The aim of this study is to evaluate the effects of corticosteroid injection verses nighttime splinting as initial treatments on wrist function, quality of life, and sleep quality in patients with rheumatoid disease-related carpal tunnel syndrome. Participants will be randomly assigned to two groups and will receive the following interventions: one group will wear a neutral position night splint for 6 weeks, and the other group will receive a single local injection of methylprednisolone 40 mg as the initial treatment. Follow-up evaluations will be conducted at 6, 12, and 18 weeks to assess wrist function, sleep quality, and quality of life, and to dynamically adjust the treatment plan.

Inclusion Criteria:

1. Patients aged no less than 18 years old with unilateral or bilateral carpal tunnel syndrome diagnosed by a specialist according to the Katz diagnostic criteria, and with at least one associated rheumatic disease;
2. Patients have had symptoms of CTS for at least six weeks, and the side with more severe symptoms is designated as the target side for the study.
3. During the current episode, the target side has not been treated.

Exclusion Criteria:

1. Patients who have plan for surgical treatment on his or her CTS within the following 6 months;
2. Received corticosteroid injections in the wrist within the past 6 months;
3. Patients who are unable to wear a splint due to trauma or other reasons;
4. Patients with clinical manifestations or electrophysiological changes indicative of significant axonal loss or denervation, including thenar muscle atrophy, sensory loss (two-point discrimination greater than 8 mm), absence of SNAP (sensory nerve action potential), absence of CMAP (compound muscle action potential) in the thenar muscles, etc.;
5. Patients who require long-term use of any form of opioids.
6. Patients who have used opioids (e.g., tramadol) or neuropathic pain medications (gabapentin, pregabalin, etc.) within the past 2 weeks;
7. Patients who have received non-recommended wrist injection treatments (e.g., 5% glucose, platelet-rich plasma, ozone, chitosan, hyaluronic acid, etc.) within the past 6 months;
8. Patients who have undergone non-recommended physical therapies (e.g., electrotherapy, magnetotherapy, laser therapy, etc.) within the past 6 months;
9. Patients who are pregnant or plan to become pregnant within the next 6 months.

Upon completion of the study for publication, by reasonable request via email to the corresponding author.