Image Interpretation: Evidence of a hypoechoic structure consistent with a ganglion cyst near cubital tunnel causing visible enlargement of ulnar nerve proximally.

Teaching Pearl: While electrodiagnostic studies (EMG/NCS) can confirm and localize ulnar neuropathy, POCUS is uniquely suited for exploring space-occupying lesions and providing real-time, dynamic anatomical assessments (Saran et al., 2025). As demonstrated in this case, ultrasound successfully identifies the cyst mechanically compressing the nerve, shifting the clinical diagnosis from an idiopathic entrapment to a definitive structural etiology (Li et al., 2018). Before any planned aspiration near a neurovascular bundle, evaluating an anechoic structure with Color Doppler is a critical safety step. Doppler ultrasound is necessary to definitively exclude vascular etiologies, such as aneurysms, by confirming the complete absence of internal blood flow within the mass (Saran et al., 2025). True ganglion cysts will consistently demonstrate an absence of Doppler flow (Norbury & Nazarian, 2019). Ultrasound-guided aspiration of a ganglion cyst offers a minimally invasive approach to deflate the mass, relieve the mechanical constriction on the ulnar nerve, and facilitate clinical recovery (Li et al., 2018). Due to lack of time at the visit, this patient was referred patient to my partner, who performed ultrasound-guided aspiration of the ganglion cyst visualized at the distal cubital tunnel. No corticosteroid injection was performed. It has been 1 year since aspiration of cyst was performed, and to date, patient has not had any further complaints of tingling/numbness in his 4th and 5th digits. Li, P., Lou, D., & Lu, H. (2018). The cubital tunnel syndrome caused by intraneural ganglion cyst of the ulnar nerve at the elbow: a case report. BMC Neurology, 18. https://doi.org/10.1186/s12883-018-1229-7 Norbury, J. W., & Nazarian, L. N. (2019). Ultrasound‐guided treatment of peripheral entrapment mononeuropathies. Muscle & Nerve, 60, 222-231. https://doi.org/10.1002/mus.26517 Saran, S., Reddy, P. S., Shirodkar, K., et al. (2025). Unveiling Guyon’s Canal: Insights into Clinical Anatomy, Pathology, and Imaging. Diagnostics, 15, 592. https://doi.org/10.3390/diagnostics15050592