21431, 가톨릭대학교 의과대학 인천성모병원 재활 의학교실

https://doi.org/10.35827/cp.2021.20.1.20

접수일 : 2020 년 7 월 26 일 , 게재승인일 : 2020 년 10 월 3 일 책임저자 : 김재민 , 인천시 부평구 동수로 56

21431, 가톨릭대학교 의과대학 인천성모병원 재활 의학교실

Tel: 032-280-5868, Fax: 032-280-5556

말초 신경병증을 초래한 건초주위 지방종

가톨릭대학교 의과대학 인천성모병원 재활의학교실

, 정형외과학교실

김세희¹ㆍ이용석²ㆍ김재민¹

Lipoma of the Tendon Sheath that Caused Peripheral Neuropathy

Sehee Kim, M.D.

, Yong-Suk Lee, M.D.

and Jae Min Kim M.D., Ph.D.

Departments of

Rehabilitation Medicine,

Orthopedic Surgery, Incheon St. Mary’s Hospital, College of Medicine, The Catholic University of Korea, Seoul, Korea

In this case report, we present a rare case of lipoma of the tendon sheath localized to the wrist which caused median entrapment neuropathy and was successfully treated with surgical excision. Dynamic examination using ultrasonography revealed the exact location of the lipoma. Electrodiagnostic study (EDX) was done before surgery to elucidate combined neuropathy, and surgery for ulnar neuropathy around elbow was also performed simultaneously. Diagnostic ultrasound can be used for dynamic examinations with real-time visualization. (Clinical Pain 2021;20:20-24)

Key Words: Lipoma, Ultrasonography, Ulnar nerve compression syndromes

INTRODUCTION

Lipomas are the most common benign tumors located in the limbs and are composed primarily of adipose tissue and typically localized to the subcutaneous fat layer. Rarely, a lipoma may be located around a tendon sheath or tendon compartment and, in this case, the lipoma is labeled as a lipoma of the tendon sheath [1].

In this case report, we present a rare case of lipoma of the tendon sheath localized to the wrist that caused median nerve compression in the carpal tunnel. Dynamic examina- tion with ultrasonography concluded the exact location of the mass. Electrodiagnostic study (EDX) was conducted before surgery to elucidate the combined neuropathy, and surgery for ulnar neuropathy around the elbow was also performed simultaneously according to the EDX results.

CASE REPORT

A 76-year-old male patient came to the orthopedics clin- ic complaining of limited motion in the left fourth and fifth fingers together with movable mass of the wrist. He also complained tingling sensation of left little finger and ring finger. There was no atrophic change of muscles on hy- pothenar aspect of hand. The power of the little and ring fingers extension was diminished to grade 4/5 according to Medical Research Council (MRC) scale. The medial half of the dorsal aspect of the hand along with the dorsal side of the fourth and fifth fingers showed decreased sensation to light touch. Tinel’s sign was positive over the ulnar nerve at the elbow with radiation to the little finger’s tips.

During the physical examination and interrogation, a pal-

pable and movable mass was found on his left wrist. The

patient reported progressive development of a soft, mobile,

and painless mass from two weeks before admission. EDX

was performed to evaluate the symptoms; and the findings

were compatible not only with median entrapment neuro-

pathy of the left wrist, but also with left incomplete ulnar

neuropathy around the elbow (Table 1 and 2). Ultrasono-

graphy was performed, and a movable mass was observed

around the tendon of the fourth flexor digitorum profundus

muscle. During the dynamic examination, the mass dis-

Table 1. Nerve Conduction Study Result of the Left upper Extremity Nerves and sites Onset latency

(ms)

Peak latency (ms)

Amplitude (μV or mV)*

Distance (cm)

CV (m/s) Sensory nerve conduction study

Median – digit III

Wrist 3.75 4.64 12.0 14 30.2

Palm 1.56 2.29 17.7 7 30.5

Ulnar – digit V

Wrist Not evoked

Dorsal ulnar – 4th intermetacarpal space

Wrist Not evoked

Motor nerve conduction study Median (APB)

Wrist 3.96 10.0 7

Elbow 7.92 9.1 22.5 56.8

Ulnar (ADQ)

Wrist 3.18 8.5 7

Below elbow 6.72 7.6 20 56.5

Above elbow 9.38 5.3 10 37.6

Ulnar (ADQ)

Wrist 2.81 7.3 7

4 cm below medial epicondyle 6.46 7.2 20 54.9

2 cm below medial epicondyle 6.72 6.7 2 76.8

Medial epicondyle 7.29 6.4 2 34.9

2 cm above medial epicondyle 7.86 6.1 2 34.9

4 cm above medial epicondyle 8.54 3.9 2 29.5

6 cm above medial epicondyle 8.96 3.6 2 48.0

*μV in sensory nerv.e conduction study and mV in motor nerve conduction study.

CV: conduction velocity, APB: abductor pollicis brevis, ADQ: abductor digiti quanti.

Table 2. Needle Electromyography Study Results of the Left Upper Extremity

Spontaneous activities MUAP Recruitment

pattern

IA Fib PSW Fasc CRD Amplitude Duration PPP

Biceps brachii N None None None None N N N N

Triceps brachii N None None None None N N N N

Flexor carpi radialis N None None None None N N N N

Flexor carpi ulnaris N None 1＋ None None N N N N

Flexor digitorum profundus, digitIV and V

N None None None None N N N N

Extensor digitorum communis N None None None None N N N N

First dorsal interosseous N None None None None N N N N

Abductor pollicis brevis N None None None None N N N N

Abductor digiti minimi N None 2＋ None None N N N Reduced

MUAP: motor unit action potential, IA: insertional activity, Fib: fibrillation potential, PSW: positive sharp wave, Fasc: fasciculation

potential, PPP: polyphasic potential.

Fig. 1. Dynamic ultrasonography. An arrow shows the ulnar nerve at the wrist, and an arrowhead indicates the soft tissue mass.

(A) Sonography was performed while the patient’s fingers were extended. (B) Sonography was also performed while the patient’s fingers were flexed.

Fig. 2. Magnetic resonance imaging (MRI) of the patient. (A) Longitudinal view of the MRI of the patient’s left wrist. An arrow shows soft tissue mass located around the tendon sheath of 4

flexor digitorum profundus muscle. (B) Transverse view of the MRI of the patient’s left wrist. An arrow shows soft tissue mass (1.4 × 0.54 × 2 cm) in the carpal tunnel. (C) Axial T1 weighted image of the MRI of the patient’s left elbow. An arrow shows edematous change of the ulnar nerve at cubital tunnel. (D) Sagittal T2 weighted image of the MRI of the patient’s left elbow. An arrow shows edematous change of the ulnar nerve.

Fig. 3. (A) An intraoperative image showing adherence of the mass to the tendon of the fourth flexor digitorum profundus muscle. (B) Gross pathologic specimen after excision.

extended (Fig. 1-A, Supplementary Video 1). The mass al- so moved along to the finger flexion (Fig. 1-B, Supplementary Video 1). Magnetic resonance imaging (MRI) was performed considering the diagnosis of synovitis of the left wrist and revealed incidentally noted soft tissue lipoma (1.4 × 0.54 × 2 cm) in the carpal tunnel (Fig. 2).

Surgical excision; carpal tunnel release; and release of the arcade of Struthers, intermuscular septum, anconeus ep- itrochlearis, Osborne’s ligament, and fascia of the flexor carpi ulnaris muscle were completed. The patient’s medial intermuscular septum, arcade of struthers, Osborne's liga- ment was thickened and ulnar nerve showed edematous change. Intra-operative findings are compatible with cubital tunnel syndrome. Complete excision of the mass was suc- cessfully done which was attached to tendon sheath of the 4th flexor digitorum profundus muscle beneath carpal tunnel. A well-defined mass was confirmed during the op-

excision was obtained (Fig. 3-B). Two weeks after surgery,

the patient visited the outpatient clinic and reported that his

symptoms had improved. At this time, full range of motion

was also restored, and painful swelling of the wrist was

Histopathological analysis concluded that the lesion was a benign lipoma.

DISCUSSION

Lipomas are the most frequent type of benign tumor in the limbs. Affected patients usually report gradual develop- ment of a soft, mobile, painless, and sometimes physically prominent mass [2]. Usually, they are predominantly lo- calized on the lower limbs but sometimes atypically may appear in an upper extremity. A number of case reports of wrist lipomas associated with neuropathy at the wrist are already present in the literature [2,3]. However, tendon sheath lipomas are exceedingly rare entities of lipomas.

There are only a few cases in the literature of tendon sheath lipomas [1].

Imaging studies may be performed for evaluation pur- poses in the context of a lipoma. Generally, standard X-ray examinations do not aid in the diagnosis because they only reveal a homogeneous opacity in the soft tissue, whereas there may also be calcifications or a degree of cortical bone condensation [4].

Classically, MRI is the visualization modality of choice for evaluation of tumors of the hand. MRI enables a certain diagnostic orientation of the tumor and reveals anatomical relationships between the tumor and the neurovascular structures [5]. Typically, lipomas appear as homogeneous masses with a sharp border and are easily diagnosable as they show an identical signal intensity to that of subcuta- neous fat in all pulse sequences and a well-defined and lo- bulated morphology [6].

Ultrasound is also an effective instrumentation modality by which to explore any existence of abnormal mass in the hand. Moreover, ultrasound supports precise differentiation of space-occupying lesions causing median nerve com- pression. Ultrasound provides a view of nerve anatomy as well as that of surrounding structures and allows real-time and painless assessment of median nerve entrapment.

Typical findings associated with nerve compression include enlargement of the nerve proximal to the site of com- pression, decreased echogenicity, and increased vascularity [2].

In this case report, the symptoms of the patient sug- gested left ulnar neuropathy at the elbow and the results of the EDX were compatible with left ulnar neuropathy at

the elbow level. However, the patient also presented with a palpable, movable mass that disappeared at the wrist lev- el when the patient’s fingers were extended. Additional di- agnostic test was needed, and dynamic ultrasonography was deemed most suitable for determining the exact loca- tion of the mass. Ultrasonography of the left wrist pre- sented a movable mass around the tendon of the fourth flexor digitorum profundus muscle and provide useful in- formation for surgical excision.

In general, the clinical manifestation of nerve com- pression should be investigated as suggesting a tumor syn- drome during a clinical examination [7]. This case report add significant information to the previously published lit- erature because this report demonstrates the utility and im- portance of musculoskeletal ultrasound in the evaluation of a rare soft-tissue mass when MRI was inconclusive. Using ultrasound and EDX, in addition to determining the exact location of the soft tissue mass that was causing the pa- tient's symptoms, the combined neuropathy in this case could be diagnosed simultaneously.

In conclusion, diagnostic ultrasound can be adopted dur- ing dynamic examinations with real-time visualization.

Practitioners should attempt to link the tumor localization with the reported nerve manifestations, and dynamic ultra- sonography can be helpful with this.

CONFLICT OF INTEREST

The authors declare that there are no conflicts of interest to disclose. This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.

SUPPLEMENTARY MATERIALS

Supplementary materials can be found via https://doi.

org/10.35827/cp.2021.20.1.20.

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