An Estimation of Lameness in Sable Island Horses Using Radiographic Evaluation of the Distal Phalanx and Hoof Capsule.

Laminitis is a painful condition that causes lameness in horses. However, monitoring this condition in feral horses is logistically difficult. Laminitis can be detected postmortem, as inflammation of the sensitive laminae of the hoof changes the relative location of the bony structures within the hoof capsule. Thus, evaluation of cadavers may be used to estimate laminitis prevalence in feral populations of horses. The objective of this study was to estimate the prevalence of laminitis in feral horses inhabiting the Sable Island National Park Reserve, Canada, using radiographic imagery on the hooves of naturally deceased horses. Radiographic indicators evaluated included coronary band extensor process distance (CE), capsular rotation (CR), palmar angle (PA), ratio of the dorsal hoof wall thickness to the length of the distal phalanx (DHWT:P3) and sole depth (SLD). Each value measured indicated the following prevalence of laminitis: CE 0% (97.5% Confidence Interval (CI) 0-4.51%), 8.75% CR (95%CI 3.59-17.2%), PA 25% (95% CI 15.99-35.94%), DHWT:P3 6.25% (95%CI 2.06-14.0%) and 65% SLD (95% CI 53.52-75.33%). The majority of indices measured for laminitis were low. These findings suggest that laminitis is fairly infrequent in the Sable Island horses evaluated in this study.

Arthroscopic approach and intra-articular anatomy of the equine atlanto-occipital joint.

OBJECTIVE: To develop arthroscopic approaches to the atlanto-occipital (A-O) and describe associated arthroscopic anatomy. STUDY DESIGN: Experimental ex vivo study and clinical case report. ANIMALS: Ten equine cadaver joints and 1 clinical case. METHODS: CT arthrograms of 8 A-O joints were performed to determine the placement of an arthroscopic portal. Arthroscopy was performed via dorsal and/or ventral approaches (dorsal or ventral to the longissimus capitis tendon) in 10 cadaveric A-O joints and the A-O joint of a 2-week-old foal with septic arthritis. Accessible cartilage was debrided in 3 cadaver joints. Accessibility and risks were assessed by review of arthroscopic images, postoperative necropsy, and computed tomography (CT). RESULTS: Dorsal and ventral outpouchings of the A-O joint were identified with CT. Arthroscopy of the dorsal pouch provided access to 50% of the dorsocranial occipital condyle and 15% of the dorsocranial atlas articular surfaces. Joint distension caused displacement of the dura. Dura perforation occurred with a blind dorsal approach in 2 of 5 joints. Dura perforation did not occur after ultrasonography-guided approaches. Arthroscopic debridement of septic arthritis and osteomyelitis was successful in 1 clinical case. CONCLUSION: Approaches to the A-O joint were determined from CT examinations. The cranial aspect of the dorsal pouch of the A-O joint was accessed via arthroscopic triangulation in all horses of this study. Ultrasound-guided joint access prevented perforation of vital structures, including the spinal canal. CLINICAL SIGNIFICANCE: Advanced imaging improves the diagnosis of A-O joint pathology. Descriptions of arthroscopic anatomy and accessibility provide important information for surgical intervention.

Multiple intravenous injections of allogeneic equine mesenchymal stem cells do not induce a systemic inflammatory response but do alter lymphocyte subsets in healthy horses.

INTRODUCTION: Intravenous (IV) injection of mesenchymal stem cells (MSCs) is used to treat systemic human diseases and disorders but is not routinely used in equine therapy. In horses, MSCs are isolated primarily from adipose tissue (AT) or bone marrow (BM) and used for treatment of orthopedic injuries through one or more local injections. The objective of this study was to determine the safety and lymphocyte response to multiple allogeneic IV injections of either AT-derived MSCs (AT-MSCs) or BM-derived MSCs (BM-MSCs) to healthy horses. METHODS: We injected three doses of 25 × 10(6) allogeneic MSCs from either AT or BM (a total of 75 × 10(6) MSCs per horse) into five and five, respectively, healthy horses. Horses were followed up for 35 days after the first MSC infusion. We evaluated host inflammatory and immune response, including total leukocyte numbers, serum cytokine concentration, and splenic lymphocyte subsets. RESULTS: Repeated injection of allogeneic AT-MSCs or BM-MSCs did not elicit any clinical adverse effects. Repeated BM-MSC injection resulted in increased blood CD8(+) T-cell numbers. Multiple BM-MSC injections also increased splenic regulatory T cell numbers compared with AT-MSC-injected horses but not controls. CONCLUSIONS: These data demonstrate that multiple IV injections of allogeneic MSCs are well tolerated by healthy horses. No clinical signs or clinico-pathologic measurements of organ toxicity or systemic inflammatory response were recorded. Increased numbers of circulating CD8(+) T cells after multiple IV injections of allogeneic BM-MSCs may indicate a mild allo-antigen-directed cytotoxic response. Safety and efficacy of allogeneic MSC IV infusions in sick horses remain to be determined.

Gross, histologic, and micro-computed tomographic anatomy of the lacrimal system of snakes.

OBJECTIVE: To describe the lacrimal system of snakes using contrast micro-computed tomography (micro-CT) with 3-dimensional reconstruction, fluorescein passage ('Jones') testing, histology, and gross dissection. ANIMALS STUDIED: One royal python and 19 snake cadavers representing 10 species. PROCEDURES: Direct observation following injection of fluorescein into the subspectacular space, micro-CT following injection of three contrast agents into the subspectacular space, gross dissection following injection of latex into the subspectacular space, and histopathology. RESULTS: Injection of fluorescein confirmed patency, but not course of the lacrimal duct. Barium enabled clear visualization of the lacrimal duct, whereas two iodinated contrast agents proved inadequate. Collectively, micro-CT, anatomic dissections, and histology suggest tears are produced by a single, large, serous, retrobulbar gland, released into the subspectacular space via several ductules, and drained through a single punctum originating in the ventronasal subspectacular space, and the lacrimal duct, which takes one of three routes of variable tortuosity before opening into the oral cavity in close association with the opening of the duct of the vomeronasal organ. CONCLUSIONS: The ophidian lacrimal duct has a generally tortuous course, and the details of its anatomy are species-variable. The tortuous course of the duct likely predisposes snakes to duct occlusion and must be considered when planning medical and surgical interventions in snakes with pseudobuphthalmos and subspectacular abscessation.

Use of digital abdominal radiography for the diagnosis of enterolithiasis in equids: 238 cases (2008-2011).

OBJECTIVE: To evaluate the sensitivity and specificity of direct digital abdominal radiography for the diagnosis of enterolithiasis in equids and to assess the effect of the number and anatomic location of enteroliths and gas distention of the gastrointestinal tract on diagnostic sensitivity of the technique. DESIGN: Retrospective case series. SAMPLE POPULATION: 238 horses and ponies ≥ 1 year old that underwent digital abdominal radiography with subsequent exploratory celiotomy or postmortem examination. PROCEDURES: For each case, 3 reviewers independently evaluated radiographic views. Radiographic images were evaluated for presence or absence and location of enteroliths and the degree of gas distention. Signalment, definitive diagnosis based on exploratory celiotomy or postmortem examination findings, and number and anatomic location of enteroliths were obtained from the medical records. RESULTS: 70 of the 238 (29.4%) equids had confirmed enterolithiasis. With regard to diagnosis of enterolithiasis via digital radiography, overall sensitivity and specificity for the 3 reviewers were 84% and 96%, respectively. Sensitivity was lower for small colon enteroliths (61.5%) than for large colon enteroliths (88.9%) and was negatively affected by gas distention of the gastrointestinal tract. Sensitivity was not affected by the number of enteroliths. CONCLUSIONS AND CLINICAL RELEVANCE: Sensitivity and specificity of digital radiography for the diagnosis of large colon enterolithiasis in equids was high. Sensitivity of digital radiography for detection of small colon enteroliths was lower than that for large colon enteroliths, but was higher than that typically associated with computed radiography. In geographic regions in which enterolithiasis in equids is endemic, digital abdominal radiography could be used as a diagnostic test for equids with colic.

Computed tomographic arthrography of the intercarpal ligaments of the equine carpus.

Injuries of the intercarpal ligaments are an important cause of lameness in performance horses. The purpose of this prospective cadaver study was to determine whether computed tomography (CT) arthrography would be a feasible method for visualizing and characterizing intercarpal ligaments in the horse. One cadaver limb from each of eight nonlame horses was collected immediately after euthanasia. For each limb, overlapping 2.0 mm CT images were acquired before and after injection of iodinated contrast medium into the antebrachiocarpal joint, middle carpal joint, and carpal sheath. Spin echo magnetic resonance imaging (MRI) sequences were acquired in three planes using a 1.5 Tesla MRI scanner in three limbs. Following MRI, colored resin was injected into the synovial structures of these three limbs, limbs were frozen, and anatomic sections were obtained in three planes. Findings from CT arthrograms were compared to findings from precontrast CT, MRI, anatomic slices, and arthroscopy. Medial and lateral palmar intercarpal ligaments, radiocarpal and transverse intercarpal ligaments, and palmar carpal ligament were visible in CT arthrograms of all limbs. The proximal and distal entheses of all ligaments were readily identifiable. Findings indicated that CT arthrography is feasible for visualizing intercarpal ligaments and may be a useful adjunct imaging technique for diagnosing lameness due to suspected carpal ligament injury in horses.

Prevalence of abnormal radiographic findings in 2-year-old Thoroughbreds at in-training sales and associations with racing performance.

OBJECTIVE: To estimate the prevalence of radiographic abnormalities (lesions) in Thoroughbred racehorses at 2-year-old in-training sales and determine whether these lesions and 1-furlong presale workout times were associated with subsequent racing performance. DESIGN: Retrospective cohort study. ANIMALS: 953 Thoroughbreds. PROCEDURES: Repository radiographs of carpal, metacarpophalangeal and metatarsophalangeal (fetlock), stifle, and tarsal (hock) joints were examined. Horses with lesions were classified by lesion type and location. Race performance variables were compared between horses with and without lesions and between horses categorized by 1-furlong presale workout times (< or ≥ 11 seconds). RESULTS: 299 horses had ≥ 1 lesion, and 654 had no lesion detected. Odds of starting a race and of earning money racing were lower for horses with any lesion and lower for horses with proximal phalangeal dorsoproximal articular margin chip fracture, proximal sesamoid bone fracture or sesamoiditis, or wedge-shaped central or third tarsal bones, compared with horses that had no lesion. For horses that raced, proximal phalangeal dorsoproximal articular margin chip fractures were associated with lower lifetime earnings, and flattening of the medial femoral condyle was associated with fewer 3-year-old racing starts, compared with values for horses that had no lesion. Horses with workout times < 11 seconds had greater odds of having lifetime starts, lifetime earnings, and maximum purse above threshold (median) values than did horses with slower workout times. CONCLUSIONS AND CLINICAL RELEVANCE: No radiographic lesions prevented all affected horses from racing. Among horses that raced, few differences were found in performance for horses with and without lesions.

Comparison of the use of scapular ultrasonography, physical examination, and measurement of serum biomarkers of bone turnover versus scintigraphy for detection of bone fragility syndrome in horses.

OBJECTIVE: To define scintigraphic, physical examination, and scapular ultrasonographic findings consistent with bone fragility syndrome (BFS) in horses; develop indices of BFS severity; and assess accuracy of physical examination, scapular ultrasonography, and serum biomarkers for BFS diagnosis. DESIGN: Prospective case-control study. ANIMALS: 48 horses (20 horses with BFS and 28 control horses). PROCEDURES: Horses underwent forelimb scintigraphic evaluation, physical examination, scapular ultrasonography, and serum collection. Scintigraphy was used as a reference standard to which physical examination, scapular ultrasonography, and concentrations of serum biomarkers (carboxy-terminal telopeptide of collagen crosslinks and bone-specific alkaline phosphatase activity) were compared for assessing accuracy in BFS diagnosis. RESULTS: A diagnosis of BFS was strongly supported on scintigraphy by ≥ 2 regions of increased radiopharmaceutical uptake, including 1 region in the scapular spine and 1 region in the scapular body or ribs; on physical examination by lateral bowing of the scapulae; and on ultrasonography by widening of the scapular spine. None of the tests evaluated were accurate enough to replace scintigraphy for mild disease; however, physical examination and scapular ultrasonography were accurate in horses with moderate to severe BFS. Serum biomarkers were not accurate for BFS diagnosis. CONCLUSIONS AND CLINICAL RELEVANCE: Scintigraphy remained the most informative diagnostic modality for BFS, providing insight into disease severity and distribution; however, physical examination and scapular ultrasonographic abnormalities were diagnostic in horses with moderate to severe disease. Proposed severity indices classified the spectrum of disease manifestations. Clearly defined criteria for interpretation of diagnostic tests aid in the detection of BFS. Severity indices may be useful for assessing disease progression and response to treatment.

Extraoral surgical correction of lingual entrapment in a Chinese goose (Anser cygnoides).

An adult female Chinese goose (Anser cygnoides) presented with a ventral displacement of the hyoid apparatus, associated with distension of the intermandibular sublingual space and of the gular skin, causing difficulties with prehension and deglutition of food and water. Physical examination revealed that the tongue was able to move normally and could be replaced into a normal anatomical position by external compression of the distended ventral intermandibular region. A mild hypoalbuminemia was the only remarkable finding of the biochemistry panel. Radiographs and computed tomography scan of the head and neck regions confirmed a normal hyoid apparatus. An extraoral surgical reconstruction of the distended intermandibular skin was performed: the excess skin was incised and resected and the margins of the incision were sutured with appropriate tissue tension to obtain a good apposition and prevent ventral displacement of the hyoid apparatus. Postoperative complication included airway obstruction by a large amount of respiratory secretions, which were successfully aspirated from the trachea. A supportive elastic bandage was placed at the level of the beak commissure during the following 24 hours in order to reduce downward pressure on the suture line and minimize the risk of dehiscence of the suture. The goose resumed eating within 4 hours following the surgery and oxygen supplementation was discontinued after 24 hours. Respiration was assessed as normal and the tongue remained permanently in normal position. The lingual entrapment did not recur during the following 18 months.

Advances in equine computed tomography and use of contrast media.

Advances in equine computed tomography have been made as a result of improvements in software and hardware and an increasing body of knowledge. Contrast media can be administered intravascularly or intrathecally. Contrast media is useful to differentiate between tissues of similar density. Equine computed tomography can be used for many different clinical conditions, including lameness diagnosis, fracture identification and characterization, preoperative planning, and characterization of skull diseases.

Use of zoledronate for treatment of a bone fragility disorder in horses.

OBJECTIVE: To assess clinical outcomes and scintigraphic findings in horses with a bone fragility disorder (BFD) treated with zoledronate (a nitrogen-containing bisphosphonate). DESIGN: Prospective uncontrolled clinical trial. ANIMALS: 10 horses with evidence of a BFD. PROCEDURES: Signalment, history, and geographic location of horses' home environments were recorded. Physical examinations, lameness evaluations, and nuclear scintigraphy were performed. Diagnosis of a BFD was made on the basis of results of clinical and scintigraphic examination. Each horse was treated with zoledronate (0.075 mg/kg [0.034 mg/lb, IV, once]) at the time of diagnosis. Horses were reevaluated 6 months after treatment. RESULTS: Affected horses were from the central and coastal regions of California and had ≥ 1 clinical sign of the disorder; these included scapular deformation (n = 2), lordosis (1), nonspecific signs of musculoskeletal pain (1), and lameness that could not be localized to a specific anatomic region (9). All horses had multiple sites of increased radiopharmaceutica uptake during initial scintigraphic evaluation of the axial skeleton and bones of 1 or both forelimbs. Six months after treatment, clinical improvement (defined as improvement in the lameness score, resolution of signs of musculoskeletal pain, or both) was detected in 9 of 10 horses; scintigraphic uptake was unchanged (n = 2) or subjectively decreased (8). No adverse effects attributed to zoledronate treatment were detected. CONCLUSIONS AND CLINICAL RELEVANCE: Treatment with zoledronate appeared to be useful in improving clinical outcome and scintigraphic findings in horses with a BFD; however, future placebo-controlled studies are necessary to accurately determine efficacy and long-term safety.

Results of computed tomography in horses with ethmoid hematoma: 16 cases (1993-2005).

OBJECTIVE: To determine whether CT provides unique information about the treatment or prognosis for horses with ethmoid hematoma (EH). DESIGN: Retrospective case series. ANIMALS: 16 horses with EH. PROCEDURES: Horses with a diagnosis of EH that had undergone a diagnostic CT study were included. Clinical features, treatment, outcome, radiographic and CT images, and histologic specimens were reviewed. RESULTS: CT provided new diagnostic information that affected treatment in 10 of 16 horses. Bilateral disease occurred in 8 of 16 horses and was undetected in 5 horses prior to CT. Paranasal sinus involvement occurred in all horses, but was incompletely defined prior to CT in 7 of 16 horses. The sphenopalatine sinus was affected in 6 of 16 horses as detected on CT; 4 of 6 of these were bilaterally affected. Medical and surgical treatments were performed. Six of 10 horses had a successful outcome, with recurrence in 4 of 10. Five of 6 patients in which treatment addressed all lesion sites identified by CT had a successful outcome. Bilateral disease did not confer a poor prognosis when all affected sites were treated. Sphenopalatine sinus involvement may have been associated with recurrence. CONCLUSIONS AND CLINICAL RELEVANCE: CT provided anatomic information that may facilitate effective treatment of horses with EH, particularly in patients with bilateral disease and paranasal sinus involvement. Computed tomography is recommended for patients in which the lesion cannot be viewed endoscopically, when sinus involvement or multifocal disease are suspected, or when the lesion has been unresponsive to treatment.

Abdominal computed radiography for the diagnosis of enterolithiasis in horses: 142 cases (2003?2007).

OBJECTIVE: To evaluate the sensitivity and specificity of abdominal computed radiography (CR) for the diagnosis of enterolithiasis in horses and to examine how these parameters are affected by the number and anatomic location of enteroliths and by gas distension of the gastrointestinal tract. DESIGN: Retrospective case series. ANIMALS: Horses ? 1 year old that underwent abdominal CR and subsequent exploratory laparotomy or postmortem examination. PROCEDURES: 3 reviewers blinded to signalment, history, clinical signs, and diagnoses separately evaluated abdominal computed radiographs of horses included in the study. Each set of radiographs was evaluated for the presence or absence of enteroliths, the amount of gas distention, and the image quality. Signalment, definitive diagnosis on the basis of findings on exploratory laparotomy or postmortem examination, and the number and location of enteroliths were obtained from medical records. RESULTS: Of the 142 cases reviewed, 58.4% (83/142) had confirmed enterolithiasis. For the 3 reviewers, overall sensitivity was 85% and specificity was 93%. Sensitivity was lower for small colon enteroliths than for large colon enteroliths (50% and 94.5%, respectively) and was significantly affected by gas distention. Sensitivity was not significantly affected by the number of enteroliths. CONCLUSIONS AND CLINICAL RELEVANCE: Computed radiography provided high sensitivity and high specificity for the diagnosis of enterolithiasis in horses. Caution should be exercised when the radiographic results are negative, as the sensitivity for small colon enterolithiasis was relatively low and gas distension negatively affected detection of enteroliths. Abdominal CR is indicated as a diagnostic test in horses examined for colic in geographic regions in which enterolithiasis is endemic.

Computed tomographic anatomy of the equine stifle joint.

OBJECTIVE: To provide a detailed computed tomography (CT) reference of the anatomically normal equine stifle joint. Sample-16 hind limbs from 8 equine cadavers; no horses had evidence of orthopedic disease of the stifle joints. PROCEDURES: CT of the stifle joint was performed on 8 hind limbs. In all limbs, CT was also performed after intra-articular injection of 60 mL of contrast material (150 mg of iodine/mL) in the lateral and medial compartments of the femorotibial joint and 80 mL of contrast material in the femoropatellar joint (CT arthrography). Reformatted CT images in the transverse, parasagittal, and dorsal plane were matched with corresponding anatomic slices of the 8 remaining limbs. RESULTS: The femur, tibia, and patella were clearly visible. The patellar ligaments, common origin of the tendinous portions of the long digital extensor muscle and peroneus tertius muscle, collateral ligaments, tendinous portion of the popliteus muscle, and cranial and caudal cruciate ligaments could also be consistently evaluated. The cruciate ligaments and the meniscotibial ligaments could be completely assessed in the arthrogram sequences. Margins of the meniscofemoral ligament and the lateral and medial femoropatellar ligaments were difficult to visualize on the precontrast and postcontrast images. CONCLUSIONS AND CLINICAL RELEVANCE: CT and CT arthrography were used to accurately identify and characterize osseous and soft tissue structures of the equine stifle joint. This technique may be of value when results from other diagnostic imaging techniques are inconclusive. The images provided will serve as a CT reference for the equine stifle joint.

Reaction to intraarterial ionic iodinated contrast medium administration in anesthetized horses.

The purpose of this report was to evaluate the frequency and type of reactions to intraarterial iodinated contrast medium injection in horses. Ninety-seven received an intraarterial injection of ionic, iodinated contrast medium for computed tomographic assessment of the distal limb. Nine (9.0%) horses developed a reaction attributable to the contrast medium administration. Of those, 4/97 (4.0%) developed a skin response (three with urticaria, one with facial edema) within 20 min. Five (5.0%) developed elevation of heart rate and/or blood pressure immediately upon administration of the contrast medium. No horse developed a severe reaction such as shock, cardiac, or respiratory arrest. No treatment was necessary in any horse.

Radiography and computed tomography in the diagnosis of nonneoplastic equine mandibular disease.

We compared the information gained from computed tomography (CT) vs. radiography in horses with nonneoplastic disease of the mandible. We hypothesized that CT would provide additional diagnostic information. Medical records, radiographs, and CT images of horses with nonneoplastic mandibular disease evaluated between 1994 and 2008 were reviewed. Nineteen horses were identified; 11 had a tooth root abscess and related disease, four had a fracture of the teeth and/or mandible, and four had a nonneoplastic mass. Both CT images and radiographs allowed identification of diseased teeth that appeared clinically normal otherwise. CT allowed identification of teeth that were clinically affected but appeared normal radiographically. Parameters such as tooth pulp involvement, lamina dura destruction, presence of bone fragments, lingual and buccal mandibular bone periosteal reaction, and cortical bone destruction were more conspicuous with CT. Performing radiography and CT in horses with nonneoplastic mandibular disease provides a more complete evaluation than either technique alone. CT contributes additional information that could otherwise be overlooked with radiographs alone in horses with a mandibular fracture. CT provides ancillary information to radiographs in horses with dental infection or a nonneoplastic mass of the mandible.

Imaging diagnosis--Arterial and venous thromboses of the proximal limb in two thoroughbred racehorses.

Thromboses of the cranial tibial vein (Horse 1) and brachial, median, and cranial circumflex humeral arteries (Horse 2) were identified as causes of unilateral lameness in two Thoroughbred racehorses. Nuclear scintigraphy was performed for suspicion of long bone stress fractures but instead allowed identification of unusual areas of increased radiopharmaceutical uptake within soft tissues of the affected limbs. Ultrasonography of these regions allowed identification of occlusive thrombi within a 25 cm length of the cranial tibial vein (Horse 1) and variable lengths of affected arteries in Horse 2. Horse 1 developed secondary infections and was euthanized. Staphylococcus aureus was isolated from all sites. The cause of thrombosis was not identified in Horse 2.

Use of contrast-enhanced computed tomography to assess angiogenesis in deep digital flexor tendonopathy in a horse.

We compared contrast-enhanced computed tomography (CT) and high field magnetic resonance (MR) imaging in a horse with deep digital flexor tendonopathy. Lesions in the distal extremity were documented grossly and histopathologically. In contrast-enhanced CT, the deep digital flexor tendon lesions were markedly contrast enhancing with evidence of angiogenesis in the core and dorsal border lesions. The lesion morphology was clearly delineated on MR imaging, but without contrast media angiogenesis cannot be identified. Gross examination, histopathologic examination, and CD31 immunohistochemistry confirmed the tendonopathy and an increased presence of small blood vessels. In this horse, deep digital flexor tendon lesions appeared similarly on contrast-enhanced CT and MR imaging. Contrast-enhanced CT may be an alternative to MR imaging for assessing tendon and ligament injury in the digit of the horse.

The computed tomographic appearance of equine temporohyoid osteoarthropathy.

Equine temporohyoid osteoarthropathy is characterized by progressive osseous proliferation of the temporohyoid articulation and surrounding structures. The diagnosis has generally been made using radiography and endoscopy of the guttural pouch. Recently, computed tomography (CT) has been used in the diagnosis of temporohyoid osteoarthropathy. This study was performed to determine the CT imaging characteristics of temporohyoid osteoarthropathy and to compare these to radiographic and endoscopic findings. CT scans from 16 horses with a final diagnosis of temporohyoid osteoarthropathy were reviewed. Five horses that had undergone CT scan for reasons other than temporohyoid osteoarthropathy were included as controls. Qualitative and quantitative data were used to describe the magnitude of the CT findings. Osseous proliferation of the stylohyoid bone and temporohyoid articulation was found to be a consistent feature of temporohyoid osteoarthropathy. Thickening of the ceratohyoid bone and proliferation of its articulation with the stylohyoid bone was frequently identified and this finding may have surgical implications. Horses with neurologic deficits had increased stylohyoid width that was significantly different than the subclinically affected side. CT evaluation also allowed the identification of subclinical bilateral disease in horses thought to be unilaterally affected based on clinical examination.