Working Diagnosis:
Volar ganglion cyst with compression of the superficial and deep ulnar nerve branches.

Treatment:
An ultrasound-guided needle aspiration of the cyst yielded 0.5 cc of gelatinous material. Cyst fenestration was also performed followed by the application of a compression dressing and wrist splint. Case Photo #4 Case Photo #5

Outcome:
The patient's pain resolved within 48 hours. Sensation and grip strength improved within 1 month. A repeat ultrasound revealed no cyst recurrence. He returned to playing badminton without return of symptoms. Case Photo #6

Author's Comments:
The ulnar nerve is most commonly compressed at the elbow in the cubital tunnel. Compression can also occur in the hand at Guyon's Canal, where it can be classified as one of the following three types:
1) Proximal to or within the canal, causing weakness and numbness.
2) Isolated compression of the deep branch at the distal canal, causing weakness without numbness.
3) Isolated compression of the superficial branch at the canal exit, causing numbness without weakness.

In this case, we present a rare case of a volar ganglion cyst causing both type 2 and type 3 compression of the ulnar nerve, diagnosed with point-of-care ultrasound and treated with ultrasound-guided aspiration. This case highlights the value of point-of-care diagnostic ultrasound and ultrasound guidance for procedural treatment of this condition.

Editor's Comments:
Ganglion cysts are common, especially in the wrist, and can be variably symptomatic depending on their size and location. They are often easily diagnosed on point-of-care ultrasound. Ganglion cysts are frequently self-limited but can be painful or exert a mass effect on local structures, as in this case. Aspiration yields characteristic viscous, gelatinous fluid and may assist with resolution.

In this case, the mass effect caused compression in Guyon's canal, yielding an ulnar neuropathy that developed insidiously over two months. A similar neuropathy can develop following an acute fracture of the hook of the hamate. A classic mechanism of injury for a hook of the hamate fracture is grounding of a golf club during a swing, causing direct forceful impact of the handle of the club into the hypothenar eminence.

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