Disclosures: Amos Song, MD: No financial relationships or conflicts of interest

Case Diagnosis: Deep fibular nerve neuritis secondary to a navicular-cuneiform dorsal-sided ganglion cyst

Case Description: A 45-year-old female was referred for left foot pain and numbness in the first webspace that onset gradually several months prior without any inciting trauma. Physical exam was notable for a 1-2 cm palpable mass along her dorsal midfoot region that was tender to palpation. She had no weakness in her lower extremities including the left extensor digitorum brevis. A diagnostic ultrasound was performed with a 13-5 MHz linear array transducer which demonstrated a noncompressible anechoic cystic structure measuring ~1.5 x 1.1 x 0.5 cm at the area of her dorsal navicular cuneiform joint. A slightly enlarged deep fibular nerve was identified as it coursed just superficial to the cystic structure. An ultrasound-guided left navicular-cuneiform ganglion cyst aspiration and triamcinolone steroid injection was performed for both therapeutic and diagnostic purposes.

Setting: Outpatient sports medicine clinic, tertiary academic medical centerAssessment/

Results: At four weeks post-injection, the patient reported >90% symptomatic relief in both pain and numbness of the left foot. She had mild residual numbness at the first webspace only with light touch.

Discussion: Deep fibular nerve neuritis can be characterized by pain, weakness, or atrophy of the foot, particularly over the extensor digitorum brevis muscle with paresthesia of the first webspace. The differential diagnosis for a deep fibular neuropathy can include neuropathy secondary to trauma (e.g. ankle sprains or fractures) or intrinsic causes including ganglion cysts. Our case demonstrates the utility of ultrasound as an efficient diagnostic and therapeutic tool to both diagnose and treat a ganglion cyst causing deep fibular neuropathy. While ganglion cysts causing deep fibular neuropathies can be rare, prompt diagnosis and treatment is essential for good clinical outcomes

Conclusion: Ultrasound should be considered early in a patient’s course to provide both prompt diagnosis and treatment of deep fibular neuritis secondary to a ganglion cyst.

Level of Evidence: Level V

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PM&R Meeting Abstracts - https://pmrjabstracts.org/abstract/the-use-of-ultrasound-in-diagnosis-and-treatment-of-a-navicular-cuneiform-ganglion-cyst-causing-deep-fibular-neuritis-a-case-report/