Ulnar neuritis, known in medical terminology also as Cubital Tunnel Syndrome, is one of the most frequently appearing and annoying conditions of chronic nerve pressure and entrapment in the upper limb, right after carpal tunnel syndrome. It is a condition that can significantly downgrade the patient’s quality of life, as it directly affects the sensation and functionality of the hand, making even the simplest daily activities difficult. To understand the condition, it is important to know a few elements about the anatomy of the region. The ulnar nerve is one of the three main nerves of the hand. It starts from the neck region, crosses the arm, passes through the elbow, and ends in the hand, giving sensation to the little finger and half of the ring finger, while controlling most of the small (intrinsic) muscles of the palm that are responsible for delicate movements. In the elbow region, the ulnar nerve passes through a very narrow, bony and ligamentous “tunnel” on the inner surface of the joint, the cubital tunnel. At this point, the nerve is located exactly under the skin, having minimal protective fat or muscle tissue around it (it is the well-known spot that when we hit it accidentally we feel a sharp pain like an “electric current”). This exact anatomical position renders it exceptionally vulnerable, exposed to direct injuries, friction, and various mechanical strains.
When the nerve is compressed, stretched excessively, or becomes inflamed within this tunnel, ulnar neuritis is caused.
Ulnar Neuritis: Causes and Risk Factors
Ulnar neuritis is not the result of a single cause, but usually arises from a combination of anatomical, mechanical, and daily factors. The main causes and mechanisms of appearance of ulnar neuritis are the following:
Prolonged or Repetitive Elbow Flexion
When we bend our elbow, the ulnar nerve stretches around the bony prominence (the medial epicondyle) like a guitar string. Prolonged or continuously repetitive movements that mandate flexion of the elbow over 90 degrees reduce the space in the cubital tunnel and interrupt the smooth blood supply to the nerve. This is frequently observed in:
- People who talk for a long time on the mobile phone holding it to their ear (the so-called “cell phone elbow”).
- Individuals who sleep in a fetal position or with their arms folded under their head/pillow.
- Occupations requiring continuous flexion, such as musicians, drivers, or computer workers who rest their elbows at the wrong height.
Direct Pressure
Because the nerve is completely superficial, continuous direct pressure on hard surfaces causes ischemia (lack of blood) to the nerve. Resting the elbow on the armrest of the chair, on the desk, or on the car door by drivers, is among the most frequent causes of its irritation.
Elbow Fractures and Anatomical Abnormalities
Elbow fractures that had arisen in the past (even during childhood) may have changed the geometry of the joint (e.g., creation of valgus deformity), resulting in the nerve stretching at an unnatural angle. In addition, bone spurs (osteophytes) from pre-existing osteoarthritis or the creation of scars from old injuries can narrow the tunnel.
Nerve Instability
In some people, the anatomical sheath of the nerve is loose. During flexion of the elbow, the nerve “slips” (subluxates) out of its position and “snaps” over the bone. This continuous friction, over the passage of time, causes severe inflammation and thickening of the nerve.
Presence of Edema in the Joint
Any condition causing a accumulation of fluid in the elbow joint, such as olecranon bursitis, rheumatoid arthritis, or even a ganglion cyst, can increase the pressure inside the cubital tunnel and crush the ulnar nerve.