[Entrapment of the ulnar nerve at the Guyon's canal]

The ulnar nerve runs at the level of the ulnar carpus through Guyon's canal. Due to the proximity to very rigid ligamentous and bony structures, space-occupying processes or fractures can easily cause compression of the ulnar nerve and its two distal branches. Pathologies of the adjacent ulnar artery can also irritate the nerve.

After cubital tunnel syndrome, this is the second most common compression syndrome of the ulnar nerve. Overall, compression at Guyon´s canal is a very rare condition, which is considered challenging due to its variability of symptoms. Since the ulnar nerve divides within Guyon's canal into its two end branches, the superficial branch and the deep branch, the clinical manifestation of nerve compression can present with mixed sensorimotor, purely sensory, or purely motor deficits.

The most common causes of compression neuropathy include ganglion cysts, aberrant muscles, fractures, or vascular anomalies within Guyon's canal. Therefore, in addition to an thorough clinical examination, the preoperative workout should also include appropriate imaging modalities (X-ray, MRI, CT, or ultrasound) as well as a neurological and electrophysiological evaluation.

Surgical exploration and decompression of the nerve at all potential sites of compression is indicated if symptoms persist or if sensorimotor deficits have existed for a longer time, in order to prevent irreversible late sequelae.