Transcranial magnetic stimulation (TMS) responses elicited in hindlimb muscles as an assessment of synaptic plasticity in spino-muscular circuitry after chronic spinal cord injury.
Electromagnetic stimulation applied at the cranial level, i.e. transcranial magnetic stimulation (TMS), is a technique for stimulation and neuromodulation used for diagnostic and therapeutic applications in clinical and research settings. Although recordings of TMS elicited motor-evoked potentials (MEP) are an essential diagnostic tool for spinal cord injured (SCI) patients, they are reliably recorded from arm, and not leg muscles. Mid-thoracic contusion is a common SCI that results in locomotor impairments predominantly in legs. In this study, we used a chronic T10 contusion SCI rat model and examined whether (i) TMS-responses in hindlimb muscles can be used for evaluation of conduction deficits in cortico-spinal circuitry and (ii) if plastic changes at spinal levels will affect these responses. In this study, plastic changes of transmission in damaged spinal cord were achieved by repetitive electro-magnetic stimulation applied over the spinal level (rSEMS). Spinal electro-magnetic stimulation was previously shown to activate spinal nerves and is gaining large acceptance as a non-invasive alternative to direct current and/or epidural electric stimulation. Results demonstrate that TMS fails to induce measurable MEPs in hindlimbs of chronically SCI animals. After facilitation of synaptic transmission in damaged spinal cord was achieved with rSEMS, however, MEPs were recorded from hindlimb muscles in response to single pulse TMS stimulation. These results provide additional evidence demonstrating beneficial effects of TMS as a diagnostic technique for descending motor pathways in uninjured CNS and after SCI. This study confirms the ability of TMS to assess plastic changes of transmission occurring at the spinal level.
Northport Veterans Affairs Medical Center, 79 Middleville Road, Bld. 62, Northport, NY 11768, United States; Department of Neurobiology and Behavior, Stony Brook University, Stony Brook, NY 11794, United States.
Hayk A
HA
Petrosyan
Northport Veterans Affairs Medical Center, 79 Middleville Road, Bld. 62, Northport, NY 11768, United States; Department of Neurobiology and Behavior, Stony Brook University, Stony Brook, NY 11794, United States.
Valentina
V
Alessi
Department of Physical Therapy, Division of Rehabilitation Sciences, Stony Brook University, Stony Brook, NY 11794, United States.
Sue A
SA
Sisto
Northport Veterans Affairs Medical Center, 79 Middleville Road, Bld. 62, Northport, NY 11768, United States.
Mark
M
Kaufman
Northport Veterans Affairs Medical Center, 79 Middleville Road, Bld. 62, Northport, NY 11768, United States; Department of Neurobiology and Behavior, Stony Brook University, Stony Brook, NY 11794, United States. Electronic address: victor.arvanian@stonybrook.edu.
Victor L
VL
Arvanian
D000818:Animals; D019054:Evoked Potentials, Motor / Q000502:physiology*; D005260:Female; D006614:Hindlimb / Q000503:physiopathology; D018482:Muscle, Skeletal / Q000503:physiopathology*; D009473:Neuronal Plasticity / Q000502:physiology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D013119:Spinal Cord Injuries / Q000503:physiopathology*; D050781:Transcranial Magnetic Stimulation / Q000379:methods*
Motor evoked potentials; Spinal cord injury; Spinal electromagnetic stimulation; Synaptic plasticity; Transcranial magnetic stimulation