Role of transcranial magnetic stimulation in differentiating motor nervous tract disorders from other causes of recumbency in four horses and one donkey.

The researchers used transcranial magnetic stimulation to investigate the reasons for the inability to stand (recumbency) in four horses and one donkey, revealing varied causes – from spinal cord damage to laminitis.

Research Objectives and Methodology

• The research aimed to discern whether descending motor tract lesions were the cause of recumbency in four horses and a donkey. This was achieved by measuring magnetic motor-evoked potentials (MMEPs)—responses generated from a muscle following a brief electrical stimulus—in the animals’ thoracic and pelvic limbs.
• Transcranial magnetic stimulation, a noninvasive method that involves using a magnetic field generator to stimulate small areas of the brain, was used to evaluate the integrity of the descending motor pathways. This technique provides an indirect evaluation of the animals’ motor tracts.

Key Findings

• The researchers discovered abnormal MMEPs in two of the five animals. In one horse, a fracture in the fifth cervical vertebra caused a lesion along the cervical spinal cord. Postmortem examination and radiography confirmed this finding.
• Another horse was found to have damage to the left forelimb’s peripheral nerves. An abscess, discovered postmortem, was compressing these nerves at the level of the last cervical vertebra.
• In the other three animals, their MMEPs were normal, indicating that their recumbency was not caused by a descending motor tract lesion. Further diagnostic examination diagnosed laminitis, rhabdomyolysis, and physitis as the causes of their recumbency.

Conclusion and Implications

• This research underscores the effectiveness of using transcranial magnetic stimulation and MMEP measurement in determining the cause of recumbency in animals, particularly in differentiating motor nervous tract disorders from other potential causes.
• The findings stress the importance of comprehensive diagnostic processes for recumbency in animals, as its causes can be varied and require different treatment routes. Irrespective of the cause, early and accurate diagnosis can streamline treatment and potentially improve prognosis.