The radial nerve can be entrapped in several places in its path down the arm, specifically in the axilla, spiral groove of the humerus, and near the lateral humeral epicondyle. The radial nerve is more commonly compressed in the spiral groove along the back of the humerus.
The radial nerve contains branches from the mid and lower cervical spine. The radial nerve joins the profunda brachii artery and vein as it enters the spiral groove between the medial and lateral heads of the tricep. It then travels down the humerus before piercing the intermuscular septum at the hiatus, approximately 10 cm above the lateral humeral epicondyle. The radial nerve supplies branches to the triceps in the upper arm before giving off branches for sensation and muscle strength for the back of the forearm.
The radial nerve can be compressed with abnormal positioning and sleeping at night or external compression from poorly fitting crutches. It occurs with chronic repetitive activities that over utilize the triceps muscle. Compression of this nerve has also been called “Saturday Night Palsy,” after falling asleep with the arm stretched over the back of a hard chair. Because the normal pain mechanisms and feedback were diminished because of intoxication, people do not change their sleep positions leading to prolonged compression and injury to the radial nerve.
The radial nerve can be compressed at different points and each location will create different symptoms. Entrapment of the nerve in the armpit area will produce changes in all motor and sensory distributions of the radial nerve, including weakness, numbness, and tingling. Compression at this spiral groove presents with temporary paralysis without pain.
Treatment for Compression of the Radial Nerve in the Armpit and Humerus
Conservative treatment will address muscle spasms, fascial restrictions, and scar tissue restricting the radial nerve and its normal movement. Rest, nonsteroidal inflammatory drugs, activity modification, and restrictions on exertion with the upper extremity will help the recovery. Manual therapy, massage therapy, Graston Technique, and Active Release Technique (ART) are excellent at addressing the myofascial and scar tissue injuries that could be compressing the nerve between the triceps and long the biceps.
Most mild cases of radial nerve entrapment will recover with rest and muscle treatments. Moderate and more severe cases may require additional treatment including exercises, stretches, posture modification, and muscular retraining of the scapula and upper extremity to reduce stress and strain on the radial nerve as it travels down the arm. These injuries and entrapments benefit from a class IV cold laser or low level laser therapy to enhance nerve regeneration and repair. Radial nerve entrapment or compression causes damage to the nerve axon, and low level lasers enhance its regeneration and repair. Nerves that are treated with low level lasers respond faster than nerves that are not treated with the class IV lasers.
Compression of the radial nerve can produce pain or weakness in the tricep or wrist extensor muscles, especially after sleeping in a very awkward position throughout the night. These cases can be can safely and properly treated with conservative treatment, and patients can expect a full recovery.