Characteristics of motor evoked potentials in patients with peripheral vascular disease

Abstract

With an aging population, it is common to encounter people diagnosed with peripheral vascular disease (PVD). Some will undergo surgeries during which the spinal cord may be compromised and intraoperative neuromonitoring with motor evoked potentials (MEPs) is employed to help mitigate paralysis. No data exists on characteristics of MEPs in older, PVD patients, which would be valuable for patients undergoing spinal cord at-risk surgery or participating in neurophysiological research. Transcranial magnetic stimulation, which can be delivered to the awake patient, was used to stimulate the motor cortex of 20 patients (mean +/- SD) age 63.2yrs (+/- 11.5) with confirmed PVD, every 10 minutes for one hour with MEPs recorded from selected upper and lower limb muscles. Data were compared to that from 20 healthy volunteers recruited for a protocol development study (28yrs (+/-7.6)). MEPs did not differ between patients symptomatic and non-symptomatic legs. MEP amplitudes were smaller in patients than in healthy participants in the upper limbs muscles, but not in lower limb muscles. Disease severity did not correlate with MEP amplitude. There were no differences over time in the coefficient of variation of MEP amplitude at each time point nor over the paradigm between groups. Latencies of MEPs were longer in patients for brachioradialis and vastus lateralis, but not in the other muscles studied. The results obtained suggest PVD alone does not impact MEPs; there were no differences between more symptomatic and less symptomatic legs. Further, disease severity did not corelate with MEP characteristics. Differences observed in MEPs between patients and healthy participants are more likely a result of ageing. With an aging population, more patients with PVD and cardiovascular risk factors will be participating in neurophysiological studies or undergoing surgery where spinal cord integrity is monitored. Our data show that MEPs from these patients can be easily evoked and interpreted.