The goal of this clinical trial is to compare the efficacy of corticosteroid injection, night splinting, and their combined use as initial treatments for adults with moderate to severe carpal tunnel syndrome (CTS), and to assess the safety and tolerability of these interventions. The primary research questions include:

• Doe corticosteroid injection, night splinting, and their combined use as initial treatments reduce the need for surgery in participants with moderate to severe CTS?
• How do these interventions affect the improvement of patient symptoms?

Participants will:

• Receive corticosteroid injection, night splinting, or their combination as initial treatments.
• Visit the clinic once every 6 weeks over a period of one year for assessments and dynamic adjustment of the treatment plan.
• Undergo periodic assessments of wrist function, quality of life, and sleep quality using standardized questionnaires.

Inclusion Criteria:

1. Patients aged no less than 18 years old with idiopathic carpal tunnel syndrome of the target side diagnosed by a specialist according to the Katz diagnostic criteria;
2. The current episode has occurred within 6 weeks without treatment before eligibility assessment, and the target side has moderate-to-severe symptoms.

Exclusion Criteria:

1. Patients who have plan for surgical treatment on his or her CTS within the following 6 months;
2. Any secodary CTS caused by comorbid diseases, including rheumatoid arthritis, psoriatic arthritis, systemic lupus erythematosus, CPPD (calcium pyrophosphate dihydrate deposition disease), etc.;
3. History of fracture or surgery on the target side of the wrist;
4. Bilateral CTS with moderate or severe symptoms in both hands;
5. Received corticosteroid injections in the wrist within the past 6 months;
6. Patients who are unable to wear a splint due to trauma or other reasons;
7. 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.;
8. Patients who require long-term use of any form of analgesic medication, such as NSAIDs (nonsteroidal anti-inflammatory drugs), opioids, acetaminophen, etc.;
9. Patients who have used NSAIDs, opioids (e.g., tramadol), neuropathic pain medications (gabapentin, pregabalin, etc.), or oral corticosteroids within the past 2 weeks;
10. 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;
11. Patients who have undergone non-recommended physical therapies (e.g., electrotherapy, magnetotherapy, laser therapy, etc.) within the past 6 months.

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