An Unusual Case of Periosteal Glomus Tumor at the Metacarpal Base Presenting as Type II CRPS: Case Report

Abstract

Background: An unusual case involving a middle-aged male with a 9-year history of presumptive chronic regional pain syndrome (CRPS) and ulnar neuropathy was referred for failure in treatment. Methods: On presentation, the patient was requesting an amputation of his arm. However, work-up uncovered a periosteal extra-digital glomus tumor on the base of the small finger metacarpal. Results: Surgical excision of the lesion resulted in rapid resolution of his pain and normal hand function was ultimately restored. Conclusions: Glomus tumors account for up to 5% of all soft tissue tumors of the upper extremity, occurring most frequently within or adjacent to the nail bed. Time from onset of symptoms to correct diagnosis may not be established for many years, especially with atypical tumor locations. Although glomus tumors have been widely reported, atypical locations of these tumors should be included in the differential diagnosis for patients with unusual chronic pain or neuropathy. Furthermore, when evaluating a chronic pain patient, our findings support the opinion that assignment of the diagnosis of CRPS should only be a diagnosis of exclusion.

Introduction

The glomus tumor is a hamartomatous proliferation of smooth muscle cells originating from preexisting normal glomus cell populations. Depending on the histologic quantities of glomus cells, smooth muscle, and blood vessels, the tumor is classified as a glomangioma, glomangiomyoma, or glomus tumor.

Paroxysmal pain and hypersensitivity to temperature and pressure are frequently reported in patients with digital or nailbed involvement. However, atypical tumor locations frequently have a myriad of nonspecific symptoms. As a result, the final diagnosis is frequently delayed for many years in extra-digital glomus cases.¹ Nondigital tumor sites occur much less frequently but have been reported throughout the upper and lower extremity, spine, pelvis, head and neck, and abdominal-thoracic cavities.^1,2 We present a difficult case involving a patient with a 9-year history of intense hand pain and ulnar neuropathy that was previously diagnosed as complex regional pain syndrome (CRPS).

Case Report

A 59-year-old African-American male with chronic intense hand/wrist pain and progressive ulnar neuropathy presented for a second opinion of his nondominant extremity. Previous evaluation and treatment with multiple other physicians resulted in a diagnosis of CRPS that had been unresponsive to treatment. At the time of his presentation, the patient stated he no longer could handle the pain and he was requesting an arm amputation. The onset of his symptoms were insidious and had intensified over the years. For the last 3 years, he noted additional symptoms of numbness/tingling.

Examination noted nonlocalized, intractable, continuous, and disproportionate hand/wrist pain with constant tingling, paresthesias, and burning along the ulnar side of his forearm/wrist that radiated into his small and ring fingers. Symptoms were exacerbated by direct contact, elbow and wrist movement, and percussion testing along the ulnar nerve at the elbow and wrist. At rest, he held his wrist and elbow flexed and there was visible mild atrophy of the forearm and abductor digiti minimi. The skin over the hand and wrist was shiny and mildly edematous. The small and ring fingers had decreased range of motion (ROM) with flexion and he was unable to make a tight fist. ROM of the shoulder and elbow were normal, and there was a 20 degree decrease in wrist flexion and extension compared to the uninvolved side. Allodynia and hyperalgesia were present over the dorsal hand and wrist. Light touch threshold to the small and ring fingers was decreased with monofilament testing (3.61 Semmes-Weinstein). There were no palpable masses, and his pulses were normal. At the time of referral, the patient’s clinical signs and symptoms were suggestive of complex regional pain syndrome in accordance with the Budapest criteria. Nerve conduction testing showed decreased motor conduction velocity, absent sensory conduction, and reduced amplitude along the ulnar nerve at Guyon’s canal and the cubital tunnel. Electromyogram testing showed increased insertional activity, increased motor unit duration, and increased polyphasic potentials to the abductor digiti minimi but was normal to the 1st dorsal interosseus muscle. Hand and wrist radiographs identified a 2 mm ulnar positive wrist and mild osteopenia, while his medical history was significant for hypertension, gout, and daily tobacco use. The presumptive diagnosis at the time of referral was type II complex regional pain syndrome secondary to chronic ulnar neuropathy. Previous stellate ganglion blocks, trials of gabapentin, occupational therapy, and avoidance of prolonged wrist/elbow flexion was of minimal to no benefit. The patient did not have a bone scan previously.

In an attempt to eliminate ulnar nerve compression as the suspected trigger for the neurogenic pain, a surgical release and decompression of the ulnar nerve at Guyon’s canal and the cubital tunnel was recommended. At surgery, the ulnar nerve appeared to be normal and there were no areas of obvious compression identified. Following surgery, the patient reported partial but noticeable improvements in his ulnar nerve function that allowed further localization to an area along the ulnar border of the left wrist.

As there was not an explanation for the on-going localized clinical findings, a noncontrasted magnetic resonance imaging (MRI) of the hand and wrist was recommended. The study showed a well-defined homogeneous but nonspecific, 1 cm circular lesion with increased signal intensity on T2 imaging, immediately adjacent to the ulnar border of the small finger metacarpal (Figure 1).

Figure 1.

Magnetic resonance imaging demonstrating signal change and mass along the ulnar border of the small finger metacarpal: (a) T-1 weighted image and (b) T-2 weighted image.

A second surgery was performed to remove the unknown lesion through a longitudinal incision at the base of the small finger metacarpal. The subcutaneous fat was normal in appearance and the abductor digiti minimi was elevated, exposing the periosteum along the ulnar border of the involved metacarpal. A 10 mm x 10 mm x 5 mm well circumscribed, soft plaque-like mass was identified on the periosteum but did not involve the cortex. Histopathology identified a well-encapsulated brown disk-like nodule of densely packed benign uniform tumor cells surrounded by a fibrous rim that stained positive for smooth muscle actin and vimentin (Figure 2). Pathology confirmed the diagnosis of glomus tumor.

Figure 2.

Photomicrograph showing a well encapsulated nodule containing tightly packed uniform tumor cells.

Within 1 week of tumor excision, the patient’s hypersensitivity and intense pain had resolved. At his 6-month follow-up, he had regained normal hand and wrist ROM and his ulnar nerve function was normal. He was also recovering hand and forearm muscle girth.

Discussion

Glomus tumors are soft tissue neoplasms that typically present as small nondistinctive tumors of the distal extremities. The initiating event for glomus cell proliferation is unknown. Glomus cell populations are specialized arteriovenous anastomoses characterized by Sucquet-Hoyer canals, which play an important role in thermoregulation. The normal glomus body is located in the stratum reticulare layer of the dermis and is more concentrated in the digital and subungual areas.³ Rare instances of malignant transformation have been described, as has an association with neurofibromatosis type I.⁴

Symptoms of glomus tumor are characterized by a triad of sensitivity to cold, localized tenderness, and severe intermittent pain, but may not always be present, especially with extra-digital tumor locations.⁵ The pain can be excruciating and worse with dependent posturing of the extremity. Although the cause of pain is not completely understood, nerve fibers containing the neurotransmitter substance P have been identified inside glomus tumors.⁵ Substance P has also been found as a mediator of neurogenic inflammation and is thought to be directly linked to the signs of complex regional pain syndrome.⁶ Although digital tumors are usually quite small, extra-digital tumors can grow to a centimeter in size over many years.

CRPS in association with extra-digital glomus tumor is rare.^4,7,8 In the few reported cases, as well as in this case, the patients demonstrated one or more of the following: major psychological consequences, suicidal tendencies, and/or request for amputation. It is not known if these symptoms are truly CRPS related or are just misclassified as such. Multiple authors have reported long delays in diagnosis (range: 4-20 years) along with complete resolution of symptoms after surgical removal of glomus tumors. In our case, the patient had been previously diagnosed with CRPS and ulnar neuropathy by multiple providers. The patient did not respond to previous treatment and the classic symptoms associated with glomus tumor were not present, further contributing to the delay in his diagnosis. Procedures on limbs actively involved with CRPS historically were thought to be high risk. However, recent literature supports that surgery on identified regional pain generators can greatly reduce a patient’s narcotic requirement and reported pain.⁹

Although not used routinely in glomus tumor investigations, advanced imaging study with a 3-phase technetium scintigraphy potentially would have identified the metacarpal lesion earlier and may have been useful in confirming the diagnosis of complex regional pain syndrome. A literature search found only 1 report of technetium 99 three-phase bone scan findings in a known case of glomus tumor involving the upper extremity.¹⁰ The authors noted that the bone scan findings were not unique to glomus tumors.

Senol et al.,¹¹ reported an unusual case of mono-neuropathy secondary to a glomus tumor adjacent to the ulnar nerve in the forearm. The authors noted that surgical excision of the tumor resulted in immediate resolution of the associated neuropathy. In our case, the ulnar neuropathy was thought to be the initiator of the CRPS, but the patient’s response to treatment suggests that the neuropathy was probably not directly related. The resultant improved ulnar nerve function, however, uncovered a more localized region of pain at the ulnar side of the wrist.

While glomus tumors predominate in the subungual areas of the digit, they can occur in a wide anatomic distribution. In a report of 1 institution’s glomus tumor experience, 56 tumors were found extra-digital (26 on the upper extremity). The average duration of symptoms was 7 years, with most patients being previously evaluated and having their condition misdiagnosed.¹

Plain radiographic features may reveal bony erosions or osteolytic lesions with sclerotic borders, which are sometimes seen in lesions involving the distal phalanx. Color-duplex ultrasonography has been shown to have high sensitivity, a high negative predictive value, and can detect glomus tumors as small as 2 mm.^12-14

MRI can detect multiple tumors and is beneficial in cases in which the diagnosis or specific location of the lesion is in question.^15,16 T1 MRI is not as useful for subungual lesions as it only demonstrates a dark, well-delineated mass. On T2 weighted images, the glomus tumor demonstrates a very high homogeneous signal intensity.^16,17 Postgadolinium and fat saturation images would further delineate the lesion. Even though this magnetic resonance (MR) signal pattern can be seen with any vascular tumor, small subungual or digital lesions are considered pathognomonic of glomus tumor. This same MR finding outside of the digit is much less specific.

Conclusion

Patients with unexplainable and/or atypical chronic upper extremity pain and neuropathy frequently present a clinical dilemma. When evaluating these patients, the diagnosis of CRPS should be a diagnosis of exclusion. In our case, the patient had been symptomatic for 9 years and had been previously diagnosed with type II CRPS and ulnar neuropathy. The rapid recovery noted in this case after tumor excision does not definitively confirm or exclude the presence of CRPS. In addition, the metacarpal base tumor was not found until after the ulnar neuropathy was addressed.

Although most commonly located within the digit, extra-digital glomus tumors are rare and may present with atypical symptoms. Glomus tumor symptoms can be so intense that some patients may request amputation or display major psychological effects and/or suicidal tendencies in cases that remain untreated. Experience has shown that excision of symptomatic glomus tumors has an immediate effect on pain and hypersensitivity. Despite an increasing number of reported cases in the literature, extra-digital glomus tumors frequently remain undiagnosed for several years. Evidence is growing to include these tumors in an already long list of differential diagnosis for patients with unexplained symptoms.