Neural Noise

Motor evoked potentials as a side-effect biomarker for deep brain stimulation

2 min read

  • Motor evoked potentials (MEPs) can serve as a side-effect biomarker for deep brain stimulation (DBS).1
  • MEPs link DBS and neuromodulation to electrophysiological outcome measures relevant to neuroprosthetics.1 1

Weekly enrichment (2026-07-20)

  • The primary study (Testini and colleagues, Clinical Neurophysiology 2025) enrolled 12 Parkinson’s disease patients with subthalamic (STN) or pallidal (GPi) DBS; contact mapping established clinical motor side-effect thresholds while EMG from cranial and arm muscles measured the presence, peak amplitude, and latency of motor evoked potentials (MEPs).2
  • MEP amplitudes increased with stimulation intensity, and latencies were shorter for cranial muscles, which were more likely to generate an MEP.2
  • Clinical and MEP thresholds correlated significantly (R² = 0.31, p = 0.0006), but most MEP thresholds fell below the clinical side-effect thresholds, indicating detection of subclinical corticospinal (CST) and corticobulbar (CBT) tract activation.2
  • MEP accuracy for predicting clinical side effects was 0.72, with a sensitivity of 0.68, specificity of 0.73, and an F1 score of 0.51.2
  • Motor side effects arise when DBS of the STN or GPi inadvertently activates the CBT/CST fibers of the internal capsule bordering the target nuclei, causing muscle contractions.2
  • Context: a follow-up characterization (25 hemispheres; 17 GPi, 8 STN) found MEPs most robust in distal upper-limb muscles, with the thenar muscle the most sensitive responder—absence of a thenar MEP predicted absence in all other muscles in 96% of cases.3
  • Context: in that dataset MEP incidence decreased from distal (ring 1) to proximal (ring 4) lead contacts (p < 0.003), and onset latencies did not differ between GPi and STN targets (p > 0.14).3
  • Context: intraoperative MEP thresholds correlate with internal-capsule proximity and can exclude future capsular side effects, providing targeting guidance that is especially valuable in asleep DBS surgery.4
  • A review of evoked potentials for STN-DBS programming positions MEPs and somatosensory evoked potentials as biomarkers to minimize the cardinal motor and paresthesia side effects, noting that subclinical activation seen at rest may only manifest later during daily activity.5

Footnotes

  1. https://www.sciencedirect.com/science/article/pii/S1388245725013513?dgcid=rss_sd_all ↩ ↩2 ↩3

  2. https://www.medrxiv.org/content/10.1101/2025.01.24.25320924v1 ↩ ↩2 ↩3 ↩4 ↩5

  3. https://doi.org/10.1016/j.clinph.2026.2111979 ↩ ↩2

  4. https://doi.org/10.1111/ner.13386 ↩

  5. https://www.nature.com/articles/s41531-026-01274-2 ↩

Graph View