Compression of the radial nerve at the elbow by a ganglion: two case reports
© Jou et al; licensee Cases Network Ltd. 2009
Received: 4 October 2008
Accepted: 22 January 2009
Published: 5 June 2009
Radial nerve compression by a ganglion in the radial tunnel is not common. Compressive neuropathies of the radial nerve in the radial tunnel can occur anywhere along the course of the nerve and may lead to various clinical manifestations, depending on which branch is involved. We present two unusual cases of ganglions located in the radial tunnel and requiring surgical excision.
A 31-year-old woman complained of difficulty in fully extending her fingers at the metacarpophalangeal joint for 2 weeks. Before her first visit, she had noticed a swelling and pain in her right elbow over the anterolateral forearm. The extension muscle power of the metacarpophalangeal joints at the fingers and the interphalangeal joint at the thumb had decreased. Sonography and magnetic resonance imaging of the elbow revealed a cystic lesion located at the area of the arcade of Frohse. A thin-walled ovoid cyst was found against the posterior interosseous nerve during surgical excision. Pathological examination was compatible with a ganglion cyst. The second case involved a 36-year-old woman complaining of numbness over the radial aspect of her hand and wrist, but without swelling or tumor in this area. The patient had slightly decreased sensitivity in the distribution of the sensory branch of the radial nerve. There was no muscle weakness on extension of the fingers and wrist. Surgical exposure defined a ganglion cyst in the shoulder of the division of the radial nerve into its superficial sensory and posterior interosseous components. There has been no disease recurrence after following both patients for 2 years.
Compression of nerves by extraneural soft tissue tumors of the extremities should be considered when a patient presents with progressive weakness or sensory changes in an extremity. Surgical excision should be promptly performed to ensure optimal recovery from the nerve palsy.
Compressive neuropathies are important and widespread debilitating clinical problems. The two most common compressive peripheral nerve disorders in the upper limb are carpal tunnel syndrome and cubital tunnel syndrome, however, radial tunnel syndrome occurs less frequently . The radial tunnel is defined as the potential space created by structures surrounding the radial nerve as well as its posterior interosseous nerve and its superficial sensory branch as they travel through the proximal forearm from the radiocapitellar joint past the proximal edge of the supinator muscle [1, 2]. Compressive neuropathies of the radial nerve in the radial tunnel can occur anywhere along the course of the nerve and may lead to various clinical manifestations, depending on which branch is involved [3, 1]. Radial nerve compression by a ganglion in the radial tunnel is not common . The clinical features of our two cases of radial nerve compression syndrome due to a ganglion are reported, and the anatomical characteristics of two possible compression sites in the radial tunnel are discussed.
Radial nerve entrapment in the radial tunnel is uncommon in peripheral nerve compressive neuropathies. There are three different types of palsy in the radial tunnel syndrome: posterior interosseous nerve palsy, neuropathy of the sensory branch of the radial nerve, and neuropathy of both nerves [1, 3]. The posterior interosseous nerve is most vulnerable to compression just beyond its origin as it passes beneath the arcade of Frohse at the proximal edge of the supinator in the radial tunnel . Compression of the posterior interosseous nerve alone may manifest as motor weakness in the distribution of the posterior interosseous nerve, resulting in inability to extend the metacarpophalangeal joints of the finger and thumb, as well as weakness in extension of the thumb at the interphalangeal joint, also called "finger drop". Usually there is not complete wrist drop, because the extensor carpi radialis longus and brevis are supplied by the radial nerve proximal to its terminal branch. Compression of the superficial sensory branch alone may present as pain and decreased sensation along the cutaneous area on the radial side of the dorsum of the hand . When a patient presents with compression neuropathy of the radial nerve below the elbow, differential diagnosis of the cause of the palsy and further determination of the location of the entrapment in the radial tunnel are important.
Compression of the posterior interosseous nerve by a ganglion was first reported by Bowen in 1966 . He recorded a ganglion developed from post-traumatic osteoarthritic elbow secondary to an old intercondylar fracture of the humerus. These cysts are most likely caused by repetitive use or by inflammatory or traumatic conditions, and result primarily from myxoid degeneration. They are associated with increasing liquefaction of collagen fibers surrounded by densifying collagen bundles, which form a delimiting capsule. Other tumors can result in a space-occupying lesion which compresses the nerve. The most common tumors causing symptoms are rheumatic synovial cysts, lipomas, fibromas and pseudoneuromas -. Usually, these tumors cause paralysis with an insidious onset.
When a ganglion is not detected by palpation in cases with palsy of the posterior interosseous nerve or sensory branch, differential diagnosis of the cause of the palsy may be difficult. Compression of nerves by extraneural soft-tissue tumors of the extremities, although not common, should be considered when a patient presents with progressive weakness or sensory changes in an extremity. This is true whether or not a soft-tissue mass is found during examination, since an occult soft-tissue tumor was found in approximately one-third of patients at the time of operation in a report by Barber .
Ultrasound and MRI have been used to detect space-occupying lesions causing nerve compression . Ultrasound allows a detailed assessment of peripheral nerve continuity with a mass, which indicates an intrinsic nerve abnormality rather than an adjacent extrinsic mass. Ultrasound has also been used to determine whether a lesion is cyst or solid. Recent advances in MRI have increased the ability to localize the region of the nerve compression, and assess the tumor's relationship to nearby neurovascular structures, enhancing pre-operative planning for a precise surgical excision.
Standard surgical management for persistent neuropathy, refractory to non-surgical treatment, is open decompression of the radial nerve. This can be done through a variety of anterior or lateral approaches. The approach includes addressing all of the potential sites of compression in addition to excising the mass lesions described previously which may cause compression of the radial nerve.
Radial nerve compression by a ganglion in the radial tunnel is an uncommon condition. We report two cases of posterior interosseous nerve and superficial sensory branch compression by a ganglion cyst. The value of this case report to the practicing physician is that it sheds light on the importance of familiarity with the possible presentation, anatomic location and differential diagnosis to facilitate corrective diagnostic approaches and timely management.
Written informed consent was obtained from both patients for publication of this case report and any accompanying images. A copy of the written consent is available for review by the Editor-in-Chief of this journal.
There was no funding for the publication of the report. Karen Kuo is thanked for help in drafting the figures and in collection of the literature.
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