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COPYRIGHT 2025 © BY THE ARCHIVES OF BONE AND JOINT SURGERY
Corresponding Author: Lilah Fones, Rothman Orthopaedic
Institute, Sidney Kimmel Medical College, Thomas Jefferson
University Hospital, Philadelphia, PA, USA
Email: lilah.fones@rothmanortho.com
Arch Bone Jt Surg. 2025;1(2):119-124 Doi: 10.22038/ABJS.2024.80728.3684 http://abjs.mums.ac.ir
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CASE REPORT
Dorsal Interosseous Muscle Weakness
from Mid-palm Ganglion Cyst
Lilah Fones, MD; Mitchell K. Freedman, DO; Pedro K. Beredjiklian, MD; Gregory G. Gallant, MD, MBA
Research performed at Rothman Orthopedic Institute, Sidney Kimmel Medical College,
Thomas Jefferson University Hospital, Philadelphia, PA, USA
Received: 24 June 2024 Accepted: 5 August 2024
Abstract
Ulnar nerve compression is commonly seen at the elbow at the cubital tunnel and the wrist at the Guyon
canal but is rarely seen in the hand. This case report describes an 18 -year-old male presenting with
seven months of atraumatic hand weakness and atrophy associated with heavy weightlifting. Exam
demonstrated isolated interosseous muscle atrophy mostly sparing the abductor digiti minimi with intact
sensation and negative nerve c ompression tests including Tinel at carpal and ulnar tunnels, Froment
sign, Wartenberg test, cross finger test, and Spurling test. Electromyography and nerve conduction
studies demonstrated prolonged distal latency, low amplitude potential, and large amplitude fibrillations
with severely reduced motor unit firing in the first dorsal interosseous muscle consistent with ulnar
nerve deep motor branch compromise. Magnetic resonance imaging revealed a ganglion cyst between
the third metacarpal shaft and the flexor profundus tendon. Given the progressi ve symptoms, ganglion
cyst excision and ulnar motor nerve branch neurolysis were performed.
Level of evidence: V
Keywords: Ganglion cyst, Interosseous muscle atrophy, Nerve compression, Neuropathy, Ulnar nerve
Introduction
Ulnar nerve compression most commonly occurs
at the elbow at the cubital tunnel but also occurs at
the wrist within the Guyon canal.1,2 The Guyon canal
is the area at the base of the hypothenar eminence from the
palmar carpal ligament to the fibrous arch of the
hypothenar muscle at the level of the hook of the hamate.
As the ulnar nerve travels within the Guyon canal it
bifurcates into the superficial branch and deep motor
branch. The superficial branch innervates the palmaris
brevis muscle and provides sensation to hypothenar
eminence, small finger, and ulnar ring finger. The deep
motor branch exits the Guyon canal by coursing around the
hook of the hamate and turning radially through the
pisohamate hiatus to innervate the hypothenar muscles,
the medial two lumbricals, the pollicis, and the
interosseous muscles.1 The location of compression along
the ulnar nerve dictates symptoms and three zones of
compression at Guyon canal have been described. Zone I is
before ulnar bifurcation causing mixed motor and sensory
symptoms. Zone II is motor branch compression distal to
the bifurcation causing isolated motor symptoms. Zone III
is superficial ulnar nerve distal to the bifurcation resulting
in isolated sensory loss.1,3,4 Masses in the hand can also
present within and around the Guyon canal as palpable
painful masses without causing neurologic symptoms.5,6
More distal ulnar nerve compression within the hand is
exceedingly rare. This case report shows a unique
presentation of a large mid-palmar ganglion cyst
compressing the distal motor branch of the ulnar nerve in
a young, active patient.
Written informed consent was obtained from the patient
for publication of this case report and accompanying
images.
Case Presentation
An 18-year-old right-hand-dominant male presented with
seven months of atraumatic right hand pain, weakness, and
atrophy associated with heavy weightlifting. Pain and
weakness worsened with weightlifting and improved after a
period of limited weightlifting. He had no pertinent medical
U
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history. The patient was a high school student active in
playing lacrosse, football, and weightlifting.
A physical exam showed thumb-index intermetacarpal
muscle wasting. There were no palpable masses in the wrist
or hand. Strength testing demonstrated 3 out of 5 strength
to the first dorsal interosseous muscle and 5- out of 5
strength to the abductor digiti minimi. The remaining
muscles tested showed 5 out of 5 strength, including the
ulnar flexor digitorum profundi. Sensation was intact in the
ulnar, radial, and median nerve distributions. Reflexes and
pulses were normal. Special tests were all negative,
including Tinel at the carpal and ulnar tunnels, Froment sign,
Wartenberg test, cross finger test, Spurling test, and
Lhermitte sign.
Nerve conduction velocity studies (NCS) revealed a
prolonged distal latency to the first dorsal interosseous with
a low amplitude potential response which did not increase
with midpalmar stimulation. Distal latency to the abductor
digiti minimi and sensory distal latency to the fifth finger
were both normal. Conduction velocity distal to and across
the elbow was normal with the recording electrode over the
abductor digiti minimi and first dorsal interosseous.
Electromyography (EMG) demonstrated large amplitude
fibrillations with severely reduced motor unit firing in the
first dorsal interosseous muscle, as well as a very mild
decrease in recruitment and polyphasiciity in the abductor
digiti minimi [Figure 1, Tables 1-3]. These findings were
consistent with the ulnar nerve mid-palm lesion with
significant subacute axonopathy affecting the first dorsal
interosseous muscle but sparing the ulnar sensory nerve
and most of the motor nerve to the abductor digiti minimi.
Abductor pollicis brevis, pronator teres, flexor digitorum
profundus, biceps and triceps muscles, and median nerve
were all normal.
Figure 1. Electromyography (EMG) and nerve conduciton studies (NCS) results demonstrating first dorsal interosseous muscle large
amplitude fibrillations with severely reduced motor unit firing and mild decrease in recruitment of the abductor digiti minimi
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Table 1.Electromyography
Muscle
Nerve
Roots
Spontaneous
Motor Unit Actio n Potentials
Recruitment
Pattern
Insertion
Activity
Fibrillation
Positive Sharp
Waves
Fasciculation
Amplitude
Duration
Polyphasic
potentials
Table 2. Sensory Nerve Conduction
Nerve/Site
Onset Latency
(ms)
Peak Latency
(ms)
Amplitude
(µV)
Distance
(cm)
Peak Difference
(ms)
Velocity
(m/s)
-
-
-
-
-
-
Table 3. Motor Nerve Conduction
Nerve
Muscle
Site
Latency (ms)
Amplitude (mV)
Duration (ms)
Relative
Amplitude
(%)
Segments
Distance (cm)
Latency
Difference
(ms)
Velocity (m/s)
Right Median
Abductor pollic is brevis (APB)
Wrist
Elbow
Right Ulnar
Abductor Digiti M inimi (ADM)
Wrist
Below Elbow
Above Elbow
Axilla
First Dorsal Int erosseou s (FDI)
Wrist
Below Elbow
Above Elbow
Midpalm
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Table 3. Continued
Left Ulnar
Abductor Digiti M inimi (ADM)
Wrist
Below Elbow
Above Elbow
First Dorsal Int erosseou s (FDI)
Wrist
Below Elbow
Above Elbow
Hand magnetic resonance imaging (MRI) MRI
demonstrated a T2-hyperintense 1.1cm x 1.2cm x 1.4cm
mass between the third metacarpal and flexor digitorum
profundus tendon of the third ray consistent with a ganglion
cyst [Figure 2]. Increased T2-hyperintense signal was also
noted within the third dorsal interosseous muscle, and to a
lesser degree in the flexor pollicis brevis muscle, consistent
with denervation edema.
Figure 2. Right hand magnetic resonance imaging (MRI), including (A) axial, (B) coronal, and (C) sagittal T2-weight images, demonstrating T2-
hyperintense 1.1cm x 1.2cm x 1.4cm mass between the third metacarpal and flexor digitorum profundus tendon. Also noted, increased T2-
hyperintense signal within the third dorsal interosseous muscle, and to a lesser degree, in the flexor pollicis brevis muscle
Given the exam, EMG/NCS, and MRI findings, ganglion cyst
excision and ulnar nerve neurolysis were indicated. Under
general anesthesia, a volar incision was made over the third
metacarpal shaft. The median nerve branches and flexor
tendons were identified, protected, and retracted to reveal
the underlying ganglion cyst superficial to the third
metacarpal shaft compressing the motor branch of the ulnar
nerve. The gelatinous cyst and stalk were excised [Figure 3a]
to decompress the ulnar motor nerve [Figure 3b] along with
the ulnar motor nerve external neurolysis.
In the immediate postoperative period, the patient
experienced paresthesias in the ulnar nerve distribution of
the volar hand. By 1.5 months postoperatively, all
paresthesias had resolved and he reported a subjective
improvement in his preoperative weakness and pain. The
exam demonstrated full hand range of motion, ability to
cross his digits, and sensation intact throughout the ulnar
nerve distribution. At that time, he was cleared to return to
all activities and was eager to return to a home-
strengthening program.
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Figure 3. Intraoperative photos demonstrating (A) mid-palmar ganglion cyst (red arrow) compressing the motor branch of the ulnar nerve
and (B) decompressed motor branch of the ulnar nerve (blue arrow) following ganglion cyst excision
Discussion
While ulnar nerve compression at the elbow and wrist are
well described, this case report demonstrates ulnar nerve
compression distal to the Guyon canal within the hand. Ulnar
nerve compression at the elbow usually presents with ulnar
dysesthesia, pain, and paresthesias in the ulnar nerve
distribution, small and ring finger clawing, and ulnar intrinsic
muscle weakness.7 Ulnar nerve compression at the wrist can
present as mixed motor and sensory, isolated motor, or
isolated sensory symptoms, sparing the dorsal hand,
depending on the zone of compression as described by Shea
and McClain in 1969.1,4 Ulnar nerve compression distal to
Guyon canal in the hand can also present with hand intrinsic
muscle atrophy and weakness, but spares sensation in the
ulnar nerve distribution. Furthermore, the specific location
of compression along the course of the ulnar nerve dictates
which ulnar intrinsic muscles are involved. This was
summarized by Wu et al who proposed an expansion of Shea
pure motor neuropathies caused by isolated compression of
the motor branch of the ulnar nerve can be further
subdivided into three categories, Wu type III, IV, and V. Type
III is compression is after the ulnar nerve bifurcation into
motor and sensory branches, but proximal to the motor
innervation of the hypothenars. Type IV is distal to
innervation to hypothenars and Type V is just proximal to the
branches to the first dorsal interosseus and adductor pollicis
muscles.4,8 In this case, the ganglion cyst primarily
compressed the ulnar motor nerve distal to the innervation
of the abductor digiti minimi, but proximal to the innervation
of the first dorsal interosseous muscles which would most
closely be described as a Wu Type V lesion.
Ganglion cysts are a well-documented cause of compression
within the Guyon canal and have been shown to cause
isolated ulnar motor nerve compression within the Guyon
canal when arising from the piso-triquetral and triquetral-
hamate joints.1,9,10 In contrast, there are very limited reports
of ganglion cysts distal to the Guyon canal in the hand and no
prior reports of a ganglion between the third metacarpal
shaft and flexor digitorum profundus tendon to the third
metacarpal. Two prior case reports have documented nearby
ganglia with variance in patient presentation. A case report
of a ganglion cyst between the third and fourth metacarpal
base showed ulnar motor nerve compression resulting in
atrophy and weakness of the adductor pollicis and first
dorsal interosseous muscle with a positive Froment sign.11
Another case report demonstrated a ganglion cyst at the
third carpometacarpal joint which resulted in isolated
interosseous muscle atrophy, a positive Froment sign, and
adductor pollicis weakness on exam.12 Alternative
compressive pathologies in the hand causing isolated ulnar
motor branch compression in case reports include
pigmented villonodular synovitis,13 leash of vessels,14 fibrous
bands,1416 leash of vessels,14 and subperiosteal
compression.17
Conclusion
This case demonstrates a unique presentation of a large
mid-palmar ganglion cyst between the third metacarpal
shaft and the flexor digitorum profundus tendon to the
third ray in a young, active patient. The ganglion resulted
in compression of the distal ulnar motor branch, resulting
in hand weakness and atrophy. In this patient, prognosis
may be guarded based on EMG/NCS testing with a lower
amplitude response to the first dorsal interosseous
indicative of significant axonal loss to the motor branch of
the ulnar nerve. However multiple patient factors may
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favor a positive prognosis for recovery via neuronal
sprouting and direct regrowth. Namely, the patient is
young, the injury is near the affected muscle, and
symptoms had only been present for seven months before
decompression. Prompt recognition of this rare nerve
compressive lesion through thorough physical exam and
early comprehensive workup including EMG, NCS, and
hand MRI allows for prompt surgical intervention before
motor endplate irreversible degeneration to optimize the
chance for full motor recovery.
Acknowledgement
N/A
Authors Contribution: Authors who conceived and
designed the analysis: LF, GGG/ Authors who collected the
data: LF, GGG/ Authors who contributed data or analysis
tools: MKF, PKB, GGG/ Authors who performed the
analysis: LF, MKF, PKB, GGG/ Authors who wrote the
paper: LF, MFK
Declaration of Conflict of Interest: The author(s) do NOT
have any potential conflicts of interest for this manuscript.
Declaration of Funding: The author(s) received NO
financial support for the preparation, research, authorship,
and publication of this manuscript.
Declaration of Ethical Approval for Study: The institution
does not require ethical approval for reporting individual
cases.
Declaration of Informed Consent: Written informed
consent was obtained from the patient for publication of this
case report and accompanying images.
Lilah Fones MD 1
Mitchell K. Freedman DO 1
Pedro K. Beredjiklian MD 1
Gregory G. Gallant MD, MBA 1
1 Rothman Orthopaedic Institute, Sidney Kimmel Medical
College, Thomas Jefferson University Hospital, Philadelphia, PA,
USA
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