What is Cubital Tunnel Syndrome?
Cubital tunnel syndrome is a condition that occurs due to compression of the ulnar nerve at the elbow, during its passage through the cubital tunnel. The cubital tunnel is a narrow passage in the elbow, made up of muscle, ligament and bone, through which the ulnar nerve passes on its way to wrist and hand. In this condition, the cubital tunnel becomes swollen and inflamed and exerts pressure on the ulnar nerve.
Cubital tunnel syndrome is the second most common compression neuropathy of the upper extremity, after carpal tunnel syndrome.
Origin & Distribution of the Ulnar Nerve
The Ulnar nerve originates from the brachial plexus which is a complex neural network in the shoulder, extending into the axilla, behind the collarbone. The nerve travels through the elbow, down the arm, and terminates in the hand.
At the elbow, the ulnar nerve passes through the cubital tunnel and runs under a small bony protrusion called the medial epicondyle, as it crosses behind the elbow. This spot in the cubital tunnel is called the “funny bone”, where the nerve is located adjacent to the skin. The “funny” thing about this “funny bone” is that when it hits a hard surface, a sharp, weird, electric shock-like sensation is felt, which can make you laugh and cry at the same time, rather like tickling!
Below the elbow, the ulnar nerve enters the muscles and passes down the forearm and into the hand through another tunnel called Guyon’s canal or ulnar canal located at the wrist. In the hand, the nerve innervates the side of the palm, the little finger and ring finger and provides sensation to these areas. It gives the small muscles the ability to perform fine motor activities and the larger ones the ability to perform coordinated tasks such as gripping and grasping.
What are the Causes of Cubital Tunnel Syndrome?
The following are the major causes of cubital tunnel syndrome:
- Ulnar Nerve Compression: This usually occurs due to bending of the elbow, but can also occur at the arcade of Struthers, which is a band of connective tissue (fascia) in the medial aspect of the distal humerus overlying the ulnar nerve.
- Overuse: During normal flexion of the elbow, the ulnar nerve experiences a 20-fold increase in pressure within the cubital tunnel. Any further force exerted by exercises (bench press) or sports (baseball) can cause neuropathy
- Tumor / Hematoma: Formation of a tumor and hematoma can cause ulnar nerve compression.
- Injury: Humerus fracture or elbow dislocation can result in swelling and fluid build-up at the elbow joint, causing compression and damage to the ulnar nerve.
- Infection & Cysts: Infectious diseases or cyst formation near the elbow joint can damage the ulnar nerve.
- Elbow Structure: The peculiar bony structure of the elbow can cause subluxation (partial dislocation) of the ulnar nerve. This makes the nerve slide back and forth over the medial epicondyle, causing nerve irritation.
- Bone Spur Formation: Formation of bone spurs (bony projections), which are associated with osteoarthritis, can damage the elbow joint and the ulnar nerve.