Did You Know? POCUS Can Help Detect Increased Intracranial Pressure

Case Presentation

A 42-year-old female presents to her primary care provider with complaints of persistent headaches for the past two weeks. She describes the headaches as intermittent, worsening in the morning, and occasionally associated with transient blurry vision. She has a history of similar headaches over the past year, prompting an emergency department (ED) visit five months ago, where a CT scan of the head was unremarkable. She is overweight but has no other significant medical history.

Her vital signs are normal. On examination, her neurological exam is non-focal. However, fundoscopic examination is challenging due to poor visualization of the retina and optic disc. Her visual acuity is 20/20 in both eyes. Given concern for idiopathic intracranial hypertension (IIH), her provider decides to perform ocular point-of-care ultrasound (POCUS) to assess the optic nerve sheath diameter (ONSD), which correlates with intracranial pressure (ICP) (Figure 1). 

What do you see and what is the diagnosis?

The optic nerve sheath, which distends in response to increased ICP, was measured at 6.0 mm—a finding consistent with elevated intracranial pressure.

Ocular POCUS Findings in IIH

1. Increased optic nerve sheath diameter:

Ocular POCUS can be an invaluable tool in evaluating headaches, particularly when increased ICP is a concern. In this case, the provider performed a bilateral ONSD measurement 3 mm posterior to the globe. 

An ONSD measurement of greater than 5.0 mm (some sources suggest a cutoff of 5.5 mm) correlates with increased ICP, supporting the diagnosis of IIH or another cause of increased pressure [1-3]. Figure 2 below shows a normal ocular ultrasound with ONSD measurements under 5mm. The optic nerve sheath is normally oval in shape, with a clearly defined border and no bulging or excessive distention. A normal ONSD on POCUS strongly suggests that the patient does not have clinically significant intracranial hypertension at that moment. Figure 3 shows annotated anatomy of the eye on ultrasound. 

2. Papilledema:

In some cases, papilledema can be visualized on ultrasound. A classic POCUS finding is the “crescent sign,” which appears as a hypoechoic (dark) crescent-shaped area at the posterior aspect of the optic nerve head, representing optic disc elevation due to increased intracranial pressure. [4] However, papilledema without an increased ONSD is not indicative of elevated ICP and may be due to other conditions such as optic neuritis, hypertensive retinopathy, or other retinal pathologies. 

Ocular POCUS to Detect Other Pathology

Ocular POCUS could also help diagnose the following conditions:

• vitreous hemorrhage
• retinal detachment
• lens dislocation
• posterior vitreous detachment
• intraocular foreign bodies. 

These conditions can be identified based on characteristic ultrasound findings, aiding in the rapid diagnosis and management of ocular complaints in a primary care setting.

Evidence 

• Studies have demonstrated a strong correlation between ONSD measurements and invasive ICP monitoring, making ocular POCUS a non-invasive alternative for screening.
• Using ONSD cut-offs between 5.0 and 5.7 mm, studies have found sensitivities of 90% and above for detecting ICP >20 mmHg. [1-3]
• In addition, ocular POCUS is relatively easy to learn. Novice users can perform ONSD measurements accurately after a 4-hour session. [5]

Case Resolution

Recognizing the abnormal ONSD measurement, the provider refers the patient for urgent ophthalmologic and neurology evaluations. A subsequent lumbar puncture confirms elevated opening pressure, consistent with idiopathic intracranial hypertension. The patient is started on acetazolamide, advised on weight management, and scheduled for close follow-up.

Impact of POCUS

In this case, ocular POCUS enabled a rapid, bedside assessment of suspected elevated intracranial pressure, guiding appropriate next steps. Without this tool, the provider may have had to rely solely on clinical suspicion, potentially delaying diagnosis and management, or sending the patient to the ED unnecessarily. 

POCUS benefits in headache evaluation include:

• Rapid, bedside assessment of ONSD to detect increased ICP.
• Non-invasive screening tool to help determine urgency for further imaging or lumbar puncture.
• Avoidance of unnecessary CT scans in recurrent headache patients without red flag symptoms.
• Potential for detecting papilledema when the direct fundoscopic exam is limited.

Conclusion

Point-of-care ultrasound (POCUS) is a valuable addition to the primary care provider's toolkit for evaluating headaches. In cases where idiopathic intracranial hypertension or increased ICP is suspected, ocular POCUS provides a fast, reliable method to assess ONSD and guide the next steps. With minimal training, providers can improve diagnostic accuracy, reduce unnecessary imaging, and expedite appropriate care.

References

1. Koziarz A, Sne N, Kegel F, et al. Point-of-care ultrasound for intracranial hypertension: A systematic review and meta-analysis. Neurology. 2019;92(7):e664-e675.
2. Kimberly HH, Shah S, Marill K, Noble V. Correlation of optic nerve sheath diameter with direct measurement of intracranial pressure. Academic Emergency Medicine. 2008;15(2):201-204.
3. Rajajee V, Vanaman M, Fletcher JJ, Jacobs TL. Optic nerve ultrasound for the detection of raised intracranial pressure. Neurocritical Care. 2011;15(3):506-515.
4. Bhosale A, Shah VM, Shah PK. Accuracy of crescent sign on ocular ultrasound in diagnosing papilledema. World J Methodol. 2017 Sep 26;7(3):108-111. 
5. Potgieter DW, Kippin A, Ngu, F, McKean C. Can Accurate Ultrasonographic Measurement of the Optic Nerve Sheath Diameter (a Non-Invasive Measure of Intracranial Pressure) be Taught to Novice Operators in a Single Training Session? Anaesthesia and Intensive Care 2011 39:1, 95-100

About the Author

Dr. Havryliuk is an emergency physician with over 15 years of clinical point-of-care ultrasound (POCUS) experience, a past Emergency Ultrasound Director at Brooklyn Hospital in NY, and the founder of Hello Sono. She is on a mission to empower clinicians with POCUS to take better and more efficient care of their patients by addressing two key barriers, lack of competency and infrastructure. 

LinkedIn: https://www.linkedin.com/in/tatiana-havryliuk-md/
Email: tatiana@hellosono.com

*POCUS images and graphics provided courtesy of Hello Sono.