Anastasia Shulga1, Pantelis Lioumis2, Erika Kirveskari3, Sarianna Savolainen4, Jyrki P Mäkelä5, Aarne Ylinen6. 1. Clinical Neurosciences, Neurology, University of Helsinki and Helsinki University Hospital, P.O. Box 372, FI-00029 Helsinki, Finland; BioMag Laboratory, HUS Medical Imaging Center, University of Helsinki and Helsinki University Hospital, P.O. Box 340, FI-00029 Helsinki, Finland. Electronic address: anastasia.shulga@helsinki.fi. 2. BioMag Laboratory, HUS Medical Imaging Center, University of Helsinki and Helsinki University Hospital, P.O. Box 340, FI-00029 Helsinki, Finland; Neuroscience Center, University of Helsinki, P.O. Box 56, FI-00014, Finland. Electronic address: pantelis.lioumis@hus.fi. 3. Clinical Neurosciences, Clinical Neurophysiology, HUS Medical Imaging Center, University of Helsinki and Helsinki University Hospital, P.O. Box 340, FI-00029 Helsinki, Finland. Electronic address: erika.kirveskari@hus.fi. 4. Validia Rehabilitation Center, P.O. Box 103, FI-00251 Helsinki, Finland. Electronic address: sarianna.savolainen@thl.fi. 5. BioMag Laboratory, HUS Medical Imaging Center, University of Helsinki and Helsinki University Hospital, P.O. Box 340, FI-00029 Helsinki, Finland. Electronic address: jyrki.makela@hus.fi. 6. Clinical Neurosciences, Neurology, University of Helsinki and Helsinki University Hospital, P.O. Box 372, FI-00029 Helsinki, Finland. Electronic address: aarne.ylinen@hus.fi.
Abstract
BACKGROUND: In spinal paired associative stimulation (PAS), orthodromic volleys are induced by transcranial magnetic stimulation (TMS) in upper motor neurons, and antidromic volleys by peripheral nerve stimulation (PNS) in lower motor neurons of human corticospinal tract. The volleys arriving synchronously to the corticomotoneuronal synapses induce spike time-dependent plasticity in the spinal cord. For clinical use of spinal PAS, it is important to develop protocols that reliably induce facilitation of corticospinal transmission. Due to variability in conductivity of neuronal tracts in neurological patients, it is beneficial to estimate interstimulus interval (ISI) between TMS and PNS on individual basis. Spinal root magnetic stimulation has previously been used for this purpose in spinal PAS targeting upper limbs. However, at lumbar level this method does not take into account the conduction time of spinal nerves of the cauda equina in the spinal canal. NEW METHOD: For lower limbs spinal PAS, we propose estimating appropriate ISIs on the basis of F-response and motor-evoked potential (MEP) latencies. The use of navigation in TMS and ensuring correct PNS electrode placement with F-response recording enhances the precision of the method. RESULTS: Our protocol induced 186±17% (mean±STE) MEP amplitude facilitation in healthy subjects, being effective in all subjects and nerves tested. COMPARISON WITH EXISTING METHOD: We report for the first time the individual estimation of ISIs in spinal PAS for lower limbs. CONCLUSIONS: Estimation of ISI on the basis of F and MEP latencies is sufficient to effectively enhance corticospinal transmission by lower limb spinal PAS in healthy subjects.
BACKGROUND: In spinal paired associative stimulation (PAS), orthodromic volleys are induced by transcranial magnetic stimulation (TMS) in upper motor neurons, and antidromic volleys by peripheral nerve stimulation (PNS) in lower motor neurons of human corticospinal tract. The volleys arriving synchronously to the corticomotoneuronal synapses induce spike time-dependent plasticity in the spinal cord. For clinical use of spinal PAS, it is important to develop protocols that reliably induce facilitation of corticospinal transmission. Due to variability in conductivity of neuronal tracts in neurological patients, it is beneficial to estimate interstimulus interval (ISI) between TMS and PNS on individual basis. Spinal root magnetic stimulation has previously been used for this purpose in spinal PAS targeting upper limbs. However, at lumbar level this method does not take into account the conduction time of spinal nerves of the cauda equina in the spinal canal. NEW METHOD: For lower limbs spinal PAS, we propose estimating appropriate ISIs on the basis of F-response and motor-evoked potential (MEP) latencies. The use of navigation in TMS and ensuring correct PNS electrode placement with F-response recording enhances the precision of the method. RESULTS: Our protocol induced 186±17% (mean±STE) MEP amplitude facilitation in healthy subjects, being effective in all subjects and nerves tested. COMPARISON WITH EXISTING METHOD: We report for the first time the individual estimation of ISIs in spinal PAS for lower limbs. CONCLUSIONS: Estimation of ISI on the basis of F and MEP latencies is sufficient to effectively enhance corticospinal transmission by lower limb spinal PAS in healthy subjects.
Authors: Anastasia Shulga; Pantelis Lioumis; Aleksandra Zubareva; Nina Brandstack; Linda Kuusela; Erika Kirveskari; Sarianna Savolainen; Aarne Ylinen; Jyrki P Mäkelä Journal: Spinal Cord Ser Cases Date: 2016-07-14