Stimulation of peroneal nerves reveals maintained somatosensory representation in transtibial amputees

Caroline Ritter; Maria Geisler; Kathrin R Blume; Sandra Nehrdich; Gunther O Hofmann; Hanna Koehler; Wolfgang H R Miltner; Thomas Weiss

doi:10.3389/fnhum.2023.1240937

Stimulation of peroneal nerves reveals maintained somatosensory representation in transtibial amputees

Front Hum Neurosci. 2023 Sep 7:17:1240937. doi: 10.3389/fnhum.2023.1240937. eCollection 2023.

Authors

Caroline Ritter^{1

2}, Maria Geisler^{1

2}, Kathrin R Blume^{1

3}, Sandra Nehrdich^{1

2}, Gunther O Hofmann^{4

5}, Hanna Koehler^{1

6}, Wolfgang H R Miltner¹, Thomas Weiss¹

Affiliations

¹ Department of Clinical Psychology, Institute of Psychology, Friedrich Schiller University Jena, Jena, Germany.
² Clinic for Psychosomatics and Psychotherapy, Jena University Hospital, Jena, Germany.
³ Institute of Psychosocial Medicine, Psychotherapy and Psychooncology, Jena University Hospital, Jena, Germany.
⁴ Berufsgenossenschaftliche Kliniken Bergmannstrost Halle/Saale, Halle, Germany.
⁵ Department of Trauma, Hand and Reconstructive Surgery, University Hospital Jena, Jena, Germany.
⁶ Biomagnetic Center, Department of Neurology, University Hospital Jena, Jena, Germany.

Abstract

Introduction: Several studies have found changes in the organization of the primary somatosensory cortex (SI) after amputation. This SI reorganization was mainly investigated by stimulating neighboring areas to amputation. Unexpectedly, the somatosensory representation of the deafferented limb has rarely been directly tested.

Methods: We stimulated the truncated peroneal nerve in 24 unilateral transtibial amputees and 15 healthy controls. The stimulation intensity was adjusted to make the elicited percept comparable between both stimulation sides. Neural sources of the somatosensory-evoked magnetic fields (SEFs) to peroneal stimulation were localized in the contralateral foot/leg areas of SI in 19 patients and 14 healthy controls.

Results: We demonstrated the activation of functionally preserved cortical representations of amputated lower limbs. None of the patients reported evoked phantom limb pain (PLP) during stimulation. Stimulation that evoked perceptions in the foot required stronger intensities on the amputated side than on the intact side. In addition to this, stronger stimulation intensities were required for amputees than for healthy controls. Exploratorily, PLP intensity was neither associated with stimulation intensity nor dipole strength nor with differences in Euclidean distances (between SEF sources of the healthy peroneus and mirrored SEF sources of the truncated peroneus).

Discussion: Our results provide hope that the truncated nerve may be used to establish both motor control and somatosensory feedback via the nerve trunk when a permanently functional connection between the nerve trunk and the prosthesis becomes available.

Keywords: MEG; peroneal nerve stimulation; phantom limb pain (PLP); somatosensory cortex (SI); somatosensory evoked fields (SEF); transtibial amputation.

Grants and funding

This study was supported by the German Social Accident Insurance (DGUV-FR145 and FR196). DGUV neither did not influence study goals nor study design, i.e., authors are fully responsible for goals and design.