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Use of magnetic motor-evoked potentials in horses with bilateral hind limb ataxia

Heidi NolletDepartment of Internal Medicine and Clinical Biology of Large Animals, Faculty of Veterinary Medicine, University of Ghent, Salisburylaan 133, 9820 Merelbeke, Belgium.

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Luc Van HamDepartment of Medicine and Clinical Biology of Small Animals, Faculty of Veterinary Medicine, University of Ghent, Salisburylaan 133, 9820 Merelbeke, Belgium.

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Francis VerschootenDepartment of Medical Imaging of Domestic Animals, Faculty of Veterinary Medicine, University of Ghent, Salisburylaan 133, 9820 Merelbeke, Belgium.

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Guy VanderstraetenDepartment of Physical Medicine and Rehabilitation, University Hospital Ghent, De Pintelaan 185, 9000 Ghent, Belgium.

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Piet DeprezDepartment of Internal Medicine and Clinical Biology of Large Animals, Faculty of Veterinary Medicine, University of Ghent, Salisburylaan 133, 9820 Merelbeke, Belgium.

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Abstract

Objective—To determine the usefulness of magnetic motor-evoked potentials (MMEPs) for assessing the integrity of the cervical, thoracic, and thoracolumbar spinal cord in horses with bilateral hind limb ataxia.

Animals—9 horses and 1 donkey with bilateral hind limb ataxia of various degrees.

Procedure—The motor cortex was stimulated magnetically, and MMEPs were recorded bilaterally from the extensor carpi radialis and cranial tibial muscles.

Results—In 5 horses and 1 donkey, MMEPs with normal onset latencies and peak-to-peak amplitude were recorded from the extensor carpi radialis muscles, whereas abnormal onset latencies and peak-topeak amplitudes were recorded from the cranial tibial muscles. In these animals, a spinal cord lesion in the thoracic or thoracolumbar segments was suspected. In 4 horses, onset latencies and peak-topeak amplitude of MMEPs recorded from the extensor carpi radialis and cranial tibial muscles were abnormal. In these horses, a cervical spinal cord lesion was suspected.

Conclusions and Clinical Relevance—Transcranial magnetic stimulation can be considered a valuable diagnostic tool for assessing the integrity of the spinal cord, and MMEPs may be used for differentiating thoracic or thoracolumbar spinal cord lesions from mild cervical spinal cord lesions that cause ataxia in the hind limbs only. (Am J Vet Res 2003;64:1382–1386)

Abstract

Objective—To determine the usefulness of magnetic motor-evoked potentials (MMEPs) for assessing the integrity of the cervical, thoracic, and thoracolumbar spinal cord in horses with bilateral hind limb ataxia.

Animals—9 horses and 1 donkey with bilateral hind limb ataxia of various degrees.

Procedure—The motor cortex was stimulated magnetically, and MMEPs were recorded bilaterally from the extensor carpi radialis and cranial tibial muscles.

Results—In 5 horses and 1 donkey, MMEPs with normal onset latencies and peak-to-peak amplitude were recorded from the extensor carpi radialis muscles, whereas abnormal onset latencies and peak-topeak amplitudes were recorded from the cranial tibial muscles. In these animals, a spinal cord lesion in the thoracic or thoracolumbar segments was suspected. In 4 horses, onset latencies and peak-topeak amplitude of MMEPs recorded from the extensor carpi radialis and cranial tibial muscles were abnormal. In these horses, a cervical spinal cord lesion was suspected.

Conclusions and Clinical Relevance—Transcranial magnetic stimulation can be considered a valuable diagnostic tool for assessing the integrity of the spinal cord, and MMEPs may be used for differentiating thoracic or thoracolumbar spinal cord lesions from mild cervical spinal cord lesions that cause ataxia in the hind limbs only. (Am J Vet Res 2003;64:1382–1386)