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Anatomic Considerations in Evaluation of the Proximal Ulnar Nerve
ELECTROMYOGRAPHY
1047-9651 / 98 $8.00 + .00
ANATOMIC CONSIDERATIONS IN EVALUATION OF THE PROXIMAL ULNAR NERVE Theresa A. Oswald, MD
In 1878, Panas 27, 31, 39 reported slowly progressive or "tardy" ulnar nerve palsy as a complication of certain elbow lesions. Although more than a century has passed since the first descriptions of proximal ulnar neuropathies, evaluation of this focal neuropathy remains challenging and perplexing. 15,61 Ulnar nerve evaluation is a frequent request of an electrodiagnostic consultant. Ulnar entrapment neuropathy is second only to carpal tunnel syndrome as a cause of upper extremity neuropathy. 20, 29, 64 In hopes of adding insight to this common electrodiagnostic puzzle, a review of relevant anatomic considerations follows. GENERAL ANATOMY: AXILLA AND ARM
The ulnar nerve is usually composed of C-8, I-I fibers which form the lower trunk and is the distal continuation of the medial cord of the brachial plexus. There are possible variations to the cervical segmental contribution. The nerve may be composed of purely C-8 fibers or C-7, C-8 fibers. If C-7 contribution is present, these fibers travel through the lateral cord and lateral root of the median nerve to the axillary outlet.72 At this level, the fibers cross distally and medially, anterior to the axillary artery, to reach the ulnar nerve. The ulnar nerve travels along the posterior wall of the axilla beneath the pectoralis minor muscle toward the upper arm. In this region, the ulnar nerve travels in a common neurovascular bundle with the median nerve, medial brachial cutaneous nerve, medial antebrachial cutaneous nerve, brachial artery, and vein. In the neurovascular bundle, the ulnar nerve is located medial to the brachial artery, between the artery and the vein.72 At the level of the insertion of the coracobrachialis muscle, the ulnar nerve separates from the neurovascular bundle and travels with the superior ulnar collateral artery.
From the Rehabilitation Physicians, Prevea Clinic, Green Bay, Wisconsin
PHYSICAL MEDICINE AND REHABILITATION CLINICS OF NORTH AMERICA VOLUME 9 • NUMBER 4 • NOVEMBER 1998
777
1047-9651 / 98 $8.00 + .00
ANATOMIC CONSIDERATIONS IN EVALUATION OF THE PROXIMAL ULNAR NERVE Theresa A. Oswald, MD
In 1878, Panas 27, 31, 39 reported slowly progressive or "tardy" ulnar nerve palsy as a complication of certain elbow lesions. Although more than a century has passed since the first descriptions of proximal ulnar neuropathies, evaluation of this focal neuropathy remains challenging and perplexing. 15,61 Ulnar nerve evaluation is a frequent request of an electrodiagnostic consultant. Ulnar entrapment neuropathy is second only to carpal tunnel syndrome as a cause of upper extremity neuropathy. 20, 29, 64 In hopes of adding insight to this common electrodiagnostic puzzle, a review of relevant anatomic considerations follows. GENERAL ANATOMY: AXILLA AND ARM
The ulnar nerve is usually composed of C-8, I-I fibers which form the lower trunk and is the distal continuation of the medial cord of the brachial plexus. There are possible variations to the cervical segmental contribution. The nerve may be composed of purely C-8 fibers or C-7, C-8 fibers. If C-7 contribution is present, these fibers travel through the lateral cord and lateral root of the median nerve to the axillary outlet.72 At this level, the fibers cross distally and medially, anterior to the axillary artery, to reach the ulnar nerve. The ulnar nerve travels along the posterior wall of the axilla beneath the pectoralis minor muscle toward the upper arm. In this region, the ulnar nerve travels in a common neurovascular bundle with the median nerve, medial brachial cutaneous nerve, medial antebrachial cutaneous nerve, brachial artery, and vein. In the neurovascular bundle, the ulnar nerve is located medial to the brachial artery, between the artery and the vein.72 At the level of the insertion of the coracobrachialis muscle, the ulnar nerve separates from the neurovascular bundle and travels with the superior ulnar collateral artery.
From the Rehabilitation Physicians, Prevea Clinic, Green Bay, Wisconsin
PHYSICAL MEDICINE AND REHABILITATION CLINICS OF NORTH AMERICA VOLUME 9 • NUMBER 4 • NOVEMBER 1998
777