Little and ring finger numb. Your elbow and your neck are both suspects.

CUBITAL TUNNEL, OR THE NECK?

Little and ring finger numb. It could be the ulnar nerve at your elbow or the C8 root in your neck, and the two are treated in completely different places.

The two candidates

The ulnar nerve passes behind the medial epicondyle — the bump on the inside of the elbow — through a tunnel that narrows every time you bend your arm. Compression there is cubital tunnel syndrome, the second most common entrapment neuropathy in the upper limb.

The C8 nerve root leaves the neck at the C7-T1 level and carries much of the same territory. Compression there is cervical radiculopathy. Both produce numbness in the little and ring fingers. Both produce hand weakness. Neither is rare.

The single most useful distinction

The dorsal cutaneous branch of the ulnar nerve leaves the main trunk well above the wrist and supplies the back of the hand on the little-finger side. It is affected in cubital tunnel and unaffected in ulnar compression at the wrist.

For the neck-versus-elbow question, the more useful separator is the medial forearm. That skin is supplied by the medial antebrachial cutaneous nerve, which branches off the plexus before the ulnar nerve exists as a separate nerve. Numbness there is not cubital tunnel. It points at the plexus or the root.

What else separates them

• Elbow position matters in cubital tunnel. Symptoms wake you at night with the arm bent, or appear on the phone, or driving with the elbow flexed.
• Neck position matters in radiculopathy. Extension and rotation toward the symptomatic side load the foramen.
• Tenderness and a Tinel sign at the elbow groove point down the arm. Nothing at the elbow points up it.
• Triceps weakness is a C7-C8 root finding, not an ulnar nerve finding — the ulnar nerve supplies nothing above the forearm.

Why the examination is not enough on its own

Because a person can have both, and because the findings overlap enough that confident bedside separation is frequently wrong. Electrodiagnostic testing localizes ulnar slowing across the elbow segment directly, and needle examination distinguishes a root lesion from a nerve lesion by which muscles are involved — specifically, whether the paraspinal muscles and the non-ulnar C8 muscles are affected.

Ultrasound has become a genuinely useful adjunct here, measuring the nerve cross-sectional area at the elbow, and there is a growing literature comparing it directly against electrodiagnosis. We use it where it adds something rather than as a replacement.

What gets treated, and how

For cubital tunnel, conservative management first: elbow extension splinting at night, activity modification, and nerve gliding, all of which have a real evidence base. Where compression is structural and progressive — and particularly where there is muscle wasting — that becomes a surgical conversation, held after the diagnosis is secure.

For a C8 root, the treatment is directed at the neck and nothing at the elbow will change it. That is why getting this right before an operation is not a formality. A cubital tunnel release performed on somebody whose problem is the neck relieves nothing and leaves a scar.

And when both are true

Compression at two points along the same nerve is double crush, and it is why some people get partial relief from a technically successful release. Where both are present, the sequence is decided on which is producing the objective loss.

Why night splinting works so well

The cubital tunnel narrows as the elbow bends, and most people sleep with their elbows flexed for hours. A simple splint holding the elbow near extension removes the single biggest daily dose of compression, and it does it without a procedure.

Three to six weeks is a fair trial. People who improve on it have both confirmed something about the diagnosis and started their own treatment, which is an unusually good return for a piece of foam and a strap.

What wasting looks like and why it matters

Look at the back of your hand between the thumb and index finger, and along the outside of the little finger. Hollowing there, particularly compared with the other side, is ulnar-supplied muscle loss. It is the finding that shifts the conversation from conservative management to a surgical opinion, because recovery of those muscles gets less complete the longer they have been denervated.

It is also easy to miss on yourself and easy to find on examination, which is a reasonable summary of why this appointment is worth having.

What surgery does and does not fix

A decompression or transposition relieves the compression. It does not reverse damage that has already happened to the nerve fibers, which is why the outcome depends heavily on how long the compression has been going on and how much objective loss there already is.

Systematic review and meta-analysis work on the surgical management of cubital tunnel syndrome has compared the techniques, and the honest summary is that the choice of technique matters less than the selection of the patient. A well-selected patient does well with either. A poorly selected patient does badly with both.

The examination findings we are looking for

• Froment sign — the thumb flexing to compensate when pinching paper, showing adductor pollicis weakness.
• Wartenberg sign — the little finger drifting away from the others at rest.
• A positive elbow flexion test held for a minute, reproducing the symptoms.
• A subluxing nerve that snaps over the medial epicondyle as the elbow bends, which changes what surgery would be appropriate.
• Sensation on the back of the hand, which is the branch that separates elbow-level from wrist-level compression.

What people ask about ulnar symptoms

My little finger goes numb when I sleep. Which is it?

Sleeping with the elbow bent is the classic cubital tunnel history. Sleeping with the neck in an unusual position can do it too. Night splinting the elbow for a few weeks is a cheap and informative trial. Sleep position, and why it is part of the plan.

Do I need a nerve test?

If a release is being discussed, yes. It is the difference between operating on the right structure and operating on a bystander. The electrodiagnostic study explained.

Can hand weakness come back?

After decompression, sensation usually recovers better than the small muscles do. Long-standing wasting recovers slowly and sometimes incompletely, which is the reason not to wait years. Double crush syndrome. Sensation recovers ahead of strength, and duration predicts both.

Should I stop leaning on my elbow?

Yes. Sustained pressure and sustained flexion are the two mechanical drivers, and removing both is genuinely first-line treatment rather than advice given while waiting for something else. How the two are separated.

Related reading

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

Sensation usually recovers ahead of strength, and duration predicts both.