Lower motor neuron (LMN) damage results in denervation of the associated muscle targets and is a significant yet under-appreciated component of spinal cord injury (SCI). Denervated muscle undergoes a progressive degeneration and fibro-fatty infiltration that eventually renders the muscle non-viable unless reinnervated within a limited time window. The distal nerve deprived of axons also undergoes degeneration and fibrosis making it less receptive to axons. In this review, we describe the LMN injury associated with SCI and its clinical consequences. The process of degeneration of the muscle and nerve is broken down into the primary components of the neuromuscular circuit and reviewed, including the nerve and Schwann cells, the neuromuscular junction, and the muscle. Finally, we discuss three promising strategies to reverse denervation atrophy. These include providing surrogate axons from local sources; introducing stem cell-derived spinal motor neurons into the nerve to provide the missing axons; and finally, instituting a training program of high-energy electrical stimulation to directly rehabilitate these muscles. Successful interventions for denervation atrophy would significantly expand reconstructive options for cervical SCI and could be transformative for the predominantly LMN injuries of the conus medullaris and cauda equina.

BACKGROUND: Spastic equinovarus foot (SEF) is a common dysfunctional foot posture after stroke that impairs balance and mobility. Selective tibial neurotomy (STN) is a simple but underutilized surgical option that can effectively address critical aspects of SEF and thereby provide enduring quality of life gains. There are few studies that examine both functional outcomes and patient satisfaction with this treatment option. OBJECTIVE: To elucidate the patient goals that motivated their decision to undergo the procedure and compare subjective and objective changes in balance and functional mobility as a consequence of surgery. METHODS: Thirteen patients with problematic SEF who had previously failed conservative measures were treated with STN. Preoperative and postoperative (on average 6 months) assessments evaluated gait quality and functional mobility. In addition, a custom survey was conducted to investigate patient perspectives on STN intervention. RESULTS: The survey showed that participants who opted for STN were dissatisfied with their previous spasticity management. The most common preoperative expectation for STN treatment was to improve walking, followed by improving balance, brace comfort, pain, and tone. Postoperatively, participants rated the improvement in their expectations and were, on average, 71 on a 100-point scale, indicating high satisfaction. The gait quality, assessed with the Gait Intervention and Assessment Tool, improved significantly between preoperative and postoperative assessment (M = −4.1, P = .01) with a higher average difference in stance of −3.3 than in swing −0.5. Improvement in both gait endurance (M = 36 m, P = .01) and self-selected gait speed (M = .12 m/s, P = .03) was statistically significant. Finally, static balance (M = 5.0, P = .03) and dynamic balance (M = 3.5, P = .02) were also significantly improved. CONCLUSION: STN improved gait quality and functional mobility and was associated with high satisfaction in patients with SEF.

BACKGROUND AND OBJECTIVES: Spastic equinovarus foot (SEF) is a common complication of stroke and other upper motor neuron injuries. It is characterized by a plantigrade and inverted foot, often with toe curling, causing significant disability from pain, gait, and balance difficulties. Management includes physical therapy, antispasticity drugs, orthoses, chemical neurolysis, or botulinum toxin, all of which may be insufficient, sedating, or transient. Selective tibial neurotomy (STN) provides a surgical option that is effective and long-lasting. Our goal is to provide a concise description of our technique for performing the STN for treatment of SEF. We discuss the standard posterior approach with surgical variations used by other groups and a medial approach, should the posterior approach be insufficient. METHODS: A posterior leg approach allows access to the tibial nerve and its branches to the bilateral gastrocnemius muscles, soleus, posterior tibialis, and extrinsic toe flexors. A medial approach is used if the toe flexors cannot be accessed sufficiently from the posterior approach. Nerve branch targets identified by preoperative functional assessment are carefully exposed and fully neurolysed distally to identify all terminal branches to each muscle of interest before neurotomy. RESULTS: The STN is a powerful tool for treating SEF, with an immediate and lasting effect. Approximately 80% of the target muscle should be denervated to ensure long-term efficacy while maintaining adequate function of the muscle through collateral innervation. CONCLUSION: The STN is a safe and effective outpatient procedure that can be performed by an experienced nerve surgeon to improve balance and ambulation and reduce pain for patients with SEF. Large clinical trials are necessary to further establish this underutilized procedure in the United States.

We have demonstrated in canines that somatic nerve transfer to vesical branches of the inferior hypogastric plexus (IHP) can be used for bladder reinnervation after spinal root injury. Yet, the complex anatomy of the IHP hinders the clinical application of this repair strategy. Here, using human cadavers, we clarify the spatial relationships of the vesical branches of the IHP and nearby pelvic ganglia, with the ureteral orifice of the bladder. Forty-four pelvic regions were examined in 30 human cadavers. Gross post-mortem and intra-operative approaches (open anterior abdominal, manual laparoscopic, and robot-assisted) were used. Nerve branch distances and diameters were measured after thorough visual inspection and gentle dissection, so as to not distort tissue. The IHP had between 1 to 4 vesical branches (2.33 ± 0.72, mean ± SD) with average diameters of 0.51 ± 0.06 mm. Vesical branches from the IHP arose from a grossly visible pelvic ganglion in 93% of cases (confirmed histologically). The pelvic ganglion was typically located 7.11 ± 6.11 mm posterolateral to the ureteral orifice in 69% of specimens. With this in-depth characterization, vesical branches from the IHP can be safely located both posterolateral to the ureteral orifice and emanating from a more proximal ganglionic enlargement during surgical procedures.

BACKGROUND AND OBJECTIVES: Cervical spinal cord injuries (SCI) result in severe loss of function and independence. Nerve transfers have become a powerful method for restoring upper extremity function, the most critical missing function desired by this patient population. Recovery of active elbow extension allows for expansion of one's workspace to reach for objects and stabilizes control at the elbow joint. Without triceps function, a patient with a cervical SCI is rendered entirely helpless when in the supine position. Our objective was to provide a concise description of the transfer of branches of the axillary nerve (AN) to the long head of the triceps branch of the radial nerve (RN) for restoration of elbow extension after cervical SCI. METHODS: An anterior, axillary approach is used for the transfer of the nerve branches of the AN (which may include branches to the teres minor, posterior deltoid, or even middle deltoid) to the long head of the triceps branch of the RN. Preoperative assessment and intraoperative stimulation are demonstrated to direct optimal selection of axillary branch donors. RESULTS: The axillary approach provides full access to all branches of the AN in optimal proximity to triceps branches of the RN and allows for tension-free coaptation to achieve successful recovery of elbow extension. Final outcomes may not be achieved for 18 months. Of our last 20 patients with greater than 12-month follow-up, 13 have achieved antigravity strength in elbow extension, 4 are demonstrating ongoing progression, and 3 are definitive failures by 18 months. CONCLUSION: The axillary to RN transfer is an important intervention for recovery of elbow extension after cervical SCI, which significantly improves quality of life in this patient population. Further large population outcomes studies are necessary to further establish efficacy and increase awareness of these procedures.

BACKGROUND AND OBJECTIVES: We present the surgical transfer of a somatic motor nerve to an autonomic target nerve to recover detrusor activation for functional voiding. The scientific basis of this hybrid nerve transfer, details of the surgical procedure, and results of its initial clinical application as they progressed over 2 years are reported. METHODS: A 30-year-old man presented with deteriorating bladder function and underwent resection of a sacral chondrosarcoma with sacrifice of all sacral nerve roots below S1 bilaterally. This eliminated bladder function and the potential for spontaneous recovery. The patient underwent functional and neurophysiological assessments and was determined to be a candidate for the procedure. Nerve transfers were performed bilaterally using a portion of the obturator nerve to reinnervate the bladder through the distal vesical branches of the inferior hypogastric plexus. He was re-evaluated at regular intervals for 2 years. RESULTS: Sensation of bladder fullness first returned at 6 months, and volitionally activated bladder contraction was demonstrated 12 months after transfer and confirmed at both 18 and 20 months by urodynamic studies. As expected, these new bladder contractions were driven by activation of the donor obturator nerve through thigh adduction and squatting and provided corresponding urinary flow. CONCLUSION: We present the results of a novel nerve transfer in which somatic axons are directed to innervate a parasympathetic target to drive volitional activation of the bladder. We delineate the baseline function and progression of recovery, including serial urodynamic assessments. These findings represent the successful clinical translation of a well-established animal model of bladder reinnervation. Although this procedure would serve a limited population and addresses only 1 key component of voiding, it provides an important clinical proof of concept that will aid in the further development of nerve transfer–based restorative options after loss of sacral innervation to the bladder.