Scott A. Katzman

Blood and Cerebrospinal Fluid α-Tocopherol and Selenium Concentrations in Neonatal Foals with Neuroaxonal Dystrophy.

Background Equine neuroaxonal dystrophy/equine degenerative myeloencephalopathy (NAD/EDM) is a neurodegenerative disorder affecting genetically predisposed foals maintained on α‐tocopherol (α‐TP)‐deficient diet. Objective Intramuscular α‐TP and selenium (Se) administration at 4 days of age would have no significant effect on serum or cerebrospinal fluid (CSF) α‐TP in healthy foals. Serum and CSF α‐TP, but not Se, would be significantly decreased in NAD/EDM‐affected foals during first year of life. Animals Fourteen Quarter horse foals; 10 healthy foals supplemented with 0.02 mL/kg injectable α‐TP and Se (n = 5) or saline (n = 5) at 4 days of age and 4 unsupplemented NAD/EDM‐affected foals. Methods Complete neurologic examinations were performed, blood and CSF were collected before (4 days of age) and after supplementation at 10, 30, 60, 120, 180, 240, and 360 days of age. Additional blood collections occurred at 90, 150, 210, and 300 days. At 540 days, NAD/EDM‐affected foals and 1 unsupplemented healthy foal were euthanized and necropsies performed. Results Significant decreases in blood, CSF α‐TP and Se found in the first year of life in all foals, with most significant changes in serum α‐TP from 4–150 days. Dam α‐TP and Se significantly influenced blood concentrations in foals. Injection of α‐TP and Se did not significantly increase CSF Se, blood or CSF α‐TP in healthy foals. NAD/EDM‐affected foals had significantly lower CSF α‐TP through 120 days. Conclusions and Clinical Importance Injection of α‐TP and Se at 4 days of age does not significantly increase blood or CSF α‐TP. Despite all 14 foals remaining deficient in α‐TP, only the 4 genetically predisposed foals developed NAD/EDM.

POSITRON EMISSION TOMOGRAPHY OF THE EQUINE DISTAL LIMB: EXPLORATORY STUDY.

Positron emission tomography (PET) is a highly sensitive, noninvasive imaging technique for quantifying biological functions of tissues. However, at the time of this study, PET imaging applications had not been reported in the horse. The aim of this exploratory study was to determine whether a portable high-resolution PET scanner could be used to image the equine distal limb. Images of the front feet and fetlocks of three research horses, with known lesions localized to the distal front limbs, were acquired under general anesthesia after administration of 18 F-fluorodeoxyglucose (18 F-FDG), with doses ranging from 1.5 to 2.9 MBq/kg. The radiation exposure measured during imaging was slightly higher than 99m Technetium scintigraphy. However, the use of general anesthesia allowed the proximity and the contact time with the patient to be minimized for the staff involved. 18 F-FDG uptake was evident throughout the soft tissues, with the highest uptake in the coronary band and the lowest uptake in the tendons. Anatomic structures could be discriminated due to the high contrast between soft tissue and bone. Detected lesions included lysis of the flexor cortex of the navicular bone, lesions of flexor tendons and suspensory ligament, and abnormal uptake through the lamina of a laminitic subject. Findings indicated that tomographic molecular imaging is feasible in the equine distal limb and could be useful as a future diagnostic technique for clinical and research studies, especially those involving tendinopathy/desmopathy and laminitis.

18 F-sodium fluoride positron emission tomography of the equine distal limb: Exploratory study in three horses

BACKGROUND Positron emission tomography (PET) is a cross-sectional, functional imaging modality that has recently become available to the horse. The use of 18 F-sodium fluoride (18 F-NaF), a PET bone tracer, has not previously been reported in this species. OBJECTIVES To assess the feasibility of 18 F-NaF PET in the equine distal limb and explore possible applications in the horse in comparison with other imaging modalities. STUDY DESIGN Exploratory descriptive study involving three research horses. METHODS Horses were placed under general anaesthesia prior to intravenous (i.v.) administration of 1.5 MBq/kg of 18 F-NaF. Positron emission tomography imaging of both front feet and fetlocks was performed using a portable scanner. Computed tomography (CT) of the distal limb was performed under a separate anaesthetic episode. Bone scintigraphy and magnetic resonance imaging (MRI) were subsequently performed under standing sedation. Images obtained from PET and other imaging modalities were independently assessed and the results correlated. RESULTS Positron emission tomography images were obtained without complication. The radiation exposure rate was similar to equine bone scintigraphy. Positron emission tomography detected focal 18 F-NaF uptake in areas where other imaging modalities did not identify any abnormalities. This included sites of ligamentous attachment, subchondral compact bone plate and the flexor cortex of the navicular bone. 18 F-NaF uptake was identified in some, but not all, osseous fragments and areas of osseous formation, suggesting a distinction between active and inactive lesions. MAIN LIMITATIONS A small number of horses were included and histopathology was not available. CONCLUSIONS 18 F-NaF PET imaging of the equine distal limb provides useful additional information when compared with CT, MRI and scintigraphy and has the potential for both research and clinical applications in the horse. The Summary is available in Chinese - see Supporting information.

ULTRASOUND‐GUIDED INJECTIONS IN HORSES WITH CRANIOVENTRAL DISTENSION OF THE COXOFEMORAL JOINT CAPSULE: FEASIBILITY FOR A CRANIOVENTRAL APPROACH

Intrasynovial access to the equine coxofemoral joint (CFJ) is inherently challenging. Blind injection techniques rely upon inconsistently palpable landmarks, and ultrasound guidance requires expertise for needle placement into the coxofemoral articulation. Aspiration is recommended to confirm intrasynovial placement and avoid sciatic nerve anesthesia. The aim of this observational, descriptive, retrospective study was to evaluate the feasibility for an alternative ultrasound-guided approach in horses with cranioventral distention of the CFJ identified during pelvic ultrasound. Thirteen horses with cranioventral CFJ distention, including 12 with severe pathology, were recruited from 2009 to 2014. Seven were excluded as they were not injected or underwent ultrasound-guided injection using a dorsal approach. The remaining six horses underwent a total of nine injections into the cranioventral recess. With the exception of one foal, all were aged horses (15-29 years) of varying breeds and uses, with prominent lameness due to subluxation (three), luxation (two), and severe osteoarthritis (one). The cranioventral recess was imaged adjacent to the proximal femur using a low-frequency curvilinear transducer placed ventral to the cranial joint margins. Using aseptic technique, spinal needles were placed cranial to the transducer and advanced caudomedially into the distended cranioventral recess. Synovial fluid was retrieved in all cases with one needle placement. Findings indicated that, when distended, ultrasound-guided access to the cranioventral CFJ recess is a feasible alternative approach and may reduce the potential for extra-synovial placement. Distention in this sample of horses was accompanied by severe pathology, also supporting the use of this approach for therapeutic interventions.

FRACTURE OF THE CENTRAL TARSAL BONE IN NONRACEHORSES: FOUR CASES

Fractures of the central tarsal bone are a rarely recognized cause of acute severe hind limb lameness in nonracehorses. Diagnosis of these fractures can be challenging and little is known about their configuration or outcome. The objectives of this retrospective case series study were to describe the clinical features, imaging findings, and outcomes of fractures of the central tarsal bone in a sample of nonracehorses. Medical records from 2001 to 2014 were searched for cases of central tarsal bone fractures in nonracehorses. All available imaging findings including radiography, ultrasound, computed tomography (CT), and/or nuclear scintigraphy were reviewed. History, clinical presentation, and outcome were collected from the records. Four horses met the inclusion criteria. All had a similar configuration as a simple nondisplaced slab fracture in a dorsomedial to plantarolateral orientation. Initial radiographs failed to reveal the fracture in three of four cases. When additional plantarolateral-dorsomedial oblique radiographic views were obtained, the fracture could be identified in all cases. Fractures of the central tarsal bone seemed to occur in a consistent dorsomedial to plantarolateral orientation in this sample of nonracehorses, which is different from the configuration previously reported in racehorses. While CT can be used for detection and assessment of these fractures, authors propose that radiography can also identify these fractures with the appropriate view. Authors recommend the use of several plantarolateral to dorsomedial radiographic projections at varying degrees of obliquity for horses with a suspected central tarsal bone fracture.

Use of a laparoscopic specimen retrieval pouch to facilitate removal of intact or fragmented cystic calculi from standing sedated horses: 8 cases (2012–2015)

OBJECTIVE To evaluate the use of a laparoscopic specimen retrieval pouch for removal of intact or fragmented cystic calculi from standing horses. DESIGN Retrospective case series. ANIMALS 8 horses (5 geldings and 3 mares) with cystic calculi. PROCEDURES Physical examination and cystoscopic, ultrasonographic, and hematologic evaluations of urinary tract function were performed for each horse. A diagnosis of cystic calculus was made on the basis of results of cystoscopy and ultrasonography. Concurrent urolithiasis or other urinary tract abnormalities identified during preoperative evaluation were recorded. Horses were sedated and placed in standing stocks, and the perineum was aseptically prepared. Direct access to the urinary bladder was gained in geldings via perineal urethrotomy or in mares by a transurethral approach. Calculi were visualized endoscopically, manipulated into the retrieval pouch, and removed intact or fragmented (for larger calculi). RESULTS For 4 geldings and 1 mare, fragmentation was necessary to facilitate calculus removal. Mean duration of surgery was 125 minutes, and trauma to the urinary bladder and urethra was limited to areas of hyperemia and submucosal petechiation. No postoperative complications were encountered for any horse. When lithotripsy was required, the retrieval pouch provided an effective means of stabilizing calculi and containing the fragments for removal. CONCLUSIONS AND CLINICAL RELEVANCE Use of the laparoscopic specimen retrieval pouch was an effective, minimally traumatic method for retrieving cystic calculi from standing horses. The pouch protected the urinary bladder and urethra from trauma during calculus removal and allowed for stabilization, containment, and fragmentation of calculi when necessary.

Bone formation transcripts dominate the differential gene expression profile in an equine osteoporotic condition associated with pulmonary silicosis

Osteoporosis has been associated with pulmonary silicosis in California horses exposed to soils rich in cytotoxic silica dioxide crystals, a syndrome termed silicate associated osteoporosis (SAO). The causal mechanism for the development of osteoporosis is unknown. Osteoporotic lesions are primarily located in bone marrow-rich sites such as ribs, scapula and pelvis. Gene transcription patterns within bone marrow and pulmonary lymph nodes of affected horses may offer clues to disease pathobiology. Bone marrow core and tracheobronchial lymph node tissue samples harvested postmortem from affected and unaffected horses were examined histologically and subjected to RNA sequencing (RNA-seq). Sequenced data were analyzed for differential gene expression and gene ontology. Metatranscriptomic and metagenomic assays evaluated samples for infectious agents. Thirteen of 17 differentially expressed transcripts in bone marrow were linked to bone and cartilage formation such as integrin binding bone sialoprotein (log2FC = 3.39, PFDR = 0.013) and chondroadherin (log2FC = 4.48, PFDR = 0.031). Equus caballus solute carrier family 9, subfamily A2 (log2FC = 3.77, PFDR = 0.0034) was one of the four differentially expressed transcripts linked to osteoclast activity. Osteoblasts were hyperplastic and hypertrophic in bone marrow from affected horses. Biological pathways associated with skeletal morphogenesis were significantly enriched in affected horses. The 30 differentially expressed genes in affected lymph nodes were associated with inflammatory responses. Evidence of infectious agents was not found. The SAO affected bone marrow molecular signature demonstrated increased transcription and heightened activation of osteoblasts. Increased osteoblastic activity could be part of the pathological mechanism for osteoporosis or a compensatory response to the accelerated osteolysis. Transcriptome data offer gene targets for inquiries into the role of osteocytes and osteoblasts in SAO pathogenesis. Viral or bacterial infectious etiology in SAO is less likely based on metatranscriptomic and metagenomic data but cannot be completely ruled out.

Lipid peroxidation biomarkers for evaluating oxidative stress in equine neuroaxonal dystrophy

Background Equine neuroaxonal dystrophy/equine degenerative myeloencephalopathy (eNAD/EDM) is a neurodegenerative disorder affecting genetically predisposed foals maintained on an α‐tocopherol (α‐TOH) deficient diet. Currently no antemortem diagnostic test for eNAD/EDM is available. Hypothesis Because α‐TOH deficiency is associated with increased lipid peroxidation, it was hypothesized that F2‐isoprostanes (F2IsoP), F4‐neuroprostanes (F4NP) and oxysterols derived from free radical oxidation would be increased in the cerebrospinal fluid (CSF) and neural tissue of eNAD/EDM affected horses and could serve as potential biomarkers for disease. Animals Isoprostane Study A: 14 Quarter horse foals (10 healthy foals and 4 eNAD/EDM affected foals) at 1 and 6 months of age. Isoprostane Study B: 17 eNAD/EDM affected and 10 unaffected horses ≥ 1‐4 years of age. Oxysterol study: eNAD/EDM affected (n = 14, serum; n = 11, CSF; n = 10, spinal cord [SC]) and unaffected horses 1‐4 years of age (n = 12, serum; n = 10, CSF; n = 7, SC). Procedures Cerebrospinal fluid [F2IsoP] and [F4NP] were assessed using gas chromatography‐negative ion chemical ionization mass spectrometry. Serum, CSF, and cervical SC [oxysterols] were quantified using high performance liquid chromatography mass spectrometry. Results were compared with respective α‐TOH concentrations. Results Spinal cord [7‐ketocholesterol], [7‐hydroxycholesterol], and [7‐keto‐27‐hydrocholesterol] were higher in eNAD/EDM horses whereas [24‐ketocholesterol] was lower. No significant difference was found in CSF [F2IsoP] and [F4NP], serum [oxysterols] and CSF [oxysterols] between eNAD/EDM affected and unaffected horses. No correlation was found between [F2IsoP], [F4NP], or [oxysterols] and respective [α‐TOH]. Conclusions and Clinical Importance In the SC, targeted markers of cholesterol oxidation were significantly increased in horses with eNAD/EDM.

18F-sodium fluoride positron emission tomography of the racing Thoroughbred fetlock: Validation and comparison with other imaging modalities in nine horses

BACKGROUND Early and accurate detection of stress remodelling in racehorses is of utmost importance to prevent catastrophic injuries. Current imaging techniques have limitations in assessing early changes predisposing to catastrophic breakdowns. Positron emission tomography (PET) using 18 F-sodium fluoride (18 F-NaF) is a sensitive method for the detection of early bone turnover and may improve early recognition of subtle injuries. OBJECTIVES To validate the clinical use of 18 F-NaF PET in Thoroughbred racehorses, to assess the value of PET in the detection of bone lesions and to compare PET results with findings of other advanced imaging modalities, clinical examination and pathology. STUDY DESIGN Experimental exploratory study. METHODS Twenty fetlocks from nine Thoroughbred racehorses were imaged using 18 F-NaF PET, computed tomography (CT) and scintigraphy. Five fetlocks were also imaged with magnetic resonance imaging and four fetlocks were also examined histologically. Imaging findings were independently reviewed by three board certified radiologists. Imaging, clinical and histopathological findings were correlated. RESULTS PET imaging was well-tolerated by all horses. PET detected focal areas of 18 F-NaF uptake in instances where other imaging modalities did not identify abnormalities, in particular in the proximal sesamoid bones. Maximal standardised uptake values could be measured to quantify the activity of lesions. Areas of 18 F-NaF uptake corresponded to regions of increased vascularity and increased osteoblastic activity. MAIN LIMITATIONS Limited number of cases. CONCLUSIONS 18 F-NaF PET imaging of the Thoroughbred fetlock is feasible and compares favourably with other imaging modalities in detecting stress remodelling in Thoroughbred racehorses. PET appears to be a beneficial imaging modality when used for early detection of stress remodelling in an effort to prevent catastrophic musculoskeletal injuries in this population of horses.

A novel ultrasonographic assisted technique for desmotomy of the palmar/plantar annular ligament in horses

Objectives To describe an ultrasound assisted technique for desmotomy of the palmar/plantar annular ligament (PAL), determine its efficacy and intraoperative complications. Study design Cadaveric and in vivo study. Animals Cadaveric limbs (n = 12), adult horses (n = 4), and clinical cases (n = 2). Methods Ultrasound assisted desmotomy of the palmar/plantar annular ligament (UAD-PAL) was performed in cadaveric limbs and in standing horses with the operated limb placed in a distal limb splint. The procedure was performed under general anesthesia and was followed by tenoscopic examination in 2 clinical cases. A hook knife was developed for the procedure. Complete transection was assessed by postmortem dissection (10 forelimbs, 10 hindlimbs) and tenoscopic examination (1 forelimb, 1 hindlimb). Thickness of PAL, surgery time, other intraoperative parameters and complications associated with the procedure were recorded. Results Complete PAL transection was accomplished in 20/22 limbs. No iatrogenic damage to adjacent intrathecal structures was identified in any case. The instrument was correctly positioned on the first attempt in 19/22 cases. The most common intraoperative complication was inadvertent subcutaneous placement of the instrument (n = 2). Significant thickening of the PAL (3 mm) was present in 1/2 limbs in which complete transection was not achieved. Conclusions UAD-PAL with the custom-made hook knife was effective at transecting the PAL with minimal intraoperative complications. The procedure can be performed in standing sedated horses. Another method should be considered in horses with thickened PAL.Objectives: To describe an ultrasound assisted technique for desmotomy of the palmar/plantar annular ligament (PAL), determine its efficacy and intraoperative complications. Study design: Cadaveric and in vivo study. Animals: Cadaveric limbs (n = 12), adult horses (n = 4), and clinical cases (n = 2). Methods: Ultrasound assisted desmotomy of the palmar/plantar annular ligament (UAD‐PAL) was performed in cadaveric limbs and in standing horses with the operated limb placed in a distal limb splint. The procedure was performed under general anesthesia and was followed by tenoscopic examination in 2 clinical cases. A hook knife was developed for the procedure. Complete transection was assessed by postmortem dissection (10 forelimbs, 10 hindlimbs) and tenoscopic examination (1 forelimb, 1 hindlimb). Thickness of PAL, surgery time, other intraoperative parameters and complications associated with the procedure were recorded. Results: Complete PAL transection was accomplished in 20/22 limbs. No iatrogenic damage to adjacent intrathecal structures was identified in any case. The instrument was correctly positioned on the first attempt in 19/22 cases. The most common intraoperative complication was inadvertent subcutaneous placement of the instrument (n = 2). Significant thickening of the PAL (3 mm) was present in 1/2 limbs in which complete transection was not achieved. Conclusions: UAD‐PAL with the custom‐made hook knife was effective at transecting the PAL with minimal intraoperative complications. The procedure can be performed in standing sedated horses. Another method should be considered in horses with thickened PAL.