Enhanced Effect of Botulinum Toxin A Injections into the Extensor Digitorum Brevis Muscle after Local Mechanical Leg Vibration: A Case Report

Background: The aim of this study was to demonstrate an increase in muscle action potentials and an enhancement of the efficacy of botulinum toxin (BoNT) after mechanical leg vibration. Methods: A 53-year-old healthy male volunteer underwent vibration ergometry training (VET) every morning and every evening for 10 min for 14 days. Compound muscle action potential (CMAP) of the right (R) and left (L) extensor digitorum brevis (EDB) muscle was analyzed by supramaximal peroneal nerve stimulation before and after VET 12 times during the 14 days. Thereafter, VET was stopped and 20 U incobotulinumtoxin (incoBoNT/A) were injected into the right EDB. During the following 10 days, CMAP of both EDBs was tested 12 times. Results: Under VET, the CMAP of both EDBs significantly increased (L: p < 0.01; R: p < 0.01). During the first 14 days, CMAP of the left EDB before VET was significantly (<0.008) lower than 20 min later after VET. This was not the case for the better trained right EDB. After day 14, CMAP of the untreated left EDB further increased for 6 days and then decreased again. In the right EDB, BoNT-treated EDB CMAP rapidly and highly significantly (p < 0.0001) decreased during the first 48 h by about 90%, from a level of about 14 mV down to a plateau of around 1.5 mV. Conclusion: Local mechanical leg vibration has a short- and long-term training effect. Compared to other studies analyzing the reduction in EDB CMAPs after BoNT injections, the reduction of EDB CMAPs in the present study observed after combined application of BoNT and VET was much faster and more pronounced.

Finger abduction as a novel function of the extensor digitorum brevis manus muscle

A 25-year-old female presented with a chronic scapho-lunate ligament injury with development of carpal instability requiring reconstruction. During a standard dorsal longitudinal mid-line approach to the carpus, an extensor digitorum brevis manus (EDBM) muscle was found taking its origin from the dorsal wrist capsule overlying the lunate with innervation from the posterior interosseous nerve (PIN). Electrical stimulation of the muscle belly demonstrated abduction of the middle finger. The EDBM is a rare anatomical variant of the extensor compartment of the wrist and may be encountered during surgical approaches. Where possible these variant muscles should be carefully dissected off underlying structures, preserved and repaired at the conclusion of a procedure to ensure no perceived functional deficit to the patient. We present a case of a previously undescribed EDBM muscle function of pure finger abduction with no extension and a surgical technique of preserving its origin. We propose that the middle finger variant of the EDBM should be re-named the extensor digitorum brevis medius to reflect our findings.

Surgical Management of Extensor Digitorum Brevis Manus Anomaly with a Dorsal Ganglion Cyst

Background The most common soft tissue tumor of the hand is the dorsal ganglion cyst and often is an indication for surgical excision. The differential diagnoses for dorsal hand masses include but are not limited to tenosynovitis, epidermoid cyst, abscess, lipoma, xanthoma, rheumatoid nodule, tophus, carpal boss, myositis ossificans, foreign body granuloma, neoplasm, and anomalous muscles. Case Description Our case report reflects the latter, a 33-year-old female who presented with a 3-year history of a symptomatic dorsal ganglion cyst of her left wrist. She is a female in her 30s, with progressive, worsening pain on wrist extension. Intraoperatively, it was determined that an anomalous extensor digitorum brevis manus (EDBM) was present and may have contributed to her pain and was excised. Literature Review The literature is sparse with the surgical management of EDBM. This case study aims to explore algorithms for managing simultaneous EDBM with a dorsal wrist ganglion, which is clinically relevant for any hand surgeon, when faced with a similar intra-operative management situation.