Carpal Tunnel Syndrome (CTS) is a median nerve entrapment syndrome which occurs at the level of the fibro-osseous carpal tunnel.

The multi-factorial causes include masses, tendonitis, synovitis, metabolic and deposition diseases, although many cases are idiopathic. There is a predilection for middle-aged women being affected more often than men. Specific occupations may exacerbate the symptoms. Diagnosis usually relies on clinical symptoms and nerve conduction studies, which are not always reliable. Utilizing ultrasound to directly image the median nerve allows for evaluation of the extrinsic causes of CTS and potentially facilitates therapeutic intervention. Enlargement of the median nerve, lack of deformability on real-time, and abnormalities of blood flow are imaging features that have been described in CTS.

Patient History

A 37-year-old woman with chronic right wrist pain was referred to ultrasound for evaluation for possible tenosynovitis and/or tendonitis. The patient had been previously injected with steroids by her clinician without significant improvement. Gray scale images were performed with a 12 MHz linear transducer. The ultrasound exam demonstrated normal appearing flexor tendons, with no abnormal fluid collection or synovial thickening. Images of proximal median nerve demonstrated a very prominent median artery (Figures 1 and 2).

Power Doppler imaging confirmed increased blood flow, both around the median nerve and within it (Figures 2 and 3). Ultrasound suggested a diagnosis of CTS based on these findings, in keeping with her rheumatologist's clinical examination.

This patient was subsequently treated with wrist immobilization and rescanned one month later. A repeat examination showed a decreased level of hyperemia, compatible with the patient's clinical improvement. It also showed a persistent abnormal gray scale appearance (Figures 4a, b), but with a decreased level of hyperemia.

The value of ultrasound in musculoskeletal imaging is its ease of use for patient and operator, adapting high-frequency probe technology to evaluate detailed anatomy. In this case, ultrasound excluded abnormalities of the tendons, synovial lining, and masses. This provided a quick diagnosis of Carpal Tunnel Syndrome.

Fig.1 - Long axis gray scale image of right forearm displaying the median nerve situated between deep and superficial flexor muscles. This study was imaged with the GE LOGIQ 700 MR - 12 MHz linear transducer.	Fig. 2 - Power Doppler sensitivity along median nerve assists in the display of a prominent median artery.	Fig. 3 - Transverse Power Doppler demonstrates increased blood flow around and within the median nerve.

Fig. 4a - Open hand: Transverse gray scale image of median nerve, one month post treatment. Median nerve appears bi-lobed with a small central cleft.	Fig. 4b - Clenched fist: The median nerve cleft appears more apparent.	Fig. 5 - Transverse Power Doppler image shows decreased level of hyperemia which is compatible with clinical improvement.

• LOGIQ 700 MR
• 12 MHz linear transducer.

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