Role of transcranial magnetic stimulation in differentiating motor nervous tract disorders from other causes of recumbency in four horses and one donkey.
Authors: Nollet H, Vanschandevijl K, Van Ham L, Vanderstraeten G, Deprez P
Journal: The Veterinary record
Summary
Recumbent horses and donkeys present a diagnostic challenge, particularly when determining whether neurological involvement underlies the inability to stand. Nollet and colleagues employed transcranial magnetic stimulation (TMS) to measure magnetic motor-evoked potentials (MMEPs) in the thoracic and pelvic limbs of five recumbent animals, thereby testing the functional integrity of descending motor pathways from the brain and brainstem to the limbs. Two animals demonstrated abnormal MMEPs: one horse had a confirmed cervical fracture (C5) causing spinal cord damage, whilst another harboured a large abscess compressing peripheral nerves at the cervico-thoracic junction—both diagnoses confirmed post-mortem. The remaining three animals exhibited normal MMEPs, with their recumbency instead attributable to laminitis, rhabdomyolysis, and physitis respectively. This work demonstrates that TMS-derived MMEP recordings offer valuable objective evidence for rapidly ruling in or out central and peripheral motor tract disease in the recumbent horse, potentially streamlining diagnostic protocols and directing treatment towards systemic or musculoskeletal causes when neurological pathways prove intact.
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Practical Takeaways
- •TMS can be a valuable diagnostic tool to quickly rule in or rule out motor tract disease in recumbent horses, helping prioritize further imaging and treatment decisions
- •Normal MMEPs in a recumbent equine should redirect investigation toward metabolic and orthopedic causes rather than neurological lesions
- •Abnormal MMEPs warrant urgent imaging (radiography, MRI) to localize spinal cord or peripheral nerve lesions and guide prognosis
Key Findings
- •Transcranial magnetic stimulation successfully differentiated motor tract lesions from non-neurological causes of recumbency in 5 equines
- •Abnormal MMEPs identified 2 animals with motor nervous system involvement: one with cervical vertebral fracture and one with peripheral nerve compression from abscess
- •Normal MMEPs in 3 animals correctly indicated non-neurological causes (laminitis, rhabdomyolysis, physitis)
- •TMS with MMEP measurement provided non-invasive diagnostic confirmation of descending motor pathway integrity