Dear Sir: The title “Spinal cord injury induced by a cervical spinal cord stimulator” is not justified by the data presented in the paper by Falowski et al. (1). The presence of the spinal cord stimulation (SCS) electrode was only one of several potential contributing factors and probably not the most important. The authors fail to mention that the MRI in Figure 3 shows a focal increase in the T2 signal in the spinal cord at the C4-5 disc space level, immediately behind a prominent disc protrusion and/or osteophyte. To my eye, this is the proximate “cause” of the spinal cord injury. The more subtle T2 signal changes extending above and below this level, at or about the levels formerly occupied by the SCS electrode, appear to be secondary (in importance and as to cause). The patient had undergone anterior C5-7 fusion 13 years before the injury, and as commonly occurs following such procedures, she developed adjacent segment degenerative changes. As is well described in the spine surgery literature, the fusion acts as a lever increasing biomechanical stress at adjacent segments, which can predispose these segments to long-term degeneration that compromises neural elements (2). To be sure, SCS electrodes occupy space, some more than others; for example, paddle electrodes occupy a greater cross-sectional area than do percutaneous electrodes. (The electrode design in this case is not specified.) The presence of an electrode in a stenotic spinal canal might increase the risk of neural injury, but the data presented in this case do not support this inference to any degree of certainty. This patient could very well have developed the same transitional segment disease and sustained the same neurologic injury in the absence of the electrode. A search for the cause of the injury might, instead, start with the event that precipitated the fall,“. . . the patient reported feeling dizzy and lightheaded after taking her routine dose of tizanidine,” a drug known to cause dizziness. In fact, blaming the fall for the spinal cord injury is simplistic; to the extent the spinal cord might already have been compromised, this might have contributed to the fall. To assert that an injury occurring in the presence of an SCS electrode is caused by the electrode is to engage in fallacious post hoc ergo propter hoc reasoning.
Neuromodulation: Technology at the Neural Interface