The purpose of this report is to describe the value of ultrasound in diagnosing and monitoring flexor carpi radialis (FCR) tenosynovitis clinically mimicking carpal tunnel syndrome. A 62-year-old female had chronic right wrist pain with numbness and tingling in the first four digits. Physical examination suggested carpal tunnel syndrome. Ultrasound and power Doppler images demonstrated tenosynovitis of the FCR tendon, but a normal median nerve. Hyperemia was extending from the inflamed tendon to the adjacent median nerve, suggesting the FCR tenosynovitis was inducing a low-grade neuritis. Follow-up ultrasound at 3 weeks was performed due to worsening symptoms and demonstrated consistent tenosynovitis, prompting additional laboratory testing which excluded an inflammatory arthritis. More aggressive therapy was introduced at this time and repeat ultrasound 6 weeks later demonstrated near resolution of FCR tenosynovitis coinciding with symptom amelioration. This case underscores the value of ultrasound as an extension of the musculoskeletal examination to improve diagnostic specificity and guide appropriate care.
The flexor carpi radialis (FCR) tendon is superficial to the scaphoid and inserts at the base of the second and third metacarpals (Fig. 1) . The FCR tendon is encased by a fibro-osseous tunnel formed by a vertical retinacular septum adjacent to the flexor retinaculum of the carpal tunnel. This fibro-osseous tunnel makes it particularly susceptible to mechanical compression as the FCR tendon occupies 90% of available space . The distal borders of this fibro-osseous tunnel consist of the retinacular septum anteriorly, the carpal tunnel medially, and the scaphoid-trapezoid joint posterolaterally . Due to their anatomic proximity, disorders of the FCR tendon (e.g., tenosynovitis) may mimic disease at the base of the thumb (e.g., osteoarthritis) or carpal tunnel syndrome (CTS) [3,4,5].
Ultrasonography (US) is widely used for evaluation of wrist and hand pathology . Recent evidence supports US in the evaluation of tenosynovitis at the wrist [7, 8], while also providing real-time patient interaction. Also, US has high sensitivity for many hand and wrist pathologies, is widely accessible, low cost, and lacks ionizing radiation .
Limited reports exist describing disorders of the FCR tendon mimicking other conditions causing volar wrist pain. We present a case of FCR tenosynovitis that mimicked CTS clinically and was diagnosed and monitored through treatment with US. We also discuss the strengths and limitations of US at the point of care in this case of FCR tenosynovitis.
Informed consent was obtained to publish the patient’s de-identified healthcare information. A 62-year-old Lebanese female presented with chronic right wrist pain that worsened 2 months prior after using her right hand to climb into a car. She denied any recent surgeries or trauma to the right wrist. Her past medical history was significant for hypertension and hypercholesterolemia. At presentation, she reported numbness and tingling in digits 1–4, pain at the base of the thumb, and a weak grip from pain. Her grip deficit was most impactful on her activities of daily living. The patient had been using an over the counter splint, for which the make and model are not known, as well as applying heat or ice per their preference with minimal change in symptoms. Inspection and palpation of the right wrist revealed good muscle tone and an immobile, tender swelling on the right forearm proximal to the wrist. The thumb and proximal wrist were also tender on palpation. Active and passive ranges of motion were restricted in all planes due to pain. Ischemic compression of the median nerve increased tingling in the hand. Hypoesthesia was present in a median nerve distribution (palmar digits 1–4) during compression of the nerve at the distal wrist crease. Phalen and Tinel testing were negative. Point of care US revealed a thickened retinaculum at the FCR tendon, internal heterogeneity, and surrounding Doppler positivity consistent with FCR tendinopathy and tenosynovitis (Fig. 2). The degree of tenosynovitis overshadowed the mild tendinopathy. The median nerve was normal in cross-sectional area and appearance. The tenosynovitis was presumed to be degenerative/overuse in origin, and a trial of care for 3 weeks was initiated and consisted of low-level laser therapy, activity modification (i.e., avoidance of wrist and thumb movement when feasible), and the introduction of a spica splint to be used during the day when feasible and at night while sleeping. At 3 weeks, there was no improvement of symptoms, including no change in reported hand sensations. Point of care US was again utilized and revealed persistent tenosynovitis, with proximity between the median nerve and inflamed FCR sheath (Figs. 3 and 4). The median nerve was again normal at US, except for surrounding hyperemia from FCR tenosynovitis (Fig. 4). Radiographs and a blood panel (ESR, CRP, rheumatoid factor, ANA, ANCA) were ordered at this time and were normal, excluding inflammatory causes of tenosynovitis. The patient declined pharmacologic intervention. Since the working diagnosis was mechanical tenosynovitis inducing a presumed low-grade median neuritis, and the patient had been refractory to care, more intensive treatment was initiated. This included manual soft tissue and joint mobilization and a home icing program. The wrist splint was also discontinued, and home exercises were prescribed. After 6 more sessions at one per week frequency, the patient reported minimal pain, mostly in the thumb, and had returned to full daily activities without reported grip impairment. An updated ultrasound documented improvement in tenosynovitis (Fig. 5).
We present a unique case of FCR tenosynovitis mimicking CTS. This case highlights the value and limitations of point of care US in the diagnosis.
Tenosynovitis of the FCR may be secondary to osteoarthritis at the thumb base, underlying FCR tendinopathy, inflammatory arthritis, or scaphoid fractures [9, 10]. Individuals with tenosynovitis may complain of focal wrist pain exacerbated by extension and dysesthesia in the distribution of the palmar cutaneous branch of the median nerve (PCBMN) . The PCBMN is the last collateral branch of the median nerve and runs parallel to the ulnar side of the FCR tendon. One report demonstrated that tenosynovitis of the FCR, as present in this case, may contribute to PCBMN neuritis . Our patient did not have paresthesia confined to this distribution, but rather to digits 1–4 suggesting tenosynovitis induced neuritis of the median nerve itself and not just the PCBMN.
Spinner et al. describe that tenosynovitis at the wrist may produce symptoms of numbness associated with fullness of the soft tissues . These patients may also have swelling in the distal aspect of the forearm as well as characteristic symptoms of CTS . Sein Oh et al. reported on three office workers with tenosynovitis and symptoms of hand paresthesia in the absence of nerve compromise on electrodiagnostic evaluation . The exact distribution of paresthesia was not discussed. The patient in our case presented with paresthesia that extended in a median nerve distribution. This atypical presentation is unlikely to be the result of tenosynovitis alone, but rather, tenosynovitis with induced low-grade neuritis.
Extensive data exists supporting the use of US in the diagnosis of CTS and there is growing evidence that high-resolution US may be used as an alternative to electrodiagnostic studies . A cross-sectional area of 10 mm2 or greater of the median nerve at the level of the pisiform bone or tunnel inlet is the most commonly used parameter to diagnose CTS on US, and sensitivity has been reported to be as high as 97.9% [13, 14]. There is class I and class II evidence that median nerve CSA at the wrist is accurate for the diagnosis of CTS . For these reasons, it was felt the normal US was diagnostic in our case to exclude entrapment neuropathy of the median nerve, prohibiting more costly and invasive electrodiagnostic testing. Additionally, 10–15% of patients with clinically defined CTS have normal nerve conduction studies . An unremarkable electrodiagnostic study does not exclude CTS, but it changes the likelihood of significant axonal loss or conduction block .
There are likely different treatment options and prognostic implications between FCR tenosynovitis and CTS, highlighting the importance of image-aided diagnosis. Updated management and prognosis for FCR tenosynovitis is primarily guided by case reports. One report outlines a case of FCR tenosynovitis in a 38-year-old male construction worker treated with an injection of betamethasone . The patient reported resolution of symptoms at 5-month follow-up. Conversely, for CTS treatment, a 2018 systematic review reported that corticosteroid injections provided greater short-term relief than oral steroids in patients with CTS . However, relief was not sustained in the long term. One prospective study demonstrated greater decreases in median nerve CSA after surgical decompression of the flexor retinaculum compared with nonsurgical management .
Our case is particularly significant as it demonstrates the role US can play in the diagnosis of volar wrist pain mimicking carpal tunnel syndrome. As the patient’s median nerve CSA was normal, CTS was effectively ruled out and another diagnosis was pursued . This does not discount low-grade median neuritis as contributing to the patient’s symptoms. Rather, intervention aimed at targeting the tenosynovitis alone was helpful. However, US imaging was not enough to ensure a proper diagnosis in this case requiring augmentation with labs for confirmation.
Inherent to any case report, inferences of treatment success cannot be made independent of natural history.
We present a unique case of FCR tenosynovitis mimicking CTS and highlight the role of US at the point care in its diagnosis. It is important that healthcare professionals are aware of the clinical implications this condition can have on management of patients presenting with volar wrist pain and dysesthesia. Future research should aim to examine the incidence and prevalence of FCR tenosynovitis mimicking CTS in volar wrist pain as management and prognosis for these two conditions are different.
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The case presented does not include any experimental procedures involving humans or animals.
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Bolles, C.L., Abdella, A. & Battaglia, P.J. Flexor Carpi Radialis Tenosynovitis Mimicking Carpal Tunnel Syndrome Diagnosed and Monitored with Ultrasound: Case Report. SN Compr. Clin. Med. 2, 797–801 (2020). https://doi.org/10.1007/s42399-020-00320-1
- Flexor carpi radialis
- Carpal tunnel syndrome