Background & Aims
The N13 component of somatosensory evoked potentials (SEP) reflects the segmental response of dorsal horn neurons.1 Recent studies showed that N13 SEPs were increased after experimentally-induced central sensitization in healthy individuals and discussed to represent enhanced dorsal horn excitability.2,3 This would propose N13 SEPs as a potential useful biomarker for central sensitization in chronic pain cohorts. While sensitization of the nociceptive system is also thought to play an essential role in the chronic pain cohort of complex regional pain syndrome (CRPS),4,5 it remains challenging to objectively assess its presence in humans.
Therefore, the aim of this study is to show increased N13 SEPs in the cohort of CRPS, which might capture spinal sensitization processes.
Methods
Twenty individuals with hand CRPS type I and 20 age- and sex-matched healthy controls will be recruited for this study. Individuals with CRPS will undergo clinical examination prior to the study. The peripheral N9 (Erb) component, the cervical N13 (C6) component and the cortical N20/P25 (C3’/C4′) complex of the SEP will be recorded after electrical stimulation of the median nerve of the affected and the unaffected hand in individuals with CRPS and from both arms in HC. Stimulation intensity will be set at the motor threshold of the M. abductor pollicis brevis. The recorded signals will be inspected for presence, amplitude and latency. The ratio of SEP component amplitudes (affected/unaffected arm) will be calculated and used for comparison between groups.
Results
Preliminary data of individuals with CRPS and matched healthy controls will be presented. Firstly, we hypothesize to find an increased ratio of N13 SEP in the cohort of CRPS compared to healthy controls. Secondly, we do not expect to find any differences in the ratio of the N9 component and the N20/P25 complex of median SEPs between the two cohorts.
Five healthy controls (2 females, 3 males, age: 27.2 ± 0.8 years) were included so far. Robust N9, N13 and N20/P25 components could be recorded after median nerve stimulation (7.1 ± 1.2 mA) of both arms in all participants. The mean latencies and amplitudes of the components were as follows: N9 9.5 ± 0.8 ms, 5.2 ± 2.8 uV; N13 12.9 ± 0.9 ms, 1.5 ± 0.5 uV; N20/P25 complex 18.3 ± 1.1 ms, 2.5 ± 0.7 uV. There was no side difference in latency or amplitude for all measured SEP components (all p > 0.31).
Conclusions
An increased ratio of N13 SEPs (affected > unaffected hand) in individuals with CRPS might reflect unilateral changes in dorsal horn excitability through sensitization processes.2 This finding would increase the understanding of the complex pathophysiological alterations in the nociceptive system in CRPS.
So far, the preliminary results of included healthy controls showed that the spinal N13 SEPs can be robustly recorded and are comparable in latency and amplitude to previously published results.6 This preliminary finding strengthens the feasibility of our study set-up for its use in chronic pain patients.
References
1.Sonoo, M., Shimpo, T., Genba, K., Kunimoto, M. & Mannen, T. Posterior cervical N13 in median nerve SEP has two components. Electroencephalogr. Clin. Neurophysiol. 77, 28–38 (1990).
2.Di Lionardo, A. et al. Modulation of the N13 component of the somatosensory evoked potentials in an experimental model of central sensitization in humans. Sci. Rep. 11, 1–10 (2021).
3.Leone, C. et al. Modulation of the spinal N13 SEP component by high- and low-frequency electrical stimulation. Experimental pain models matter. Clin. Neurophysiol. 156, 28–37 (2023).
4.Marinus, J. et al. Clinical features and pathophysiology of Complex Regional Pain Syndrome – current state of the art. Lancet Neurol. 10, 637–648 (2011).
5.Eldufani, J., Elahmer, N. & Blaise, G. A medical mystery of complex regional pain syndrome. Heliyon 6, e03329 (2020).
6.Pietro, G. Di et al. The N13 spinal component of somatosensory evoked potentials is modulated by heterotopic noxious conditioning stimulation suggesting an involvement of spinal wide dynamic range neurons: N13 modulation by heterotopic noxious conditioning stimulation. Neurophysiol. Clin. 51, 517–523 (2021).
Presenting Author
Florin Allmendinger
Poster Authors
Florin Allmendinger
MSc
Spinal Cord Injury Center, Balgrist University Hospital, University of Zurich
Lead Author
Martin Schubert
MD
Spinal Cord Injury Centre, Balgrist University Hospital, University of Zurich
Lead Author
Caterina Leone
MD PhD
Department of Human Neuroscience, Sapienza University of Rome
Lead Author
Florian Brunner
MD PhD
Department of Physical Medicine and Rheumatology, Balgrist University Hospital, University of Zurich
Lead Author
Michèle Hubli
Spinal Cord Injury Research Center
Lead Author
Topics
- Assessment and Diagnosis