Case report: Minimally invasive method to activate the expiratory muscles to restore cough

Context: Spinal cord stimulation (SCS) via disc electrodes surgically placed via laminotomy incisions has been shown to restore an effective cough in subjects with spinal cord injury (SCI). The purpose of this study was to evaluate a new method of expiratory muscle activation utilizing spinal cord wire leads, which can be implanted with minimally invasive techniques. Methods: In a subject with SCI, parallel wire leads with two electrode contacts were inserted percutaneously through a needle, advanced to the T9, T11 spinal levels and connected to an implanted radiofrequency receiver. Stimulus parameters were set at values resulting in near maximum airway pressure generation (Paw) (40V, 50Hz, 0.2ms). Paw was measured at functional residual capacity (FRC) and total lung capacity (TLC) as an index of expiratory muscle strength. Results: Paw during spontaneous efforts was 20 cmH(2)O (8.6% predicted). Bipolar (T9-T11) SCS resulted in Paw of 84 and 103 cmH(2)O, at FRC and TLC respectively. Monopolar (T9 only) SCS resulted in Paw of 61 and 86 cmH(2)O, at FRC and TLC respectively. This subject experienced much greater ease in raising secretions with use of SCS and no longer required other methods of secretion management. Conclusion: SCS via wire leads, which can be implanted using minimally invasive techniques, may provide a new useful method to restore an effective cough and possibly reduce the morbidity and mortality associated with respiratory tract infections in patients with SCI.