The cubital nerve, also known as the ulnar nerve, is a significant component of the arm’s nervous system, often recognized for the tingling sensation it produces when impacted. This sensation is commonly referred to as hitting the “funny bone,” which highlights the nerve’s exposed position. The cubital nerve plays a role in both sensation and movement in the forearm and hand, making its location and function important for overall arm dexterity and feeling.
Anatomical Location of the Cubital Nerve
The cubital nerve begins its journey from the brachial plexus, a network of nerves originating in the neck, and descends down the arm. In the upper arm, it travels along the medial side, initially with major blood vessels, before passing through a fibrous band known as the arcade of Struthers in some individuals. It then moves to the posterior compartment of the arm.
As the nerve approaches the elbow, it takes a distinctive path around the back of the medial epicondyle, the bony prominence on the inside of the elbow. This specific area is often called the “funny bone” due to the nerve’s superficial position. Here, the cubital nerve passes through a narrow space called the cubital tunnel, which is bordered by the medial epicondyle, the olecranon process of the ulna, and a ligament forming its roof. The cubital tunnel guides the nerve from the upper arm into the forearm.
After navigating the cubital tunnel, the cubital nerve continues its course into the forearm by passing between the two heads of the flexor carpi ulnaris muscle. It then travels along the ulna before reaching the wrist. At the wrist, the nerve enters the hand through another passageway called Guyon’s canal, finally distributing its branches throughout the hand.
Function and Common Sensations
The cubital nerve serves a dual purpose, providing both motor control and sensory perception to specific areas of the forearm and hand. For motor control, the nerve innervates certain muscles in the forearm, including the flexor carpi ulnaris and part of the flexor digitorum profundus, which are involved in wrist flexion and finger movement. It also controls most small muscles within the hand, contributing to fine motor skills like grasping, pinching, and finger spreading.
For sensation, the cubital nerve is responsible for providing feeling to the little finger and the inner half of the ring finger. It also supplies sensation to the corresponding parts of the palm and the back of the hand.
The “funny bone” sensation occurs because the cubital nerve is vulnerable as it passes through the cubital tunnel at the elbow. Here, the nerve has limited protection, covered only by skin and minimal soft tissue. When this unprotected segment is struck, the impact directly stimulates the nerve fibers, leading to a sudden, electric shock-like feeling that radiates down the arm into the little and ring fingers. This temporary compression or irritation results in the tingling, numbness, or sometimes painful feeling associated with hitting the “funny bone.”