Transcranial magnetic stimulation and spinal cord injury

Transcranial magnetic stimulation (TMS) is a relatively new technology that uses magnets to stimulate the brain. This is taken from emedicine:

The development of transcranial magnetic stimulation (TMS), in 1985, opened new possibilities for MEP studies. Barker et al created a new type of cortical magnetic stimulator, based on the principle of electromagnetic induction. [5] The device is composed of a main unit, which contains a bank of heavy-duty capacitors. The hand-held part is freely movable so that it can be placed over any part of the body. The investigator holds the stimulating coil tangentially over the motor cortex, and a technician holds a digitizing pen over the stimulating coil to record its 3-dimensional position; this allows stereotactic mapping of the motor cortex. MEPs are recorded with surface electrodes, which are placed over small hand muscles.

The slowing of the speed with which the TMS stimulation results in excitation of the peripheral nerves may be a easy and accurate way to determine if there is injury to the nervous system.
DrO

J Vet Intern Med. 2019 Sep 6.
Determination of magnetic motor evoked potential latency time cutoff values for detection of spinal cord dysfunction in horses.
Rijckaert J1, Pardon B1, Saey V2, Raes E3, Van Ham L4, Ducatelle R2, van Loon G1, Deprez P1.

Author information:
1. Department of Large Animal Internal Medicine, Faculty of Veterinary Medicine, Ghent University, Merelbeke, Belgium.
2. Department of Pathology, Bacteriology and Poultry Diseases, Ghent University, Merelbeke, Belgium.
3. Department of Veterinary Medical Imaging and Small Animal Orthopedics, Ghent University, Merelbeke, Belgium.
4. Small Animal Department, Faculty of Veterinary Medicine, Ghent University, Merelbeke, Belgium.
Abstract
BACKGROUND:

Transcranial magnetic stimulation (TMS) and recording of magnetic motor evoked potentials (MMEP) can detect neurological dysfunction in horses but cutoff values based on confirmed spinal cord dysfunction are lacking.
OBJECTIVES:

To determine latency time cutoff for neurological dysfunction.
ANIMALS:

Five control horses and 17 horses with proprioceptive ataxia.
METHODS:

Case-control study with receiver operating characteristic curve analysis, based on diagnostic imaging, TMS, and histopathological findings. Horses were included if all 3 examinations were performed.
RESULTS:

Diagnostic imaging and histopathology did not show abnormalities in the control group but confirmed spinal cord compression in 14 of 17 ataxic horses. In the remaining 3 horses, histopathological lesions were mild to severe, but diagnostic imaging did not confirm spinal cord compression. In control horses, latency time values of thoracic and pelvic limbs were significantly lower than in ataxic horses (20 ± 1 vs 34 ± 16 milliseconds, P = .05; and 39 ± 1 vs 78 ± 26 milliseconds, P = .004). Optimal cutoff values to detect spinal cord dysfunction were 22 milliseconds (sensitivity [95% CI interval], 88% [73%-100%]; specificity, 100% [100%-100%]) in thoracic and 40 milliseconds (sensitivity, 94% [83%-100%]; specificity, 100% [100%-100%]) in pelvic limbs. To detect spinal cord dysfunction caused by compression, the optimal cutoff for thoracic limbs remained 22 milliseconds, while it increased to 43 milliseconds in pelvic limbs (sensitivity, 100% [100%-100%]; specificity, 100% [100%-100%] for thoracic and pelvic limbs).
CONCLUSIONS AND CLINICAL IMPORTANCE:

Magnetic motor evoked potential analysis using these cutoff values is a promising diagnostic tool for spinal cord dysfunction diagnosis in horses.