Objective-To assess the feasibility of measuring cord dorsum potentials (CDPs) in anesthetized clinically normal dogs after caudal nerve stimulation, determine the intervertebral site of maximum amplitude and best waveform of the CDP, and evaluate the effects of neuromuscular blockade. Animals-8 male and 4 female dogs (age, 1 to 5 years). Procedures-Dogs were anesthetized, and CDPs were recorded via needles placed on the dorsal lamina at intervertebral spaces L1-2 through L7-S1. Caudal nerves were stimulated with monopolar electrodes inserted laterally to the level of the caudal vertebrae. Dogs were tested without and during neuromuscular blockade induced with atracurium besylate. The CDP latency and amplitude were determined from the largest amplitude tracings. Results-CDPs were recorded in 11 of 12 dogs without neuromuscular blockade and in all dogs during neuromuscular blockade. The CDP was largest and most isolated at the L4-5 intervertebral space (3 dogs) or the L5-6 intervertebral space (9 dogs); this site corresponded to the segment of insertion of the first caudal nerve. Onset latencies ranged from 2.0 to 4.7 milliseconds, and there was no effect of neuromuscular blockade on latencies. Amplitudes of the CDPs were highly variable for both experimental conditions. Conclusions and Clinical Relevance-CDPs were recorded from all dogs tested in the study; neuromuscular blockade was not critical for successful CDP recording but reduced muscle artifact. This technique may be useful as a tool to assess the caudal nerve roots in dogs suspected of having compressive lumbosacral disease or myelopathies affecting the lumbar intumescence.

Objective—To determine the effects of syringomyelia on electromyography (EMG) findings, somatosensory-evoked potentials (SEPs), and transcranial magnetic motor-evoked potentials (TMMEPs) in Cavalier King Charles Spaniels (CKCSs). Animals—27 client-owned CKCSs that underwent prebreeding magnetic resonance imaging screening or investigation of clinical signs consistent with syringomyelia. Procedures—In dogs with (n = 11) and without (16) magnetic resonance imaging-confirmed syringomyelia, the median nerve in each thoracic limb was stimulated and SEPs were recorded over the C1 vertebra; onset latency and latency and amplitude of the largest negative (N1) and positive (P1) peaks were measured. The TMMEPs were recorded bilaterally from the extensor carpi radialis and tibialis cranialis muscles; onset latencies in all 4 limbs were measured. Bilateral systematic needle EMG examination was performed on the cervical epaxial musculature, and the number of sites with spontaneous activity was recorded. Results—In dogs with syringomyelia, amplitudes of N1 and P1 and the amplitude difference between P1 and N1 were significantly smaller than those recorded for dogs without syringomyelia (approx 2-fold difference). No difference in SEP latencies, TMMEP latencies, or the proportion of dogs with > 2 sites of spontaneous activity detected during EMG examination was detected between groups. Conclusions and Clinical Relevance—Results indicated that SEP amplitude at the C1 vertebra was a more sensitive measure of spinal cord function in CKCSs with syringomyelia, compared with results of EMG or TMMEP assessment. Measurement of SEP amplitude may have use as an objective assessment of the evolution and treatment of this disease.

Objective—To compare biomechanical characteristics of vertebral segments after vertebral body plating or laminar stabilization following complete incision of the annulus fibrosus. Sample—Vertebral segments from T13 through L3 obtained from 18 canine cadavers. Procedures—A 4-point bending moment was applied in flexion and extension to the intact vertebral segments to determine a baseline range of motion (ROM) and neutral zone (NZ). Vertebral columns were then destabilized by creating a defect in the intervertebral disk via complete incision of the ventral aspect of the annulus fibrosus. The bending moment was applied again after stabilization was accomplished via vertebral body plating or with laminar stabilization (n = 9 vertebral segments/stabilization technique). The ROM and NZ were compared with their baseline values and among treatment groups. Finally, load-to-failure testing was performed in flexion. Results—Mean relative ROM and NZ for segments treated with laminar stabilization were significantly lower than those for segments treated with vertebral plates. Conclusions and Clinical Relevance—Analysis of in vitro results suggested that laminar stabilization of vertebral segments provided greater stiffness than did vertebral body plating.

Muscle loss associated with disease (cachexia) or with aging (sarcopenia) is common in dogs, but clinically relevant methods for quantifying muscle loss are needed. We previously validated an ultrasound method of quantifying muscle size in dogs in a single breed. The goal of this study was to assess the variability and reproducibility of the Vertebral Epaxial Muscle Score (VEMS) in other dog breeds. Static ultrasound images were obtained from 38 healthy, neutered dogs of 5 different breeds between 1- and 5-years-old. The maximal transverse right epaxial muscle height and area at the level of the 13th thoracic vertebra (T13) were measured. Length of the 4th thoracic vertebra (T4) was measured from thoracic radiography. Ratios of the muscle height and area to vertebral length (height/T4 and area/T4, respectively) were calculated to account for differences in body size among breeds. Reproducibility testing was performed on 2 dogs of each breed (26% of the total) to determine intra- and inter-investigator reproducibility, as well as intra-class correlation. Mean height/T4 = 1.02 ± 0.18 and mean area/T4 = 3.32 ± 1.68. There was no significant difference for height/T4 (P = 0.10) among breeds, but breeds were significantly different in area/T4 (P < 0.001). Intra-class correlation ranged from 0.80 to 0.99. Testing showed better reproducibility for height/T4 compared to area/T4. The VEMS using height/T4 was valid and reproducible for healthy dogs of different sizes and body conformations. Studies assessing this technique in dogs with congestive heart failure and other diseases associated with muscle loss are warranted.

OBJECTIVE To evaluate dynamic movement of the diaphragm of clinically normal dogs by use of fluoroscopy and to obtain quantitative data of diaphragmatic excursion during spontaneous breathing. ANIMALS 8 healthy male Beagles with no history of respiratory tract disease. PROCEDURES Fluoroscopy was performed during stabilized respiratory conditions. The beam center was located at the level of the diaphragm, and diaphragmatic motion was recorded during 3 respiratory cycles in dogs positioned in left lateral, right lateral, and dorsal recumbency. Extent of excursion of the diaphragmatic cupula and both crura, difference in excursion between the left and right crura, and ratios of the excursions of the diaphragmatic cupula and left and right crura to the length of the eighth thoracic vertebra were determined. RESULTS Diaphragmatic crural excursion was symmetric for dogs in right lateral recumbency, and the crural excursion was approximately three-quarters of the vertebral length; however, crural excursion appeared to be asymmetric for dogs in left lateral recumbency. Mean ± SD difference in excursion between the right and left crura was 22.68 ± 8.68% for left lateral recumbency, 16.63 ± 9.22% for right lateral recumbency, and 18.11 ± 12.96% for dorsal recumbency. CONCLUSIONS AND CLINICAL RELEVANCE Results indicated that the fluoroscopic view of a dog positioned in right lateral recumbency may allow better evaluation of the symmetry of diaphragmatic excursion, compared with results for other recumbency positions. This study provided quantitative data on the excursion of diaphragmatic movement observed by use of fluoroscopy in clinically normal Beagles.

OBJECTIVE To characterize and compare MRI susceptibility artifacts related to titanium and stainless steel monocortical screws in the cervical vertebrae and spinal cord of canine cadavers. SAMPLE 12 canine cadavers. PROCEDURES Cervical vertebrae (C4 and C5) were surgically stabilized with titanium or stainless steel monocortical screws and polymethylmethacrylate. Routine T1-weighted, T2-weighted, and short tau inversion recovery sequences were performed at 3.0 T. Magnetic susceptibility artifacts in 20 regions of interest (ROIs) across 4 contiguous vertebrae (C3 through C6) were scored by use of an established scoring system. RESULTS Artifact scores for stainless steel screws were significantly greater than scores for titanium screws at 18 of 20 ROIs. Artifact scores for titanium screws were significantly higher for spinal cord ROIs within the implanted vertebrae. Artifact scores for stainless steel screws at C3 were significantly less than at the other 3 cervical vertebrae. CONCLUSIONS AND CLINICAL RELEVANCE Evaluation of routine MRI sequences obtained at 3.0 T revealed that susceptibility artifacts related to titanium monocortical screws were considered mild and should not hinder the overall clinical assessment of the cervical vertebrae and spinal cord. However, mild focal artifacts may obscure small portions of the spinal cord or intervertebral discs immediately adjacent to titanium screws. Severe artifacts related to stainless steel screws were more likely to result in routine MRI sequences being nondiagnostic; however, artifacts may be mitigated by implant positioning.

OBJECTIVE To evaluate whether a low-dosage regimen of prednisolone induces bone loss and whether administration of alendronate sodium prevents glucocorticoid-induced osteopenia in dogs by measuring trabecular bone mineral density (BMD) with quantitative CT. ANIMALS 8 healthy Beagles. PROCEDURES In 4 dogs, prednisolone was administered PO at a dosage of 2 mg/kg once daily for 2 weeks, 1 mg/kg once daily for 4 weeks, and 0.5 mg/kg once daily for 3 weeks. In the other 4 dogs, alendronate sodium (2 mg/kg, PO, q 24 h) was whether administered for 9 weeks in addition to the same dosage of prednisolone used in the prednisolone-treated dogs. Before (day 0 [baseline]) and 21, 42, 63, and 150 days after the start of treatment, BMD of the lumbar vertebrae was measured by quantitative CT. RESULTS BMD in the prednisolone treatment group decreased to 84.7% of the baseline value on day 42, increased to 87.9% on day 63, and recovered to 91.6% on day 150. In the prednisolone-alendronate treatment group, BMD decreased to 91% of the baseline value on day 21, increased to 93.8% on day 63, and then recovered to 96.7% on day 150. Bone mineral density in the prednisolone treatment group was generally lower, albeit not significantly, than that of the prednisolone-alendronate treatment group on each examination day. CONCLUSIONS AND CLINICAL RELEVANCE BMD temporarily decreased after low-dosage prednisolone administration; however, it gradually improved during tapering of the prednisolone dosage. These results have suggested that a low dosage of prednisolone can be used with little concern for development of osteopenia in dogs.

Objective: To evaluate perineal analgesic effects of 3 doses of neostigmine coadministered epidurally with lidocaine to geldings. Animals: 6 healthy geldings. Procedures: A few days before each treatment, a catheter was inserted between the first and second coccygeal vertebrae via the caudal approach in each gelding; the catheter tip was threaded approximately 10 cm cranial into the midsacral region. Each horse received 4 epidural treatments: 2% lidocaine (0.2 mg/kg) alone and 3 doses of neostigmine (0.5, 1, or 2 μg/kg) coadministered with that same dose of lidocaine. Horses were restrained in stocks in a standing position. Heart rate, blood pressure, respiratory rate, rectal temperature, intestinal motility, analgesia, behavior, and ataxia were determined before treatment (time 0; baseline); at 5, 10, 15, 30, 45, 60, 75, and 90 minutes; and every 30 minutes thereafter until the cessation of analgesia. Results: All doses of neostigmine coadministered with lidocaine improved and extended the duration of analgesia in the perineal region of the geldings. Total duration of analgesia was not a dose-dependent effect (120, 150, and 150 minutes for 0.5, 1, and 2 μg/kg, respectively). All treatments induced mild or moderate ataxia. Cardiovascular changes were within acceptable limits. Conclusions and Clinical Relevance: Administration of neostigmine (1 μg/kg) combined with lidocaine (0.2 mg/kg) in the caudal epidural space induced analgesia for 2.5 hours with a low prevalence of adverse effects in standing conscious geldings. Epidural doses of neostigmine greater than these should be avoided because they may cause undesirable effects in geldings.

OBJECTIVE To compare the percentage of the C3-C7 vertebral canal occupied by the spinal cord in small-breed dogs with that in Doberman Pinschers and Great Danes with and without cervical spondylomyelopathy (CSM). ANIMALS 30 small-breed dogs (body weight, < 15 kg), 15 clinically normal Doberman Pinschers, 15 Doberman Pinschers with CSM, 15 clinically normal Great Danes, and 15 Great Danes with CSM. PROCEDURES In a retrospective study, sagittal and transverse T2-weighted MRI images of the cervical (C3 to C7) vertebral column obtained from dogs that met study criteria and were free of extensive abnormalities that could affect the spinal cord diameter between January 2005 and February 2015 were reviewed. The area and height of the vertebral column and spinal cord were measured at the cranial and caudal aspect of each vertebra from C3 to C7, and the percentage of the vertebral canal occupied by the spinal cord at each location was calculated and compared among groups of dogs. RESULTS Mean percentage of the vertebral canal occupied by the spinal cord was greatest for small-breed dogs and lowest for Great Danes, but did not differ between Doberman Pinschers and small-breed dogs at approximately half of the locations evaluated or between Doberman Pinschers with and without CSM or between Great Danes with and without CSM. CONCLUSIONS AND CLINICAL RELEVANCE Results suggested that the percentage of the vertebral canal occupied by the spinal cord, although expected to increase with vertebral canal stenosis, may not have a primary role in the pathogenesis of CSM.

OBJECTIVE To assess effects of vertebral distraction-fusion techniques at a treated segment (C5-C6) and an adjacent segment (C4-C5) of canine cervical vertebrae. SAMPLE Cervical vertebrae harvested from cadavers of 10 skeletally mature Beagles. PROCEDURES Three models (intact, titanium plate, and polymethylmethacrylate [PM MA]) for stabilization of the caudal region of the cervical vertebrae (C4 through C7) were applied to the C5-C6 vertebral segment sequentially on the same specimens. Biomechanical assessments with flexion-extension, lateral bending, and axial rotational tests were conducted after each procedure. Range of motion (ROM) for a torque load applied with a 6-axis material tester was measured at C4-5 and C5-6 and calculated by use of a 3-D video measurement system. RESULTS In both the plate and PMMA models, ROM significantly increased at C4-5 and significantly decreased at C5-6, compared with results for the intact model. The ROM at C5-6 was significantly lower for the plate model versus the PMMA model in lateral bending and for the PMMA model versus the plate model in axial rotation. Conversely, ROM at C4-5 was significantly higher in axial rotation for the PMMA model versus the plate model. No significant differences were identified in flexion-extension between the PMMA and plate models at either site. CONCLUSIONS AND CLINICAL RELEVANCE Results of this study suggested that vertebral distraction and fusion of canine vertebrae can change the mechanical environment at, and may cause disorders in, the adjacent segment. Additionally, findings suggested that effects on the adjacent segment differed on the basis of the fusion method used.