1539 - Left Pisiform Enthesophyte Causing Ulnar Neuropathy at Guyon’s Canal

Thursday, February 19, 2026

5:00 PM - 6:30 PM AST

Presenting Author(s)

DR

Dawn A. Rice, DO

Resident Physican
The Wright Center for GME
Scranton, Pennsylvania, United States

Co-Author(s)

CC

Colleen Crawford, DO

Resident Physician
The Wright Center
Scranton, Pennsylvania, United States
LB

Lucian Bednarz, MD

Attending Physician
Northeastern Rehabilitation Associates
Scranton, Pennsylvania, United States

Submitter(s)

DR

Dawn A. Rice, DO

The Wright Center for GME
Scranton, Pennsylvania, United States

Case Diagnosis: Left ulnar neuropathy at Guyon’s canal involving the deep motor branch

Case Description: A 74-year-old right-hand dominant female presented with several months of left wrist pain in the ulnar distribution described as achy and burning, worsened by lifting and grasping. She denied weakness or numbness. No prior evaluations had been completed. Electrodiagnostic testing demonstrated fibrillations and positive sharp waves in the first dorsal interosseous and abductor digiti minimi, with sparing of the flexor carpi ulnaris. Distal motor latency of the left abductor digiti minimi was prolonged with reduced amplitudes, while conduction velocities were preserved. Bilateral ulnar sensory responses of the fifth digit, median sensory, and radial sensory responses were normal. These findings of severe chronic ulnar neuropathy at the wrist sparing sensory fibers are consistent with a deep palmar motor lesion. Ultrasound revealed an irregular enthesophyte at the palmar aspect of the pisiform bone, representing the likely site of compression.

Discussions: Ulnar neuropathy is second only to carpal tunnel as the most frequent entrapment neuropathy of the upper extremity, usually occurring at the elbow due to its superficial course. This case involves a rarer site at Guyon’s canal, secondary to an irregular pisiform enthesophyte. It is important to distinguish an ulnar neuropathy from a C8 radiculopathy, as presenting symptoms can be similar. In this patient, electrodiagnostic studies demonstrated a Type II pattern of ulnar neuropathy at the wrist, with ADM latency prolongation correlating to a proximal deep palmar motor lesion affecting ulnar-innervated hand muscles while sparing the superficial sensory branch. This emphasizes how electrodiagnostic testing not only localizes the precise site of entrapment but also guides management when surgery is considered.

Conclusions:
This case highlights a rare entrapment mononeuropathy often missed without NCS/EMG. Physiatrists should consider distal ulnar neuropathy in patients with isolated hand or wrist pain, even without weakness or sensory loss.