## 3 Treatments for Spinal Cord Injury
### Epidural Electrical Stimulation (EES)  
Epidurals for spinal cord injury have been used in the past to relieve pain. However, they are now being used to improve motor function in patients with SCI [22]. EES treatment involves implanting an epidural stimulator between the spinal cord and the vertebrae, also known as the epidural space. This implant is placed on the lumbar region of the spinal cord, and it aims to release electrical impulses at the damaged site to invoke a voluntary response in the lower limb [23]. A study was performed by [PERSON] et al., which showed the effects of epidural electrical stimulation and its correlation with the positioning of the electrodes relative to the SCI. This study showed that the closer the electrode of the EES was to the lesion site on the spinal cord, the more effective the electrical impulses were when causing leg spasms. [PERSON] et al. further used a central pattern generator (CPG), which used neuronal circuits to be able to produce rhythmic locomotor patterns upon activation. This was used in conjunction with the EES to improve volitional motor  
Figure 2: The testing process of the ultrasonically powered battery-free spinal cord implant in a rat [16]. control. In the paper, 'Epidural Spinal Cord Simulation of Spinal Cord Injury in Humans: A Systemic Review', [PERSON] et al. describe the implantation approach of the EES device and the impact it has on spinal networks and reflex pathways. The electrodes on the EES device are implanted with a surgical or percutaneous approach as they are attached to the dorsum of the dura. The surgical approach is performed through the laminotomy method, which requires various individual multi-column paddle leads consisting of 16 contacts. On the other hand, the percutaneous approach requires multi-contact leads that only use eight independent programmable contacts. Once either of these methods is used to implant the device, it is implanted into the deep tissue and is attached to either a subcutaneous pulse generator or an external pulse generator. The study tested the EES device on animals and then on patients with SCI. The results showed that there was a high success rate when measuring locomotor function [22]. However, a limitation of this device is that the electrode itself is attached to a pulse generator. This generator also needs to be implanted, which increases the risk during surgery, as well as the risk of human error. Furthermore, this pulse generator would supposedly have an average battery life of an implantable device, which is estimated to be 5 years, after which it would need to be removed and a new one implanted. Furthermore, [PERSON] et al. conducted a study including 21 incomplete spinal cord injury patients, 11 of who received EES combined with physical therapy (PT), while the remaining 10 patients only received PT as a control group [24]. All 21 patients had 1.5 T MRI scans pre-surgery to receive sagittal and axial images of their respective spinal cord injury sites to help guide the implantation of the EES electrode, as well as CT scans to rule out the chances of spinal cord compression. The patients then underwent an Electromyography/Motor Somatosensory Evoked Potentials (EMG/SEP) examination to assess lower limb functions to eliminate patients with complete SCI. All patients received PT for 4-5 h every day for the length of the study (19-25 months), which included a range of lower limb training such as cycling, quadriceps training, and reduced-weight treadmill training. The EES surgery involved the implantation of a Medtronic spinal cord electrode (Model 39565) and a Medtronic EES stimulator (Model 37714). Figure 3, below, shows an example of the device implantation for a patient with a lumbar enlargement between T11 and T12. Each patient was anatomically different at the site of enlargement. After 7-10 days of success, an implantable stimulator was placed between the subcutaneous fat and the muscular fascial space in the abdomen.