Ganglion cysts around the elbow joint are unusual, with fewer than 25 citations (most of which are case reports) in the English-language literature. Among the many causes of elbow pain, cysts are chiefly diagnosed by advanced imaging. When an elbow ganglion or perineural cyst is symptomatic, treatment has ranged from nonoperative to surgical intervention. Our case report is the first documented ultrasound-guided aspiration and cortisone injection to successfully alleviate a patient’s symptoms. The procedures and outcomes of minimally invasive ultrasound-guided aspiration and steroid injections have not been described for cysts around the elbow. The patient and patient’s guardian provided written informed consent for print and electronic publication of this case report.
Case Report
A 14-year-old female freshman varsity softball pitcher on multiple teams presented with 6 months of vague right elbow pain. She was unable to pitch and had intermittent sharp pain localized to the lateral proximal forearm. She was, however, able to bat without pain and denied any radiating paresthesias. Despite a reduction in sports activities, the symptoms did not improve.
On physical examination, there was preserved strength that was symmetric with the contralateral side of all major muscles innervated by the radial nerve in the right arm, including full wrist, thumb, and finger extension. Sensation was intact to light touch in all major nervous distributions of the right and left upper extremities. She was tender to palpation at the radiocapitellar joint anteriorly, as well as just distally. The patient was also tender with motion through the proximal radial head. She had pain with resisted finger extension; however, resisted supination elicited no discomfort or pain.
The initial diagnostic workup included radiographs of the right elbow, a magnetic resonance imaging (MRI) scan, and an ultrasound. Elbow radiographs revealed no abnormalities. The MRI scan showed a well-circumscribed ovoid T2-hyperintense structure within the supinator muscle measuring 0.6×0.6×0.4 cm (longitudinal × anteroposterior × transverse), just deep to the split of the superficial and deep radial nerves (Figures 1A-1C). A musculoskeletal ultrasound was performed to further characterize and determine the relationship to neurovascular structures. Longitudinal (Figure 2A) and transverse (Figure 2B) images showed a hypoechoic cystic structure, separate from any local nerve, and without Doppler flow, consistent with what was seen on MRI. Additionally, there was an apparent stalk communicating with the anterior margin of the radiocapitellar articulation, seen on longitudinal images, suggesting an extension of the joint capsule (Figure 3A).
We diagnosed the patient with a radiocapitellar ganglion cyst. Her symptoms continued despite several sessions of physical therapy and cessation from all throwing. Given the ultrasound and MRI findings, and continuation of the symptoms despite conservative treatment, alternative treatment plans were discussed with the patient. These included continued activity modification and nonoperative treatment, open excision of the cyst, or aspiration of the cyst under ultrasound guidance. All appropriate risks and benefits were discussed, including possibility of nerve damage given the proximity of the cyst to the radial nerve branches. After a thorough discussion with both patient and family, a plan was made to undergo aspiration under ultrasound guidance. This was carried out using a lateral-to-medial in-plane approach, transverse to the radius. Using a 19-g, 1.5-inch needle (Figure 3B), 1 mL of serosanguinous fluid was aspirated from the cyst, followed by injection of 40 mg methylprednisolone sodium succinate.
The patient made a dramatic recovery within 8 days after aspiration. On examination, she had full strength to resisted flexion, extension, pronation, and supination; had no tenderness to palpation over the supinator; and no pain with resisted finger extension. She began dedicated physical therapy and a gradual return to throwing. She was able to return to her original level of softball activities 2 months after the aspiration. The patient continued to be symptom-free 26 months after the aspiration/injection. There was no evidence of recurrence of the ganglion on repeat ultrasound at her most recent follow-up (Figures 4A, 4B).
Discussion
Our review of the English-language literature identified 23 reports of cysts in and around the supinator muscle. Ganglion cysts are benign lesions that are uncommonly seen about the elbow. This highlights the rarity of this diagnosis, as well as the need for recognition of its existence. Cysts located in the substance of the nerve1-5 and extraneural ganglia causing symptomatic nerve compression have been described. These extraneural ganglia have been reported to cause compression of the ulnar nerve,1-4,6 posterior interosseous nerve (PIN),5,7-12 and radial nerve,13 and isolated compression of the radial sensory branch.14-17 Ganglion cyst compression in the elbow can result in pain, decreased motor function, and decreased sensation. The PIN syndrome is primarily a motor deficiency, whereas isolated compression of the sensory branches of the radial nerve presents as pain along the radial tunnel and extensor muscle mass.17