Sub-study to Spinal Cord Stimulation to Restore Cough

Patients with cervical and thoracic spinal cord injuries often have paralysis of a major portion of their expiratory muscles - the muscles responsible for coughing - and therefore, lack a normal cough mechanism. Consequently, most of these patients suffer from a markedly reduced ability to clear airway secretions, a factor which contributes to the development of recurrent respiratory tract infections such as pneumonia and bronchitis. In fact, pneumonia is a major cause of death in this patient population. In a recent clinical trial, we have shown that the expiratory muscles can be electrically activated by spinal cord stimulation (SCS), a technique which involves the surgical placement of disc electrodes on the surface of the spinal cord. This method is successful in achieving an effective means of expiratory muscle activation, as demonstrated by the generation of large airway pressures and peak airflow rates. Importantly, SCS facilitates secretion removal, reduces the need for caregiver support, reduces the incidence of respiratory tract infections and improves life quality. This method therefore has the potential to reduce health care costs and improve survival in spinal cord injured subjects. The purpose of this trial is to directly compare activation of the expiratory muscles using wire electrodes, which can be inserted percutaneously through a needle, with the previously employed disc electrodes. In this trial, researchers will study 6 adults (18-70 years old) with spinal injuries (T5 level or higher), at least 12 months following the date of injury. After an evaluation including medical history, a brief physical examination, and initial testing, each participant will undergo a surgical procedure to implant small electrodes (metal discs) over the surface of the spinal cord on the lower back to stimulate the expiratory muscles and restore cough. Prior to permanent implantation of this system, wire and disc electrodes will be compared by assessing the degree of expiratory muscle activation with each electrode type. The disc electrodes will then be permanently implanted, allowing the participant to have use of a fully functioning stimulation system to restore an effective cough.