Cognitive dysfunction in cats: a syndrome we used to dismiss as 'old age'

Abstract

Practical relevance: Cognitive dysfunction syndrome (CDS) is a widely accepted diagnosis in dogs, with established treatment options. In cats, however, our understanding of cognitive dysfunction is still being shaped by ongoing research in the field, and limited treatment options are available. Recent clinical studies indicate that old age in the cat is accompanied by increased behavioural signs such as wandering, vocalization and night-time activity that are not attributable to identifiable medical problems. It is essential, therefore, that veterinarians include behavioural well-being in the routine care of senior cats.

Patient group: While the exact age of onset is not established, studies suggest that age-related behavioural changes consistent with cognitive dysfunction are prevalent in cats as early as 10 years of age and that prevalence increases significantly in older cats.

Clinical challenges: The diagnosis of cognitive dysfunction requires the identification of geriatric behavioural changes that are not caused by other medical problems, although the two may not be mutually exclusive. Therefore, the practitioner must rely heavily on owner reports and history to ensure prompt diagnosis and treatment. The absence of any approved dietary or pharmaceutical interventions for cognitive dysfunction adds a further challenge, although several possibilities exist.

Evidence base: This article draws on recent research that has produced neuropathological, cognitive and behavioural evidence for cognitive dysfunction in aging cats. As an impetus to further our understanding of this disease and potential treatment options, the authors propose a behavioural checklist that might aid in the clinical diagnosis of feline CDS and discuss treatment options that have proven successful in the canine counterpart of this disease.

(A) Aβ1–16 (using antibody 6E10) is distributed as a diffuse cloud in the outer molecular layer of the hippocampus (arrow-heads) and appears again in the subiculum (arrow) in a 17-year-old cat

(B) Two layers of cortical immunostaining for Aβ1–16 can be observed in the parietal cortex of an 18-year-old cat, suggesting both input and output to this brain region may be compromised

(C) The cerebellum typically remains devoid of Aβ but it was observed within Purkinje cells (arrows) in an 18-year-old cat

(D) A higher magnification of the cerebellum shows that Aβ accumulates as aggregates within the cytoplasm of Purkinje cells

(E) In one 21-year-old cat that had seizures, hyperphosphorylated tau (immunostaining with PHF-1) accumulates within individual neurons in the hippocampus

FIG 1

Cognitive test apparatus for cats. The subject in the picture is being tested on a discrimination and reversal learning test that occurs in two phases. Initially, the cat is required to learn that food is consistently found under one of the two objects (eg, yellow block). In reversal learning, which declines with age in cats, the object-reward association is reversed such that the cat then needs to learn that the food is now found only under the blue block. In either case, the incorrect coaster is baited with an unattainable reward, which prevents the cat from successfully responding using olfactory cues. Courtesy of CanCog Technologies, Toronto, ON

Switch, a 12-year-old male cat, interacting with a couple of enrichment devices: (left) a food-filled toy dangling from the doorway (Fun Kitty, Premier Pet Products), and (below) a food-filled toy that he is rolling around the floor (Slim Cat, PetSafe)

Patches at 19 years of age