Surgical restoration of hand function in tetraplegia

Abstract

It is with great interest that we read the illustrative case report by Hill et al. [1] in a recent issue of Spinal Cord Series and Cases (Hill EJ, El-Haj M, Giles JA, Fox IK. Using electrodiagnostics to define injury patterns amenable to nerve transfer surgery in tetraplegia: an illustrative case report. Spinal Cord Series and Cases. 2020; 6: 1–6.). In this report, the authors describe how patterns of neuronal injury due to cervical spinal cord injury (SCI) can be discerned by adding to the clinical examination electrodiagnostics to guide the timing and selection of nerve transfer to achieve optimal outcomes. The case concerned a 20-year-old man who had suffered a cervical SCI 8 months previously. Classified as American Spinal Cord Injury Association A at the C7 level, the injury caused dependency in activities of daily living. His goal was to regain active grip function so he could catheterize and feed himself. Preoperative electrodiagnosis revealed a complex mixture of upper and lower motor neuron injuries in the intended recipient nerves originating from the C7–Th1 segments in the right upper limb. Specifically, the radial compound muscle action potential (CMAP) was absent and the ulnar CMAP was reduced, but the median CMAPs were intact, apart from absent activation of the flexor digitorum superficialis muscle. The absence of radial nerve CMAPs implied a mixture of upper and lower motor neuron injuries, whereas the intact median nerve indicated a functioning peripheral nerve and injured upper motor neurons. Intraoperative nerve stimulation confirmed a satisfactory motor response in the median nerve. Based on these results and the patient’s preferences and goals, the selection of nerve transfer procedures included transfer of the brachialis nerve to the anterior interosseous nerve and the flexor digitorum superficialis nerve fascicles of the median nerve to restore digit flexion and transfer of the supinator nerve to the posterior interosseous nerve to restore digit extension. Although nerve transfers yield somewhat less predictable results than tendon transfers, we agree that selective nerve transfers offer exciting opportunities to restore function in tetraplegia [2]. They are more appealing than tendon transfer in some situations; for example, they allow direct reanimation of the muscle without altering its biomechanics and may produce finer motor control and more natural movements than tendon transfer. Further advantages include less extensive surgical dissection [3], shorter duration of hospitalization and rehabilitation, and fewer restrictions, thereby reducing health care use and cost [2]. Last but not least, selective nerve transfer is a fascinating alternative in the absence of locally suitable tendon transfer options, as in International Classification for Surgery of the Hand in Tetraplegia group 0 [4]. Another unique advantage is that sacrifice of a single nerve can potentially restore multiple paralyzed muscles. For example, the supinator motor nerves can be transferred directly to the posterior interosseous nerve to restore thumb and finger extension [5]. The main objective of the case report was to describe the use of electrodiagnostics to define injury patterns rather than to present the clinical outcome. Yet, we would like to comment on the surgical procedures and the functional outcome in this case. First, we would like to highlight the importance of selecting a restorative surgical procedure that does not risk loss of important donor muscle function. * Lina Bunketorp Käll [email protected]