Cubital Tunnel Syndrome: Ulnar Nerve Entrapment at the Elbow

Written by Jim Lewis R. NCS.T, CNCT

Updated September 2026 ·11 min read

Cubital tunnel syndrome is compression of the ulnar nerve at the elbow, and it is the second most common entrapment neuropathy after carpal tunnel — a ranking Jim Lewis R. NCS.T, CNCT states plainly in his course: “the second most common entrapment site is actually ulnar neuropathy across the elbow.”

What makes it different from carpal tunnel is that localisation genuinely changes management. The ulnar nerve can be compressed at the elbow, at the wrist, or be affected by a problem at the nerve root or in the brachial plexus, and the symptoms overlap enough that the examination alone often cannot separate them. The nerve conduction study is built to.

This guide covers the symptoms and the populations it appears in, how the study localises the lesion, the technique that narrows it further, and what distinguishes an elbow lesion from one at the wrist. It sits under our clinical reference to electrodiagnostic testing.

Cubital tunnel syndrome symptoms

Dr. Gisele J. Girault describes the presentation as numbness and tingling in the hand and fingers, specifically the fourth and fifth fingers — the ring and little finger.

Because the ulnar nerve also supplies most of the intrinsic muscles of the hand, weakness is part of the picture rather than an advanced complication. Grip weakness is the commonly reported form, and it is the finding that distinguishes a nerve problem from a purely sensory complaint.

The anatomy explains why the elbow is where it happens. The ulnar nerve runs in close proximity to the medial epicondyle on the inside of the elbow, and Girault emphasises how exposed it is — “it’s very superficial. You can actually feel the ulnar nerve. It’s just under the skin.”

Dr. Robert Stall adds the bedside test: Tinel’s sign, tapping or percussing the cubital tunnel to reproduce the symptoms of an ulnar entrapment neuropathy. The tunnel sits posterior to the medial epicondyle — the spot commonly called the funny bone.

Who develops it, and why

Girault’s clinical observations point at mechanical load and at the tunnel narrowing for other reasons.

Sustained pressure on the elbow. She commonly sees it in people who rest an elbow on an armchair, and in long-distance truck drivers resting an arm on an armrest for long periods — compressing the ulnar nerve directly at the elbow.

Diabetes. Both cubital and carpal tunnel syndromes are more prominent in diabetic patients, because diabetics tend to have peripheral neuropathies in which the longest nerves are affected first, leaving the nerve less able to tolerate a focal compression on top of it.

Pregnancy. The mechanism here is fluid. The extra water carried in pregnancy narrows the cubital and carpal tunnels, compressing nerves that were previously accommodated.

The unifying principle Girault teaches across all three tunnels — cubital, carpal and tarsal — is the same: a relatively superficial nerve passes through a tunnel roofed by a ligament or retinaculum, and the syndrome develops when that tunnel gets smaller.

How the nerve conduction study localises the compression

The strategy is to bracket the suspected lesion, and Lewis explains the reasoning in plain terms: with any entrapment neuropathy, “I wanna try to get below and above the entrapment site” — because a segment that conducts normally on one side of a lesion and abnormally on the other identifies the lesion, in his phrase, like a “red flashing light. Here’s the problem.”

So the ulnar study uses three stimulation sites rather than the two a routine nerve would take: the wrist, below the elbow, and above the elbow. The recording is made over the abductor digiti minimi in the hand — a muscle Lewis has students find on themselves by spreading the fingers and feeling where the bulk sits.

One detail of the below-elbow site matters technically. Because the entrapment is typically at the retroepicondylar groove, the below-elbow stimulation should not be placed too far distally — putting more tissue between the stimulator and the nerve forces the current higher and blurs the comparison the whole study depends on.

Inching studies

When bracketing shows a lesion between two points, the same logic can be applied at higher resolution.

Lewis describes it as a direct extension of the principle: “if I can get below and above the entrapment site, I can kind of say, here’s where the problem is. Well, if I can do that in little smaller segments, I can even be more accurate. And this is what we call an inching study.”

Stimulating at short intervals across the elbow narrows the lesion from a segment to a point, which is what a surgical decision benefits from. The trade is patient time and comfort, so it is applied where the localisation will change what happens next rather than routinely.

He makes the same argument for additional measurements generally — more data gives a statistical advantage, and it is worth taking “especially if it’s close to normal or close to abnormal, if it’s right on the edge.”

Elbow or wrist: the finding that separates them

Ulnar compression at Guyon’s canal at the wrist produces a similar complaint in the same fingers, and one examination finding distinguishes it before any electrode is placed.

The dorsal cutaneous branch of the ulnar nerve leaves the main trunk in the forearm, well above the wrist. A lesion at the elbow is proximal to that branch point and so affects it; a lesion at the wrist is distal to it and spares it. Lewis puts the consequence concisely — in wrist compression, “the dorsum of the hand is preserved.”

So numbness extending to the back of the hand argues for the elbow. Numbness confined to the palmar surface of the ring and little fingers argues for the wrist. It is the kind of detail Lewis returns to throughout the course, describing the work as “putting pieces of a puzzle together — do they make sense? Do they fit?”

Two other possibilities belong on the list: a C8 or T1 radiculopathy, and a lower trunk brachial plexus lesion. Both can produce ulnar-pattern symptoms, and both are separated from an elbow lesion by needle examination of muscles that share the root but not the nerve. The general approach is covered in what a nerve conduction test diagnoses.

What the study says about severity

The same two measures that grade carpal tunnel apply here, and Lewis’s summary of what each represents is the most useful sentence for reading any report: “myelin’s got more to do with speed. The number of axons has more to do with the number of axons.”

Slowing across the elbow with preserved response amplitudes indicates demyelination — the earlier and more recoverable state. A drop in amplitude indicates axon loss, and denervation in the ulnar-supplied hand muscles on needle examination indicates that loss has progressed. That distinction bears directly on how urgently surgical decompression is discussed, in the same way it does for the median nerve at the wrist. The parallel study is set out in carpal tunnel electrodiagnostic testing.

As with any surprising result, technical factors come first. Limb temperature above all — a cold arm conducts slowly and mimics demyelination.

Non-surgical treatment, and one comparison worth knowing

Activity modification and elbow padding address the mechanical cause where sustained pressure is the driver, and for many patients that is the whole treatment.

Where injection is considered, Stall reports a head-to-head finding that runs against the usual assumption: comparisons have found sterile 5% dextrose injection more effective than corticosteroid for ulnar nerve entrapment at the elbow. He also notes that most published data on platelet-rich plasma in peripheral neuropathy has concentrated on the entrapment neuropathies, carpal tunnel and ulnar among them.

The dextrose technique and its rationale are covered in perineural injection therapy.

One anatomical caution applies to any needle near the medial epicondyle. Dr. Glenn Barnes notes that in approximately 10% to 15% of the population the ulnar nerve dislocates out of the cubital tunnel and moves anterior to the medial epicondyle when the elbow is flexed — which is why medial elbow procedures are performed with the elbow in full extension.

For clinicians

Ulnar studies across the elbow are among the techniques where small errors in distance measurement and stimulation site produce confident-looking wrong answers, which is why they are learned hands-on with supervision. Empire teaches nerve conduction and needle EMG technique across the pain management academy.