The slap test for laryngeal adductory function in horses with suspected cervical spinal cord damage

The paper describes the assessment and practical implications of a laryngeal adductory reflex in a series of 30 ataxic and 64 non-ataxic horses. The reflex was evoked by slapping the saddle region just caudal to the withers. In normal horses this produced a flickering adductory movement of the contralateral arytenoid cartilage which was observed endoscopically. Abolition of the laryngeal response was encountered in in 3 situations:--(1) Disruption of the afferent impulse occurred in those horses in which there was significant spinal cord pathology affecting the pathway from the cranial thoracic region to the medulla. (2) Disruption of the efferent impulse was manifest when damage to the adductory component of the recurrrent laryngeal nerve prevented normal adduction. (3) The reflex was abolished in tense or frightened horses, possibly due to interference from higher centres. The laryngeal adductory reflex was considered to be a useful diagnostic and prognostic aid in the assessment of ataxia and spinal cord lesions in the horse.