A study of an electrodiagnostic technique for the evaluation of equine recurrent laryngeal neuropathy

The electrodiagnostic measurement of the thoracolaryngeal reflex (TLR) ('sl ap test') latency was compared to 5 other diagnostic techniques used for ev aluation of laryngeal function, namely laryngeal muscle palpation, resting and immediately postexercise endoscopic examinations, and palpable and endo scopic responses to the TLR. Compared to resting endoscopy, the electrodiag nostic measurement of TLR latency was not found to be an accurate test for the evaluation of recurrent laryngeal neuropathy (RLN), nor was laryngeal m uscle palpation or the endoscopic response to the TLR. Twenty-five (71%) of 35 Clydesdale horses examined were affected by RLN; 16 (46%) had mild, 5 ( 14%) moderate, 3 (9%) severe hemiparesis and 1 (3%) had total laryngeal par alysis. Within these 35 horses, physical traits such as height or neck leng th did not correlate with the incidence or severity of RLN. Ten control pon ies showed no evidence of abnormal laryngeal function.