Evaluation of repetitive nerve stimulation in young dogs

Abstract

ABSTRACTEvaluation of neuromuscular transmission requires a complete electrodiagnostic evaluation including repetitive nerve stimulation. Supra‐maximal stimulation of the peroneal nerve and recording of the compound muscle action potentials from the cranial tibial muscle were under‐taken in 25 young dogs of two to 18 months of age. Proximal stimulation in the trochanteric fossa and distal stimulation in the popliteal fossa were chosen for small and large breeds, respectively. Highly consistent results were obtained when the examined muscle was kept at a constant temperature and the limb was firmly fixed. Neither sex‐ (14 females, 11 males) nor age‐ related (mean = 4·4 months] differences in neuromuscular transmission were found, but frequency‐dependent phenomena were observed. These became more distinct with high frequency stimulation. Pseudofacilitation (n = 16/15 Hz; n = 7/50 Hz), was found to range within certain limits (6 to 26 per cent/15 Hz; 13 to 31 per cent/50 Hz). Its mean values at 50 Hz stimulation were apparently higher (26·88 per cent) than those at 15 Hz stimulation (11·3 per cent). Decremental responses occurred mainly with application of tetanic stimulation frequency (n = 1/15 Hz; n = 12/50 Hz) and may represent blocking of neuromuscular transmission. Each of these reaction patterns usually started to occur at the fourth potential of a series (81 per cent/15 Hz; 94 per cent/50 Hz) and remained constant during the second half of the stimulation train in most cases. The occurrence of post‐tetanic phenomena in healthy dogs is poorly understood. Post‐tetanic potentiation observed in the present material (24 per cent) may represent pseudofacilitation following high stimulation frequency (50 Hz/100 pulses).