Transcranial Magnetic Stimulation and Transcranial Electrical Stimulation in Horses.

Depending on the localization of the lesion, spinal cord ataxia is the most common type of ataxia in horses. Most prevalent diagnoses include cervical vertebral stenotic myelopathy (CVSM), equine protozoal myeloencephalitis (EPM), trauma and equine degenerative myeloencephalopathy (EDM). Other causes of ataxia and weakness are associated with infectious causes, trauma and neoplasia. A neurologic examination is indispensable to identify the type of ataxia. In addition, clinical neurophysiology offers tools to locate functional abnormalities in the central and peripheral nervous system. Clinical EMG assessment looks at the lower motoneuron function (LMN) and is used to differentiate between neuropathy in peripheral nerves, which belong to LMNs and myopathy. As LMNs reside in the spinal cord, it is possible to grossly localize lesions in the myelum by muscle examination. Transcranial (tc) stimulation techniques are gaining importance in all areas of medicine to assess the motor function of the spinal cord along the motor tracts to the LMNs. Applications in diagnostics, intraoperative neurophysiological monitoring (IONM), and evaluation of effects of treatment are still evolving in human medicine and offer new challenges in equine medicine. Tc stimulation techniques comprise transcranial magnetic stimulation (TMS) and transcranial electrical stimulation (TES). TMS was first applied in horses in 1996 by Mayhew and colleagues and followed by TES. The methods are exchangeable for clinical diagnostic assessment but show a few differences. An outline is given on the principles, current clinical diagnostic applications and challenging possibilities of muscle evoked potentials (MEP) from transcranial stimulation in horses.

Nervous system modulation through electrical stimulation in companion animals.

Domestic animals with severe spontaneous spinal cord injury (SCI), including dogs and cats that are deep pain perception negative (DPP-), can benefit from specific evaluations involving neurorehabilitation integrative protocols. In human medicine, patients without deep pain sensation, classified as grade A on the American Spinal Injury Association (ASIA) impairment scale, can recover after multidisciplinary approaches that include rehabilitation modalities, such as functional electrical stimulation (FES), transcutaneous electrical spinal cord stimulation (TESCS) and transcranial direct current stimulation (TDCS). This review intends to explore the history, biophysics, neurophysiology, neuroanatomy and the parameters of FES, TESCS, and TDCS, as safe and noninvasive rehabilitation modalities applied in the veterinary field. Additional studies need to be conducted in clinical settings to successfully implement these guidelines in dogs and cats.

State-of-the-Art Diagnostic Methods to Diagnose Equine Spinal Disorders, With Special Reference to Transcranial Magnetic Stimulation and Transcranial Electrical Stimulation.

Spinal cord disorders are a common problem in equine medicine. However, finding the site of the lesion is challenging for veterinarians because of a lack of sensitive diagnostic methods that can assess neuronal functional integrity in horses. Although medical imaging is frequently applied to help diagnose corticospinal disorders, this approach does not reveal functional information. For the latter, transcranial magnetic stimulation (TMS) and more recently transcranial electrical stimulation (TES) can be useful. These are brain stimulation techniques that create either magnetic or electrical fields passing through the motor cortex, inducing muscular responses, which can be recorded either intramuscularly or extramuscularly by needle or surface electrodes. This permits the evaluation of the functional integrity of the spinal motor tracts and the nerve conduction pathways. The interest in TES in human medicine emerged these last years because unlike TMS, TES tends to bypass the motor cortex of the brain and predominantly relies on direct activation of corticospinal and extrapyramidal axons. Results from human medicine have indicated that TMS and TES recordings are mildly if not at all affected by sedation. Therefore, this technique can be reliably used in human patients under either sedation or full anesthesia to assess functional integrity of the corticospinal and adjunct motor tracts. This opens important new avenues in equine medicine.