The nerve is particularly vulnerable to injury when there has been a disruption in the normal anatomy. The most common site of ulnar nerve entrapment is at the elbow, followed by the wrist.Causes or structures which have been reported to cause ulnar nerve entrapment include:
Problems originating at the neck: thoracic outlet syndrome, cervical spine pathology, compression by anterior scalene muscles
Problems originating in the chest: compression by pectoralis minor muscles
Brachial plexus abnormalities
Elbow: fractures, growth plate injuries, cubital tunnel syndrome, flexorpronator aponeurosis, arcade of Struthers
Forearm: tight flexor carpi ulnaris muscles
Wrist: fractures, ulnar tunnel syndrome, hypothenar hammer syndrome
Artery aneurysms or thrombosis
Other: Infections, tumors, diabetes, hypothyroidism, rheumatism, and alcoholism

Cubital tunnel syndrome
The most common location of ulnar nerve impingement at the elbow is within the cubital tunnel, and is known as cubital tunnel syndrome. The tunnel is formed by the medial epicondyle of the humerus, the olecranon process of the ulna and the tendinous arch joining the humeral and ulnar heads of the flexor carpi ulnaris muscle. While most cases of injury are minor and resolve spontaneously with time, chronic compression or repetitive trauma may cause more persistent problems. Commonly cited scenarios include:

Sleeping with the arm folded behind neck, elbows bent. Pressing the elbows upon the arms of a chair while typing. Resting or bracing the elbow on the arm rest of a vehicle. Bench pressing. Intense exercising and strain involving the elbow.Compression of the ulnar nerve at the medial elbow may occasionally be caused by an epitrocheloanconeus muscle, an anatomical variant.
Since cases of LMG that were manifestations of granulomatosis with polyangiitis, a vascular inflammatory but not malignant disease, the term lethal midline granuloma is considered confusing and obsolete. References


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