This 44-year-old female presents with right wrist pain. You are shown five images. A coronal proton density (image 1), a coronal proton density fat suppression (image 2), two sagittal proton density fat suppression (images 3 and 4), and an axial or short-axis proton density (image 5). A hyperintense mass around the ulna is obvious.
Q1 – With regard to the pink arrows in images 1 and 2, what do you think the significance is?
Q2 – What is your differential diagnosis for a septated cystic mass of the wrist?
Q3 – What are masses that are associated with a “tail sign”?
Q4 – What is the most common location for ganglion pseudocyst in the wrist? How about the second most common?
A1 – The pink arrows (images 1 and 2; 6 and 7) demonstrate a tail extending back to the joint capsule and subsheath portion of the extensor carpi ulnaris.
A2 – (a) ganglion pseudocyst, (b) epidermoid, (c) myxoma, (d) capsular cyst, (e) pisotriquetral bursal cyst, or (f) capsulosynovial cyst associated with inflammatory arthritis (such as rheumatoid).
A3 – (a) ganglion with a tail to either the capsule or sheath of a tendon, (b) neural tumor with a tail to a nerve, (c) aneurysm or pseudoaneurysm with a tail to a vessel, or (d) capsular or synovial cyst with a tail to a joint.
A4 – The most common is along the dorsal scapholunate interval near the dorsal limb of the scapholunate ligament (SL) and the radial limb of the intercarpal ligament. Sometimes these project at the junction of the scaphoid and base of the capitate dorsally.
The second most common location is along the palmar aspect of the wrist near the volar SL ligament and capsule near the base of the radioscaphocapitate extrinsic or the base of the radial lunatotriquetral ligament extrinsic.
In other words, a ganglion in this location is extremely atypical. Its intimacy with the extensor carpi ulnaris is problematic as it relates to dynamic motion (i.e. can restrict).
The blue arrow on image 8 also corroborates the dorsal tail of a ganglion pseudocyst, and the yellow arrow on image 9 shows the septated mass, sagittally.
In image 10, the green arrow shows the mass’s close proximity to the extensor carpi ulnaris (image 10, purple arrow), displacing it medially.
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