Synovial cysts in cats

Synovial Cysts and Myxomas in 16 Cats

This report describes the clinical and pathologic characteristics of cystic and myxomatous lesions of synovial joints in 16 cats. The average age was 13.4 years. The elbow was most commonly affected (12/16), and all lesions were unilateral. Degenerative joint disease was a frequent concurrent but bilateral condition. The lesions consisted of fluid-filled cysts lined by synoviocytes (3 cases), solid foci of stellate cells in a myxomatous matrix (2 cases), or a combination of the two (11 cases). In some cases there were areas of transition between the cystic and myxomatous lesions. Mitoses and other features of malignancy were rare to nonexistent. In the 13 cats with follow-up information, the lesion gradually increased in size over a period of years. None of the cats died or were euthanized because of this lesion. We propose that some cats with degenerative joint disease develop synovial cysts, which have the potential to transform to a synovial myxoma.

Use of greater omentum in the surgical treatment of a synovial cyst in a cat

A 13-year-old cat was diagnosed with a synovial cyst originating from the glenohumeral joint. The cat presented with severe front limb lameness and a non-painful fluctuating swelling on the medial aspect of the humerus. Radiographic examination showed severe bilateral shoulder osteoarthritis with osteophyte formation. The mass was surgically resected and histopathology confirmed the diagnosis of a synovial cyst. Three weeks postoperatively the cyst recurred. Surgical resection was repeated followed by omentalisation of the defect. Throughout the following 3 months the cyst did not recur. Unfortunately, for reasons unrelated to the presented disease, the cat was euthanized shortly afterwards, therefore making a long-term follow-up impossible.

Medial humeral epicondylitis in clinically affected cats

OBJECTIVE

To describe the clinical signs and histologic changes in cats clinically affected with medial humeral epicondylitis (MHE) and evaluate long-term outcome after either conservative or surgical treatment.

STUDY DESIGN

Prospective cohort study.

ANIMALS

Client-owned cats (n = 17) with MHE.

METHODS

Cats diagnosed with MHE, based on clinical signs, radiographs and computed tomography (CT), were prospectively recruited. Cats were treated conservatively for an initial 4 weeks, followed by either surgery or continued conservative treatment. Followup examinations were performed at 6 and 12 weeks and at 6-49 months.

RESULTS

Cats had a mean age of 10.3 years and presented for chronic lameness. Examination revealed pain on palpation caudodistal to the medial epicondyle and by exerting antebrachial supination/pronation with elbow and carpal flexion. Lameness was restricted to 1 limb although CT revealed bilateral disease in 11/17 cats. Free mineralized joint bodies were identified in 9/17 cats. Nine cats were treated surgically and 8 cats were treated conservatively. Intraoperative findings included new bone formation at the origin of the humeral head of the flexor carpi ulnaris muscle with displacement and adhesions of the ulnar nerve. Microscopic examination revealed neurogenic myopathy in 4/9 cats treated surgically. Seven of 9 cats treated surgically were free from lameness by 12 weeks. Seven of 8 cats treated conservatively were chronically lame throughout the study.

CONCLUSIONS

Cats with forelimb lameness should be evaluated for MHE. This condition is associated with free joint bodies and neurogenic myopathy. Surgical treatment is associated with excellent outcome in the majority of cats.

Ganglion cyst arising from the composite occipito-atlanto-axial joint cavity in a cat

A four-year-old, female spayed Domestic Longhaired cat was referred for evaluation with a two month history of initial inability to jump progressing to ambulatory tetraparesis. Magnetic resonance imaging studies demonstrated a cystic lesion arising from the composite occipito-atlanto-axial joint cavity and extending to the region of the occipital bone and the axis. The lesion surrounded the spinal canal, causing moderate dorsal spinal cord compression at the atlanto-occipital joint. A dynamic myelographic study demonstrated attenuation of the dorsal contrast column at the atlanto-occipital joint when the cervical spine was positioned in extension. Partial excision of the cyst capsule by a ventral approach resulted in long-term (64 months) resolution of clinical signs. Histological evaluation was consistent with a ganglion cyst. An intra-spinal ganglion cyst arising from the composite occipito-atlanto-axial joint cavity may be considered as an uncommon differential diagnosis for cats with cervical myelopathy.

Equine articular synovial cysts: 16 cases

OBJECTIVE

To report the clinical findings, diagnosis, treatment and outcome of equine patients with articular synovial cysts.

STUDY DESIGN

Retrospective case series.

ANIMALS

Horses (n = 16) with articular synovial cysts.

METHODS

Horses diagnosed with articular synovial cysts (1988-2009) at 2 veterinary teaching hospitals were studied. Signalment, history, clinical signs, diagnostic methods and treatment were retrieved and telephone follow-up was obtained.

RESULTS

Sixteen horses with articular synovial cysts were identified. Lameness was the reason for referral in most (n = 9) horses. Diagnosis was based on a combination of palpation and imaging studies, including radiography, ultrasonography and/or arthrography. Excision of the cyst was performed in 8 horses. Outcome was available for 4 surgically and 2 conservatively treated horses. Lameness resolved in 3 horses treated surgically and the 4th died for unrelated reasons. The 2 conservatively treated horses performed satisfactorily for the rest of their career.

CONCLUSIONS

Equine articular synovial cysts are rare and can be associated with lameness. The cysts had a synovial lining in all horses where it was assessed. Surgical excision may be successful in resolving the lameness and allowing selected horses to return to work.

Musculoskeletal oddities in the cat: an overview of some curious causes of lameness

PRACTICAL RELEVANCE

Cats, both young and old, can suffer a variety of weird and wonderful musculoskeletal conditions that are a cause of lameness. These include developmental, metabolic and nutritional bone diseases, ectopic mineralisation disorders, conditions that cause lameness or exercise intolerance and primarily or secondarily affect muscle, and lastly pad conditions.

CLINICAL CHALLENGES

These conditions are mostly rare and can be challenging to diagnose. The aim of this review is to bring these conditions to the attention of practitioners so that, if they are encountered, further research around the topic can be undertaken. Radiographic changes and diagnostic tests that can be used to try to confirm diagnoses are described.

EVIDENCE BASE

These unusual causes of lameness are the subject of multiple single case reports or small case series, many of which are relatively old. The evidence presented here is drawn from these articles. However, it is not possible within the scope of this review to discuss all the conditions in as much detail as they may warrant, or to make reference to every article relating to them.

Synovial cyst of the fifth digit in a cat

A synovial cyst of the fifth digit of the left forelimb in a 15-year-old cat was diagnosed. Radiographs showed severe osteoarthritis of the interphalangeal and metacarpophalangeal joints with soft tissue swelling. An ultrasound examination of the digit revealed a cystic structure. Following amputation of the digit, the cyst recurred 3 months later palmar to the carpus and metacarpus. The aetiology of synovial cysts is discussed.

Absolute and relative cell counts for synovial fluid from clinically normal shoulder and stifle joints in cats

OBJECTIVE

To determine absolute and relative cell counts for synovial fluid from grossly, radiographically, and histologically normal shoulder and stifle joints in healthy cats.

DESIGN

Clinical study.

ANIMALS

52 cats scheduled to be euthanatized for unrelated reasons.

PROCEDURE

Arthrocentesis of the shoulder and stifle joints was performed bilaterally, and synovial fluid was analyzed for absolute WBC count, WBC morphology, and percentages of neutrophils and mononuclear cells. Joints were examined grossly and radiographically, and synovial membrane specimens were submitted for histologic examination. Synovial fluid samples that were contaminated with blood and samples from joints with any gross, radiographic, or histologic abnormalities were excluded.

RESULTS

82 of the 208 synovial fluid samples were excluded because abnormalities were identified during physical examination; the volume of fluid obtained was insufficient for analysis; there was evidence of blood contamination; or the joint had gross, radiographic, or histologic abnormalities. Median WBC count for the remaining 126 synovial fluid samples was 91 cells/microL (96.4% mononuclear cells and 3.6% neutrophils); WBC count was not significantly different between left and right joint samples or between shoulder and stifle joint samples. Body weight was associated with synovial fluid WBC count, with WBC count increasing as body weight increased. Sixteen of the 52 (30%) cats had radiographic evidence of osteoarthritis involving at least 1 joint.

CONCLUSIONS AND CLINICAL RELEVANCE

Results suggest that synovial fluid can be obtained reliably from shoulder and stifle joints in cats.