Carpal Tunnel Syndrome Caused by Idiopathic Tumoral Calcinosis: A Case Report

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Abstract

INTRODUCTION

Carpal tunnel syndrome (CTS) is one of the most common forms of hand mononeuropathy12,14). It is caused by pressure on the median nerve within the carpal tunnel of the wrist, resulting in pain and numbness in the first three digits and the radial half of the fourth digit12). In severe cases, progressive CTS can lead to atrophy of the muscles innervated by the median nerve, causing weakness in hand pinching12).

The pathophysiology of CTS is multifactorial, with most cases being idiopathic due to nerve entrapment by the transverse carpal ligament9). However, CTS can also result from endocrinopathies, trauma, pregnancy, amyloidosis, or space-occupying lesions, such as tumoral calcinosis and lipomas7,9,12).

Tumoral calcinosis is a rare histopathological condition characterized by periarticular deposition of a solitary, dense calcified mass composed of calcium pyrophosphate dihydrate (CPPD) and calcium carbonate14). It most commonly affects areas around the hip, shoulder, and elbow but rarely involves the hands11,14). This report presents a case of secondary CTS caused by idiopathic tumoral calcinosis.

CASE REPORT

A 78-year-old, previously healthy woman presented to our hospital with numbness and worsening sensory impairment in her right thumb, index, middle fingers, and the radial half of her ring finger, which had persisted for six months. She also complained of volume loss in her thenar muscle (Fig. 1). Despite undergoing several injections, physical therapy, and taking nonsteroidal anti-inflammatory drugs and gabapentin, her symptoms showed no improvement.

Fig. 1.

A gross photo showing thenar muscle atrophy compared to healthy side.

Physical examination revealed no restriction in the range of motion of the wrist or fingers. The patient exhibited a positive Phalen’s sign and Tinel’s sign on the volar side of her wrist. Nerve electrodiagnostic testing suggested severe right median nerve neuropathy at the wrist level, confirming the diagnosis of CTS.

Laboratory results showed calcium levels of 9.3 mg/dL (normal range, 8.6–10.0 mg/dL), phosphate levels of 3.0 mg/dL (normal range, 2.5–4.5 mg/dL), and uric acid levels of 3.7 mg/dL (normal range, 2.4–7.0 mg/dL). Other laboratory tests, including endocrine and rheumatology panels, were normal.

Plain radiographs of the right wrist revealed a calcified mass on the volar side of the wrist joint (Fig. 2). Computed tomography (CT) imaging showed a regular-margined, hyperdense, amorphous mass within the carpal tunnel, measuring 1.9 × 1.1 × 0.5 cm³ (Fig. 3).

Fig. 2.

A plain radiograph showing a calcified mass on the volar side of the wrist joint.

Fig. 3.

Computed tomography showed an amorphous mass in the carpal tunnel, with a volume of 1.9 × 1.1 × 0.5 cm³.

A confirmatory magnetic resonance imaging (MRI) scan of the right hand and wrist revealed a solitary oval-shaped calcification with a low intensity lesion on both T1 and T2 weighted images, located centrally in the carpal tunnel between the flexor tendons, at the lunate-capitate junction, compressed tendon & median nerve, resulting in median nerve swelling. The cortex and bone marrow of the surrounding bone look normal (Fig. 4).

Fig. 4.

A confirmatory magnetic resonance imaging (MRI) of the right hand and wrist showed a solitary oval calcification (low-intensity lesion both in T1 and T2-weighted images), located in the carpal tunnel centrally between the flexor tendons of the wrist, at the lunate and capitate.

Given the ineffectiveness of conservative treatment, an open carpal tunnel release and excisional biopsy were performed. A 4 cm incision was made on the volar side of the wrist, and the transverse carpal ligament was transected. After retracting the median nerve, the calcified mass was visualized over the carpal bones. There was no adhesion to surrounding tissues (Fig. 5). Histological examination revealed calcified debris within fibrous connective tissue (Fig. 6), confirming the diagnosis of tumoral calcinosis.

Fig. 5.

The calcified mass was shown over the carpal bones.

Fig. 6.

Microscopic appearance of the excised calcified mass.

Three months after the surgery, radiographs showed no evidence of recurrence (Fig. 7), and the patient's hand pain and numbness were completely resolved.

Fig. 7.

Plain radiograph following removal of the calcification.

DISCUSSION

Although most CTS cases are idiopathic, some cases are secondary to vascular abnormalities, tenosynovitis, mal-united distal radial fractures, or space-occupying lesions7). This case presents a rare instance of secondary CTS caused by a space-occupying mass of tumoral calcinosis in the carpal tunnel. To date, few cases have been reported since 1980. Inui et al.7) reported a 54-year-old female patient with CTS with tumoral calcinosis in 2015. Also, Abdallah et al.1) reported a 52-year-old female patient who had CTS with tumoral calcinosis in 2022.

Harkess and Peters5) suggested the following criteria for diagnosing tumoral calcinosis in 1967; first, the presence of a large, painless, calcified mass around articular sites, second, the absence of abnormal values of serum calcium or phosphorus, third, no association with renal diseases, metabolic disorders, or collagen diseases, fourth, manifestation of the disease before the age of twenty, fifth, evidence of familial or racial predisposition, last, recurrence of the lesion, particularly after incomplete excision5). These criteria may aid in the diagnosis of tumoral calcinosis; however, they are limited by the lack of multiple imaging modalities compared to those available today. In these days, we can utilize multiple imaging tool including CT, MRI. Most cases of tumoral calcinosis consist of solid calcified lesion, but some cases have cystic component with calcified layers, sedimentation sign on CT10). In T1-weighted MRI, mass looks inhomogeneous but mostly low signal intensity that was predominantly nodular and probably related to the long T1 of the calcific deposits10).

Tumoral calcinosis is usually a benign condition4). It is considered a periarticular calcium deposit like tumor, regardless of preexisting disease, age, or gender6). It is classified into two types: primary and secondary. The primary type is the most common and is characterized by tumoral calcinosis without hyperphosphatemia13). The secondary type is associated with conditions such as chronic renal failure, hyperparathyroidism, hypervitaminosis D, malignancy, sarcoidosis, and scleroderma8). Therefore, a thorough laboratory workup is essential to rule out these conditions. In the present case, no other calcified masses were observed, the patient had no familial history, and lab findings were normal, suggesting a non-familial, localized primary tumoral calcinosis.

CTS is typically suspected based on the patient's symptoms and physical examination. The diagnosis is confirmed with electrophysiological testing12). Idiopathic CTS is more common in middle aged women, often with bilateral involvement2). Therefore, for unilateral CTS, further investigations are necessary to identify underlying causes7,15). MRI and ultrasound are useful in determining the cause of secondary CTS3,15).

Tumoral calcinosis is an uncommon cause of secondary CTS, and diagnosis can be challenging. However, characteristic findings may be seen on plain radiographs, CT and MRI. Carpal tunnel release and mass excision resulted in a favorable outcome. If symptoms recur, it may indicate a recurrence of tumoral calcinosis, necessitating follow-up radiographs to monitor for recurrence.

CONCLUSION

This case highlights a rare instance of CTS caused by tumoral calcinosis, a benign condition characterized by the deposition of CPPD and calcium carbonate. Tumoral calcinosis, although typically affecting joints around the hip, shoulder, and elbow, can also lead to CTS when it forms a space-occupying mass within the carpal tunnel. While CTS is usually idiopathic, secondary causes like tumoral calcinosis should be considered, especially when symptoms do not improve with standard treatments. In this case, a successful diagnosis was made through imaging, and the patient achieved full recovery following carpal tunnel release and excision of the calcified mass. Regular follow-up is recommended to monitor for any recurrence of the condition.

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