613 - An Unusual Cause of Posterolateral Elbow Pain: A Case Report

Case Diagnosis: Left radial nerve schwannoma

Case Description: A 58-year-old woman presented with a 7-year history of atraumatic left posterolateral elbow pain. She described intermittent, unpredictable stabbing pain approximately 2 cm proximal to the left lateral olecranon without radiation or paresthesias. Despite evaluations by multiple physicians and extensive diagnostic workups, no definitive cause was found. She tried various medications, physical therapy, and cervical epidural steroid injections without relief. Cervical spine MRI demonstrated age-related degenerative changes and left elbow MRI was unremarkable.  Electrodiagnostic testing was normal. An ultrasound-guided radial nerve perineural steroid injection at the supinator level provided 7-day symptom resolution. Twelve months later, she noticed a left axillary mass, reproducing her elbow pain when compressed. Diagnostic ultrasound revealed 2.84cm x 3.09cm x 3.46cm left axillary mass compressing the radial nerve against the humerus. Brachial plexus MRI and biopsy confirmed radial nerve schwannoma. Surgical excision of the mass provided 100% relief of her posterolateral elbow symptoms at 2-month follow-up.

Discussions:

Schwannomas are rare tumors that affect the peripheral nervous system. They typically present in the head and neck, causing varying symptoms depending on nerves and structures they compress. On ultrasound, schwannomas are characterized as homogeneous, well-defined hypoechoic masses. They are often ovoid-shaped, and one can see the tumor origin and relation to the affected nerve. In our case, the patient’s schwannoma encapsulated the left radial nerve in the axillary region eliciting difficult-to-localize posterolateral elbow pain.



Conclusions:

 
Due to its rarity, schwannomas are challenging to diagnose early. Ultrasound is readily available, making it a quick diagnostic tool for peripheral nerve lesions. Due to its relative ease of use, availability, quick contralateral comparisons, and safety, ultrasound is an ideal option for quick diagnosis when schwannoma is suspected. Surgical resection is recommended for complete symptom resolution.