PMC6920165_01
(A) FDML: Flexor Digiti Minimi Longus; PB: Palmaris Brevis; PL: Palmaris Longus; PCL: Palmar Carpal Ligament; FCU: Flexor Carpi Ulnaris; FCR: Flexor Carpi Radialis; FDS: Flexor Digitorum Superficialis; (B) FDMB: Flexor Digiti Minimi Brevis and ADM: Abductor Digiti Minimi muscles are visualized. PCL and PB are reflected to visualize the FDML muscle belly passing through Guyon's canal.
gr1.jpg
PMC6920165_01_gr1.jpg
fig0005
The muscle belly passed through Guyon's canal (Fig. 1A). The tendon of this muscle was traced to its insertion (Fig. 1B). The tendon of the anomalous muscle shared an insertion with the ADM and the FDMB (Fig. 1B).
(A) FDML: Flexor Digiti Minimi Longus is reflected out of Guyon's canal; PB: Palmaris Brevis (reflected); UA: Ulnar Artery; UN: Ulnar Nerve; (B) The tortuous SPA: Superficial Palmar Arch and CPDA: Common Palmar Digital Arteries are visible.
gr2.jpg
PMC6920165_01_gr2.jpg
fig0010
Deep to the FDML, the ulnar artery, superficial palmar arch and common digital arteries were all unusually tortuous (Fig. 2A and B) but with a normal pattern.
(A) FDML: Flexor Digiti Minimi Longus (reflected); FDMB: Flexor Digiti Minimi Brevis; MN: Median Nerve; UA: Ulnar Artery; UN: Ulnar Nerve; SUN: Superficial branch of the Ulnar Nerve; DUN: Dorsal branch of the Ulnar Nerve; Black Arrow: Aberrant branch of the dorsal branch of the ulnar nerve; Black Arrowheads: branches of the aberrant branch of the dorsal branch of the ulnar nerve on palmar surface of hand and anastomosing with the SUN; White Arrowhead: branch of the superficial ulnar nerve innervating FDMB; (B) White Arrows: Connection between SUN and MN, Red dashed lines: hourglass constriction of the MN.
gr3.jpg
PMC6920165_01_gr3.jpg
fig0015
Proximal to Guyon's canal, before the dorsal branch of the ulnar nerve became cutaneous to the dorsal surface of the hand, it gave off an aberrant branch which then divided into two branches (Fig. 3A). Branches of the superficial ulnar nerve (which is often considered a cutaneous nerve except its branch to the palmaris brevis muscle) were seen innervating the FDMB (Fig. 3A). The median nerve had narrowing within the carpal tunnel and widening again distally, indicating the possibility of carpal tunnel syndrome (Fig. 3B). Two aberrant anastomosis between the common palmar digital branches of the median and superficial ulnar nerves were also identified (Berretini anastomosis) (Fig. 3B).
(A) SUN: Superficial branch of the Ulnar Nerve; MN: Median Nerve; RMN: Recurrent branch of the Median Nerve; APB: Abductor Pollicis Brevis; White Arrowhead: Belly of first lumbrical originating from the epineurium of the median nerve; (B) Red Arrowhead: Belly of first lumbrical originating from the flexor tendon sheaths; (C) Black Arrowhead: Belly of first lumbrical originating from the FDP: Flexor Digitorum Profundus tendon.
gr4.jpg
PMC6920165_01_gr4.jpg
fig0020
One aberrant belly originated from the epineurium of the median nerve (Fig. 4A). Another aberrant belly originated from the flexor tendon sheath within the carpal tunnel (Fig. 4B). The third/normal belly originated from the radial side of the flexor digitorum profundus tendon deep to the other two heads (Fig. 4C). All muscle bellies fused distally and inserted into the extensor expansion (Fig. 4C).