Do you remember the last time you got a bad cold and lost most or all of your voice? It was annoying, but not a serious problem. Well, the same is not true for pets. If their voice changes or is lost it is a big deal and not just a cold.
The Voice Box or Larynx
Animals are able to make sounds by creating vibrations of vocal cords or folds. These fibrous cords are part a rigid chamber at the beginning of the trachea or windpipe called the larynx or voice box. The vocal folds open and close the opening of the trachea, producing the characteristic bark and growls of dogs, the meow and purr of cats, and our own voices. When the vocal folds close, they close the tracheal airway. This is why we can’t breathe and talk at the same time. The same is true when dogs bark and cats meow.
The cat is unique in that its vocal fold cords have an additional membrane called the ventricular cords that are used for purring. They can vibrate these rapidly without closing the trachea completely and can breathe when they are purring. So how do animals lose their voice?
Reasons for Voice Loss
Vocal sounds are made by the physical vibration of the vocal folds. The vibrations are initiated and controlled by nervous signals from the brain through nerves to the larynx. Changes or loss of voice are caused for two reasons: mechanical interference with vocal cord vibration or lack of stimulation of the nerves to the vocal cords.
Simply put, this is anything that physically makes it hard for the vocal cords to vibrate. Our cold virus is a good example. The swelling from infection and inflammation interferes with normal cord function and our voice changes. However, upper respiratory infections are not the major source of voice loss in dogs and cats.
Although some young animals may have voice changes with severe neonatal virus infections, this seldom happens in older animals. Mechanical interference is more likely to be caused by:
- Abscesses — Foxtails eaten by dogs and sometimes cats can lodge in the tonsils, throat, and larynx and cause major swelling. Cat fight abscesses are another type of abscess that could interfere with vocal cord function. I have had patients with severe abscess in the throat caused by swelling from sewing needles and bones that got lodged in the laryngeal area.
- Trauma — Severe injury, both penetrating and non-penetrating can cause swelling that interfere with vocal fold function.
- Tumors and Cancer — Benign or malignant tumors can occur in and around the larynx and trachea, and can crowd and cause pressure on normal tissue and cause voice changes or loss
Decreased or non-stimulation of the nerves to the vocal cords will cause paralysis and voice changes or loss. There are many causes of neurological interference.
- Hereditary paralysis — Young dogs of certain breeds are born with abnormalities of the nerves to the larynx. Dalmatians, Bouvier des Flandres, Rottweilers, and white-coated German shepherds can be stricken with laryngeal paralysis at different times of infancy depending on breed.
- Breed Acquired paralysis — St. Bernards, Newfounlands, Irish Setters, and Labrador and Golden Retrievers are prone to laryngeal paralysis later in life.
- Tumors and cancer — Primary tumors of the nerves that control the vocal cords can cause a loss of stimulation. Non-nerve tissue tumors in the throat, neck, and chest can “pinch” laryngeal nerves and quiet the vocal cords.
- Infections — Severe chest infections can cause swelling that also interferes with the nerves to the larynx.
- Hypothyroidism in dogs — Hypothyroidism in dogs can affect nerve function, especially to the larynx. I have seen several of these cases during my veterinary career.
- Autoimmune conditions — An animal’s own white blood cells can turn on its own nerves, injure the nerve, and limit nerve impulses to the larynx and vocal cords.
- Muscle disorders — The vocal cords are a muscle. Autoimmune muscle disorders can block the neuromuscular junction and result in voice change or loss.
Unlike us, colds and flus are not the major reason for voice changes and loss in pets. If your dog or cat is losing their bark or meow do not put off a visit to your vet. Many of these conditions are treatable or easily managed.
With less treatable conditions, early intervention can lead to a longer, higher quality of life.
Dr. Ken Tudor