A case of calcifying nodules in the wrist as a regional cause of carpal tunnel syndrome

A 72-year-old woman presented to the emergency department due to pain and paraesthesia in the median nerve distribution of the right hand. The pain was unresponsive to painkillers. The patient reported a distal radius fracture one month ago and a history of gout.

The posteroanterior (PA) wrist radiograph (Figure 1A) identified a sclerotic nodular opacity superimposed at the level of the base of metacarpal III and IV (blue arrow) and an additional nodular opacity at the base of the capitate (yellow arrow). The lateral wrist radiograph reveals the larger nodular opacity palmar to the base of metacarpal III and IV (blue arrow) and the smaller nodular opacity palmar to the base of the capitate (yellow arrow). In addition, a fracture of the distal radius with intra-articular extension was found.

The computer tomography (CT) scan (Figure 2) in the axial (A, C) and coronal plane (B, D) revealed a large calcified nodule (19 x 7 x 15 mm) palmar to the capitate bone and metacarpal III (blue arrow) with a smaller one (10 x 3 x 7 mm) located in the carpal tunnel at the level of the lunate bone (yellow arrow). Reconstructions in the paracoronal (E) and parasagittal (F) reconstructions demonstrate both nodules in the same plane.

The axial proton density (PD) image (Figure 3) and axial T2 magnetic resonance images (Figure 4) demonstrate a sharp delineated, hypointense mass (blue arrow) in the carpal tunnel, without any surrounding soft tissue components. Limited palmar mass-effect was present. The axial T1 weighted image after Gadolinium contrast administration showed no enhancement of the calcifying nodule (blue arrow, Figure 5), nor enhancement of the surrounding soft tissues. Note degraded imaging findings due to field inhomogeneity artefacts.

Most cases of carpal tunnel syndrome (CTS) are idiopathic. Several occupational risk factors for CTS are known and primarily due to repetitive motions and manual labor, along with direct vibrations to the wrist (e.g. work in construction, the computer or textile sector). Nonoccupational risk factors include the female sex, high age, metabolic-endocrine causes (e.g. diabetes mellitus, obesity, hypothyroidism, acromegaly), and treatment with certain drugs (e.g. Tamoxifen). [1,2]

Regional causes of CTS are due to intrinsic anatomy of the patient (e.g. a wider palm and variations of the hook of the hamate) and increased content in the carpal canal leading to median nerve compression (e.g. tenosynovitis, osteoarthritis, trauma, and space-occupying lesions). Lipomas, fibromas, epidermal cysts, ganglion cysts, and calcifying are the most prevalent space-occupying lesions and they contribute to approximately 3% of CTS. [3-7] The study of Nakamichi et al. found no regional causes in patients with bilateral CTS (n=108). [4] On contrary, regional causes were found in 35% of patients with unilateral CTS (n=20), of which a calcifying mass was found in 10%. [4] An atypical presentation and non-remission of symptoms after surgery warrant consideration of different, regional causes. [3] Further work-up best involves ultrasound or MRI to identify regional abnormalities, as these abnormalities can change the therapeutic approach. [1,5] Calcifications such as in our case might be more easily identified using CT, while MRI is more sensitive to soft tissue masses. [6,7] A possible pitfall is treating a unilateral CTS using an endoscopic carpal tunnel release without excluding regional causes, as this will not suffice in patients with regional causes of CTS. [3]

Initially, the patient’s symptoms were attributed to sequelae from a radius fracture, but this seemed unlikely since the trauma was only one month ago. A standard laboratory didn’t reveal an elevated uric acid level, hypercalcemia, or inflammatory parameters. The calcifying nodules were considered the underlying cause of CTS in this patient. The EMG investigation supported this theory and showed axonal loss and signs of denervation of the median nerve. This patient received an open carpal tunnel release with excision of the calcifications. These nodules were examined by a pathologist, who confirmed the calcific origin.

In conclusion, unilateral CTS justifies further investigation using ultrasound or MRI to detect a possible regional cause. Regional causes of CTS are best treated using open carpal tunnel release, as recommended to the patient in question. [1,3,5-7]

Written informed patient consent for publication has been obtained.