Review Question - QID 4557

The clinical presentation is most consistent with a C6 radiculopathy. This would be cause by a a paracentral cervical disc herniation at C5/6.

The differential diagnosis for neuropathic pain in the upper extremity includes peripheral neuropathies, cervical radiculopathy, and peripheral musculoskeletal conditions. Cervical radiculopathy is characterized by unilateral dermatomal distribution of pain which often improves with abduction of the shoulder. A C6 radiculopathy is characterized by weakness to brachioradialis (elbow flexion weakness at a midpoint between supination and pronation), ECRL weakness (wrist extension weakness), sensory changes in the thumb, and a diminished brachioradialis reflex.

Rhee et al. report the differential diagnosis of cervical radiculopathy includes peripheral nerve entrapment syndromes; brachial plexus injury; Parsonage-Turner’s syndrome; and tendinopathies of the shoulder, elbow, and wrist. They report that selective cervical nerve root injections can be useful in confirming the source of symptoms if they improve for a time after the injection, and that electromyography and nerve conduction tests may help differentiate radiculopathy from peripheral entrapment disorders.

Viikari-Juntura et al. investigated validity of the shoulder abduction test in the diagnosis of cervical radiculopathy. They found this test was highly specific but had low sensitivity. Thus, the recommend this test as a valuable aid in the clinical examination of a patient with neck and arm pain.

Illustration A shows the dermatomal distribution of C6. Illustration B shows some key differences between the cervical spine and lumbar spine nerve root anatomy. It shows that in the cervical spine the nerve root travels above the corresponding pedicle whereas in the lumbar spine it travels below the corresponding pedicle. In addition, due to the direct lateral trajectory of the cervical nerve root, both a central and foraminal disc affect the same nerve root. This differs in the lumbar spine where due to the descending path of the nerve root, a paracentral and foraminal (far lateral) disc often affect different nerve roots.

Incorrect Answers:
Answer 1: Lateral epicondylitis, caused by tendinosis and inflammation at origin of ECRB, present with lateral forearm pain and weakness to wrist extension. However, pain relieved by shoulder abduction and paresthesias of the thumb are not characteristic of tennis elbow.
Answer 2: Compression of the posterior interosseous nerve by the proximal edge of supinator is a common cause of PIN compression syndrome. This condition is characterized by painless weakness to wrist extension with noticeable radial deviation.
Answer 3: Compression of the ulnar nerve in Guyon's canal is cause of ulnar tunnel syndrome. This condition is characterized by paresthesias in ulnar 1-1/2 digits and clawing of the ring and little fingers.
Answer 5: A foraminal disc herniation at C6/7 would lead to a C7 radiculopathy. This would be characterized by decreased triceps reflexes, weakness of elbow extension and wrist flexion, and paresthesias of the index and middle finger.