A new method for recording H-reflexes from the plantar muscles of dogs

Assessment of the F wave technique for motor unit number estimation in normal dogs

Motor unit number estimation (MUNE) is an electrophysiological technique to quantify the number of motor units in a muscle. A previous study examining MUNE in dogs used an incremental method. The purpose of this study was to examine the use of the F wave method in dogs and to provide information about this technique. Seven healthy laboratory dogs were examined using the F wave method by stimulating either a single site or multiple sites. In the multiple site stimulation F wave (MSS-F) method, the nerve was stimulated at several close sites along the deep peroneal nerve innervating the extensor digitorum brevis muscle. Test-retest was performed with a 1 week interval in all dogs using both techniques. In this preliminary study, median MUNE values were 88 (range 27-187) using the single site stimulation F wave (SSS-F) method and 68.5 (range 47-106) using the MSS-F method. The intra-class correlation coefficients between the two sets of data for each method were 0.20 and 0.09 for left and right SSS-F, respectively, and 0.77 and 0.69 for left and right MSS-F, respectively. MSS-F had less intra-individual variability of MUNE values and was more reproducible. These results indicate that MSS-F can be performed in dogs. MUNE using MSS-F might help with quantitative evaluation of motor neurone dysfunction and progression of diseases affecting motor neurones.

The effect of loco-regional anaesthesia on motor activity induced by direct stimulation of the sciatic nerve in dogs

A prospective, randomised, blinded, case-controlled clinical study was designed using client-owned dogs undergoing unilateral pelvic limb orthopaedic surgery, to determine the effect on induced motor activity by electrical stimulation of the sciatic nerve distal to the site of local anaesthetic administration. Dogs were administered 0.5% bupivacaine either extradurally or via a femoral and transgluteal sciatic electrolocation-guided nerve block prior to pelvic limb surgery. Motor response to electrical stimulation of branches of the sciatic nerve was tested and the minimum current required to induce muscle twitch was recorded prior to bupivacaine administration. Provided sensory blockade had been deemed successful intraoperatively, testing was repeated postoperatively, with each dog acting as its own control. Paired t-tests were performed to compare pre- and postoperative minimum currents. Eleven dogs administered extradural and 11 dogs administered femoral and sciatic perineural bupivacaine were eligible for post-operative testing. All dogs displayed normal motor response to electrical stimulation of the sciatic nerve at both sites tested before and after bupivacaine administration. There was no significant difference in the minimum current required to induce muscle twitch between pre- and post-operative testing (P = 0.31 sciatic site, P = 0.36 peroneal site), nor between the two groups using different loco-regional anaesthetic techniques (minimum P = 0.13). This study shows that stimulation of the sciatic nerve distal to the site of bupivacaine administration induces motor activity, despite adequate sensory blockade. This is relevant in surgical cases where mechanical stimulation of the sciatic nerve might be expected and needs to be recognised to avoid postoperative neurapraxia.

Electrophysiology in neuromuscular disease

Electrophysiologic assessment of the peripheral nervous system is an integral part of the diagnostic workup for neuromuscular disease. This article is designed to provide insight into the importance and limitations of the various testing procedures now available in veterinary electrophysiology and to provide the reader with an understanding of the theory behind each of these procedures. The article also provides a guideline for the interpretation and clinical significance of each of the available tests.