High-resolution sonography of posttraumatic neuroma of the superficial radial nerve.

Abstract

B ö hm J et al. High-Resolution Sonography of Posttraumatic Neuroma ... Cen Eur Neurosurg 2011; 72: 158 – 160 Introduction ▼ The superfi cial radial nerve (SRN) is a sensory branch of the radial nerve which supplies the dorsolateral aspect of the hand and the fi rst 3 digits. The radial nerve, a nerve with mixed fi bers, branches into the pure motor posterior interosseous nerve and the pure sensory superfi cial radial nerve just above the arcade of Frohse in the proximal forearm. In the distal forearm, the superfi cial radial nerve transverses a superfi cial subcutaneous course between the tendons of the brachioradialis and extensor carpi radialis longus muscles as it crosses the lateral edge of the radius. Many factors may contribute to the development of a lesion of the SRN. The most common anatomic site of compression corresponds to the area of transmission of the nerve from its submuscular position beneath the brachioradialis muscle to its subcutaneous position on the surface of the extensor carpi radialis longus muscle. In patients with de Quervain tendosynovitis, secondary irritation of the SRN is frequent. Other common causes include postsurgical injury, external compression and trauma [1] . Patients usually complain of therapy-resistant pain and, consequently, inability to work. Surgery is considered in recalcitrant pain syndrome. Lesions of the SRN are characterized by tenderness on percussion, positive Hoff mann-Tinel-sign, electrifying pain, allodynia and paresthesias in the area of innervation. The diagnosis is based substantially on clinical presentation. Nerve conduction studies are usually performed to confi rm the diagnosis; however, often there are false negative results with diffi culty to identify the exact site of the lesion [2, 3] . The SRN, although small in size, can be visualized with high-resolution sonography using specifi c landmarks [4] . This report describes the role of highresolution sonography in the study of traumatic neuromas of the superfi cial radial nerve and the postoperative result for the fi rst case. Presentation of Cases ▼ Case 1 A 48-year-old female patient with a distal radius fracture and plate osteosynthesis complained of recalcitrant pain and paresthesias in the SRN area after plate removal. It was noted that the pain gradually intensifi ed and a circumscribed spot of tenderness with allodynia, a few centimeters above the styloid process, was verifi ed. Electrophysiological studies were not tolerated. High-resolution sonography was performed on a Toshiba Aplio XV SSA700A scanner with a linear array transducer of 12 MHz. Scanning transversely, the superfi cial radial nerve was fi rst identifi ed approximately 7 cm proximal to the level of the styloid process and the course of the nerve was followed distally over the dorsolateral aspect of the forearm. The nerve was found between the extensor carpi radialis longus and fl exor carpi radialis muscle, just above the palpable bony prominence of the radius muscle, which served as a landmark. On transverse scan, the cross-sectional area of the normal part of the scanned nerve was 3 mm 2 ( ● ▶ Fig. 1 ) with a typical honeycomb appearance. More distally, the nerve was found to be enlarged and hypoechogenic with the cross-sectional area of 30 mm 2 over 0.9 cm with preserved continuity ( ● ▶ Fig. 2 ). The patient requested a surgical therapy because of the recalcitrant pain syndrome. The neuroma-incontinuity was resected and the nerve was reconstructed using a graft of the sural nerve ( ● ▶ Fig. 3 ). Complete pain relief was observed soon after surgery and at the 3-month follow-up. Sonography demonstrated the 1.6 mm (width) × 20 mm (le ng th) nerve graft and the distal normal SRN with a diameter of 0.7 mm ( ● ▶ Fig. 4 ). The tra n sition zones between nerve and transplant were of normal diameter without scarring. Histologic examination confi rmed the neuroma-in-continuity. Su ppo rtive therapy with pregabalin was administered.