Sensory Decline (Senior) in Dogs

Dogs, like all living things, experience many changes due to the aging process and senior dogs frequently experience a decline in their sensory abilities. Vision, hearing, and sense of smell can all be affected by the process of aging or by diseases that are more common in senior pets like diabetes and cancers. Although some dogs may benefit from surgical intervention, many of these disorders are not reversible, and simple adjustments to the environment can improve their quality of life.

Aging triggers many changes in the canine mind and body. Senior dogs with sensory decline frequently require surgical intervention or changes to their environment to continue getting the best out of their lives.

The symptoms that your senior pet may exhibit will depend on the sense that is affected, the severity of the decline, and if there are any underlying causes contributing to the problem. Dogs that are having difficulty seeing may stumble more often and may have trouble adapting to changes like moving to a new house or moving the furniture. Dogs with hearing deficits may seem to be ignoring you, or they may stop greeting you at the door when you return home. Some dogs may be more easily startled when they are unable to hear, leading them to snap more often. The most common symptom that your dog will exhibit if they are having trouble smelling is a loss of interest in certain foods. 

• Stumbling
• Hearing loss leading to changes in behavior such as easy startling or snapping
• Change in interests related to food

 Types

• Hearing - A dog’s hearing is much more acute than a human’s hearing, allowing them to pinpoint where a sound is coming from and to hear more frequencies than we can; as they age, this acuteness often diminishes to varying degrees 
• Smell - Complete loss of smell, known as anosmia, is rare in dogs, but a somewhat diminished capability to smell is common; as a dog’s sense of smell is an integral part of tasting things, food may become less interesting to them  
• Vision - This is typically both the most common sense to be affected by old age, and often the first; there are several factors that can increase an animal’s chances of developing trouble seeing

Although these changes are in small part simply due to the natural process of aging, there are some diseases and conditions that are known for more commonly afflicting the senses of senior dogs. These can include: 

• Brain tumors
• Cataracts
• Decreased tear production (keratoconjunctivitis sicca) 
• Degradation of nerves in the ear
• Glaucoma
• Nasal cancer
• Oxidative Damage
• Thinning of the sensory hairs in the ear

Whether you bring your senior pet into the veterinary clinic due to the declining senses themselves or for a regular medical examination, the examining vet will want to make a quick evaluation of senses. Typically, the veterinarian will check for problems with the retinas, evaluate the opacity of the lens, and provide testing for glaucoma, or refer you to a veterinary ophthalmologist who can.  The dog’s response to loud or startling sounds outside its range of vision will also be evaluated and the ears will be checked to ensure they are not blocked by wax or foreign objects. 

The dog’s doctor will also ask the owner of the animal for a behavioral history which will help to evaluate the severity and the progression of the diminished capability. The behavioral history is also the most likely way to reveal olfactory decline, as the main symptom is a lack of interest in food, which is often stimulated by wet food or warmed food, with a stronger smell. If there is an indication of a decline in one or more of the senses and the standard tests have not given an origin of the decline, additional tests may be ordered. These tests may include a brainstem auditory evoked response (BAER) test, an auditory brainstem response test (ABR), dilation of the pupils, and x-rays and ultrasound imaging of the head area.

The treatment for sensory decline will depend on the sense in question and which underlying causes are exacerbating the condition. Treating any underlying conditions for sensory decline, such as diabetes, injury, or infection, may either improve the affected senses or slow the decline.  Treatment for glaucoma may include either topical or oral medications to relieve the pressure, but this is not always successful, and the removal of the eye may be the best option.

Cataracts with high opacity or an inconvenient placement may require surgical removal if the animal is to see again, but if the opacity is still low, antioxidants specifically designed for the ocular health of canines may help to slow the progression of this condition. Any obstructions in the ear will be removed, including wax, foreign objects, or growths, but in the majority of cases, hearing loss is irreversible. Loss of olfactory sensation is also typically irreversible but is rarely total.

There are several ways to improve the quality of life for dogs who have experienced a sensory decline. If your dog has decreased vision or has gone blind, they generally navigate their immediate environment by memory, so if residences are changed or if the furniture has moved it is important to walk the dog around the new environment on a leash a few times to familiarize them with the new configuration. 

If your dog is developing issues with their hearing, keeping them on a leash when not in a fenced area or in the house is recommended as they may not be able to hear your commands, and emphasizing hand gestures for training will help you communicate with your canine companion. Dogs who have a reduced sense of smell may be encouraged to eat by using food with high smell value, heating the food, or adding water or broth to the food.