Cause is unknown
As with Alzheimer’s disease, the exact cause of cognitive disorder is unknown. As pets age, their brains may receive less oxygen hypoxic due to decreased cardiac (heart) output, anemia, hypertension (high blood pressure) and arteriosclerosis from fibrosis, endothelial proliferation, mineralization, and amyloid deposition. Decreased levels of neurotransmitters including serotonin and choline, increased levels of monoamine oxidase B (MAOB) which causes decreased dopamine levels, and increased free radicals (oxidizing chemicals that damage and kill cells through inflammation) may also be seen in geriatric pets.
Microscopically, beta amyloid plaques within the brain and its blood vessels are seen in pets with cognitive disorder (as in people with Alzheimer’s). These plaques are a hallmark of the brain damage that occurs in both Alzheimer’s and cognitive disorder.
All these biochemical and pathological changes progress as the pet ages if treatment does not occur. Obviously, early treatment is important and may prevent progression of cognitive disorder.
Clinical signs vary
Clinical signs in dogs and cats can vary between pets and the severity of the disease, but are generally often mistaken for “normal signs of aging” or attributed to the pet “acting senile”. In general, clinical signs include the following:
* Staring at the wall
* Lack of awareness of surroundings
* Occasional lack of recognition of the owner
* Lethargy/lack of energy
* Excess sleep (especially during the day)
* House-training problems (usually urinating inside the house or eliminating outside the litterbox)
Diagnosis based on exclusion
There is no specific diagnostic test (other than postmortem brain biopsy) for cognitive disorder. Diagnosis is based upon clinical signs and laboratory testing to exclude other disorders that might cause similar signs (hypo/hyperthyroidism, adrenal disease, etc.).
A number of natural therapies have been recommended for treating cognitive disorder in pets, including Omega-3 fatty acids (fish oil), antioxidants (vitamin C and E, resveratrol), herbs (such as ginkgo biloba) and nutritional supplements (including SAMe, phosphatidylserine and phosphatidylcholine). Since it is beyond the scope of this article to have an in-depth discussion of each therapy, I will focus on two that have been well researched.
1. SAMe (Novifit, Virbac) SAMe is formed in the body (mainly in the liver) through the combination of methionine with adenosyl-triphosphate, and is not supplied in the diet. SAMe functions as a methyl donor in the formation of a variety of compounds (neurotransmitters, proteins, membrane phospholipids, nucleic acids, choline, etc.) and increases levels of serotonin and dopamine metabolites, improves neuron membrane fluidity, and enhances binding of neurotransmitters to receptors.
Levels of SAMe decline sharply after birth and continue to decline as part of the aging process. While generally safe, SAMe contraindications in people include bipolar disorder, migraine headaches, Parkinson’s disease, and active bleeding.
Co-administration of SAMe and SSRI medications, MAO inhibitors, 5-HTP and TCAs requires caution or avoidance as some patients may be at risk for a higher incidence of serotonin syndrome and/or synergistic CNS depressant effects.
No direct contraindications are noted in pets but prudence suggests similar caution.
Recently, a SAMe product (Novifit, Virbac) has been introduced to the market as a natural treatment for canine and feline cognitive disorder. Studies in dogs (n=14) and cats (n=16) showed improvement in reversal learning in treated patients when compared with non-treated patients. Reversal learning is a memory test that measures executive function, which is defined as a set of mental processes that help connect past experience with present action, and is needed for goal-directed behavior. Executive function has been shown to be impaired by age.
Researchers concluded that the study supported the use of Novifit to help improve cognitive health in aged dogs and cats, with potential benefits on executive function, especially in the early stages of cognitive dysfunction syndrome. 2. Phosphatidylcholine (Cholodin, MVP Laboratories) Choline is a component of several major phospholipids (including phosphatidylcholine and sphingomyelin) that are critical for normal cell membrane structure and function. The body uses choline to maintain water balance; as a source of methyl-groups (for methionine formation) to control cell growth and gene expression; as a component of surfactant; and to produce acetylcholine. Supplemental choline may increase the production of acetylcholine and reverse clinical signs of cognitive disorder.
Choline supplementation is very safe. In pets, rare instances of excitability/nervousness have been reported, but lowering the dosage resolved this side effect.
It has been suggested that aging people and pets begin to lose cholinergic receptors and have decreased levels of acetylcholine. Since oral choline administration increases plasma choline levels, and since brain levels of acetylcholine increase as plasma choline levels increase, administering choline may improve neurological disorders that result from decreased acetylcholine.
Choline, specifically the patented product Cholodin (MVP Laboratories), has been shown in studies to reverse clinical signs of cognitive disorder. For the dog study, 21 dogs of various breeds ten years of age and older were enrolled. For the cat study, 21 cats ten years of age and older were also enrolled. Pets were chosen for the study based on owner observation of clinical signs consistent with cognitive disorder that couldn’t be attributed to other illness after physical examination and laboratory testing. At the conclusion of the study (two months following treatment), owners were asked to evaluate improvement in clinical signs: 82% of dogs showed improvement as did 77% of cats.
Regardless of the treatment chosen, early diagnosis and intervention is key to minimizing the incidence of cognitive disorder in pets. Regular “senior pet” checkups that include a full physical examination, blood profile, urinalysis, and microscopic fecal analysis, ideally every six to 12 months for pets five years of age and older, will facilitate communication and allow for early diagnosis.
References and suggested reading
Araujo JA, Faubert ML, Brooks ML, Landsberg GM, Lobprise H. NOVIFIT® (NoviSAMe®) Tablets Improve Executive Function in Aged Dogs and Cats: Implications for Treatment of Cognitive Dysfunction Syndrome. Intern J Appl Res Vet Med. 2012.Vol 10(1): 90-98. Fetrow CW, Avila J. Professional’s handbook of complementary and alternative medicines, 3rd ed. St. Philadelphia (PA): Lippincott Williams & Wilkins: 2004:730–58.Goldstein, R, ed. Integrating complementary medicine into veterinary practice. St. Louis (MO): Wiley-Blackwell; 2008:541. Hand M, Thatcher C, Remillard R, et al. Small animal clinical nutrition, 5th ed. Topeka (KS): Mark Morris Publishing; 2010:93–94. Landsberg G, Denenberg S, Araujo J. Cognitive Dysfunction in Cats: A syndrome we used to dismiss as “old age”. 2010 J Fel Med Surg. 12: 837-848. Messonnier SP. The natural health bible for dogs & cats: your A-Z guide to over 200 herbs, vitamins, and supplements, Three Rivers Press, NY, 2001:56–57, 233. Messonnier SP. Natural Care for Aging Pets, Today’s Health and Wellness – July/August 2001 (pgs. 20,21). Pizzorno J, Murray M. Textbook of natural medicine, 3rd ed. St. Louis (MO): Churchill Livingstone; 2005:817, 853, 856, 135-1238, 1603, 1654. Pizzorno J, Murray M, Joiner-Bey H. The clinician’s handbook of natural medicine, 2nd ed. St. Louis (MO): Churchill Livingstone; 2008:17, 20, 559–60. Ruehl WW, Hart BL: Canine Cognitive Dysfunction. In Psychopharmacology of Animal Behavior Disorders (Dodman NH, Schuster L, eds.). Boston: Blackwell Scientific, 1998; pp. 283-304. Stargrove M, Treasure J, McKee D. Herb, nutrient, and drug interactions: clinical implications and therapeutic strategies. St. Louis (MO): Mosby Elsevier; 2008:824–1. Wynn S, Marsden S. Manual of natural veterinary medicine: science and tradition. St. Louis (MO): Mosby; 2003:323.