Cubital tunnel syndrome (ulnar neuritis)

What it means

The ulnar nerve travels from the neck down the arm and passes through a snug passageway on the inner side of the elbow called the cubital tunnel before continuing into the forearm and hand. This is the nerve responsible for the tingling "funny bone" jolt when you bump the inside of your elbow. Cubital tunnel syndrome develops when this nerve becomes compressed, stretched, or irritated within that tunnel, most often from repetitive elbow bending, leaning on the elbow for long periods, or, less commonly, a nearby cyst, bone spur, or anatomical variation that narrows the space.

Why it appears on a CT or MRI report

MRI of the elbow can directly show ulnar nerve irritation, appearing as a thickened or swollen nerve with brighter signal than expected, sometimes alongside fluid or a structural cause of compression such as a ganglion cyst, thickened tissue band, or bone spur within the tunnel. The report usually describes the nerve's caliber and signal, its exact position relative to the bony groove (since the nerve can subluxate, or slip in and out of the groove, with elbow movement), and any mass or structural narrowing found nearby. Nerve conduction studies, done separately from imaging, are often used alongside MRI to confirm how well the nerve is conducting signals.

What it usually means

Cubital tunnel syndrome is the second most common nerve compression problem in the arm, after carpal tunnel syndrome. It typically causes tingling or numbness in the ring and little fingers, sometimes worsened by bending the elbow, such as while sleeping or talking on the phone, and can progress to weakness or clumsiness in the hand — trouble with fine tasks like buttoning a shirt or a weakening grip — if compression continues over time. Many mild cases improve with activity changes, padding, and avoiding prolonged elbow flexion. More persistent, painful, or weakness-causing cases may need splinting, physical therapy, or, if conservative measures fail or there is visible muscle wasting, surgery to release or reposition the nerve.

When to follow up

See a doctor, hand surgeon, or neurologist if you notice ongoing tingling or numbness in the ring and little fingers, elbow discomfort with bending, or hand weakness, especially if it's affecting grip strength or fine motor tasks. Earlier evaluation tends to lead to better recovery, since prolonged, severe compression can cause muscle wasting in the hand that doesn't fully reverse even after the nerve is decompressed. Sudden, severe weakness or loss of sensation deserves prompt medical attention to rule out a more urgent nerve or spinal cause.

A plain-language way to picture it

Picture the ulnar nerve as a garden hose running through a narrow gap between a fence post and a wall at the elbow — every time you bend your arm, that gap tightens slightly around the hose. Do that occasionally and the hose is fine, but lean on it, bend it repeatedly, or let something narrow the gap further, and the hose gets pinched more and more, so less "water" — nerve signal — gets through to the far end. That's why easing up on the pressure and bending, at least for a while, is usually the first and most effective step toward relief.