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Age / Sex : 54 / F
Chief complaint : Numbness and tingling sensation in left hand
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Two weeks later, you can see the final diagnosis with a brief discussion of this case. (Please submit only one answer)
Courtesy : Joon-Yong Jun, Seoul St. Mary's
Hospital, The Catholic University of Korea
Diagnosis: Guyon’s canal (Ulnar tunnel) syndrome caused by ganglion cyst
Discussion
Findings: There is a multilocular cystic lesion with thin
enhancing wall at the ulnar side of the hamate hook, which extends distally
deep into the carpal tunnel. Denervation myopathy presented with diffuse
increased muscle signal and fatty infiltration involves dorsal and volar interosseous,
and lumbricalis muscles of 3rd to 4th web spaces.
Differential Diagnosis:
Diagnosis:
Guyon’s
canal (Ulnar tunnel) syndrome caused by ganglion cyst
Discussion:
Guyon’s
canal (ulnar tunnel) is a fibro-osseous tunnel which houses the ulnar nerve,
artery, and veins. It located just medial and superficial to the carpal tunnel.
The pisiform bone forms the medial boundary at proximal and the hook of the
hamate forms the lateral boundary. The palmar carpal ligament forms the roof of
the canal, while transverse carpal ligament, pisohamate and pisometacarpal
ligament, and opponens digiti minimi forms the floor. The ulnar nerve branches
off the sensory branch running in proximity to the ulnar artery, and the motor
branch, which courses more deeply, adjacent to the medial surface of the hamate
hook. Entrapment neuropathy at Guyon's canal can develop due to extrinsic
compression (e.g., bicycle handle bars) and intrinsic space-occupying lesions
such as ganglion, lipoma, ulnar artery aneurysm, and accessory abductor digiti
minimi). The site of compression may be classified into three zones: zone 1
(proximal ulnar nerve before bifurcation), zone 2 (deep motor nerve), zone 3
(superficial sensory nerve).
MRI findings
of ulnar neuropathy include enlarged fascicles, and abnormally increased T2
signal intensity of the ulnar nerve although these findings are not visible in
the present case. Denervation myopathy of innervating muscles are, as shown in
this case, presented with diffuse increased signal on fluid-sensitive
sequences, fatty infiltration, and atrophy of the hypothenar muscles, 3rd/4th
lumbricals, and interossei muscles.
References:
1. Andreisek G, Crook DW, Burg
D, Marincek B, Weishaupt D. Peripheral neuropathies of the median, radial, and
ulnar nerves: MR imaging features. Radiographics. 2006;26:1267–87
2. Kim S, Choi J, Huh Y, et
al. Role of magnetic resonance imaging in entrapment and compressive
neuropathy—what, where, and how to see the peripheral nerves on the
musculoskeletal magnetic resonance image: part 2. Upper extremity. Eur Radiol.
2007;17:509–22
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