A rare case of first motor branch of median nerve schwannoma

Unusual Motor Hand Neuropathies: Causes, Diagnosis, and Evaluation of Motor Impairments

Background Isolated hand motor nerve injuries, specifically those affecting the recurrent motor branch of the median nerve and the deep motor branch of the ulnar nerve, are rarely reported in medical literature. Diagnosing and quantifying these injuries pose significant challenges due to their uncommon nature and the variety of mechanisms that can cause them. Methodology This study reviews six unusual cases of isolated damage to the recurrent motor branch of the median nerve and the deep motor branch of the ulnar nerve, including cases with combined injuries. The etiologies include various traumatic and compressive mechanisms, such as a blow from the thenar to the back of a knife blade, long-distance cycling, impact from a broken shovel handle, knife injury, and damage from a screw while using a cordless screwdriver. In one case, the cause was indeterminate. Diagnostic methods involved clinical evaluation, electrophysiological testing (nerve conduction studies and electromyography), and high-resolution ultrasound imaging. A thorough medical history was also crucial in understanding the injury mechanisms. Results The cases demonstrated a range of causes for isolated hand motor nerve injuries, with both traumatic and compressive mechanisms identified. The diagnostic process highlighted the value of integrating clinical assessments, electrophysiological data, and ultrasound imaging to accurately diagnose and understand the extent and nature of the injuries. Conclusions Isolated motor nerve injuries in the hand can arise from diverse and often unexpected causes. Comprehensive clinical evaluation, supported by electrophysiological testing and ultrasound imaging, is essential for accurate diagnosis and management. A detailed medical history is invaluable in identifying the mechanism of injury, which is critical for developing an appropriate treatment plan. The study underscores the importance of a multidisciplinary approach in diagnosing and treating these rare neuropathies.

Recurrent Median Nerve Injury in a Weight Lifter

Recurrent median neuropathy is an uncommon injury that can be commonly mistaken for other pathological causes. It is important to be aware of the potential causes and symptoms of injury as delay in diagnosis can lead to permanent decrease in hand function and disability. This case is a description of a 33-year-old male patient who previously presented with radicular symptoms and had complete resolution of his pain after a C7 selective nerve root block. Several months after presentation, he developed significant thenar atrophy, localized pain, and weakness associated with weight lifting activities. He was originally diagnosed with a recurrence of his C7 symptoms and a wrist sprain and was treated with a prednisone taper and wrist splint. After no improvement, he was referred to a physiatrist at an outpatient orthopedic clinic where he was examined and found to have a recurrent median neuropathy on electrodiagnostic studies. A left hand MRI was ordered which demonstrated no anatomical evidence of a compressive nerve lesion, and it was concluded that his injury was secondary to direct compression from high intensity weight lifting.

High-resolution ultrasound visualization of the recurrent motor branch of the median nerve: normal and first pathological findings

Purpose

To evaluate in a prospective study the possibility of visualization and diagnostic assessment of the recurrent motor branch (RMB) of the median nerve with high-resolution ultrasound (HRUS).

Materials and methods

HRUS with high-frequency probes (18–22 MhZ) was used to locate the RMB in eight fresh cadaveric hands. To verify correct identification, ink-marking and consecutive dissection were performed. Measurement of the RMB maximum transverse-diameter, an evaluation of the origin from the median nerve and its course in relation to the transverse carpal ligament, was performed in both hands of ten healthy volunteers (n = 20). Cases referred for HRUS examinations for suspected RMB lesions were also assessed.

Results

The RMB was clearly visible in all anatomical specimens and all volunteers. Dissection confirmed HRUS findings in all anatomical specimens. Mean RMB diameter in volunteers was 0.7 mm ± 0.1 (range, 0.6–1). The RMB originated from the radial aspect in 11 (55%), central aspect in eight (40%) and ulnar aspect in one (5%) hand. Nineteen (95%) extraligamentous courses and one (5%) subligamentous course were detected. Three patients with visible RMB abnormalities on HRUS were identified.

Conclusion

HRUS is able to reliably visualize the RMB, its variations and pathologies.

Key Points

• Ultrasound allows visualization of the recurrent motor branch of the median nerve.

• Ultrasound may help clinicians to assess patients with recurrent motor branch pathologies.

• Patient management may become more appropriate and targeted therapy could be improved.

Electronic supplementary material

The online version of this article (doi:10.1007/s00330-016-4671-1) contains supplementary material, which is available to authorized users.