Detection of an epidermoid cyst in the foot of a horse by use of magnetic resonance imaging.
Authors: Sanz, Sampson, Schneider, Gavin, Baszler
Journal: Journal of the American Veterinary Medical Association
Summary
# Editorial Summary A 4-year-old Quarter Horse presented with a 10-month history of moderate forelimb lameness that proved diagnostically elusive: palpation and hoof testers revealed nothing abnormal, yet radiography and ultrasonography similarly failed to identify any pathology despite localisation of pain to the digital region via palmar digital nerve block. Magnetic resonance imaging identified the culprit—a circumscribed soft tissue mass within the digital flexor tendon sheath dorsal to the deep digital flexor tendon—which was subsequently confirmed as an epidermoid cyst and removed tenoscopically with transection of the distal digital annular ligament. The horse achieved 90% lameness improvement following local anesthetic injection into the tendon sheath and returned to full training and competition within 6 months post-operatively. This case underscores MRI's diagnostic value for chronic foot lameness when conventional imaging techniques fail to identify structural abnormalities, particularly where diagnostic anesthesia has successfully localised pain to a specific anatomical site. For practitioners managing persistent forelimb lameness unresponsive to farriery and conventional diagnostics, MRI warrants consideration before pursuing empirical treatment or assuming behavioural causes.
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Practical Takeaways
- •Consider MR imaging when lameness is localized to a specific anatomic region by diagnostic anesthesia but conventional imaging (radiography, ultrasonography) fails to identify a cause
- •Soft tissue masses within synovial structures like the digital flexor tendon sheath may be invisible on radiographs and ultrasound but readily apparent on MR imaging
- •Tenoscopic treatment of digital flexor tendon sheath lesions, combined with appropriate post-operative management including intra-synovial therapy, can return performance horses to competition
Key Findings
- •MR imaging identified a circumscribed soft tissue mass in the distal digital flexor tendon sheath that was not detected by radiography or ultrasonography
- •Palmar digital nerve block eliminated lameness, confirming the lesion was in the forelimb foot
- •Tenoscopic removal of the mass resulted in 90% lameness improvement and successful return to full training and competition at 6 months post-surgery