Evaluation of foot pain in the standing horse by magnetic resonance imaging

The records of 41 horses with previously undiagnosed foot pain that had been examined by standing magnetic resonance imaging were reviewed and follow-up information was obtained from their owners two years after the examination. A range of soft tissue and osseous abnormalities were identified, with multiple lesions frequently occurring. Deep digital flexor tendonitis was recorded in 12 of the horses, and distension of the distal interphalangeal joint was identified in 15, but it was not always associated with lameness; in contrast, distension of the navicular bursa was always associated with lameness in the seven affected horses. Navicular bone lesions were identified in 13 of the horses, often in the absence of radiographic changes. Follow-up information was obtained for 35 of the horses, 27 of which were alive; of these, 16 had returned to their previous level of performance. Of the five horses with navicular bursal changes, four had been euthanased owing to lameness and the other had returned to work at a reduced level.     

Use of magnetic resonance imaging to diagnose distal sesamoid bone injury in a horse

CASE DESCRIPTION: A 5-year-old Appaloosa mare was examined for severe left forelimb lameness of 4 months' duration. CLINICAL FINDINGS: Lameness was evident at the walk and trot and was exacerbated when the horse circled to the left. Signs of pain were elicited in response to hoof testers placed over the frog of the left front hoof, and a palmar digital nerve block eliminated the lameness. Radiographs revealed no abnormalities, but magnetic resonance imaging (MRI) revealed increased bone density in the medullary cavity of the distal sesamoid (navicular) bone in the proton density and T2-weighted images and a defect in the fibrocartilage and subchondral bone of the flexor cortex. TREATMENT AND OUTCOME: Because of the absence of improvement after 4 months and the poor prognosis for return to soundness, the mare was euthanatized. An adhesion between the deep digital flexor tendon and the flexor cortex defect on the navicular bone was grossly evident, and histologic evaluation revealed diffuse replacement of marrow trabecular bone with compact lamellar bone. Changes were consistent with blunt traumatic injury to the navicular bone that resulted in bone proliferation in the medullary cavity. CLINICAL RELEVANCE: Use of MRI enabled detection of changes that were not radiographically evident and enabled accurate diagnosis of the cause of lameness. Navicular bone injury may occur without fracture and should be considered as a differential diagnosis in horses with an acute onset of severe unilateral forelimb lameness originating from the heel portion of the foot.     

Standing low-field magnetic resonance imaging as a diagnostic modality for solar keratoma in a horse

A 22-year-old Friesian gelding was presented with a history of chronic, nonresolving lameness localised to the right front foot. Radiographs showed a smoothly marginated circular lucent area with a rim of increased opacity adjacent to the solar canal of the distal phalanx. The magnetic resonance imaging (MRI) revealed a reversed V-shaped smoothly demarcated space-occupying mass causing invagination of the solar laminae towards the solar canal arch and deformity of the adjacent surface of the distal phalanx. The mass was removed surgically and submitted for histopathology, which revealed a keratoma and periosteal fibrosis. Six weeks post-surgery the horse returned to the previous work level and 8 months follow-up showed no recurrence of keratoma. This report highlights the usefulness of MRI as a diagnostic modality for solar keratoma.     

Standing low-field magnetic resonance imaging in horses with chronic foot pain

Objective Conventional imaging modalities can diagnose the source of foot pain in most cases, but have limitations in some horses, which can be overcome by using magnetic resonance imaging (MRI). However, there are no reports of the MRI appearance and prevalence of foot lesions of a large series of horses with chronic foot lameness. Methods In the present study, 79 horses with unilateral or bilateral forelimb lameness because of chronic foot pain underwent standing low‐field MRI to make a definitive diagnosis. Results Of the 79 horses, 74 (94%) had alterations in >1 structure in the lame or lamest foot. Navicular bone lesions occurred most frequently (78%) followed by navicular bursitis (57%), deep digital flexor tendonopathies (54%) and collateral desmopathy of the distal interphalangeal joint (39%). Effusion of the distal interphalangeal joint was also a frequent finding (53%). Conclusion Low‐field MRI in a standing patient can detect many lesions of the equine foot associated with chronic lameness without the need for general anaesthesia.     

Computed tomographic and magnetic resonance imaging of a coup contrecoup traumatic brain injury in a horse

A 3-year-old Thoroughbred mare found recumbent in the field was referred for further assessment with suspicion of a skull fracture. Neurological examination identified compulsive tight circling to the left, and hypermetria in all four limbs. The mare was obtunded, with a mild head tilt to the right, absent menace response of the right eye and decreased facial sensation on the right. Standing computed tomographic examination revealed a subtle depression fracture of the dorsal calvarium and moderate intra-axial midline shift consistent with a traumatic brain injury (TBI). Despite supportive treatment, the mare deteriorated and was subjected to euthanasia. Post-mortem high field magnetic resonance imaging revealed findings consistent with a small cerebral contusion adjacent to the fracture site, and moderate to severe ipsilateral cerebral oedema within the caudal cerebrum and rostral brainstem, consistent with a coup contrecoup TBI. Brainstem lesions indicate a poor prognosis and support the decision for euthanasia. This is the first report of the imaging findings of a coup contrecoup TBI in a horse.     

Intraspinal epidermoid cyst in a dog

A 2-year-old female Rottweiler was examined because of progressive gait deficits consistent with transverse myelopathy between the T2 and L3 spinal cord segments. Myelography confirmed an intramedullary spinal cord lesion between T13 and L1, so the dog was euthanatized. At necropsy, an intramedullary epidermoid cyst was confirmed in the T13 and L1 spinal cord segments. The epidermoid cyst probably resulted from a congenital cause.     

Standing low‐field magnetic resonance imaging of a comminuted central tarsal bone fracture in a horse

This report describes the use of low‐field standing magnetic resonance imaging (MRI) in the diagnosis and clinical decision making process in a 14‐year‐old Dutch Warmblood mare with a comminuted central tarsal bone fracture. Magnetic resonance imaging in the standing horse was preferred over computed tomography examination under general anaesthesia because the animal had sustained the injury during a poor recovery from a previous general anaesthetic episode. Magnetic resonance imaging examination identified a comminuted central tarsal bone fracture with a configuration that was not identifiable with radiography. Due to extensive comminution of this fracture, conservative management was pursued. Standing low‐field MRI examination enabled safe examination of this animal and provided useful diagnostic information whilst facilitating the clinical decision making process.     

The use of magnetic resonance imaging in the diagnosis of neurological disease

Magnetic resonance imaging (MRI) data were correlated with clinical and cerebrospinal fluid (CSF) findings in one cat and two dogs with brain lesions. In all three cases, localization of the lesions, as determined clinically, was confirmed using MRI. Magnetic resonance imaging also helped us to define the full extent of the lesion(s) in each case. In one case, the lesion would have been diagnosed as purely inflammatory based on the abnormalities in the CSF. The MRI study, however, showed a homogeneous mass with circumferential changes characteristic of peritumoral edema or inflammation. In two cases, the MRI findings were confirmed at necropsy. An MRI study was also done on a normal dog, demonstrating the variable contrast and anatomical detail possible using this technique. We also discuss difficulties in identifying tumor type using MRI.     

Electroacupuncture-induced neural activation detected by use of manganese-enhanced functional magnetic resonance imaging in rabbits

OBJECTIVE: To investigate the effects of acupuncture on neural activity detected by use of manganese-enhanced functional magnetic resonance imaging (fMRI) and elucidate the relationship between somatic acupoint stimulation and brain activation. ANIMALS: 40 New Zealand White rabbits. PROCEDURE: Manganese-enhanced fMRI was performed in anesthetized rabbits manipulated with electroacupuncture (EA) on Zusanli (ST-36) and Yanglingquan (GB-34) acupoints. Image acquisition was performed on a 1.5T superconductive clinical scanner with a circular polarized extremity coil. T1-weighted images were acquired sequentially as follows: baseline, after mannitol injection, after manganese infusion, and 5 and 20 minutes after initiation of EA. RESULTS: Changes in focal neural activity were detected by use of manganese-enhanced fMRI. Stimulation on Zusanli (ST-36) for 5 minutes resulted in activation of the hippocampus, whereas stimulation on Yanglingquan (GB-34) resulted in activation of the hypothalamus, insula, and motor cortex. Activation became less specific after 20 minutes of EA. Furthermore, stimulation on ipsilateral acupoints led to bilateral brain activation. CONCLUSIONS AND CLINICAL RELEVANCE: Each acupoint has a corresponding cerebral linkage, and stimulation on these points resulted in time-dependent neural activation. Understanding the linkage between peripheral acupoint stimulation and central neural pathways may provide a useful guide for clinical applications of acupuncture.     

Surgical management of an ethmoid cyst in a horse.

A 2-year old Thoroughbred filly was examined for a 1-month history of persistent nasal discharge. Contrast radiography revealed a circumscribed mass within the right maxillary sinus which extended to the frontal sinus and ethmoid labyrinth. A discrete attachment of the mass to the ethmoid labyrinth was identified at surgery. Surgical removal of the mass eliminated the nasal discharge. On gross examination, the external structure of the mass was similar to a turbinate with a thin bony wall covered by a smooth mucosal membrane. The internal structure of the lesion had a lining membrane with multiple 1-3 cm in diameter fluid filled cystic structures. The histological appearance of the multiloculated structure was similar to the ethmoid labyrinth. This, combined with the single site of attachment to the ethmoid labyrinth, suggested that the cyst was ethmoidal in origin.     

Treatment of a mandibular bone cyst by use of a corticocancellous bone graft in a horse.

A 1-year-old Appaloosa stallion had a mass on the right rostral hemimandible. The mass was firm, did not cause signs of pain, and was identified as a bone cyst by radiography and biopsy. Surgical correction included curettage of the cystic cavity and grafting the defect with both cortical and cancellous bone. By 5 months, the cystic cavity was ossifying; continued remodeling with an increase in bone density was apparent 22 months after surgery.     

Malignant melanoma in the foot of a horse

A 24-year-old horse had a malignant melanoma of the right forefoot. Because surgical excision of the melanoma was incomplete, as determined by histologic examination of the excised tissue margins, the tumor margins were injected with a matrix therapeutic implant containing cis-diamminedichloroplatinum, epinephrine, and purified bovine collagen matrix. The foot healed and the horse remained clinically free of disease for 26 months before recurrence of malignant melanoma. Surgical exploration of the digit revealed extensive involvement of the foot, and the horse was euthanatized.     

Evaluation of the diagnostic accuracy of skeletal scintigraphy for the causes of front foot pain determined by magnetic resonance imaging

There is good correlation between increased radiopharmaceutical uptake anywhere in the feet of sports or leisure horses and the presence of foot pain. However, low sensitivity of scintigraphy for identifying lesions contributing to foot pain as determined by magnetic resonance imaging (MRI) has been reported. The aim of this retrospective, cross‐sectional, analytical study was to assess the accuracy of scintigraphy for identifying the cause(s) of foot pain, using MRI as the reference standard. Sports and leisure horses that underwent both skeletal scintigraphy and MRI of the front feet between March 2008 and December 2014 and for which a definitive diagnosis of the cause(s) of front foot pain was reached were included (121 feet of 70 horses). Imaging studies were evaluated retrospectively, blindly. Agreements between scintigraphic localization of increased radiopharmaceutical uptake and subjective categorization of lesions with MRI diagnosis were assessed using Kappa statistics (κ). Measures of diagnostic accuracy were calculated. Sensitivity of increased radiopharmaceutical uptake varied among regions (31.8–76.2%) but specificity was at least high for all (84.6–100%). Agreements between both scintigraphy measures and MRI diagnosis were substantial for the distal phalanx (palmar processes and body) (κ = 0.77 and κ = 0.74, respectively), and ungular cartilages and chondral ligaments (κ = 0.62, for both). When all regions were combined, agreements of increased radiopharmaceutical uptake (κ = 0.49) and relevance categorization (κ = 0.45) with MRI diagnosis were moderate. In conclusion, skeletal scintigraphy does not meet the minimum reliability level for a diagnostic test, but is reliable for identification of osseous trauma to the distal phalanx and ungular cartilages.