F-wave conduction velocity, persistence, and amplitude for the tibial nerve in clinically normal cats

OBJECTIVE: To establish a method of F-wave evaluation and to determine normative values of F-wave parameters, including F-wave conduction velocity, persistence, and amplitude for the tibial nerve in cats. ANIMALS: 30 clinically normal cats. PROCEDURES: F-waves elicited in the interosseous muscles by stimulation of the tibial nerve were recorded, and linear regression analyses of the shortest latency versus the length of the tibial nerve and the limb length were performed. F-wave persistence was calculated by dividing the number of recorded F-waves by the number of stimuli. RESULTS: The correlation coefficient between F-wave latency and nerve length was 0.92, and that between F-wave latency and limb length was 0.58. Mean +/- SD F-wave conduction velocity of the tibial nerve was calculated to be 97.1 +/- 5.0 m/s. Linear regression analysis yielded the regression equation as follows: F-wave latency (milliseconds) = 2.60 + (0.02 x nerve length [mm]). Mean F-wave persistence and amplitude were 98.7 +/- 2.3% and 1.01 +/- 0.62 mV, respectively. CONCLUSIONS AND CLINICAL RELEVANCE: Results indicated that nerve length should be used for nerve conduction studies of F-waves in felids. The regression equation for F-wave latency, conduction velocity, persistence, and amplitude may contribute to the diagnosis of nervous system diseases or injury in cats, such as trauma to the spinal cord or diabetic neuropathy.     

Motor nerve conduction velocity and latency in the dog

Supramaximal percutaneous nerve stimulation was used in motor nerve conduction velocity studies conducted in ten middle-aged, clinically normal dogs. Dogs were separated into two groups; dogs in one group weighted less than or equal to 7.5 kg and dogs in the other group weighted greater than or equal to 15.9 kg. Mean values and SEM were recorded for radial (72.1 +/- 1.9 m/s), median 65.6 +/- 2.1 m/s), ulnar (58.9 +/- 1.0 m/s), tibial (68.2 +/- 1.4 m/s), and peroneal (79.8 +/- 1.8 m/s) nerves. Values for latency, amplitude, and duration for proximal and distal evoked potentials were recorded. Analysis of mean nerve conduction velocity values for all nerves between the two groups indicated no statistical difference (P greater than 0.05). However, the two groups were statistically different (P less than 0.05) when values for distal latency and measurements of nerve length were compared. These data suggest that if latency is substituted for velocity measurements, various populations of dogs must be considered to clarify interpretation.     

F-wave latency and F-wave conduction velocity for the tibial nerve in clinically normal dogs

OBJECTIVE: To establish a method of F-wave examinations and to determine values of F-wave conduction velocity (FWCV) and F-wave latency for the tibial nerve of clinically normal dogs. ANIMALS: 21 clinically normal dogs. PROCEDURE: The F-waves were elicited from the interosseous muscles via stimulation of the tibial nerve. The FWCV was determined by using the F-wave shortest value and the surface distance corresponding to the tibial nerve length. Correlation between the smallest latency value of the F-wave and the length of the tibial nerve and between the FWCV and rectal temperature were closely examined. RESULTS: F-wave latency was proportional to the length of the tibial nerve (correlation coefficient, 0.929). Mean +/- SD FWCV was 77.98 +/- 8.62 m/s. Regression equation was as follows: F-wave latency = 2.799 + (0.029 X length of the tibial nerve).The FWCV was increased when the measured rectal temperature was high. Correlation coefficient between FWCV and rectal temperature was 0.665. CONCLUSIONS AND CLINICAL RELEVANCE: In the study reported here, we established a reliable method for clinical evaluation of the F-wave. When assessing nerve conduction velocity, it is essential to measure nerve length along the pathway that the nerve impulse travels. This method of F-wave examination is a useful diagnostic tool for the evaluation of suspected dysfunction of the peripheral nervous system.     

Development and verification of saphenous, tibial and common peroneal nerve block techniques for analgesia below the thigh in the nonchondrodystrophoid dog

OBJECTIVE: To document simple and reliable local, infiltrating nerve blocks for the saphenous, tibial and common peroneal nerves in the dog. STUDY DESIGN: Laboratory technique development; in vivo blind, controlled, prospective study. ANIMALS: Twenty canine cadavers and 18 clinically normal, client-owned dogs. METHODS: A peripheral nerve blockade technique of the tibial, common peroneal, and saphenous nerves was perfected through anatomic dissection. Injections were planned in the caudal thigh for the tibial and common peroneal nerves, and in the medial thigh for the saphenous nerve. Cadaver limbs were injected with methylene blue dye and subsequently dissected to confirm successful dye placement. Clinically normal dogs undergoing general anesthesia for unrelated, elective procedures were randomly assigned to treatment (bupivacaine; n = 8) or control (saline; n = 8) nerve blocks of the nerves under study. Upon recovery from general anesthesia, skin sensation in selected dermatomes was evaluated for 24 hours. RESULTS: Cadaver tibial, common peroneal, and saphenous perineural infiltrations were successful in nonchondrodystrophoid dogs (100, 100, and 97%, respectively.) Intraneural injection was rare (1%; 1/105; tibial nerve) in cadaver dogs. In the treatment group of normal dogs, duration of loss of cutaneous sensation in some dermatomes (saphenous, superficial and deep peroneal nerve) was significantly different than control dogs; the range of desensitization occurred for 1-20 hours. No clinical morbidity was detected. CONCLUSIONS: This technique for local blockade of the tibial, common peroneal, and saphenous nerves just proximal to the stifle is easy to perform, requires minimal supplies and results in significant desensitization of the associated dermatomes in clinically normal, nonchondrodystrophoid dogs. CLINICAL RELEVANCE: This technique may be an effective tool for post-operative analgesia to the femoro-tibial joint and distal pelvic limb. Other applications, using sustained-release drugs or methods, may include anesthesia/analgesia in high-risk patients or as a treatment for chronic pelvic limb pain or self-mutilation.     

Evaluation of a Midhumeral Block of the Radial,Ulnar, Musculocutaneous and Median (RUMM Block) Nerves for Analgesia of the Distal Aspect of the Thoracic Limb in Dogs

Objective: To evaluate a technique for midhumeral peripheral nerve blockade in the dog. Study Design: Cadaveric technique development; in vivo placebo‐controlled, prospective crossover study. Animals: Canine cadavers (n=38) and 8 clinically healthy, adult hound dogs. Methods: A technique for peripheral block of the radial, ulnar, musculocutaneous, and median nerves (RUMM block) was evaluated using cadaver limbs. Eight purpose‐bred, research dogs were anesthetized; a RUMM block was performed on each thoracic limb. One limb from each dog randomly received 0.5% bupivacaine and the opposite limb was assigned to receive sterile saline solution as a control. After recovery from anesthesia, skin sensation at selected dermatomes was evaluated for 24 hours using a mechanical stimulus. Weight‐bearing, conscious proprioception, and withdrawal reflex were also evaluated. One month after initial testing, each dog was reanesthetized and each limb received the opposite treatment. Results: Sensory thresholds were significantly increased over baseline measurements when compared with control limbs for all nerves. Complete sensory block was achieved in radial (15/16), ulnar (3/16), musculocutaneous (8/16), and median (11/16) nerves, using a mechanical stimulus of analgesia. Complete simultaneous block of all nerves was only obtained in 1 of 16 limbs. Conclusion: RUMM block resulted in desensitization of the skin in the associated dermatomes for 4–10 hours. Complete sensory block of the dermatomes supplied by the radial nerve was most consistent. Clinical Relevance: RUMM block may be an effective technique to provide adjunctive analgesia for dogs undergoing surgery of the distal aspect of the thoracic limb.     

Cortical somatosensory-evoked potentials in the horse

Cortical somatosensory-evoked potentials (SEP) were recorded from thoracic and pelvic limbs in 15 horses (13 Thoroughbreds and 2 Quarter Horses). Ulnar nerve SEP were evoked by electrical stimulation of the lateral palmar branch of the ulnar nerve at the level of the metacarpophalangeal joint. Recordings were taken between electrodes at 2 cm lateral to the vertex (contralateral to the stimulated limb) and the midpoint of the interorbital line. Four peaks were found in all recordings: N1, P1, N2, and P2. Latencies to the peaks were 39.0 +/- 2.7, 45.5 +/- 5.3, 50.4 +/- 5.2, and 62.3 +/- 3.7 ms (mean +/- SD), respectively. Tibial nerve SEP were evoked by stimulation of the lateral plantar nerve branch of the tibial nerve at the level of the metatarsophalangeal joint. Recordings were taken between electrodes at the vertex (contralateral to the stimulated limb) and the midpoint of the interorbital line. Four peaks were also found in all tibial nerve SEP recordings: N1, P1, N2, and P2. Latencies to the peaks were 64.6 +/- 11.8, 84.5 +/- 9.7, 121.2 +/- 11.6, and 134.0 +/- 11.1 ms, respectively. Amplitude variability was high for the ulnar nerve and the tibial nerve SEP. There was no effect of sex seen on peak latency or amplitude, and peak latencies were not affected by body length.     

Resistance of the Peripheral Nervous System to the Effects of Chronic Canine Hypothyroidism

Background: Hypothyroidism has been implicated in the development of multiple peripheral mono‐ and polyneuropathies in dogs. The objectives of this study were to evaluate the clinical and electrophysiologic effects of experimentally induced hypothyroidism on the peripheral nervous system of dogs. Hypothesis: Chronic hypothyroidism will induce peripheral nerve sensorimotor dysfunction. Animals: Eighteen purpose‐bred, female dogs. Methods: Prospective, longitudinal study: Hypothyroidism was induced by radioactive iodine administration in 9 dogs, and the remaining 9 served as untreated controls. Neurological examinations were performed monthly. Electrophysiologic testing consisting of electromyography (EMG); motor nerve conduction studies of the sciatic‐tibial, radial, ulnar, and recurrent laryngeal nerves; sciatic‐tibial and ulnar F‐wave studies; sensory nerve conduction studies of the tibial, ulnar, and radial nerves; and evaluation of blink reflex and facial responses were performed before and 6, 12, and 18 months after induction of hypothyroidism and compared with controls. Results: Clinical evidence of peripheral nervous dysfunction did not occur in any dog. At 6 month and subsequent evaluations, all hypothyroid dogs had EMG and histologic evidence of hypothyroid myopathy. Hypothyroid dogs had significant (P≤ .04) decreases in ulnar and sciatic‐tibial compound muscle action potentials over time, which were attributed to the concurrent myopathy. No significant differences between control and hypothyroid dogs were detected in electrophysiologic tests of motor (P≥ .1) or sensory nerve conduction velocity (P≥ .24) or nerve roots (P≥ .16) throughout the study period, with values remaining within reference ranges in all dogs. Conclusion: Chronic hypothyroidism induced by thyroid irradiation does not result in clinical or electrophysiologic evidence of peripheral neuropathy, but does cause subclinical myopathy.     

The effect of the tarsal joint positions on the tibial nerve motor action potential latency in dog: electrophysiological and anatomical studies

This study has been carried out to determine the effect of neutral position, hyperextension and hyperflexion of the tarsal joint on the tibial nerve, motor action potential latency and tarsal canal compartment pressure in dogs with the aid of electrophysiological and anatomical methods. Totally twenty healthy mongrel dogs were used. Latency of motor nerve action potential (MNAPL) studies of tibial nerve via surface stimulating and needle recording electrodes was performed on right hind limbs of all the dogs. The compartment pressures of the tarsal canal with the pressure transducer were determined from both limbs from ten of the dogs. In one dog, tarsal regions of both left and right limbs were demonstrated using magnetic resonance imaging (MRI). Two dogs were euthanatized and tarsal regions of the dogs were sectioned for correlative anatomy. Nerve conduction studies showed that the MNAP latency of the tibial nerve were 3.55 +/- 0.097 ms, 3.76 +/- 0.087 ms and 3.39 +/- 0.097 ms in neutral, hyperextension and hyperflexion positions, respectively. Hyperflexion of the tarsal joint caused prolongation of the MNAP latency of the tibial nerve with the highest pressure value being determined in tarsal canal. From the anatomical viewpoint, the distance between the flexor hallucis longus muscle and the superficial digital muscle was the shortest during hyperflexion and the plantar branch of saphenous artery, lateral and medial plantar nerves located more laterally in cadaver and MR imaging sections. As a result of this study, it is thought that tarsal region diseases as well as long time splint in the hyperflexion position as applied in the Ehmer sling can affect the compartment pressure and nerve tension because of occupying in the tarsal canal. Raising pressure and nerve stretching in the tarsal canal compartment could cause deficiencies in the conduction velocity of the tibial nerve. This might be a result of tarsal tunnel syndrome in the dog. Clinicians could consider this syndrome in cases of tarsal region diseases as well as application of long time splint in hyperflexion of tarsal joints in dogs.     

Electroneurographic examination of the ulnar and radial nerves in the dog: reference values, biological variation and reproducibility

The radial and ulnar nerves were examined electrophysiologically in 90 normal dogs. In 66 of these dogs, aged between one and eight years, the reference values were established for 27 variables. Multicomponent sensory nerve action potentials were encountered at the proximal recording site in the ulnar nerve in 68 per cent of the dogs in the reference group and in the radial nerve in 26 per cent. Differences between the sexes were not significant, nor were differences between two breeds of similar body size. There were no significant age related differences between the ages of one and eight years. Limb length, measured as the distance between sensory stimulation site (digits) and proximal recording site (elbow), was found to have a significant effect on the velocity, amplitude, number of positive peaks and duration of the nerve action potentials. The variation in results of repeated measurements of velocities ranged from 0 to 11 per cent. The relative error in velocities due to errors in measurement of distance and latency ranged from 1 to 12 per cent.     

Effects of endurance training on standard and signal-averaged electrocardiograms of sled dogs

OBJECTIVE: To determine the effect of endurance training on QRS duration, QRS-wave amplitude, and QT interval. ANIMALS: 100 sled dogs in Alaska. PROCEDURE: Dogs were examined in early September (before training) and late March (after training). During the interim, dogs trained by pulling a sled with a musher (mean, 20 km/d). Standard and signal-averaged ECG were obtained before and after training. RESULTS: Endurance training significantly increased mean QRS duration by 4.4 milliseconds for standard ECG (mean +/- SEM; 62.3 +/- 0.7 to 66.7 +/- 0.6 milliseconds) and 4.3 milliseconds for signal-averaged ECG (51.5 +/- 0.7 to 55.8 +/- 0.6 milliseconds) without changing body weight. Increase in QRS duration corresponded to a calculated increase in heart weight (standard ECG, 23%; signal-averaged ECG, 27%). Signal-averaged QRS duration was correlated with echocardiographically determined left ventricular diastolic diameter for the X orthogonal lead (r = +0.41), Y orthogonal lead (r = +0.33), and vector (r = +0.35). Training also increased QT interval (234 +/- 2 to 249 +/- 2 milliseconds) and R-wave amplitude in leads II and rV2, increased peak-to-peak voltage and S-wave amplitude in the Y orthogonal lead, and decreased Q-wave amplitude in the Y orthogonal lead. CONCLUSIONS AND CLINICAL RELEVANCE: Electrocardiographic changes reflected physiologic cardiac hypertrophy in these canine athletes in response to repetitive endurance exercise. The QRS duration increases in response to endurance exercise training and, therefore, may be of use in predicting performance in endurance activities.     

Sensory and motor neuropathy in a Border Collie

A 5-month-old female Border Collie was evaluated because of progressive hind limb ataxia. The predominant clinical findings suggested a sensory neuropathy. Sensory nerve conduction velocity was absent in the tibial, common peroneal, and radial nerves and was decreased in the ulnar nerve; motor nerve conduction velocity was decreased in the tibial, common peroneal, and ulnar nerves. Histologic examination of nerve biopsy specimens revealed considerable nerve fiber depletion; some tissue sections had myelin ovoids, foamy macrophages, and axonal degeneration in remaining fibers. Marked depletion of most myelinated fibers within the peroneal nerve (a mixed sensory and motor nerve) supported the electrodiagnostic findings indicative of sensorimotor neuropathy. Progressive deterioration in motor function occurred over the following 19 months until the dog was euthanatized. A hereditary link was not established, but a littermate was similarly affected. The hereditary characteristic of this disease requires further investigation.     

Tibial nerve somatosensory evoked potentials in dogs with degenerative lumbosacral stenosis

OBJECTIVE: To determine somatosensory evoked potentials (SEPs) in dogs with degenerative lumbosacral stenosis (DLS) and in healthy dogs. STUDY DESIGN: Clinical and experimental study. ANIMALS: Dogs with DLS (n = 21) and 11 clinically normal dogs, age, and weight matched. METHODS: Under anesthesia, the tibial nerve was stimulated at the caudolateral aspect of the stifle, and lumbar SEP (LSEP) were recorded percutaneously from S1 to T13 at each interspinous space. Cortical SEP (CSEP) were recorded from the scalp. RESULTS: LSEP were identified as the N1-P1 (latency 3-6 ms) and N2-P2 (latency 7-13 ms) wave complexes in the recordings of dogs with DLS and control dogs. Latency of N1-P1 increased and that of N2-P2 decreased as the active recording electrode was moved cranially from S1 to T13. Compared with controls, latencies were significantly delayed in DLS dogs: .8 ms for N1-P1 and 1.7 ms for the N2-P2 complex. CSEP were not different between groups. CONCLUSIONS: Surface needle recording of tibial nerve SEP can be used to monitor somatosensory nerve function of pelvic limbs in dogs. In dogs with DLS, the latency of LSEP, but not of CSEP, is prolonged compared with normal dogs. CLINICAL RELEVANCE: In dogs with lumbosacral pain from DLS, the cauda equina compression is sufficient to affect LSEP at the lumbar level.     

The effects of medetomidine on radial nerve blockade with mepivacaine in dogs

OBJECTIVE: To compare the sensory and motor effects of adding medetomidine to mepivicaine, administered either perineurally or systemically, for radial nerve block in dogs. STUDY DESIGN: Prospective randomized cross-over study. ANIMALS: Six healthy Beagles, aged 18.7 +/- 6.3 months and weighing 10.4 +/- 1.3 kg. METHODS: Dogs were anesthetized briefly with sevoflurane on three separate occasions and received each treatment administered in random order: mepivacaine 5 mg kg(-1) perineurally around the radial nerve with saline 0.01 mL kg(-1) intramuscularly (CONTROL); mepivacaine 5 mg kg(-1) and medetomidine 0.01 mg kg(-1) combined, perineurally with saline 0.01 mL kg(-1) intramuscularly (MEDPN); mepivacaine 5 mg kg(-1) perineurally around the radial nerve with medetomidine 0.01 mg kg(-1) intramuscularly (MEDIM). All nerve blocks were performed with the aid of a nerve locator. Motor effects were evaluated based on the ability to bear weight. Sensory effects were evaluated by the response to a graded-electrical stimulus. These were evaluated at 5-minute intervals for the first hour, and at 10-minute intervals thereafter. Mean intervals were calculated as follows: time to motor block onset, duration of motor block, time to peak sensory block, duration of peak sensory block (i.e. period of no response to maximal stimulus intensity), and duration of residual sensory block (i.e. time to return to baseline sensory function). Treatment means were compared using a one-way analysis of variance for repeated measures and, where significant differences were noted, a Student-Newman-Keuls test was applied; p < 0.05 was considered significant. RESULTS: Medetomidine, administered either systemically or perineurally, significantly prolonged duration of peak motor block, peak sensory block, and residual sensory block compared with CONTROL. CONCLUSION: Medetomidine prolonged sensory and motor blockade after radial nerve block with mepivacaine in dogs. CLINICAL RELEVANCE: Medetomidine may prove to be a useful adjunct to peripheral nerve blockade with local anesthetics.     

Intraoperative Monitoring of Ischiatic Nerve Function with Sensory Evoked Potentials

Serial recordings of sensory evoked potentials (SEP) generated in response to stimulation of each tibial nerve were obtained from 23 anesthetized dogs. Five dogs were anesthetized for 3 hours to evaluate changes in serial SEP during general anesthesia. Nonsurgical and surgical manipulations were performed on one hind limb of five dogs to determine the effects of limb positioning and nerve retraction on SEP. In 13 dogs, the ischiatic nerve was exposed surgically and retracted until the SEP deteriorated and disappeared, to determine the relationship between amount of tension on the nerve and the time to complete deterioration of the SEP. Sensory evoked potential waveforms, which consisted of two to five peaks, were stable throughout the anesthetic period. The first two peaks were the most stable. Latency of the first two peaks was the easiest and most reliable parameter to evaluate. Although the peak latency in recordings from the superior hind limb was always slightly longer, SEP recordings from the inferior limb were good controls to monitor nerve function. There was considerable variation in sensitivity to nerve retraction. The technique proved to be a reliable way to monitor nerve function in normal anesthetized dogs.     

Fracture of the proximal tibial epiphysis and tuberosity in 10 dogs

Ten dogs were presented with fractures of the proximal tibial epiphysis and tuberosity. All dogs had a cranioproximal-caudodistal angulation of the tibial plateau. Six dogs had marked caudal displacement of the proximal tibial epiphysis, five of which had also sustained fractures of the proximal fibula. The estimated mean angle of inclination of the tibial plateau of affected limbs was 45.8 +/- 9.6 degrees, which was significantly greater (P<0.0005) than the estimated mean angle of the normal contralateral limb 26.2 +/- 6.6 degrees. The mean angle of inclination of the tibial plateau of dogs with fibular fractures (n=5) was not significantly different from dogs without fibular fractures (n=5) (P>0.25). Five dogs were treated conservatively and five were treated by three different methods of surgical repair. Surgically treated dogs had significantly greater preoperative tibial plateau angles (P<0.05). All dogs regained full limb usage, regardless of the method of treatment chosen.     

The reference values of the T-wave of the patellar tendon reflex in normal dogs

The T-wave of the patellar tendon reflex (PTR) was recorded in 24 neurologically normal dogs. The surface electromyogram (EMG) was recorded as the T-wave from the vastus lateralis muscle (VL) in response to percussion of the patellar tendon. The distance of the reflex arc (DRA) was measured along the straight line between the spinous process of L5 and the greater trochanter (GT), and between GT and the patellar ligament (PL). There was a significant correlation (P<0.001) of the latency with the DRA on each side, but no difference in the slopes of the relationships between right and left VL was shown. The regression line between the DRA and the latency of all data was Y = 0.0216X + 1.693, where Y = latency in ms, X = DRA in mm. The mixed sensory-motor conduction velocity was estimated as 84.6 +/- 5.5 m/s. In contrast, there was no significant correlation between the DRA and the amplitude of the T-waves. The mean (mean-CV) and standard deviation (SD-CV) of all CV (coefficient of variation) in each dog were 9.14 +/- 3.65% in latency and 3.54 +/- 1.14% in amplitude, indicating that the use of a simple hand-held reflex hammer is sufficient to record the reproducible T-wave of the PTR even in unanesthetized dogs. This method was applied to a case with minimal paraparesis, and the latency of the T-wave of the PTR in the right hind limb with slight proprioceptive deficit was outside of the upper limit of the 95% confidence interval between latency and the DRA. In conclusion, this method may be used in neurological diagnosis to quantify more precisely the PTR in dogs.     

Electromyographic evaluation of conduction time and velocity of the recurrent laryngeal nerves of clinically normal dogs

In 25 adult dogs of various breeds, recurrent laryngeal nerve fibers were electrically stimulated at 2 points along their extralaryngeal course. Evoked compound muscle action potentials were recorded in the ipsilateral intrinsic laryngeal muscles, using a percutaneous needle electrode. Latencies, amplitudes, and durations were measured. Latencies were correlated with neck length (r = 0.88 on left and 0.82 on right). Five of the dogs were euthanatized, and the nerve length between the 2 stimulating needle electrodes was measured; calculated conduction velocities (mean +/- SD) were 55 +/- 6 m/s (left) and 57 +/- 6 m/s (right). In 38 additional canine cadavers, the lengths of the exposed left and right recurrent laryngeal nerves were correlated with neck length (r = 0.44 on left and 0.56 on right). A linear regression model is proposed for predicting normal latencies, despite variations in neck length among different breeds of dogs.     

Cortical somatosensory evoked potentials in cows.

A method was developed to record cortical somatosensory evoked potentials (SEP) from thoracic and pelvic limb stimulation in cows. Recordings were similar in latency and amplitude to those reported for horses. Correction for conduction pathway length did not alter the average latency values because the cows of the study were uniform in size; however, the data provided will enable use of this normative data with smaller or larger individual animals. Although latency variability for the SEP peaks was low, variability of the amplitude measurements was high. This observed variability was similar to that seen in other species. Validity of the recorded responses was indicated by lack of a tibial nerve SEP in 1 cow that had been given a tibial nerve conduction block, using lidocaine, and by repeatability of the response in 2 recordings taken 1 year apart in the same cow.     

Motor Fibers in the Canine Distal Caudal Cutaneous Sural Nerve—Dual Innervation of the Hind Limb Plantar Muscles

The function of the communicating branch of the distal caudal cutaneous sural (DCCS) nerve to the tibial nerve was investigated in 7 adult dogs and was found to contain the motor component of this nerve. This function was studied by direct visualization of the contraction of the hind limb plantar muscles and by direct electrophysiologic recording of motor unit action potentials in these muscles, following stimulation of the DCCS nerve. Contraction of all of the mm. interossei, the mm. lumbricales, the m. adductor digiti quinti and the m. adductor digiti secundi was observed with the stimulation of either the tibial or the DCCS nerves, although there was a qualitative variability in the plantar muscles exhibiting the strongest contraction with stimulation of the latter nerve. This communicating branch was not found in one of the experimental dogs, suggesting some individual variability in the DCCS nerve anatomy and subsequent function. This study conclusively demonstrated that the canine DCCS nerve contains both motor and sensory nerve fibers, which is similar to this nerve in the rat, but anatomically and functionally different to that in the human and the cat.     

Electrophysiologic Assessment of Acute Polyradiculoneuropathy in Dogs: Comparison with Guillain-Barré Syndrome in People

Electrophysiologic investigations of motor and sensory nerve as well as ventral nerve root function were performed on 12 dogs with suspected acute canine polyradiculoneuropathy (ACP) at different stages and with different severity of disease. The most reliable electrophysiologic indicators of ACP were electromyographic changes (occurring in 100% of affected dogs), significantly decreased compound muscle action potential amplitudes (in 75, 90, and 100% of affected dogs at all sites along the sciatic/tibial, radial, and ulnar nerves, respectively), increased minimum F-wave latencies (67%), increased F ratios (92%), and decreased F-wave amplitudes (67%). These findings suggest that ACP represents a peripheral motor axonopathy, with demyelination and axonal involvement also occurring in ventral nerve roots. Evidence of peripheral demyelination was present in some dogs although it was overshadowed by the prominent axonopathy. ACP more closely resembles the acute axonal or intermediate forms of Guillain-Barré syndrome in people.