Page 693 - Small Animal Clinical Nutrition 5th Edition

718 Small Animal Clinical Nutrition

Box 35-1. Clinical Observation of Cognitive Dysfunction Syndrome in Cats.
VetBooks.ir The presenting complaints of 83 senior cats referred to veterinary feline cases in which concurrent medical conditions could not be

behaviorists were house soiling (73%), intraspecies aggression (10%),
aggression toward people (6%), excessive vocalization (6%), restless- entirely ruled out. Thus, although signs of anxiety are common in aging
cats, age-related brain pathology (CDS), environmental changes and
ness (6%) and excessive grooming (4%). However, there is a much medical problems might be factors. Conversely, the diagnosis of a
wider range of subtler and more frequent behavioral changes seen by medical problem does not exclude CDS because both could exist con-
owners that may not be reported and are unlikely to require referral. currently.
A second study was intended to evaluate the prevalence of clinical To date, few systematic laboratory studies have looked at changes
signs in a population of otherwise healthy cats that were presented for in cognition across the lifespan of cats. As described above, however,
annual examination or other routine care. Owners of 154 cats aged 11 owners of senior cats report age-related behavioral problems. It is also
and older were asked, using a questionnaire (similar to the canine known that cats develop age-related neuropathology that theoretically
questionnaire in Table 35-1), about whether their cats showed any underlies cognitive decline (described in detail below). For example,
behavioral signs such as altered activity levels, increased anxiety, night one study found that development of diffuse senile plaques in the
waking, increased vocalization, house soiling, altered responsiveness brains of three aged cats was correlated with behavioral changes
to stimuli, alterations in interactions with people or other cats and evi- including wandering, confusion and inappropriate vocalization. In a
dence of confusion or disorientation. After removing cats with medical more recent study, a range of cognitive deficits from mild to severe,
problems, 50% of those aged 15 years or older were diagnosed with including wandering, inappropriate vocalization, confusion/getting lost,
cognitive dysfunction syndrome (CDS); altered activity levels, aimless decreased grooming, lethargy, loss of housetraining and decreased
activity and excessive vocalization were reported most commonly. affection and recognition of owners, was reported in four out of five
Additionally, 28% of cats aged 11 to 15 years had signs of CDS; cats aged 16 years and older. Development of laboratory-based tests
altered social interactions were reported most commonly. for cats will allow the correlation of age-related behavioral problems
In an attempt to further determine some of the more common with neuropathological changes and may allow detection of cognitive
behavioral problems for which owners seek veterinary advice, 100 decline in younger cats, as has been found in dogs.
recent Veterinary Information Network (VIN) postings about senior cat
(aged 12 to 22 years) behavioral problems were reviewed. The most AGE-RELATED NEUROPATHOLOGY IN CATS
common complaints were vocalization, altered sleep-wake cycles, Beta-amyloid (Aβ) has also been studied in the brains of cats although
night-time anxiety, nighttime restlessness, inappropriate elimination not as extensively as in dogs. The first study to look at Aβ pathology in
including spraying, confusion, disorientation, wandering, pacing, anx- cats consisted of immunohistochemical staining of the brain of three
iousness, restlessness, irritability, aggression, fear/hiding, increased family cats aged 15, 16 and 20 years old. According to their owners,
attachment/“clingy” behavior and decreased interaction with owners.A all cats exhibited abnormal behavior within the final years of life includ-
few problems were reported in only single cats. These included depar- ing wandering, confusion and night-time howling. The 20-year-old cat
ture anxiety, pica (cardboard) and scratching. Pain (e.g., arthritis, den- was specifically described as having behavior “suggestive of
tal), decreased mobility, metabolic problems including hyperthyroidism, Alzheimer’s Disease.” Pathologic analyses revealed that all three cats
renal and hepatic disease, hypertension, concurrent drug therapy, displayed age-dependent increases in Aβ pathology very similar to that
vision or hearing loss and forebrain lesions (particularly meningiomas) found in aged dogs, with diffuse deposits (sometimes spanning the
were the primary rule outs suggested by VIN specialists. Although entire cortical depth) and smaller, denser deposits in various cortical
many of these cases had sufficient workups to rule out all possible layers. Senile plaques were also assessed in seven aged cats of vari-
medical causes including physical and neurologic examinations, urinal- ous breeds (12 to 20 years old) that had no abnormal behavioral
yses, blood tests (including thyroxine measurement), radiographs and reports when they were alive. In this study, only three aged cats, two
blood pressure evaluation, few cats had magnetic resonance imaging. 18 year olds and one 20 year old, had senile plaques that were
Furthermore, the effects of arthritis and hearing and vision loss were immunoreactive for Aβ in the temporal and occipital cortex. In another
difficult to assess. In 11 cases, a recent change in the household study in which the brains of seven Siamese and seven domestic short-
including the death of another pet may also have contributed to anxi- hair cats (aged 7.5 to 21 years old) were examined, Aβ deposition was
ety. In comparison to the canine data (See text.), there were far more detected by various antibodies in different brain structures of all 14

aging dogs, which then progresses to repetitive behaviors, rest- impairments at an initial interview developed at least one sign
less pacing and compulsive disorders. of CDS at a followup interview 12 to 18 months later. In the
same study, 48% of dogs that initially displayed one behavioral
Risk Factors disturbance had impairments in two or more categories at fol-
Age is a risk factor for CDS. Behavioral disturbances are re- lowup (Bain et al, 2001).
ported with increasing frequency in dogs around 11 years of age To date, age is the only risk factor for CDS that has been sys-
(Bain et al, 2001; Landsberg et al, 2003; Neilson et al, 2001). tematically studied in the clinic and laboratory, although other
Initially, these changes might be subtle and seem innocuous to risk factors are possible, such as breed (larger breeds might have
the client; however,in many cases they progress to include more an earlier age of onset), previous head trauma or occurrence of
clinical signs and/or signs of increasing severity that affect the microvascular accidents. Consistent breed differences in suscep-
pet’s quality of life and the owner’s ability to care for the pet. tibility to CDS have not been reported; however, a potential
For example, in one study, 22% of senior dogs that had no genetic predisposition for development of CDS can be inferred