The release worked halfway. That is the clue, not the failure.

CARPAL TUNNEL, OR THE NECK?

This mistake runs in both directions and costs people years. Carpal tunnel gets released and the hand stays numb. A neck gets injected and the hand stays numb. The reason is the same in both cases: nobody localized the lesion before treating it.

Why the two look alike

The C6 nerve root supplies the thumb and index finger. The median nerve, compressed at the wrist, supplies the thumb, index, middle and half the ring finger. The overlap at the thumb and index is almost complete, and that is where most hand symptoms are reported.

So a person pointing at their thumb has described a territory served by two structures thirty centimetres apart. Both are common. Both increase with age. And a study of patients with cervical radiculopathy found carpal tunnel features present at a rate that makes coincidence a poor assumption.

The features that actually separate them

• Night waking. Carpal tunnel wakes people, typically in the small hours, and they shake the hand to relieve it. A cervical root rarely does this in the same stereotyped way.
• Where it stops. Carpal tunnel does not go above the wrist in most people. Radicular pain travels from the neck down and frequently involves the shoulder or scapula first.
• Neck movement. If turning or extending the neck reproduces the hand symptoms, that is the neck. If it does nothing, that is evidence but not proof against it.
• Sparing of the thenar eminence. The palm over the thumb muscle bulk is supplied by a branch that leaves before the tunnel, so numbness there argues against carpal tunnel and toward something more proximal.
• The little finger. Involved means it is not carpal tunnel. That is ulnar territory or C8, and it changes the whole question.
• Reflexes and myotomal weakness. A diminished brachioradialis or triceps reflex points at a root. Carpal tunnel does not alter reflexes.

Which direction the error usually runs

More often, a neck problem gets called carpal tunnel — because the hand is where the patient feels it, because carpal tunnel is the more common diagnosis, and because a release is a straightforward operation that gets offered. The tell is a release that produced partial or no benefit.

The reverse happens too, and is worse in one respect: an MRI showing foraminal narrowing is easy to find in anybody over fifty, so a genuine carpal tunnel in a person with an ordinary degenerate neck gets attributed upstream and treated with injections that were never going to reach it.

The test that settles it

Nerve conduction studies with needle EMG. Conduction studies localize a median neuropathy at the wrist and grade it; needle EMG looks for the myotomal pattern of a root lesion. Together they answer the question that examination and imaging leave open.

One caveat carried over from that page and worth repeating here: a normal EMG does not exclude radiculopathy, because it detects axon loss rather than irritation. A normal study plus a convincing radicular story means the workup continues, not that the neck is exonerated.

When it is both

Frequently. Finding one does not end the examination, and that principle has a name — double crush. A mildly irritated root and a mildly narrowed tunnel together produce symptoms neither would cause alone, and treating one gives a partial result that reads as failure.

The metabolic thread under both

Carpal tunnel and cervical degeneration share risk factors that nobody raises in either clinic. Diabetes, obesity, hypothyroidism and inflammatory arthropathy all raise carpal tunnel risk substantially, and the same insulin resistance that thickens the flexor retinaculum glycates the collagen in the neck.

That is why the two so often present together in the same person. It is also the part of this that is modifiable, and the only part that reduces the chance of the next entrapment.

What a good examination covers in ten minutes

• Sensation tested by territory — thumb, index, middle, ring, little — not “does your hand feel normal”.
• Thenar bulk and abductor pollicis brevis strength, which is the muscle carpal tunnel weakens.
• Reflexes at biceps, brachioradialis and triceps.
• Spurling’s test at the neck, and Phalen’s and Tinel’s at the wrist — all in the same appointment.
• The elbow, because ulnar neuropathy there is the third candidate and is regularly skipped.

None of that requires equipment and all of it is more informative than another scan. If your assessment did not include the neck and the elbow as well as the wrist, the differential was never actually done.

If a release is being offered

Three questions worth asking first. Has the neck been examined in the same appointment? Has an electrodiagnostic study confirmed a median neuropathy at the wrist, and how severe? And if there is also a cervical finding, which is expected to be the dominant one?

A release for a confirmed, appropriately severe carpal tunnel is a good operation with a high success rate. A release performed on a hand whose numbness was coming from C6 is a good operation on the wrong structure, and the disappointment afterward is frequently attributed to the patient.

There is also a step between doing nothing and operating that frequently gets skipped. For mild to moderate compression we perform ultrasound-guided hydrodissection — separating the nerve from the tissue it has adhered to using fluid rather than an incision. It is done here, it takes fifteen minutes, and it does not close off a later release if one is needed.

What happens when neither is the answer

A proportion of people have hand symptoms from neither the neck nor the wrist. A peripheral polyneuropathy — commonly diabetic — produces symmetrical, glove-distribution numbness starting in the feet. Thoracic outlet involves the lower trunk and gives ulnar-side symptoms with positional provocation. And a few have a central cause.

Symmetrical symptoms in both hands, or symptoms in the feet as well, should redirect the workup entirely. That is worth saying because it is the pattern most often forced into a carpal tunnel diagnosis it does not fit.

What people ask when the hand is numb and nobody agrees why

I had a carpal tunnel release and it only half worked. What now?

That is one of the most common presentations here and it usually means there was a second lesion. A cervical root, or a proximal median or ulnar problem, that was never tested for. Electrodiagnosis and a proper cervical examination is the next step, not a repeat release. Hydrodissection for carpal tunnel.

My little finger is numb too. Is that carpal tunnel?

No. The little finger is ulnar territory or C8. That points at the elbow or at the lower cervical roots, and it is a genuinely useful thing to notice. Cubital tunnel, or the neck?. The finger map is the fastest way to separate ulnar territory from C8.

Can neck treatment fix carpal tunnel?

No. If the median nerve is compressed at the wrist, treating the neck does not reach it. That is exactly why localizing the lesion first matters more than choosing a treatment. The electrodiagnostic study explained.

Do I need an MRI or a nerve test?

If the question is which structure, the nerve test is the informative one. Imaging tells you what the neck looks like, which in most adults is degenerate and unhelpful for this particular question. Double crush syndrome.

Related reading

• EMG and nerve conduction studies
• Double crush syndrome
• Cervical radiculopathy
• Cubital tunnel, or the neck?
• When your hands are the problem
• Thoracic outlet syndrome