Guyon's canal entrapment occurs when the ulnar nerve is compressed as it passes through the pisohamate tunnel at the wrist, commonly seen in long distance cyclists who lean on handlebars. Symptoms can include pure motor, pure sensory, or mixed deficits depending on the location of entrapment. The most common cause is a ganglion from the triquetrohamate joint, while other rare causes include a fractured hook of hamate bone or ulnar artery aneurysm from hammer use.

2. Guyon’s canal
 Entrapment of ulner nerve in the pisohamate tunnel.
 Often seen in long distance cyclists, who lean with the
pisiform pressing on handle bars

3. Compression
 Ulner nerve can be compressed as it passes through
Guyon’s canal at the ulner border of wrist

4. Symptoms
 Symptoms can be
 Pure motor
 Pure sensory
 Or mixed
Depending on precise location of entrapment

5. Causes
 A ganglion from the triquetrohamate joint is the most
common cause
 Fractured hook of hamate and ulner artery aneurysm
(over use of hammer) but is rare

6.  Preservation of sensation in the dorsal branch of the
ulner nerve suggest entrapment at the wrist rather
than elbow, thus power to flexsor carpi ulnaris and
flexsor digitorum profundus to the little finger will be
maintained.