Assistant Professor Touro University Concord, California, United States
Case Diagnosis: Guyon Tunnel Syndrome
Case Description: A 63-year-old female presented for a 2-month follow-up for a right-hand injury following a dog bite. Physical exam revealed intact sensation to light touch, except at the volar tip of the right 4th and 5th digits, and normal RUE strength. Radiographs of her right wrist revealed “mild disuse osteopenia and an incompletely healed oblique fracture of the distal ulnar metaphysis with new bone formation and aligned fracture fragments”. Electrodiagnostic studies at the wrist showed 4.5 ms latency for motor and 4.0 ms for sensory right ulnar nerves, with a sensory CV of 30 m/s. The right dorsal ulnar cutaneous nerve showed no abnormalities. Needle EMG findings revealed increased amplitude in the right FDI and ADM. Additionally, the right median sensory nerve showed a latency of 4.0 ms and CV of 35 m/s.
Discussions: Guyon Canal syndrome is a rare form of ulnar neuropathy at the wrist that is commonly caused by ganglion cysts, fractures, or repetitive wrist trauma. In this patient’s case, however, the condition is associated with an incompletely healed distal ulnar fracture following traumatic injury, making her presentation especially rare. The patient’s paresthesia of the 4th and 5th digits, without motor deficits, are consistent with zone 3 Guyon Canal Syndrome. Electrodiagnostic studies correlate with this diagnosis, showing prolonged latency and reduced CV in the ulnar sensory nerve, indicating ulnar sensory neuropathy. Additionally, needle EMG findings of neurogenic changes in the right FDI and ADM, coupled with normal results in the right dorsal ulnar cutaneous nerve, further localize this neuropathy to the wrist. Continued monitoring with additional imaging and electrodiagnostic studies may clarify the mechanism of injury, track nerve recovery, and guide future management.
Conclusions: This is a unique case of Guyon Tunnel Syndrome developing after a traumatic wrist injury following a dog bite.
