VOTW: Idiopathic Intracranial Hypertension

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Hi all,

This week’s VOTW was a case from several months ago brought to you by future ultrasound fellow Dr. Jennie Xu!

A 23 year old female w/ hx of migraines was referred to the ED by an ophthalmologist for 4 weeks of intractable headache and three days of vomiting and vision changes. The patient was told she had a "pinched nerve in her eye". She was seen in another ED 1 week ago with a normal head CT. She had no focal deficits on exam. An ocular POCUS was performed which showed…

Clip 1 shows a fan thru of a normal appearing globe. Posterior to the eye, an edematous optic nerve sheath is seen. The optic nerve sheath diameter (ONSD) measured 0.65cm on the right and 0.68cm on the left. The optic disc also appears to be elevated. This is concerning for sonographic papilledema.

Given the concern for intracranial hypertension, a lumbar puncture was performed with an opening pressure > 50mmHg (the CSF actually spouted over the top of the measuring column like a water fountain ⛲).

Optic nerve sheath diameter (ONSD)

The optic nerve sheath communicates directly with the intracranial space. For the few of us that are not great at the fundoscopic exam, measuring the ONSD might be an easier alternative to evaluate for papilledema (but see test characteristics below).

How to:

  1. Use a linear probe

  2. Use a lot of gel over a closed eye lid

  3. Find the hypoechoic optic nerve and the more echogenic nerve sheath surrounding the nerve

  4. Measure the entire sheath from outer edge to outer edge at a depth of 3mm posterior to the globe (see image above)

Measurements

< 5mm is normal

5 – 6mm is a grey zone

>6mm is abnormal

Evidence

These cutoffs have a sensitivity 88-100%, specificity 63-95% for papilledema (1). The problem is many patients end up in the 'grey zone'.

*A normal ONSD does not necessarily indicate normal intracranial pressure (ICP). A dilated ONSD might also be normal for that patient, so correlate clinically!

 **ONSD unfortunately can't be used to estimate a specific ICP.

So the next time you find yourself wanting to do a fundoscopic exam, whip out your probe instead! (or use the new retinal camera in fast track...)

Back to the patient

Neurology was consulted, the patient was started on acetazolamide, and admitted to medicine. Interestingly, her CSF VZV PCR was positive so she was diagnosed with VZV meningitis. She was started on antivirals and did well overall. Her vision problems and headaches improved.

References:

  1. Shevlin, C. (2015). Optic nerve sheath ultrasound for the bedside diagnosis of intracranial hypertension: pitfalls and potential. Critical Care Horizons, 1(1), 22-30.

  2. Farkas, J. (2017). PulmCrit: Algorithm for diagnosing ICP elevation with ocular sonography. (https://emcrit.org/pulmcrit/pulmcrit-algorithm-diagnosing-icp-elevation-ocular-sonography/)

This is my last post as your ultrasound education fellow 😢. If you've read this far, I appreciate you! Thanks Dr. Danta for coming up with most of my titles ha ha ha... Dr. Ariella Cohen will take us thru the home stretch!! 🙌

VOTW: Twinkle Artifact

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This week's VOTW is brought to you by Dr. Sanghvi and the UST!

An 80 year old male w/ hx of CVA, non-verbal, PEG dependence, hx urosepsis presented from a nursing home w/ hypotension and “rule out sepsis”. Given the broad differential, the UST performed multiple scans including aorta, echo, chest, FAST, renal and bladder. The left kidney showed hydronephrosis and a POCUS of the bladder was performed which showed...

Clip 1 shows a transverse view of the bladder w/ color doppler placed over the L ureterovesicular (UVJ) junction demonstrating “twinkle artifact” 🌟. This indicates the presence of a stone!

The stone can also be seen without color doppler in clip 2 as a hyperechoic structure with posterior acoustic shadowing. It is associated with upstream hydroureter which can be seen as the clip fans thru. The rectum posteriorly is also distended and filled w/ stool.

Twinkle Artifact

Twinkle artifact

While we often only find indirect signs for ureteral stones on POCUS (hydronephrosis/hydroureter), you might sometimes be able to find the culprit stone on your bladder views. They are easy to miss since the bladder wall is also echogenic, especially if the stone is small. This is where twinkle artifact can be useful!!

When color doppler is used over a rough, hyperechoic, irregular object like a stone, the ultrasound waves get reflected internally within the stone, tricking the machine into thinking that there is movement, resulting in the stone being highlighted by a rainbow doppler signal. Sometimes it will have a rainbow tail extending away from the probe.

The presence of twinkle artifact has a high positive predictive value for the presence of kidney stone (1) and is more sensitive for detection of small stones than is acoustic shadowing (2).

Back to the patient

A CTAP showed three obstructing L ureteral stones, largest being 9mm. Urology was consulted and patient underwent L ureteral stent placement with findings of “pus behind left ureteral stone”. The patient was admitted to the MICU for septic shock.

References

  1. Dillman J, Kappil M, Weadock W et al. Sonographic Twinkling Artifact for Renal Calculus Detection: Correlation with CT. Radiology. 2011;259(3):911-6. doi:10.1148/radiol.11102128 

  2. Hosn S, Rutten C, Murphy A, et al. Twinkling artifact. Reference article, Radiopaedia.org (Accessed on 20 Feb 2024) https://doi.org/10.53347/rID-21828

VOTW: Interstitial Ectopic Pregnancy

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This week’s VOTW is brought to you by… none other than our fantastic ED Medical Director Dr. Nubaha Elahi and Dr. Waters!

A 44 year old female G5P3 w/ hx of Essure procedure (a 99.3% effective method of contraception) presented to the ED with bilateral eye swelling x1 week. She also had a positive home pregnancy test and vaginal spotting. Without being mislead by the initial chief complaint on a busy fast-track shift the team performed a POCUS of the pelvis which showed...

Clip 1 shows a transabdominal view of the uterus with an empty gestational sac and a thick walled complex R adnexal cyst/mass. In the setting of a bHCG of 37000, this is concerning for an ectopic pregnancy!

Clip 2 shows a transvaginal view of the uterus with an eccentrically located gestational sac containing a fetal pole. Given the concern for interstitial ectopic, the team measured the endomyometrial mantle thickness (nice!) which was 1cm (still within normal range, however approaching the 8mm cutoff).

**The Essure procedure involved inserting metal coils in bilateral fallopian tubes to cause scarring. In 2018 it was taken off of the market because it was associated with many complications including ecotpic pregnancies. 

Endomyometrial mantle thickness measurement

Interstitial ectopic

An interstitial ectopic is a pregnancy implanted in the myometrium. It carries a higher rate of shock and hemoperitoneum and higher maternal mortality compared to the other ectopic pregnancies due to the highly vascular myometrium (1)

Think about interstitial ectopic pregnancy if you see an eccentrically placed gestational sac and measure the EMM.

Endomyometrial mantle (EMM) measurement

  • EMM = thickness of the endometrium + myometrium

  • Measure from outer edge of the gestational sac to outer edge of the uterus at the THINNEST portion that you see (image 1)

  • EMM <8mm is concerning for an interstitial ectopic pregnancy

Back to the patient

OBGYN was consulted who admitted the patient for a laparoscopic hysterectomy. The final diagnosis was right interstitial ectopic pregnancy!

We’ve reviewed many ectopic pregnancy cases caught on POCUS recently- an example of a diagnosis where POCUS truly is saving lives! Keep up the great work!

References:

  1. Rastogi R, Gl M, Rastogi N, Rastogi V. Interstitial ectopic pregnancy: A rare and difficult clinicosonographic diagnosis. J Hum Reprod Sci. 2008 Jul;1(2):81-2. doi: 10.4103/0974-1208.44116. PMID: 19562051; PMCID: PMC2700669.