A new method for recording and analysing evoked motor potentials from dogs

Traumatic and iatrogenic sciatic nerve injury in 38 dogs and 10 cats: Clinical and electrodiagnostic findings

BACKGROUND

Reports describing sciatic nerve injuries (SNI) and their outcome are scarce in veterinary medicine.

HYPOTHESIS

Describe the causes of traumatic and iatrogenic SNI and evaluate which clinical and electrodiagnostic findings predict outcome.

ANIMALS

Thirty-eight dogs and 10 cats with confirmed SNI referred for neurologic and electrodiagnostic evaluation.

METHODS

Clinical and electrodiagnostic examination results, including electromyography (EMG), motor nerve conduction studies, muscle-evoked potential (MEP), F-waves, sensory nerve conduction studies, and cord dorsum potential (CDP), were retrospectively evaluated. Quality of life (QoL) was assessed based on owner interviews.

RESULTS

Surgery (42%) and trauma (33%) were the most common causes of SNI; in dogs, 24% were caused by bites from wild boars. Ability to flex and extend the tarsus was significantly associated with positive outcome in dogs. Mean time from onset of clinical signs until electrodiagnostic evaluation was 67 ± 65 (range, 7-300) days and 65 ± 108 (range, 7-365) days for dogs and cats, respectively. A cut-off amplitude of 1.45 mV for compound motor action potentials (CMAP) was predictive of positive outcome in dogs (P = .01), with sensitivity of 58% and specificity of 100%.

CONCLUSIONS AND CLINICAL IMPORTANCE

Clinical motor function predicts recovery better than sensory function. Electrodiagnostic findings also may play a role in predicting the outcome of SNI. Application of the proposed CMAP cut-off amplitude may assist clinicians in shortening the time to reassessment or for earlier suggestion of salvage procedures. Owners perceived a good quality of life (QoL), even in cases of hindlimb amputation.

Long-term outcome of Miniature Schnauzers with genetically confirmed demyelinating polyneuropathy: 12 cases

BACKGROUND

A demyelinating polyneuropathy with focally folded myelin sheaths was reported in 3 Miniature Schnauzers in France in 2008 and was predicted to represent a naturally occurring canine homologue of Charcot-Marie-Tooth (CMT) disease. A genetic variant of MTRM13/SBF2 has been identified as causative in affected Miniature Schnauzers with this polyneuropathy.

OBJECTIVE

To provide data on the long-term progression in affected Miniature Schnauzers from Spain confirmed with the MTRM13/SBF2 genetic variant.

ANIMALS

Twelve Miniature Schnauzers presented between March 2013 and June 2019.

METHODS

Only dogs presented with consistent clinical signs and homozygous for the MTRM13/SBF2 genetic variant were included. Clinical signs, age of onset and presentation, time from onset to presentation, treatment, outcome, and time from diagnosis to final follow-up were retrospectively reviewed.

RESULTS

The hallmark clinical signs at the time of presentation were regurgitation with radiologically confirmed megaesophagus (11/12) and aphonic bark (11/12) with or without obvious neuromuscular weakness despite electrodiagnostic evidence of appendicular demyelinating polyneuropathy. Age of onset and clinical presentation were 3-18 and 4-96 months, respectively. Treatment was mostly symptomatic and consisted of head elevation during meals, antacids, prokinetics, bethanechol, sildenafil, mirtazapine, or some combination of these. During the follow-up period (7-73 months), clinical signs were unchanged in (11/12) cases with aspiration pneumonia developing occasionally (6/12) and being the cause of death in 1 dog.

CONCLUSIONS AND CLINICAL IMPORTANCE

Demyelinating polyneuropathy of Miniature Schnauzers tends to remain stable over the long term leading to a good prognosis with preventive feeding measures and symptomatic treatment to control aspiration pneumonia.

Comparison of the Two Types of Stimulating Electrodes in the Study of Motor Nerve Conduction in Dogs

In this research two kinds of stimulation electrodes were compared in motor nerve conduction study: needle electrodes used in human medicine and electrodes made of injection needles connected to the stimulator via alligator-type electrodes. A study was conducted in 22 mixed-breed dogs. The resulting values of the potential amplitudes of the stimulus, the parameters of the complex muscle potentials, and the motor nerve conduction velocity were statistically compared. There was no statistical difference between the parameters obtained with the two types of stimulation electrodes. The results of our research constitute a basis for improving present-day procedures, improving aseptic procedures, reducing tissue trauma during research and lowering research costs due to the introduction of injection-needle electrodes and their benefits into the study of motor nerve conduction in animals.

The design of and chronic tissue response to a composite nerve electrode with patterned stiffness

OBJECTIVE

As neural interfaces demonstrate success in chronic applications, a novel class of reshaping electrodes with patterned regions of stiffness will enable application to a widening range of anatomical locations. Patterning stiff regions and flexible regions of the electrode enables nerve reshaping while accommodating anatomical constraints of various implant locations ranging from peripheral nerves to spinal and autonomic plexi.

APPROACH

Introduced is a new composite electrode enabling patterning of regions of various electrode mechanical properties. The initial demonstration of the composite's capability is the composite flat interface nerve electrode (C-FINE). The C-FINE is constructed from a sandwich of patterned PEEK within layers of pliable silicone. The shape of the PEEK provides a desired pattern of stiffness: stiff across the width of the nerve to reshape the nerve, but flexible along its length to allow for bending with the nerve. This is particularly important in anatomical locations near joints or organs, and in constrained compartments. We tested pressure and volume design constraints in vitro to verify that the C-FINE can attain a safe cuff-to-nerve ratio (CNR) without impeding intraneural blood flow. We measured nerve function as well as nerve and axonal morphology following 3 month implantation of the C-FINE without wires on feline peripheral nerves in anatomically constrained areas near mobile joints and major blood vessels in both the hind and fore limbs.

MAIN RESULTS

In vitro inflation tests showed effective CNRs (1.93  ±  0.06) that exceeded the industry safety standard of 1.5 at an internal pressure of 20 mmHg. This is less than the 30 mmHg shown to induce loss of conduction or compromise blood flow. Implanted cats showed no changes in physiology or electrophysiology. Behavioral signs were normal suggesting healthy nerves. Motor nerve conduction velocity and compound motor action potential did not change significantly between implant and explant (p  >  0.15 for all measures). Axonal density and myelin sheath thickness was not significantly different within the electrode compared to sections greater than 2 cm proximal to implanted cuffs (p  >  0.14 for all measures).

SIGNIFICANCE

We present the design and verification of a novel nerve cuff electrode, the C-FINE. Laminar manufacturing processes allow C-FINE stiffness to be configured for specific applications. Here, the central region in the configuration tested is stiff to reshape or conform to the target nerve, while edges are highly flexible to bend along its length. The C-FINE occupies less volume than other NCEs, making it suitable for implantation in highly mobile locations near joints. Design constraints during simulated transient swelling were verified in vitro. Maintenance of nerve health in various challenging anatomical locations (sciatic and median/ulnar nerves) was verified in a chronic feline model in vivo.

Electromyographical, Ultrasonographical and Morphological Modifications in Semitendinous Muscle after Transposition as Ventral Perineal Muscle Flap

The aim of this study was to evaluate modifications occurring in semitendinous muscle after transposition as a ventral perineal muscle flap using electromyography, ultrasonography, and morphological studies. Ten male crossbreed dogs of 3-4 year old were used. The left semitendinous muscle was cut close to the popliteus lymph node, rotated and sutured at the perineal region. The contralateral muscle was considered as control. Motor nerve conduction studies of both sciatic-tibial nerves, and electromyographic and ultrasonographic examinations of both semitendinous muscles were performed before surgery and 15, 30, 60, and 90 days postoperatively. Semitendinous muscle samples were collected for morphological analysis 90 days after surgery. No alterations were observed in clinical gait examinations, or in goniometrical and electroneuromyographical studies in pelvic limbs after surgery. Electromyography demonstrated that the transposed muscle was able to contract, but atrophy was detected by ultrasonography and morphological analysis.

Padronização da determinação da velocidade de condução nervosa sensitiva dos nervos tibial e peroneal de cães clinicamente sadios, pela utilização de eletrodos de superfície

O presente trabalho teve como objetivo a padronização dos valores de referência de velocidade de condução nervosa sensitiva dos nervos tibial e peroneal em cães clinicamente sadios, pela utilização de eletrodos de superfície. Em todos os sítios de estimulação, captação, referência e terra foram utilizados eletrodos do "tipo jacaré", exceto na captação do estímulo no nervo peroneal, próximo à articulação fêmur-tibial, onde o registro só foi possível com a utilização de eletrodo de agulha. Foram utilizados 30 cães, 11 machos e 19 fêmeas, sem raça definida, com idade entre dois e seis anos. Os valores médios das medidas dos potenciais evocados pela estimulação sensitiva dos nervos tibial e peroneal foram: latência inicial, 1,82±0,30ms (1,30 a 2,55ms) e 1,57±0,29ms (1,01 a 2,16ms), amplitude de pico a pico, 96,48±45,78miV (41,6 a 214miV) e 121,25±57,49miV (54,8 a 299miV) e duração, 1,97±0,69ms (1,01 a 3,56ms) e 2,37±0,85ms (1,11 a 3,94ms), respectivamente. Os valores médios das medidas de velocidade de condução nervosa sensitiva dos nervos tibial e peroneal foram, respectivamente, 62,14+7,71ms (50,0 a 77,2ms) e 65,18+6,42ms (53,8 a 79,2ms), respectivamente.

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.

Laser nerve repair by solid protein band technique. II: assessment of long-term nerve regeneration

A total of 18 adult male Wistar rats had left tibial nerve repaired by either the laser-solder technique or a more conventional microsuture technique. The diode laser power was 90 mW and the radiation dose 16 J/mg. Three months postoperatively electrophysiology showed that the average compound muscle action potential (CMAP) of the laser repair group was not significantly different from the CMAP of the sutured nerves. Light microscopy confirmed regeneration of myelinated axons in both groups of animals. The laser-solder technique, when used with such parameters, proved to be a reliable method to achieve satisfactory peripheral nerve anastomosis and nerve regeneration.

Laser-activated solid protein bands for peripheral nerve repair: an vivo study

BACKGROUND AND OBJECTIVE

Severed tibial nerves in rats were repaired using a novel technique, utilizing a semiconductor diode-laser-activated protein solder applied longitudinally across the join. Welding was produced by selective laser denaturation of solid solder bands containing the dye indocyanine green.

STUDY DESIGN/MATERIALS AND METHODS

An in vivo study, using 48 adult male Wistar rats, compared conventional microsuture-repaired tibial nerves with laser solder-repaired nerves. Nerve repairs were characterised immediately after surgery and after 3 months.

RESULTS

Successful regeneration with average compound muscle action potentials of 2.5 +/- 0.5 mV and 2.7 +/- 0.3 mV (mean and standard deviation) was demonstrated for the laser-soldered nerves and the sutured nerves, respectively. Histopathology confirmed comparable regeneration of axons in laser- and suture-operated nerves.

CONCLUSION

The laser-based nerve repair technique was easier and faster than microsuture repair, minimising manipulation damage to the nerve.

Determinação da velocidade de condução nervosa motora dos nervos radial e ulnar de cães clinicamente sadios

O presente trabalho teve como objetivo a padronização dos valores de referência de velocidade de condução nervosa motora dos nervos radial e ulnar em cães clinicamente sadios. Para tanto, foram utilizados 30 cães, 11 machos e 19 fêmeas, sem raça definida, com idade entre dois e seis anos. Os valores médios das medidas do potencial muscular produzidos por meio de estimulação proximal e distal do nervo radial foram, respectivamente: latência inicial, 2,46+0,72ms e 1,58+0,62ms, amplitude de pico a pico, 8,79+2,26mV e 9,52+2,42mV e duração, 2,85+0,76ms e 2,71+0,75ms. Os respectivos valores do nervo ulnar foram: latência inicial, 4,17+0,53ms e 2,67+0,38ms; amplitude de pico a pico, 10,72+2,60mV e 11,72+2,81mV e duração, 2,23+0,38ms e 2,04+0,35ms. Os valores médios das medidas de velocidade de condução nervosa motora dos nervos radial e ulnar foram, respectivamente, 66,18+7,26m/s e 60,50+7,86m/s.

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.

Long-term duct-occluded segmental pancreatic autografts: absence of microvascular diabetic complications

BACKGROUND

Current insulin therapies for control of glucose metabolism in patients with type I diabetes mellitus prevent major metabolic consequences of insulin deficiency, but none prevents or arrests long-term complications. In experimental models of canine diabetes, retinopathy, neuropathy, and nephropathy have been shown to develop within 5 years. The aim of this study was to determine in a canine model whether glucose control provided by segmental duct-occluded pancreas autografts could prevent the long-term complications of diabetes.

METHODS

Thirty-five outbred mongrel dogs underwent segmental pancreas autotransplantation with residual pancreatectomy. Follow-up over 5 years included endocrine, retinal fundus photography, fluorescein angiography, and nerve conduction studies. At endpoint, analysis of organ specific changes was undertaken.

RESULTS

Long-term survival was achieved in 14 dogs for 4 to 5 years and in 3 dogs for 3 to 5 years. Glycosylated hemoglobin levels remained within normal limits, although response to glucose challenge was suboptimal. Fundus photography and fluorescein angiography demonstrated the absence of retinal vascular aneurisms, capillary leakage, and obliteration. Retinal digest showed no vascular changes and normal endothelial/pericyte ratios. Nerve conduction was normal, and histology of nerves revealed normal density of myelinated fibers and absence of intrafascicular vessels and glycogen deposits, with no change in spectrum of fiber diameters and ovoids. Renal histology revealed no evidence of nephropathy with normal glomerular basement membranes.

CONCLUSIONS

We have demonstrated that duct-occluded segmental pancreatic autografts are capable of providing satisfactory metabolic control for up to 5 years, thereby preventing development of the long-term microvascular complications of diabetes.

Neuromuscular transmission studies in the healthy dog: EMG and muscle force measurement after repetitive nerve stimulation

In 10 healthy anaesthetized female dogs the ulnar and the mandibular nerve were stimulated supramaximally by repetitive electric impulses according to a fixed programme. To evaluate the neuromuscular transmission system the course of the evoked compound muscle action potential and the near-isometric force of forelimb and masticatory muscles were studied respectively. The presented results are comparable to values obtained from small hand muscles of conscious, healthy human subjects. The simultaneous measurement of both the electrical and the force response may improve the diagnostic accuracy of the examination in presumed neuromuscular transmission failure in the dog, as it does in humans.