Uneven Sweating and Intermittent Lameness in a Horse

Uneven Sweating and Intermittent Lameness in a Horse

Damage to peripheral nerves and/or blood vessels can result in local areas of sweating.

Photo: Courtesy Lyall, Christchurch, New Zealand

Q. I have a 12-year-old Standardbred mare that in the last six months has developed an unusual sweat pattern. This sweat pattern can occur while out riding or just when she’s standing in the paddock. Occasionally, she will limp on this leg but there is no swelling or heat associated with the area. I’ve included a photo for your review.

I had a veterinarian examine the mare, and she stated there is no issue and to keep riding her, but I have this nagging feeling that I need a second opinion. What could be causing this issue?

Lyall, Christchurch, New Zealand

A. Damage to peripheral nerves and/or blood vessels can result in local areas of sweating similar to the signs you have seen in your mare, often in very specific regional patterns. The damage can be due to actual nerve injury or secondary to nerve compression from some other enlarged structure, such as a lymph node or internal abscess.

It’s interesting that you describe an intermittent lameness in her left front limb. With subtle lameness, it can be difficult to discern whether it is due to a musculoskeletal or neurologic problem. The lameness you describe could be related to the same local nerve or musculoskeletal trauma that resulted in her abnormal sweating pattern.

A consultation with a veterinary internal medicine specialist would be useful to further explore whether there’s a neurologic cause for your horse’s interesting signs. A complete neurologic examination might reveal some other subtle functional changes that would help localize the area affected and make a diagnosis. An electromyography (EMG), a test used to identify local nerve damage and dysfunction, would also be useful to better clarify the cause of both the abnormal sweat pattern and any gait abnormality that might be present. An EMG is done with standing sedation in horses and is generally well tolerated by the patient.

About the Author

Martha Mallicote, DVM, Dipl. ACVIM

Martha Mallicote, DVM, Dipl. ACVIM, is a large animal clinical assistant professor at the University of Florida. Her interests include neonatology and endocrine disease.

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