What causes carpal tunnel, and what helps? Injections buy time; surgery lasts longer

The tingling, numbness and pain that wake people at night and blur the line between "my hand fell asleep" and something worth treating usually trace to one mechanism: the median nerve being squeezed where it passes through the wrist. That is carpal tunnel syndrome, and its symptoms — tingling, numbness and pain in the hand that may radiate to the forearm or shoulder — follow from that entrapment [s2]. The useful question is not what it is but what actually helps, and two Cochrane reviews give a clearer answer than most conditions can offer.

What causes it

Carpal tunnel syndrome is a clinical picture caused by irritation of the median nerve at the carpal tunnel in the wrist [s1]. The tunnel is a narrow passage bounded by wrist bones and a tough ligament; anything that raises pressure inside it — swelling, repetitive loading, fluid retention — can compress the nerve and produce the classic hand symptoms [s1] [s2]. Most symptomatic cases are treated without surgery, at least to start [s2]. This piece is about what the trials show for the common treatments, not a diagnosis: the same symptoms can arise from problems higher up the arm or neck, which is why assessment matters.

The evidence for steroid injections

The first review examined local corticosteroid injection — a shot of steroid into the wrist — and pooled 12 studies with 671 participants [s1]. Two high-quality randomised trials, together enrolling 141 participants, showed clinical improvement at one month or less after a local steroid injection compared with a placebo injection, with a relative risk of 2.58 (95% confidence interval 1.72 to 3.87) [s1]. In plain terms, injection roughly doubled the chance of short-term improvement.

The catch is durability. The reviewers found that significant symptom relief beyond one month has not been demonstrated [s1]. An injection also outperformed steroid taken as a pill: compared with oral corticosteroid, the injection gave significantly more improvement at 12 weeks (mean difference -7.10, 95% CI -11.68 to -2.52 on a symptom score) [s1]. But it did not clearly beat every alternative — against anti-inflammatory medication plus splinting, symptoms did not improve significantly more at eight weeks (mean difference 0.10, -0.33 to 0.53) [s1]. And two injections were no better than one (mean difference -3.80, -9.27 to 1.67) [s1]. The honest summary: a steroid injection reliably helps for about a month, and the case for repeating it or expecting lasting relief is weak.

The evidence for surgery

The second review compared surgery — releasing the ligament that roofs the tunnel — with non-surgical treatment, and found four randomised trials involving 317 participants [s2]. Three of them, with 295 participants (148 assigned to surgery and 147 to non-surgical care), reported improvement at three months, and the pooled estimate favoured surgery, with a relative risk of 1.23 (95% CI 1.04 to 1.46) [s2]. Two trials with 245 participants measured outcomes at six months, again favouring surgery, with a relative risk of 1.19 (1.02 to 1.39) [s2]. The advantage is real but not enormous, and surgery carries its own risks and recovery that conservative options do not.

What it adds up to

Read together, the two reviews sketch a sensible ladder rather than a single fix. A local steroid injection gives dependable short-term relief and can buy time or settle a flare, but its benefit fades within weeks [s1]. Splinting and anti-inflammatory treatment perform comparably to injection over the first couple of months [s1]. Surgery delivers a modestly higher chance of improvement that holds at three and six months, which matters most for symptoms that keep returning [s2].

Both reviews come with limits worth stating. The injection evidence rests heavily on two good trials among twelve of mixed quality, and it could not show anything about relief past a month [s1]. The surgical review pooled only a few trials and did not settle every question about which patients gain most or for how long [s2]. Neither tells an individual what to do — that depends on how severe the nerve compression is, how long it has lasted, and factors a clinician has to weigh. What the trials do establish is the shape of the choice: injections for the short term, surgery for the longer.