Ultrasound

Idiopathic Intracranial Hypertension

THE CASE

A 22 year-old female with a medical history of migraines and obesity who presents to the Emergency Department with a headache. Her headache was gradual in onset, but has progressively worsened and has not been relieved with NSAIDs. She describes the headache as dull and pounding with photophobia and phonophobia. She also notes associated nausea but no vomiting, and no associated neurologic complaints. She does note that she thinks during a previous ED visit at an outside hospital she was told she may have “high pressure in her head” but she does not remember the details and is not on any medication for it. A bedside ocular ultrasound was performed and the following images were obtained:

Figure 1. Transverse view of right eye

Figure 1. Transverse view of right eye

Figure 2. Transverse view of left eye

Figure 2. Transverse view of left eye

DIAGNOSIS

An LP was performed and the opening pressure was mildly elevated at 33 cm H2O that decreased to 18 cm H2O with removal of 20 cc of fluid. The remainder of labs and imaging were normal. The patient was diagnosed with Idiopathic Intracranial Hypertension and started on Diamox with outpatient neurology and ophthalmology follow-up. On follow-up she reports resolution of headaches.

DISCUSSION

The ultrasound images were obtained using the 7.5 MHz high frequency linear probe. The ophthalmic setting was used given its lower thermal index, thus decreasing the risk of injury to the eye from heat exposure. For patient comfort, a non-adhesive sterile dressing was placed over eye prior to application of a copious amount of ultrasound gel. The ultrasound probe was placed lightly over the gel in a transverse orientation with probe marker to the patient’s right and with careful attention not to exert pressure on the globe. The probe was angled superiorly and inferiorly slowly until the optic nerve came into view as a black stripe extending posteriorly from the rear of the globe. The nerve sheath diameter was then measured 3 mm posterior to the optic disc. For a more accurate value, an average of 2-3 measurements can be taken.

The relationship between intracranial pressure and optic nerve sheath diameter has been well established. In general, an optic nerve sheath diameter of >5.0 mm is considered abnormal, however there remains some controversy about the exact diameter of the optic nerve sheath that best predicts elevated intracranial pressure. For example, one prospective blinded observational study by Kimberly et al. in 2008 found that an optic nerve sheath diameter >5.0 mm correlated with an elevated intracranial pressure with a sensitivity of 100% and a specificity of 63%. Another 2013 study by Amini et al measured the optic nerve sheath diameter of 50 atraumatic patients undergoing lumbar puncture and found that an optic nerve sheath diameter greater then 5.5 mm correlated with an elevated ICP (>30 mm Hg) with a sensitivity and specificity of 100%. Finally, a third study by Qayyum found a sensitivity of 100% and specificity of 75% for a cutoff of 5.0 mm.

In general, measurement of optic nerve sheath diameter appears to be a useful adjunct for detection of elevated intracranial pressure due to the fact that it is non-invasive, easily performed at bedside, and has good sensitivity for detecting increased intracranial pressure. Though a normal optic nerve sheath diameter does not exclude a life-threatening intracranial process, an elevated optic nerve sheath diameter can further support a diagnosis of elevated intracranial pressure when in the right clinical context.

Faculty Reviewer: Dr. Kristin Dwyer

Additional resources

  1. Blaivas, M. , Theodoro, D. and Sierzenski, P. R. (2003), Elevated Intracranial Pressure Detected by Bedside Emergency Ultrasonography of the Optic Nerve Sheath. Academic Emergency Medicine, 10: 376-381.

  2. Dubourg J, Javouhey E, Geeraerts T, Messerer M, Kassai B. Ultrasonography of optic nerve sheath diameter for detection of raised intracranial pressure: a systematic review and meta-analysis. Intensive Care Med. 2011 Jul;37(7):1059-68.

  3. Irazuzta JE, Brown ME, Akhtar J. Bedside Optic Nerve Sheath Diameter Assessment in the Identification of Increased Intracranial Pressure in Suspected Idiopathic Intracranial Hypertension. Pediatr Neurol. 2015 Aug 28.

  4. Qayyum H, Ramlakhan S. Can ocular ultrasound predict intracranial hypertension? A pilot diagnostic accuracy evaluation in a UK emergency department. Eur J Emerg Med. 2013;20(2):91–97.

  5. Shevlin C. Optic Nerve Sheath Ultrasound for the Bedside Diagnosis of Intracranial Hypertension: Pitfalls and Potential. Critical Care Horizons 2015; 1: 22-30.

  6. Tayal VS, Neulander M, Norton HJ, et al. Emergency department sonographic measurement of optic nerve sheath diameter to detect findings of increased intracranial pressure in adult head injury patients. Ann Emerg Med. 2007 Apr;49(4):508-514.

Take My Breath Away

Case Presentation

A 31 year old female with no significant PMH presents to the Emergency Department with left-sided chest pain that started suddenly 3 hours ago while sitting in a lecture hall.  She describes the pain as a constant stabbing sensation in her left anterior chest that radiates to her left neck.  She endorses feeling short of breath and lightheaded.  She has never had a sensation like this before.  The patient denies smoking, fevers, chills, and trauma.  Her vital signs are unremarkable, and her physical exam is notable for decreased breath sounds in the left upper lung field. 

 

Ultrasound Exam

Left Anterior.jpg


The above images are of the left anterior chest and were acquired using the linear probe.  The curvilinear probe may also be used for lung ultrasound.

Diagnosis:  Left spontaneous pneumothorax (PTX)

 

What do we see in these images?

In the video, we see a pleural line that is static without the classic “sliding.”  In an ultrasound of a healthy normal lung, we should see a to-and-fro movement or shimmering of the pleural line. This has often been described as ants on a log. In the case of pneumothorax, however, there is air between the visceral and parietal pleura that prevents visualizing of the visceral pleura and inhibits lung sliding. 

In the still image of M-mode, we see a pattern of horizontal lines above and below the pleura.  This pattern is referred to “barcode” sign, and is indicative of a lack of movement.

 

Is U/S good at detecting pneumothorax?

Sensitivity Specificity
U/S 78.6 98.4
CXR 39.8 99.3


Ultrasound is both a quick and reliable tool for the diagnosis of pneumothorax.  In fact, ultrasound is more accurate than chest radiography at detecting PTX in the supine patient.

 

Faculty Reviewer: Dr. Kristin Dwyer 

References:

  1. Alrajab S, Youssef AM, Akkus NI, Caldito G. Pleural ultrasonography versus chest radiography for the diagnosis of pneumothorax: review of the literature and meta-analysis. Critical Care. 2013;17(5):R208. doi:10.1186/cc13016.

  2. Husain LF, Hagopian L, Wayman D, Baker WE, Carmody KA. Sonographic diagnosis of pneumothorax. Journal of Emergencies, Trauma, and Shock. 2012;5(1):76-81. doi:10.4103/0974-2700.93116.

A Bowel Inside a Bowel: Intussusception

The Case

A 14 month-old female with no significant PMH who presented to the Emergency Department with vomiting. Per mom, patient was well yesterday, but today has been refusing food, crying and vomiting. Patient has had no known sick contacts and her vaccinations are up to date. A review of systems was performed and was otherwise negative.

Physical Exam

Vital signs were within normal limits. Patient was listless with decreased responsiveness, but not in distress. No evidence of respiratory compromise. Abdominal exam was unremarkable, with no focal tenderness and no guarding, rigidity or rebound. During the time the examiner was present in the room, the patient had one episode of crying inconsolably and then vomiting.

An abdominal ultrasound was performed and the diagnosis was revealed to be Intussusception

Ultrasound

Ultrasound has been shown to be 97.9% sensitive and 97.8% specific for diagnosing ileocolic intussusception. To evaluate for intussusception, start with the high frequency low penetration linear transducer. In most young children this transducer will provide adequate depth. In an older child, you may have to use the higher penetration curvilinear transducer. If available, use warm gel to minimize patient discomfort and thereby increasing your changes of obtaining clear images. Begin in the transverse plane and slide your probe up to the right upper quadrant, across, and then down the left side, interrogating for the intussusception (Figure 1).

Figure 1: Suggested path of the ultrasound transducer to evaluate for intussusception.  (https://www.acep.org/how-we-serve/sections/emergency-ultrasound/news/september-2018/pediatric-emergency-ultrasound-deep-dive-on-pocus-for-intussusception/)

Figure 1: Suggested path of the ultrasound transducer to evaluate for intussusception.

(https://www.acep.org/how-we-serve/sections/emergency-ultrasound/news/september-2018/pediatric-emergency-ultrasound-deep-dive-on-pocus-for-intussusception/)

Most of the intussusceptions will be found on the right hand side, and are described as a “target sign” when you are viewing the intestinal intussusception in transverse or the “sandwich sign” in long axis.  The “lawn-mower” approach can be used, similar to the approach for SBO, and graded compression along your path can help move bowel gas out of the way to better evaluate the intestine. The hyperechoic rings are the mucosa and muscularis and the hypoechoic portion is the submucosa.  

Case Discussion

Intussusception is the most common abdominal emergency in early childhood, with the majority of cases occurring in patients <2 years of age. It occurs when the bowel telescopes in on itself and gets stuck. The peristaltic waves of the bowel causes waves of pain in the patient. The classic triad is described as pain, vomiting and bloody stools. Ultrasonography is the preferred diagnostic modality to evaluate for intussusception, given the high sensitivity and specificity (97.9% and 97.8% respectively) when performed by a skilled clinician. Ultrasound also has a high negative predictive value (approaching 99.7%) and can rule out intussusception in a majority of patients. Intussusception presents on ultrasound as a peripheral hypoechoic ring surrounding a central echogenic focus described as either a "target sign” or a “doughnut sign.” (Figure 2a) The visualized doughnut represents the layers of the intestinal wall that have invaginated into themselves. Color doppler can be applied to evaluate for tissue ischemia. (Figure 2b) The most common type of intussusception, ileocolic (as in this case) is usually found in the right lower quadrant. There is usually associated focal tenderness in the right lower quadrant (though this patient was non-tender). Treatment of a non-perforated intussusception typically consists of reduction via air enema, but sometimes operative management is indicated.

Figure 2: Ultrasound image of intussusception

Figure 2: Ultrasound image of intussusception