Ulnar tunnel syndrome

Ulnar tunnel syndrome
Other names	Guyon's canal syndrome
	Cartoon depiction of classic ulnar sensory distribution, including mid-4th and 5th fingers. Note that this diagram does not portray hand muscles affected by ulnar neuropathy.
Specialty	Orthopedic surgery

Ulnar tunnel syndrome, also known as Guyon's canal syndrome or Handlebar palsy, is caused by entrapment of the ulnar nerve in the Guyon canal as it passes through the wrist.^[1] Symptoms usually begin with a feeling of pins and needles in the ring and little fingers before progressing to a loss of sensation and/or impaired motor function of the intrinsic muscles of the hand which are innervated by the ulnar nerve. Ulnar tunnel syndrome is commonly seen in regular cyclists due to prolonged pressure of the Guyon's canal against bicycle handlebars. Another very common cause of sensory loss in the ring and pink finger is due to ulnar nerve entrapment at the cubital tunnel near the elbow, which is known as cubital tunnel syndrome.

Causes

While being idiopathic in some cases, causative factors of the ulnar tunnel syndrome include tumors, ganglion cysts, repetitive use, anatomical variations, and diseases of the neighboring blood vessels (thrombosis or aneurysm of the ulnar artery).^[2]

Diagnosis

Classification

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 hammate fractures
Zone 2	Surrounding deep motor branch ulnar nerve	Motor only	Ganglia & hook of hammate 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.

Treatment

Initial line of treatment is with anti-inflammatory drugs or cortisone injections. There have been trials with gloves which help protect the ulnar nerve from compression. The most radical treatment option is surgery to relieve tension in the volar carpal ligament which forms the roof of Guyon's canal, thereby reducing compression on the ulnar nerve.^[3]^[4]

References

^ ^a ^b Hatch, Daniel (August 20, 2014). "Ulnar Tunnel Syndrome". Orthobullets. Retrieved Sep 7, 2014.
^ 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. ISSN 0015-5616. PMID 26774628.
^ 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. PMID 19282410.
^ 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. PMID 21547883.