Electrically elicited blink reflex in horses with trigeminal and facial nerve blocks

Sonia Anor From the Departement de Patologia I Produccions Animals, Facultat de Veterinaria, Universitat Autonoma de Barcelona, 08193 Bellaterra, Barcelona, Spain (Anor, Monreal, Pumarola); and the Unitat de Neurofisiologia, Hospital del Mar de Barcelona, Passeig Maritim 25–29, 08003 Barcelona, Spain (Espadaler).

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Josep M. Espadaler From the Departement de Patologia I Produccions Animals, Facultat de Veterinaria, Universitat Autonoma de Barcelona, 08193 Bellaterra, Barcelona, Spain (Anor, Monreal, Pumarola); and the Unitat de Neurofisiologia, Hospital del Mar de Barcelona, Passeig Maritim 25–29, 08003 Barcelona, Spain (Espadaler).

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Lluis Monreal From the Departement de Patologia I Produccions Animals, Facultat de Veterinaria, Universitat Autonoma de Barcelona, 08193 Bellaterra, Barcelona, Spain (Anor, Monreal, Pumarola); and the Unitat de Neurofisiologia, Hospital del Mar de Barcelona, Passeig Maritim 25–29, 08003 Barcelona, Spain (Espadaler).

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Marti Pumarola From the Departement de Patologia I Produccions Animals, Facultat de Veterinaria, Universitat Autonoma de Barcelona, 08193 Bellaterra, Barcelona, Spain (Anor, Monreal, Pumarola); and the Unitat de Neurofisiologia, Hospital del Mar de Barcelona, Passeig Maritim 25–29, 08003 Barcelona, Spain (Espadaler).

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Abstract

Objective

To reassess reference values for the components of the electrically induced blink reflex, document reference values for facial motor nerve conduction velocity, and demonstrate usefulness of the blink reflex as a diagnostic tool in peripheral facial and trigeminal nerve dysfunction in horses.

Animals

10 healthy adult horses (8 males, 2 females) without neurologic abnormalities.

Procedure

Blink reflex tests were performed by electrical stimulation of the supraorbital nerve and facial (auriculopalpebral) nerve. Reflex and direct muscle-evoked potentials of the orbicularis oculi muscles were recorded from concentric needle electrodes inserted bilaterally in these muscles. Supraorbital and auriculopalpebral nerve blocks were performed by lidocaine hydrochloride injections.

Results

Supraorbital nerve stimulation elicited 2 or 3 ipsilateral and 1 contralateral reflex muscle potential in the orbicularis oculi muscles. Auriculopalpebral nerve stimulation elicited a direct and a reflex potential in the ipsilateral orbicularis oculi muscle. After left supraorbital nerve block, no responses could be elicited ipsilaterally or contralaterally upon stimulation of the blocked nerve, but bilateral responses were obtained upon stimulation of the right supraorbital nerve. After right auriculopalpebral nerve block, no responses were recorded from the right orbicularis oculi muscle upon stimulation of left or right supraorbital nerves.

Conclusions and Clinical Relevance

Reference values for the components of the blink reflex and facial motor nerve conduction velocity will allow application of these tests to assist in the diagnosis of equine neurologic disorders involving the trigeminal and facial nerves, the brainstem, and the cranial end of the cervical segment of the spinal cord. This study reveals the usefulness of the blink reflex test in the diagnosis of peripheral trigeminal and facial nerve dysfunction in horses. (Am J Vet Res 1999;60:1287–1291)

Abstract

Objective

To reassess reference values for the components of the electrically induced blink reflex, document reference values for facial motor nerve conduction velocity, and demonstrate usefulness of the blink reflex as a diagnostic tool in peripheral facial and trigeminal nerve dysfunction in horses.

Animals

10 healthy adult horses (8 males, 2 females) without neurologic abnormalities.

Procedure

Blink reflex tests were performed by electrical stimulation of the supraorbital nerve and facial (auriculopalpebral) nerve. Reflex and direct muscle-evoked potentials of the orbicularis oculi muscles were recorded from concentric needle electrodes inserted bilaterally in these muscles. Supraorbital and auriculopalpebral nerve blocks were performed by lidocaine hydrochloride injections.

Results

Supraorbital nerve stimulation elicited 2 or 3 ipsilateral and 1 contralateral reflex muscle potential in the orbicularis oculi muscles. Auriculopalpebral nerve stimulation elicited a direct and a reflex potential in the ipsilateral orbicularis oculi muscle. After left supraorbital nerve block, no responses could be elicited ipsilaterally or contralaterally upon stimulation of the blocked nerve, but bilateral responses were obtained upon stimulation of the right supraorbital nerve. After right auriculopalpebral nerve block, no responses were recorded from the right orbicularis oculi muscle upon stimulation of left or right supraorbital nerves.

Conclusions and Clinical Relevance

Reference values for the components of the blink reflex and facial motor nerve conduction velocity will allow application of these tests to assist in the diagnosis of equine neurologic disorders involving the trigeminal and facial nerves, the brainstem, and the cranial end of the cervical segment of the spinal cord. This study reveals the usefulness of the blink reflex test in the diagnosis of peripheral trigeminal and facial nerve dysfunction in horses. (Am J Vet Res 1999;60:1287–1291)

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