the future? Is it an extension of the physical examination? Will it replace the physical exam?

No.

Point-of-care ultrasound is a diagnostic test. It is a rapid, bedside, noninvasive, accurate, diagnostic test, but still a diagnostic test. It can certainly augment data obtained through physical examination and medical interviews, and adds to information obtained by blood assays and radiology studies.

It is performed using FDA-approved medical devices by clinicians with specialized training. Images used for medical decision-making may be archived and shared with colleagues from multiple specialties. Quality assurance programs improve clinician accuracy and accountability. These are not physical examination characteristics. These are qualities of good diagnostic tests.

There is and will continue to be debate about this issue. Whether we think about point-of-care ultrasound as a diagnostic test or part of the physical examination has ramifications for training, documentation, archiving, and billing.

We recommend checking the guidelines relevant to your specialty and making up your own mind on this issue. In either camp some things remain constant: train well and use ultrasound to enhance the care you provide your patients.