Feline Cognitive Dysfunction

Overview

Cognitive dysfunction syndrome (CDS) is a condition that leads to an overall progressive decline in cognitive function and increase in brain pathology. Similar pathological changes are seen in dogs and humans with Alzheimer's disease (AD); canine CDS is being researched as a naturally occurring mode of AD. Similar pathological changes have also been observed in the cat. In comparative studies of the effect of selegiline, a drug licensed for the treatment of canine CDS, similar responses were seen in canine and human patients. Effects of feline cognitive dysfunction (FCD) include impairment of memory, learning, information processing and perception, as well as increased behavioural disinhibition; this leads to observed signs of confusion/disorientation, deranged sleep patterns, inappropriate elimination, and reduced social interaction. Previously learned behaviours, such as elimination habits, may be forgotten and affected cats show increased fear and anxiety. Disinhibition can lead to an increase in irritability and aggressiveness. Social relationships with both other animals and humans can also be affected. In general, cognitive dysfuncion is less frequently reported in cats than dogs. It is thought that FCD affects 28% of cats between the ages of eleven and fourteen, and 50% of cats over fifteen years old . Although clinical signs in cats generally seem to become evident at around ten to eleven years old, neurones in the caudate nucleus start to show functional changes by six-seven years of age. Diagnosis of CDS in cats is a greater challenge than in dogs, as the signs are often less apparent due to the cat's independent outdoor lifestyle.

Investigation

Behaviours signs of FCD include:

• Reduced activity

Moves around the home environment less, plays, and grooms less, but sleeps more.

• Unusual sleeping patterns

Sleeping longer during the day, waking up at night, restless when asleep, increased vocalisation at night.

• Disorientation

Getting lost, even in familiar places, staring either at specific things, aimless wandering, inability to find way around or over objects.

• Memory and learning

Inappropriate elimination outside litter tray, including in sleeping areas or near food. May be unable to recognise people or other pets.

• Social behaviour

Decreased interest in being stroked, or interacting with people or other animals or becomes increasingly dependent and doesn't like being alone.

• Anxiety

Restlessness, increaesed vocalisation and general irritability.

Since a number of these signs could arise from, or be aggravated by medical conditions, it is essential to complete a medical and behavioural history for the accurate diagnosis of FCD, this is especially important in older animals. This should be accompanied by a laboratory work up, as well as a thorough physical examination with special consideration of neurological conditions. As with all behavioural disorders it is important to ensure that any medical causes for unusual behaviour are ruled out. Medical conditions which could cause behaviour similar to that of FCD include:

• Arthritis
• Dental pain
• Thyroid dysfunction
• Diabetes mellitus
• Neoplasms
• Gastrointestinal conditions
• Reduced sight and/or hearing
• Urinary tract disease
• Hepatic disease
• Hypertension
• Neurologic conditions, including neoplasms, motor and sensory deficits
• Infectious causes, including FIV, FeLV
• Stress

Although all medical causes for FCD must first be excluded and if present treated, their presence does not necessarily eliminate the simultaneous existences of FCD. Conversely, failure to treat concurrent painful or debilitating conditions, such as arthritis, will lead to an apparent failure of response to FCD treatment.

Treatment

Depending on signs, treatment can include the following:

• Maintaining an environment that is stable and easily accessible by the animal
• Medication to improve sleep patterns
• Medication to improve cognitive function
• Medication to alleviate emotional problems (e.g. anxiety)

No drugs are currently licensed to treat FCD, however selegiline and propentofylline are sometimes used unlicensed. Serotonergic drugs, such as fluoxetine or clomipramine, may be used to reduce anxiety in cats that show predominantly emotional changes with minimal reduction in cognitive function, whereas drugs such as selegiline may be used when cognitive impairment is the predominant feature. It is important to note that selegiline must not be used concurrently with an SRI/SSRI drug, and that there should be a 2-week washout between the use of these drug types in order to avoid serotonin syndrome. There is little peer reviewed evidence supporting the clinical efficacy of dietary modification and supplementation in FCD, but diets and supplements including elevated levels of antioxidants, carnitine, phosphatidylserine, arginine, B vitamins and fish oils are commercially promoted for the treatment of FCD based on effects in dogs and laboratory animals.

Treatment and Management Approaches to Specific Behavioural Aspects of FCD

• Inappropriate Elimination: The many other potential underlying and aggravating medical and behavioural factors should be ruled out and/or treated. Increasing the number of litter trays available, either on different floors or in different rooms which are obvious to the cat and easily accessible (without high edges or being high up) may help avoid house soiling problems.
• Disorientation: Ensure that locations of food, water and litter trays are constant and that the cat's daily routine is maintained as much as possible. If a cat is extremely disorientated or confused it can help to reduce the area accessible to the cat, so it can find its way around more easily.
• Unusual Sleeping Patterns: Loss of eyesight and hearing may affect the cat's sleep patterns. Increasing daytime and evening activity through play and simulated foraging may enable the cat to sleep better at night, but sedatives may be needed. Anxiety associated with darkness or absence of owners at night may be improved with anti-anxiety medications.
• Exaggerated Vocalisation: This may be related to anxiety, or confusion and disorientation; the underlying cause should be addressed. Artificial pheromones such as the synthetic analogue of the F3 fraction of feline facial and flank marking pheromone may help to reduce stress, by increasing the strength of core territory chemical marks, but this has not been specifically tested in cats with FCD. Serotonergic medication, such as fluoxetine, may be used to reduce anxiety, or medication and diet modification may be used to improve cognition.
• Reduced Activity: The use of a specialised diet for elderly felines may help stimulate activity and mental function.
• Social Behaviour: If there are other animals in the household, provide various sleeping areas so the older cat is able to find a safe place to rest if it does not want to interact.

Changes to the cat's environment should be kept to an absolute minimum where possible. If changes are necessary they should be made very gradually and carefully, taking special care to reassure the cat, so as not to induce stress which can cause the display of further symptoms of FCD.

Prognosis

FCD is a progressive illness, however management and treatment measures can help to slow this gradual decline and occasionally allow cats to regain some of their lost mental function. In order to attempt to slow progression prompt intervention early on in the disease process is essential.