Orthopedics

Case Reports 

Unilateral Carpal Tunnel Syndrome Caused by an Occult Palmar Lipoma

A. Erdem Bagatur, MD; Merter Yalcinkaya, MD

Abstract

Carpal tunnel syndrome usually presents bilaterally and space-occupying lesions should be suspected in patients with unilateral symptoms, especially with a long history and when the symptomatic hand shows severe neurophysiologic impairment, while the contralateral hand is neurophysiologically intact. Approximately half of patients with unilateral symptoms have positive electrodiagnostic test results in the asymptomatic, contralateral hand. Space-occupying lesions are known to cause carpal tunnel syndrome and the incidence of space-occupying lesions in unilateral carpal tunnel syndrome is higher than that of bilateral carpal tunnel syndrome. It is easy to detect a mass when it is palpable, but occult lesions may be overlooked easily.

Whenever a patient presents with unilateral symptoms and unilateral neurophysiologic impairment, the possibility of a space-occupying lesion compressing the median nerve should be kept in mind in the differential diagnosis. This article presents 2 cases of patients with occult deep palmar lipomas compressing the median nerve and causing unilateral symptoms of carpal tunnel syndrome. We stress the importance of imaging studies in patients with unilateral symptoms that are usually not used in carpal tunnel syndrome. While both patients’ symptomatic hands showed severe neurophysiologic impairment, the contralateral hands were totally intact, which is contradictory with a long history. The reported patients were evaluated and magnetic resonance images revealed intra-tunnel lesions. Although lipomas are the most common soft tissue tumor in the body, <5% of the benign tumors of the hand are lipomas. Since the thick palmar fascia is strong, a deep lipoma may not be recognized although nerve compression symptoms may be gross.

Any process that causes a rise in pressure in the carpal tunnel may lead to compression of the median nerve. Since carpal tunnel syndrome presents bilaterally in >50% of cases,1-3 the probability of a certain etiology should be kept in mind when the condition is unilateral. Space-occupying lesions are known to cause carpal tunnel syndrome and the incidence of space-occupying lesions in unilateral carpal tunnel syndrome is higher than that of bilateral carpal tunnel syndrome.4 It is easy to detect a mass when it is palpable, but occult lesions may be overlooked easily. This article presents 2 cases of patients with occult palmar lipomas extending into the carpal tunnel, causing unilateral median nerve compression.

Patient 1

A 63-year-old man presented with numbness, loss of strength, and awakening pain in the right hand of 3 years’ duration. On clinical examination a mild thenar atrophy was observed and Phalen’s test was positive, Tinel’s sign was negative.

Nerve-conduction studies of the median nerve revealed an absence of digit-to-wrist sensory nerve action potential in the right side, and distal motor latency was 6.1 milliseconds. Needle electromyography findings included fibrillation activity, decreased recruitment, and abnormalities in the configuration of the motor unit action potential. The left hand was neurophysiologically intact.

Both clinical symptoms and signs and the neurophysiological tests showed severe carpal tunnel syndrome in one hand while the contralateral hand was completely healthy, implying a secondary disease. No external signs or palpable masses were present. Magnetic resonance imaging (MRI) showed a 5×4×2-cm soft tissue mass in the deep palmar space extending into the carpal tunnel and compressing the flexor tendons and the median nerve (Figure 1).

Figure 1: MRI revealed a space-occupying lesion in the deep palmar space extending into the carpal tunnel with bright and homogenous signal characteristic of fatty tissue on T1-weighted coronal (repetition time [TR], 300 milliseconds; echo time [TE], 9 milliseconds) and axial (TR, 400 milliseconds; TE, 9 milliseconds) images. Arrows are outlining the radial and ulnar sides of the soft tissue mass.

The patient underwent Bier block and open carpal tunnel release, and mass excision…

Abstract

Carpal tunnel syndrome usually presents bilaterally and space-occupying lesions should be suspected in patients with unilateral symptoms, especially with a long history and when the symptomatic hand shows severe neurophysiologic impairment, while the contralateral hand is neurophysiologically intact. Approximately half of patients with unilateral symptoms have positive electrodiagnostic test results in the asymptomatic, contralateral hand. Space-occupying lesions are known to cause carpal tunnel syndrome and the incidence of space-occupying lesions in unilateral carpal tunnel syndrome is higher than that of bilateral carpal tunnel syndrome. It is easy to detect a mass when it is palpable, but occult lesions may be overlooked easily.

Whenever a patient presents with unilateral symptoms and unilateral neurophysiologic impairment, the possibility of a space-occupying lesion compressing the median nerve should be kept in mind in the differential diagnosis. This article presents 2 cases of patients with occult deep palmar lipomas compressing the median nerve and causing unilateral symptoms of carpal tunnel syndrome. We stress the importance of imaging studies in patients with unilateral symptoms that are usually not used in carpal tunnel syndrome. While both patients’ symptomatic hands showed severe neurophysiologic impairment, the contralateral hands were totally intact, which is contradictory with a long history. The reported patients were evaluated and magnetic resonance images revealed intra-tunnel lesions. Although lipomas are the most common soft tissue tumor in the body, <5% of the benign tumors of the hand are lipomas. Since the thick palmar fascia is strong, a deep lipoma may not be recognized although nerve compression symptoms may be gross.

Any process that causes a rise in pressure in the carpal tunnel may lead to compression of the median nerve. Since carpal tunnel syndrome presents bilaterally in >50% of cases,1-3 the probability of a certain etiology should be kept in mind when the condition is unilateral. Space-occupying lesions are known to cause carpal tunnel syndrome and the incidence of space-occupying lesions in unilateral carpal tunnel syndrome is higher than that of bilateral carpal tunnel syndrome.4 It is easy to detect a mass when it is palpable, but occult lesions may be overlooked easily. This article presents 2 cases of patients with occult palmar lipomas extending into the carpal tunnel, causing unilateral median nerve compression.

Case Reports

Patient 1

A 63-year-old man presented with numbness, loss of strength, and awakening pain in the right hand of 3 years’ duration. On clinical examination a mild thenar atrophy was observed and Phalen’s test was positive, Tinel’s sign was negative.

Nerve-conduction studies of the median nerve revealed an absence of digit-to-wrist sensory nerve action potential in the right side, and distal motor latency was 6.1 milliseconds. Needle electromyography findings included fibrillation activity, decreased recruitment, and abnormalities in the configuration of the motor unit action potential. The left hand was neurophysiologically intact.

Both clinical symptoms and signs and the neurophysiological tests showed severe carpal tunnel syndrome in one hand while the contralateral hand was completely healthy, implying a secondary disease. No external signs or palpable masses were present. Magnetic resonance imaging (MRI) showed a 5×4×2-cm soft tissue mass in the deep palmar space extending into the carpal tunnel and compressing the flexor tendons and the median nerve (Figure 1).

Figure 1A: MRI revealed a space-occupying lesion in the deep palmar space extending into the carpal tunnel Figure 1B: MRI revealed a space-occupying lesion in the deep palmar space extending into the carpal tunnel Figure 1C: MRI revealed a space-occupying lesion in the deep palmar space extending into the carpal tunnel

Figure 1: MRI revealed a space-occupying lesion in the deep palmar space extending into the carpal tunnel with bright and homogenous signal characteristic of fatty tissue on T1-weighted coronal (repetition time [TR], 300 milliseconds; echo time [TE], 9 milliseconds) and axial (TR, 400 milliseconds; TE, 9 milliseconds) images. Arrows are outlining the radial and ulnar sides of the soft tissue mass.

The patient underwent Bier block and open carpal tunnel release, and mass excision were performed through an extended palmar incision starting proximal to the transverse wrist crease and extending to the midpalmar crease (Figure 2). Histological examination revealed mature adipose tissue consistent with a lipoma. Seven years and 6 months postoperatively, the patient remains asymptomatic.

Figure 2: Intraoperative photograph shows the yellowish tumor in the deep palmar space
Figure 2: Intraoperative photograph shows the yellowish tumor in the deep palmar space.

Patient 2

A 54-year-old woman presented with numbness, progressive loss of fine motor skills, and awakening pain in the right hand of 2 years’ duration. On clinical examination Phalen’s test and Tinel’s sign were positive.

Sensory nerve conduction velocity values from the first and third digits to the wrist were 31 and 34.3 milliseconds, respectively; distal motor latency was 5.6 milliseconds. Electromyography revealed fibrillation activity, decreased recruitment, and abnormalities in the configuration of the motor unit action potential. The left hand was neurophysiologically intact.

Both clinical symptoms and signs and neurophysiological tests showed severe carpal tunnel syndrome in one hand while the contralateral hand was completely healthy, implying a secondary disease. No external signs or palpable masses were present. Magnetic resonance imaging showed a 5×3×2-cm soft tissue mass in the deep palmar space extending into the carpal tunnel and compressing the flexor tendons and the median nerve (Figure 3).


Figure 3A: A space-occupying lesion in the deep palmar space Figure 3B: A space-occupying lesion in the deep palmar space Figure 3C: A space-occupying lesion in the deep palmar space

Figure 3: A space-occupying lesion in the deep palmar space extending into the carpal tunnel with hyperintense signal characteristic of fatty tissue on T1-weighted (TR, 680 milliseconds; TE, 21 milliseconds) axial images, proximal (left) to distal (right) is seen.

The patient underwent Bier block and carpal tunnel release, and mass excision were performed through an extended palmar incision starting proximal to the transverse wrist crease and extending to the midpalmar crease (Figure 4). Histological examination revealed mature adipose tissue consistent with a lipoma. One year and 5 months postoperatively, the patient remains asymptomatic and MRI showed no recurrence of the mass.

Figure 4: Intraoperative photograph shows the tumor covering the deep palmar space
Figure 4: Intraoperative photograph shows the tumor covering the deep palmar space, the median nerve, and tendons.

Discussion

It is widely known that idiopathic carpal tunnel syndrome usually presents with bilateral symptoms,1-3 and in patients who present with unilateral symptoms, 38% to 50% were reported to have positive electrodiagnostic test results in the asymptomatic, contralateral hand.5

Since patients who have unilateral symptoms but bilateral neurophysiologic impairment develop symptoms in the contralateral hand with time, it is assumed that in some cases bilaterality may be time-dependent. Hence, a patient with longstanding unilateral symptoms, severe neurophysiologic impairment in the symptomatic hand, and no neurophysiologic findings in the contralateral hand should alert the physician about the probable secondary nature of the disorder.

Although carpal tunnel syndrome is usually idiopathic, a certain etiology can be detected in some patients. Any process like space-occupying lesions, tenosynovitis due to connective tissue diseases, aneurysms, or malunited distal radial fractures that cause a rise of the pressure within the carpal tunnel may lead to carpal tunnel syndrome.

Nakamichi and Tachibana4 reported an increased incidence of space-occupying lesions in unilateral compared with bilateral carpal tunnel syndrome and concluded that when the condition is unilateral and the etiology is not clear, a space-occupying lesion should be suspected.

Whenever a patient presents with unilateral symptoms and unilateral neurophysiologic impairment, the possibility of a space-occupying lesion compressing the median nerve should be kept in mind in the differential diagnosis. The reported patients were evaluated and MRI studies revealed intra-tunnel lesions. Furthermore, while both patients’ symptomatic hands showed severe neurophysiologic impairment, the contralateral hands were completely intact, which is contradictory with a history of >2 years.

Although lipomas are the most common soft tissue tumor in the body, they are not frequently found in the hand, representing <5% of the benign tumors of the hand.6,7 Compression of peripheral nerves by lipomas is unusual and only a few cases have been reported in the literature.4,6-8 Lipomas in the hand were classified by Mason9 as superficial and deep palmar lipomas; the deeper ones are less common than the superficial ones. Since the thick palmar fascia is strong, a lipoma may not be recognized although nerve compression symptoms may be gross.

Imaging studies, especially MRI, which are usually not used in idiopathic carpal tunnel syndrome, should be remembered in patients with unilateral symptoms, especially with a long history and when the symptomatic hand shows severe neurophysiologic impairment, while the contralateral hand is intact.

If a space-occupying lesion is detected, MRI can also delineate the relationship between the tumor and adjacent structures allowing the surgeon to plan the operation. Furthermore, MRI can help in the differentiation of a lipoma from a liposarcoma.6

References

  1. Bagatur AE, Zorer G. The carpal tunnel syndrome is a bilateral disorder. J Bone Joint Surg Br. 2001; 83(5):655-658.
  2. Kulick RG. Carpal tunnel syndrome. Orthop Clin North Am. 1996; 27(2):345-354.
  3. Padua L, Padua R, Nazzaro M, Tonali P. Incidence of bilateral symptoms in carpal tunnel syndrome. J Hand Surg Br. 1998; 23(5):603-606.
  4. Nakamichi K, Tachibana S. Unilateral carpal tunnel syndrome and space-occupying lesions. J Hand Surg Br. 1993; 18(6):748-749.
  5. Corwin HM, Kasdan ML. Electrodiagnostic reports of median neuropathy at the wrist. J Hand Surg Am. 1998; 23(1):55-57.
  6. Babins DM, Lubahn JD. Palmar lipomas associated with compression of the median nerve. J Bone Joint Surg Am. 1994; 76(9):1360-1362.
  7. Leffert RD. Lipomas of the upper extremity. J Bone Joint Surg Am. 1972; 54(6):1262-1266.
  8. Flores LP, Carneiro JZ. Peripheral nerve compression secondary to adjacent lipomas. Surg Neurol. 2007; 67(3):258-262.
  9. Mason ML. Tumors of the hand. Surg Gynec Obstet. 1937; 64:129-148.

Authors

Dr Bagatur is from Medical Park Bahçelievler Hospital and Dr Yalcinkaya is from Istanbul Education and Research Hospital, Istanbul, Turkey.

Drs Bagatur and Yalcinkaya have no relevant financial relationships to disclose.

Correspondence should be addressed to: Merter Yalcinkaya, MD, Zumrutyuva Mh Atayurt Cd Tokerler Apt No. 4 B Blok D. 1 Basinkoy Florya 34153, Istanbul, Turkey.

doi: 10.3928/01477447-20090818-20

10.3928/01477447-20090818-20

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