Depiction of classic ulnar sensory distribution, including ulnar-4th and 5th fingers. Note that this diagram does not portray hand muscles affected by ulnar neuropathy.
Ulnar tunnel syndrome, also known as Guyon's canal syndromeorHandlebar palsy, is ulnar neuropathy at the wrist where it passes through the ulnar tunnel (Guyon's canal).[1] The most common presentation is a palsy of the deep motor branch of the ulnar nerve causing weakness of the interosseous muscles. Ulnar tunnel syndrome is usually caused by a ganglion cyst pressing on the ulnar nerve, other causes include traumas to the wrist and repetitive movements, but often the cause is unknown (idiopathic).[2] Long distance bicycle rides are associated with transient alterations in ulnar nerve function.[3] Sensory loss in the ring and small fingers is usually due to ulnar nerve entrapment at the cubital tunnel near the elbow, which is known as cubital tunnel syndrome, although it can uncommonly be due to compression at the wrist.
Ulnar neuropathy at the wrist is often associated with a mass such as a ganglion cystorthrombosis or an aneurysm of the ulnar artery.[4] The role of activities and exposure is less certain.
Three locations (zones) in which the ulnar nerve can be compressed within Guyon canal
Ulnar tunnel syndrome may be characterized by the location or zone within the Guyon's canal at which the ulnar nerve is compressed. The nerve divides into a superficial sensory branch and a deeper motor branch in this area. Thus, Guyon's canal can be separated into three zones based on which portion of the ulnar nerve are involved. The resulting syndrome results in either muscle weakness or impaired sensation in the ulnar distribution.[1]
Location
Symptoms
Associations
Zone 1
Proximal (prior to ulnar nerve bifurcation)
Mixed motor & sensory
Ganglia & hook of hamate fractures
Zone 2
Surrounding deep motor branch ulnar nerve
Motor only
Ganglia & hook of hamate fractures
Zone 3
Surrounding superficial sensory branch of ulnar nerve
Sensory only
Ulnar artery pathology
Zone 2 type syndromes are most common, while Zone 3 are least common.
The role of gloves which help protect the ulnar nerve from compression is unclear. Palsy of the ulnar motor nerve isolated to the wrist is treated with operative decompression, often with concomitant ganglion excision. The surgery is to divide the volar carpal ligament which forms the roof of Guyon's canal, thereby reducing compression on the ulnar nerve.[5][6]
^Depukat, Paweł; Mizia, Ewa; Kuniewicz, Marcin; Bonczar, Tomasz; Mazur, Małgorzata; Pełka, Piotr; Mróz, Izabela; Lipski, Marcin; Tomaszewski, Krzysztof (2015). "Syndrome of canal of Guyon - definition, diagnosis, treatment and complication". Folia Medica Cracoviensia. 55 (1): 17–23. ISSN0015-5616. PMID26774628.
^Okutsu I, Hamanaka I, Yoshida A (April 2009). "Pre- and postoperative Guyon's canal pressure change in endoscopic carpal tunnel release: correlation with transient postoperative Guyon's canal syndrome". J Hand Surg Eur Vol. 34 (2): 208–11. doi:10.1177/1753193408100122. PMID19282410.
^Assmus H, Antoniadis G, Bischoff C, Hoffmann R, Martini AK, Preissler P, Scheglmann K, Schwerdtfeger K, Wessels KD, Wüstner-Hofmann M (May 2011). "Cubital tunnel syndrome - a review and management guidelines". Cent Eur Neurosurg. 72 (2): 90–8. doi:10.1055/s-0031-1271800. PMID21547883.
