Carpal Tunnel Syndrome Injections & Hydrodissection

Carpal tunnel syndrome is one of the most common nerve compression problems we see, and one of the most treatable. A precise, ultrasound-guided injection around the median nerve can settle the night-time symptoms quickly and, for many, buy months to years of relief.

What is carpal tunnel syndrome?

Carpal tunnel syndrome (CTS) occurs when the median nerve becomes compressed as it passes through the carpal tunnel, a narrow passageway in your wrist formed by the carpal bones and a thick ligament (the transverse carpal ligament). The median nerve controls sensation in your thumb, index, middle and half of your ring finger, plus some small thumb muscles. When it's compressed, you get the characteristic symptoms.

Think of it like a motorway traffic jam, when the tunnel is too narrow for the traffic (nerve signals) trying to pass through, everything backs up and stops working properly.

Why does it happen?

Anything that reduces space in the tunnel, or increases the tissue volume within it, can cause CTS. Common risk factors:

• Female, women are affected 3–4 times more often than men
• Age 40–60, though it can occur at any age
• Pregnancy, fluid retention commonly causes temporary CTS (often in the third trimester)
• Diabetes or thyroid disease, both significantly increase risk
• Overweight/obesity, increases pressure in the tunnel
• Inflammatory arthritis, rheumatoid, psoriatic
• Menopause, hormonal changes can contribute
• Previous wrist injury or fracture, can alter the anatomy

Despite popular belief, it isn't caused by typing or computer work alone, these may aggravate symptoms but are rarely the sole cause. And many people develop it with no clear cause at all.

How do I know if I have it?

The symptoms are quite characteristic, which makes diagnosis relatively straightforward:

• Tingling, pins and needles, or numbness in the thumb, index, middle and ring fingers, but usually not the little finger (this is key)
• Symptoms worse at night, often waking you; you need to "shake out" your hand for relief
• Weakness or clumsiness, dropping things, difficulty with buttons or zips
• Pain in the hand, wrist or forearm (sometimes radiating up)
• Symptoms worse with driving, holding a phone or reading
• Wasting of the thumb-base (thenar) muscles in severe, long-standing cases

If your little finger is prominently affected, that suggests an ulnar nerve problem rather than isolated CTS, the median nerve doesn't supply the little finger.

How is it diagnosed?

CTS is primarily a clinical diagnosis based on your symptoms and examination. I'll assess Tinel's sign (tapping over the nerve), Phalen's test (holding the wrists flexed), sensation in the median nerve distribution, and the strength and bulk of the thumb-base muscles. I also perform an ultrasound scan, in CTS the median nerve appears swollen (enlarged cross-sectional area), which supports the diagnosis, excludes other causes and guides the injection.

Do I need nerve conduction studies?

Not always. For straightforward CTS with classic symptoms and supportive examination, I'm happy to proceed with injection without nerve conduction studies (NCS). You may need NCS if the diagnosis is unclear or atypical, symptoms are severe/progressive, there's thenar wasting or objective weakness, additional nerve involvement is suspected, or you're considering surgery (some surgical pathways require it).

Treatment options

Conservative management (wrist splinting, especially at night, activity modification, ergonomics, managing diabetes/thyroid, weight loss) works for some, particularly mild, intermittent symptoms. If you've tried these for 6–12 weeks without adequate relief, it's time to consider more definitive treatment.

Ultrasound-guided corticosteroid injection offers excellent short-term relief for many patients and can delay, or in some cases avoid, the need for surgery. For severe, long-standing cases that don't respond, carpal tunnel release surgery (dividing the transverse carpal ligament) is highly effective. But many patients respond so well to injection that they never need it.

The procedure

Under direct ultrasound visualisation, I inject corticosteroid and local anaesthetic into the carpal tunnel, carefully positioning the needle adjacent to, never into, the median nerve. The ultrasound is what makes this safe and accurate.

• Positioning, you sit comfortably with your hand palm-up
• Ultrasound examination, I visualise the nerve, assess its size, and plan the safest approach
• Local anaesthetic, the skin is numbed first and given time to work
• Injection, under continuous ultrasound guidance, the corticosteroid is placed around the nerve
• Check, I confirm your fingers and wrist are moving normally

The whole procedure takes about 15–20 minutes. The corticosteroid reduces inflammation and swelling in the tunnel, decreasing pressure on the nerve so it can function normally again.

What does it feel like, and what are the risks?

Done properly with adequate local anaesthetic, it isn't painful, you may feel pressure, or an odd sensation down into the fingers as the medication spreads (normal). Risks are minimal: a temporary increase in symptoms for 24–48 hours (uncommon), infection (extremely rare with sterile technique), minor bruising, and, avoided with ultrasound, inadvertent nerve injection. If you're diabetic: the steroid can raise blood sugar for 1–2 weeks; I won't inject if your HbA1c is above 8.5 (type 1 or insulin-treated).

Hydrodissection, an emerging option

In selected cases, hydrodissection of the median nerve may be considered as an alternative or adjunct to steroid injection. It's an ultrasound-guided technique where fluid is injected around the nerve to separate it from surrounding structures (the flexor tendons and transverse carpal ligament), reducing mechanical compression, improving nerve mobility, and releasing adhesions.

Where a standard injection targets inflammation, hydrodissection targets the mechanical component of compression. The injectate is typically saline, sometimes with local anaesthetic and in some protocols 5% dextrose, and it can be performed with or without corticosteroid. It may suit you if you have recurrent symptoms after a standard injection, prefer to minimise steroid exposure, have ultrasound evidence of nerve flattening or reduced glide, or have contraindications to corticosteroids. It's not a replacement for surgery in severe CTS, but appears safe under ultrasound guidance with a low complication rate reported in the literature.

Your recovery timeline

Ergonomics, splinting & recurrence

Keep your wrists in a neutral position during activities (not flexed or extended), take regular breaks from repetitive tasks, and use ergonomic tools or a wrist rest. Night splinting keeps the wrist neutral during sleep and I generally recommend continuing it for a few months after injection to maximise benefit and reduce recurrence. If you're overweight, even modest weight loss (5–10%) can help.

Repeat injections are appropriate if you had good relief that has worn off, at least 3 months have passed, and you haven't already had 2–3. If you've had multiple injections with only temporary benefit, surgical release offers more definitive, permanent relief, consider it sooner rather than later if you have significant thumb-base wasting or profound weakness, as there's a point beyond which nerve recovery is incomplete.

Real patient stories

Frequently asked questions

References