Magnetic Motor Evoked Potentials for Assessing Spinal Cord Integrity in Dogs with Intervertebral Disc Disease

Magnetically elicited transcranial motor evoked potentials (MEPs) were studied in 37 dogs with type 1 intervertebral disc (IVD) disease. The waveforms were recorded from both cranial tibial muscles before and after surgery. The latencies and amplitudes obtained were compared to those of a control population (n = 14). MEPs were recordable in all dogs with mild or no neurologic deficits, but they were recordable in only 50% of ambulatory dogs that were severely ataxic. MEPs could not be elicited from nonambulatory dogs. There was a significant attenuation of the amplitudes in all clinical cases, even if the dogs demonstrated back pain alone. Significantly prolonged latencies were associated with neurologic deficits. MEPs were not good predictors of neurologic recovery. The responses obtained from the side where the disc material was found were not different from those recorded from the opposite side. MEPs were very sensitive to lesions of the spinal cord, as indicated by the significant changes in the waves in patients with mild or no neurologic deficits and in the loss of response in dogs that still demonstrated purposeful movement. Neurologic exams provided more accurate diagnoses and prognoses than did MEPs in dogs with IVD disease.     

A comparison of the actions of platelet activating factor (PAF) antagonists WEB 2170 and WEB 2086 in the horse

Foster, A.P., Cunningham, F.M., Andrews, M.J., Lees, P. A comparison of platelet activating factor (PAF) antagonists WEB 2170 and WEB 2086 in the horse. J. vet. Pharmacol. Therap. 16, 477–487.
The effects of the selective platelet activating factor (PAF) receptor antagonist WEB 2170 on PAF-induced responses in equine cells and tissues have been examined and compared with those of WEB 2086. In initial experiments WEB 2170 was shown to inhibit in vitro platelet aggregation in a dose-dependent, competitive reversible manner (pA₂= 7.21). Co-administration of the antagonists with either PAF or histamine also inhibited PAF, but not histamine, induced wheal formation and PAF-induced neutrophil accumulation in vivo in equine skin. Intravenous (i.v.) administration of both drugs at a dose of 0.1 mg/kg blocked PAF-induced ex vivo platelet aggregation. The inhibition produced by WEB 2170 was greater and, at 30 min, this drug also reduced the slope and maximal response. Wheal formation in the skin was significantly inhibited for up to 6 h by WEB 2170 administered i.v., the reduction being more prolonged than that obtained with WEB 2086. Neutrophil accumulation in the skin was also significantly reduced for up to 24 h by WEB 2170, whilst no significant inhibition was produced by WEB 2086. These results demonstrate that WEB 2170, like WEB 2086, is an effective antagonist of PAF in the horse. Moreover, when given i.v., WEB 2170 appears to be a more potent PAF inhibitor than WEB 2086.     

A Biomechanical Evaluation and Assessment of the Accuracy of Reduction of Two Methods of Acetabular Osteotomy Fixation in Dogs

Objective—To compare the accuracy of reduction, biomechanical characteristics, and mode of failure of two methods of acetabular osteotomy repair. Study Design—Acetabular osteotomies were created in 16 paired hemipelves and stabilized with a screw/wire/polymethylmethacrylate composite fixation technique (SWP) or a 2-mm veterinary acetabular plate (VAP). Eight intact hemipelves were used as controls. Sample Population—Twelve canine cadavers. Methods—Accuracy of osteotomy reduction was evaluated grossly and by measurement of articular incongruencies formed in polyvinylsiloxane impression casts. Acetabula were loaded in modified bending until failure using a universal testing machine. Data from load-deformation curves were used to determine the biomechanical characteristics of the repaired and intact acetabula. Mode of failure was evaluated grossly and radiographically. Results—Osteotomy reduction was superior in acetabula stabilized with SWP. Mean values ± standard deviation for load at failure and stiffness of the intact acetabula were 2,796 ± 152.9 N and 267.5 ±61.9 N/mm. Corresponding values for SWP and VAP were 1,192 ± 202.7 N and 136.3 ± 76.5 N/mm, and 1,100.5 ± 331.6 N and 110.0 ± 51.3 N/mm, respectively. The mean load at failure and stiffness of intact acetabula was significantly greater than acetabula stabilized with SWP or VAP. There was no significant difference between SWP and VAP for load at failure or stiffness. Failure of acetabula stabilized with SWP occurred by fracture of the polymethylmethacrylate and ventrolateral bending of the wires. Acetabula stabilized with VAP failed by ventrolateral twisting of the plate and bending of the caudal screws. Conclusions—SWP and VAP provide comparable rigidity, however, the SWP facilitates more accurate osteotomy reduction. Clinical Relevance—These findings support the use of the SWP technique as an alternative method of acetabular fracture repair.     

Endoscopy of the Calcaneal Bursa in Horses

Objective —To describe endoscopic approaches to the calcaneal bursa and clinical findings in 2 horses with calcaneal bursitis.
Study Design —Cadaver evaluations and retrospective case reports.
Animals —12 cadavers and 2 adult horses.
Methods —Cadaver specimens of the calcaneal bursa were evaluated with a rigid arthroscope and gross dissection to determine the endoscopic appearance of anatomic structures located within the bursa. The site(s) for placement of the arthroscope and instrument(s) was determined based on cadaver dissection and endoscopic examination.
Results —Placement of the arthroscope 1 cm dorsal to the superficial digital flexor tendon (SDFT) and 1 cm distal to the medial or lateral aspect of the SDFT retinaculum allowed consistent examination of the tuber calcis, proximal aspect of the long plantar ligament, calcaneal tendon of the gastrocnemius muscle inserting on the tuber calcis, SDFT and the proximal and distal extent of the bursa. Lesions observed and treated with use of endoscopy included local bone necrosis of the proximoplantar aspect of the tuber calcis and damage of the origin of the long plantar ligament in one horse. Mild disruption of the superficial digital flexor tendon and long plantar ligament were observed and debrided in another horse.
Conclusions —Endoscopic exploration of the calcaneal bursa is clinically feasible to treat infectious and noninfectious bursitis and to help identify the cause(s) of undiagnosed bursitis or lameness associated with the calcaneus, superficial digital flexor tendon, tendon of the gastrocnemius muscle, and the long plantar ligament.
Clinical Relevance —An endoscopic approach to the calcaneal bursa is recommended whenever possible to decrease complications associated with surgery in this region and improve the diagnosis of infectious and non-infectious calcaneal bursitis.     

Locking Compression Plates for Pancarpal Arthrodesis in a Thoroughbred Filly

Objective— To report treatment of a comminuted ulnar carpal (UC) bone fracture associated with carpal instability by pancarpal arthrodesis using 2 locking compression plates (LCP).
Study Design— Case report.
Animals— A 2-year-old Thoroughbred filly.
Methods— An UC fracture and luxation of the proximal row of carpal bones was diagnosed radiographically. Pancarpal arthrodesis was performed with 2 LCP positioned dorsolaterally and dorsomedially and centered over the carpus through a single skin incision. The filly was maintained in a full limb cast for 15 days, followed by a tube cast for 14 days, and subsequently a full limb bandage with caudal splint for 21 days.
Results— Two LCP provided appropriate carpal stability resulting in a pasture sound horse 6 months after surgery. The filly was discharged from the hospital 63 days after surgery, walking well with only a slight mechanical lameness.
Conclusion— Use of 2 LCP applied on the dorsomedial and dorsolateral aspect of the carpus can provide carpal stability for pancarpal arthrodesis.
Clinical Relevance— Excellent stability of the carpal joints can be achieved with 2 LCP.     

COMPARISON OF MAGNETIC RESONANCE IMAGING AND MYELOGRAPHY IN 18 DOBERMAN PINSCHER DOGS WITH CERVICAL SPONDYLOMYELOPATHY

Eighteen Doberman pinscher dogs with clinical signs of cervical spondylomyelopathy (wobbler syndrome) underwent cervical myelography and magnetic resonance (MR) imaging. Cervical myelography was performed using iohexol, followed by lateral and ventrodorsal radiographs. Traction myelography was performed using a cervical harness exerting 9 kg of linear traction. MR imaging was performed in sagittal, transverse, and dorsal planes using a 1.5 T magnet with the spine in neutral and traction positions. Three reviewers independently evaluated the myelographic and MR images to determine the most extensive lesion and whether the lesion was static or dynamic. All reviewers agreed with the location of the most extensive lesion on MR images (100%), while the agreement using myelography was 83%. The myelogram and MR imaging findings agreed in the identification of the affected site in 13-16 dogs depending on the reviewer. MR imaging provided additional information on lesion location because it allowed direct examination of the spinal cord diameter and parenchyma. Spinal cord signal changes were seen in 10 dogs. Depending on the reviewer, two to four dogs had their lesions classified as dynamic on myelography but static on MR images. Myelography markedly underscored the severity of the spinal cord compression in two dogs, and failed to identify the cause of the signs in another. The results of this study indicated that, although myelography can identify the location of the lesion in most patients, MR imaging appears to be more accurate in predicting the site, severity, and nature of the spinal cord compression.     

ULTRASONOGRAPHIC APPEARANCE OF THE LOWER URINARY TRACT IN FIFTEEN NORMAL HORSES

The purpose of this study was to describe the normal ultrasonographic appearance of the caudal portion of the equine ureters, pelvic urethra, and urinary bladder and to assess ureteral contractility. Fifteen horses with no evidence of urinary tract disease (five females, five intact males and five geldings) were studied. The lower urinary tract was evaluated ultrasonographically using a transrectal approach. The normal ultrasonographic appearance and anatomic location of structures of the lower urinary tract were evaluated and anatomic relationships described. Both ureters were identified dorsal to the bladder and at their openings into the bladder. Their relationship and different appearance from the male deferent ducts/ampullae and vesicular glands was noted. Ultrasonographic measurements of the diameter of the ureters and urethra were obtained and the ureteral, urethral, and urinary bladder wall thickness recorded. The normal parameters established in this study will be useful during sonographic examination of horses with suspected urinary tract disease. Transrectal ultrasonographic examination is valuable in assessing the presence and frequency of ureteral contractions as well as in detecting structural abnormalities of the lower urinary tract. The use of high-frequency transrectal ultrasound transducers allows for excellent visualization of the structures of the equine lower urinary tract.     

Studies on cultured and gill-attached Paramoeba sp. (Gymnamoebae: Paramoebidae) and the cytopathology of paramoebic gill disease in Atlantic salmon, Salmo salar L., from Tasmania

Abstract. The normally free-living amoeba Paramoeba sp. is associated with epithelial hyperplasia on the gills of Atlantic salmon, Salmo salar L., in Tasmania. Gill-attached paramoebae were significantly larger than cultured ones. Unlike cultured paramoebae, gill-attached ones had small electron-dense, cytoplasmic deposits and small surface projections at the host-parasite interface. Examination of sequential samples of Tasmanian salmon gills from spring to summer indicated that pathological changes in the gill filaments were associated only with the presence of Paramoeba ; the parasite was also associated with necrosis of surface epithelial cells, and cytoplasmic processes passed into and between surface cells of hyperplastic gill epithelium. The evidence points to the paramoebae as primary opportunistic pathogens causing mechanical and possibly chemical damage. Based on size and ultrastructure, the Paramoeba sp. most closely resembles P. pemaquidensis Page.