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USMLE® Step 1 Question of the Day: Fundoscopy findings

Osmosis Team
Nov 22, 2023

This week, we are sharing another USMLE® Step 1-style practice question to test your knowledge of medical topics. Today's case focuses on a 66-year-old man with altered mental status, headache, and more. Can you identify the fundoscopy finding that affects a diagnostic lumbar puncture? Test your diagnostic skills with this USMLE Step 1 question.

A 66-year-old man is brought to the emergency department by his partner to evaluate his altered mental status. The patient’s partner states that he said he had a headache and blurry vision earlier that morning with associated nausea and vomiting. He tried taking acetaminophen with minimal relief. His past medical history includes hypertension and a 35 pack-year smoking history. His temperature is 38.5°C (101.3°F), pulse is 102/min, and blood pressure is 158/98 mmHg. There is spontaneous flexion of the hips with passive flexion of the neck. Which of the following findings on fundoscopy contraindicates the performance of a diagnostic lumbar puncture?

A. Edematous optic disc with blurred margins

B. Enlarged optic cup with an increased cup/disc ratio

C. Extensive retinal hemorrhage and venous engorgement

D. Retinal neovascularization

E. Crinkling of retinal tissue 

Scroll down for the correct answer!

The correct answer to today's USMLE® Step 1 Question is...

A. Edematous optic disc with blurred margins

Before we get to the Main Explanation, let's look at the incorrect answer explanations. Skip to the bottom if you want to see the correct answer right away!

Incorrect answer explanations

B. Enlarged optic cup with an increased cup/disc ratio

Incorrect: This finding suggests open-angle glaucoma, which typically presents as progressive peripheral vision loss with findings of an enlarged optic cup with an increased cup/disc ratio (“cupping” of the optic disc) on fundoscopy. 

C. Extensive retinal hemorrhage and venous engorgement

Incorrect: This fundoscopic finding is often observed in patients with retinal vein occlusion. Patients typically present with sudden onset, painless, monocular vision loss.

D. Retinal neovascularization

Incorrect: Formation of new blood vessels (neovascularization) is often seen in the advanced stages of diabetic retinopathy. This finding occurs secondary to retinal ischemia and subsequent upregulation of pro-angiogenic cytokines, namely, vascular endothelial growth factor (VEGF). Neovascularization is not a contraindication to the performance of a lumbar puncture.

E. Crinkling of retinal tissue 

Incorrect: Retinal detachment typically presents as flashes or floaters followed by sudden, painless visual field loss in the affected eye. Vision loss typically begins in the periphery and progresses toward loss of the central visual axis over hours to weeks. A fundoscopic examination may demonstrate wrinkling/crinkling of retinal tissue or changes in blood vessel direction. These fundoscopic findings do not suggest papilledema and hence do not contraindicate the performance of a lumbar puncture.

Main Explanation

This patient presents with fever, altered mental status, and a positive Brudzinski sign--concerning meningitis. Unless contraindicated, every patient with suspected meningitis should undergo lumbar puncture (LP). Suppose a lumbar puncture is performed in the setting of increased intracranial pressure (ICP). In that case,  a cerebral herniation may ensue due to the rapid change in intracavitary pressure as cerebrospinal fluid is removed for analysis. Any diagnostic physical exam findings that suggest elevated ICP (e.g., papilledema) prohibit the performance of this procedure. 

Papilledema refers to swelling of the optic disc and has multiple etiologies. Meningitis may cause elevated ICP via obstructive hydrocephalus or impaired cerebrospinal fluid absorption due to  inflammation at the level of arachnoid granulations. Fundoscopic findings of papilledema demonstrate an enlarged blind spot and an elevated, edematous disc, with blurred disc margins and engorged blood vessels.

 

table of the causes of papilledema

Major Takeaway

Papilledema refers to swelling of the optic disc. Fundoscopic examination typically shows an elevated, edematous disc, with blurred disc margins and engorged blood vessels.

References

Chen, J. J., & Bhatti, M. T. (2019). Papilledema. International Ophthalmology Clinics, 59(3), 3–22. doi:10.1097/iio.0000000000000274

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The United States Medical Licensing Examination (USMLE®) is a joint program of the Federation of State Medical Boards (FSMB®) and National Board of Medical Examiners (NBME®). Osmosis is not affiliated with NBME nor FSMB.