Introduction
The term Cognitive Dysfunction Syndrome (CDS) has been used to refer to the changes of behavior related to aging with cognitive skills deterioration, that do not stem completely from medical conditions and that are a consequence of a degenerative process of the SNC.(8)
Clinical Signs/Behavioral Changes
The term cognition, refers to mental processes that take place inside the animals and cannot be observed directly, it includes: memory, learning, conscience and perception.(5)
The changes of behavior related to aging can gather in 5 categories:
1. Loss of proper elimination behavior
2. Disorientation
3. Alteration or decrease of the interactions with the owners
4. Alteration of the sleep-wake cycle
5. Decrease of general activity
The behavior problems mentioned above can have several etiologies, therefore, it is necessary to rule out the medical causes before diagnosing CDS. The CDS is important because it constitutes a more frequent consultation to the veterinarian, due to medical knowledge and technology there is an increase number of dogs that come to an advanced age.(5,8)
Another relevant aspect takes root in that the CDS could be an equivalent to Alzheimer's disease in humans and it's study will help to understand the responsible mechanisms for this illness; the dog might be considered as a geriatric patient who presents signs related to the CDS as a model to study the Alzheimer type dementia (ATD) and to achieve a major advance in the investigation of the above mentioned illness.(5,8)
Prevalence of the CDS
It is difficult to know at what age CDS can start showing signs of, but his prevalence is higher with the overcome of the years. The life expectancy after the diagnosis is about 1.5-2 years.(1,3,5,8)
Etiology and Pathogenesis
In the dogs, senility is accompanied by some neuropathological lesions and changes in the neurotransmitters. It is known that the CDS in dogs is caused by the physical and chemical changes that take place in the brain due to aging.(2,3)
Histopathology
The neuropathology of the CDS in dogs is located especially in the cerebral cortex and in the hypocampus. The more significant histopathological remarks are the accumulations of ß-amyloid protein and the formation of plaques.
Physiopathology
Abnormalities exist in the neurotransmitters: decrease or unbalance of acetylcholine, serotonin, norepinephrine and dopamine. The loss of dopamine and norepinephrine can contribute to the cognitive deficits in the brains of old animals.(8)
The enzyme MAO-B catalyzes the decrease of the dopamine, producing free radicals. Some of the physical changes we can observe are: ventricles dilation, decrease of the size and cerebral mass, decrease in the blood flow, decrease in the number of neuron cells, fibrosis in meninges, degeneration of white brain and cerebellar mass and deposition of protein ß-amyloid plaques.
The decrease in the capacity of learning as a consequence of aging seems to be related to alterations in the function of the hypocampus.(2,4)
The diagnosis is completely confirmed by means of histopathologic tests of the brain tissue, since at first, diagnosis is by means of exclusion, ruling out possible competing pathologies and the most subjective observation of clinical unspecific signs that could be related to CDS.
Treatment of CDS
The CDS cannot be cured, but there are some therapeutic possibilities that are palliative and that can slow down the progress of the illness.
Treatment
1. Make a diagnosis to determine underlying pathology and be able to treat it accordingly.
2. Determine stimuli that causes or reinforce the problem.
3. Make environmental modifications that facilitate movement and social interaction in the patient.
4. Use behavior modification techniques to reinforce proper behaviors.
5. Pharmacological intervention:
a. Selegiline, a MAOI, to enhance dopamine
b. Nicergoline, an alpha adrenergic blocker, to enhance blood flow to the brain
6. Geriatric diet or the use of antioxidants to protect cells membranes and get rid of free radicals that are neurotoxic.(5)
"Didy", Presentation of a Clinical Case of CDS
Signalment: "Didy" intact female domestic mixed dog, 14 years old.
Chief complaint: aggression towards another dog in their household.
Findings in the case history: aggressiveness against her companion dog, barks at objects, looks at the wall for long periods, spatial disorientation within the house (roaming without a definite course), changes in the appetite, night insomnia, sleeps much during daytime, moans and vocalizes, urine and feces inside house.
Day 1, January 15th, 2005
Consultation at the HVE UNAM.
Anamnesis: The owners mention that "Didy" began to fight with her partner since November, attacks him for no reason, then, later returns to him and licks him as if nothing had happened. Two weeks ago, after fighting, she remained completely rigid and started barking, the owners were talking to her but she was not paying any attention, sometimes although there was no fighting, she began to bark to the window or to the wall. "Didy" does not want to go out and they have to drag her out to eliminate, the owner told the medical staff that she has diminished her general interaction with the human group and they notice a notable lack of interest to be with the human beings and to her canine partner.
She also shows some pain when getting up or while walking, there is a remarkable halitosis and bilateral opaqueness of crystalline.
Laboratory tests were made to know the general Physical status of "Didy", the results showed: hyperbilirubinemia and hyperphosphoremia, (hemolysis, lipemia). Hyperproteinemia, hyperglobulinemia and high values of triglycerides.
She was sent home medicated with Chondroitin sulfate 1 tab PO SID and vitamin E 400 UI PO SID until the next consultation.
Evaluation was suggested in the sections of orthopedics, soft tissue, ophthalmology; an EKG and dental cleanliness.
Integral profile is programmed. We arranged to meet in 13 days for more lab tests and in one month for a behavior consultation.
Day 31st, February 16th, 2005
Didy arrives for her behavior consultation at the HVE for her aggression problem and other undesirable behaviors.
Clinical History:The owners report "Didy" as showing aggressiveness against another dog, barking at objects, looking at the wall, getting lost, (does not find the door), walks around the house, collides with objects, remains a lot of time jammed behind an armchair and has stopped eating. The owners said also that "Didy" sleeps very much during daytime, and does not allow the owners to sleep at night because she strolls and wails constantly, urinates and defecates inside house. "Didy" does not want to go out anymore and they have to drag her out to eliminate. She has diminished the social interaction with the owners and with her canine partner.
Presumptive Diagnosis: Cognitive dysfunction syndrome associated with a loss of general sensorial function.
We send her home with this treatment:
Create an ideal environment for "Didy" where she feels comfortable and safe.
Clear off furniture and objects out of her way.
Create a much more predictable and reliable routines in her daily activity.
Educate owners not to punish her for vocalizing or eliminating inside.
To supervise her in a more close by way, lead her to eliminate more frequently out and when this is not possible keep her in an area of easy cleanliness.
Give her privileged attention time without the other dog's presence.
Supervise the interaction between both dogs, separate them if supervision is not possible, and favor the leadership of "Duke" over "Didy".
Increase walks and increase stimuli with "interactive toys".
Relaxation massages in pleasure body spots.
Gradual change in the diet to geriatric dog food.
A daily capsule of 400 UI of Vitamine E.
Selegiline 10 mg every 24 h AM.
Day 36 February 21st, 2005
"Didy´s" owners arrive at the hospital mentioning that the problem has been increasing. The owners told us that they can't give "Didy" the attention required and that the signs that "Didy" presents are already intolerable for a good quality of life so they ask to euthanize "Didy".
To discard some other problems, a general physical exam is realized, also a neurological, orthopedic, ophthalmologic examination and laboratory tests, since there were other differential diagnosis to be made due to the behavior showed by "Didy", it was possible to think as the first differential diagnosis a brain tumor such as meningioma or astrocytoma.
As the second presumptive diagnosis we have the CDS.
The euthanasia was performed.
Findings at the Necropsy
In the brain cranial cavity: the leptomeninges presented white areas and road surfaces compatible with calcification.
Microscopic description: presents gliosis, satellitosis and diffuse neuralgia, some neurons were appreciated as hyperchromatic. Likewise, red congo material (+) is observed in the average layer of some blood vessels compatible with amyloidosis.
Morphologic Diagnosis
Brain: Gliosis, satellitosis and diffuse moderate neuralgia with neuronal multifocal necrosis and deposits of congo red material (+) compatible with amyloidosis.
Comment: The histomorphologic alterations described earlier suggest that this animal coursed with the illness known as "Cognitive dysfunctional syndrome" (CDS) described in old dogs.
Discussion
The CDS is little known both by the Veterinarians and by the owners of affected pets. The CDS leads to behavioral changes in the patient and these changes lead as well to a deterioration in the human-animal bond with a dissolution of the affective tie between owner and dog. What is then translated in the decision of the owner to euthanize the patient; the whole situation could be avoided by knowing more thoroughly this pathology and considering it to be a differential diagnosis when a geriatric patient should arrive at the clinic. In order to do that, it is necessary to realize a complete clinical history and suitable physical exam to rule out systemic illnesses by means of laboratory tests. It is also very important to educate owners as to have real expectations with the treatment options, having only the option to slow down the process of cognitive malfunction and to increase the quality of life of the patient during the course of the illness.
Conclusion
It is important to stress out that, on having improved the quality of life of the small species, there has given the opportunity to live longer, this has increased the number of geriatric patient attended by veterinarians that work with dogs and cats; for which they must know the illnesses that affect them, being one of the most common but less recognized the CDS
References
1. Dodman N, Shuster L, Psicofarmacología de los trastornos del comportamiento animal. Buenos Aires República de Argentina: Intermédica 2000
2. Manteca X, Etología clínica veterinaria del perro y del gato. 2a ed. Barcelona España: Gráfica In Multimédicas S.A. 2003
3. Juarbe-Diaz, Behavior problems in older dogs. Knoxville: University of Tennesse, College of Veterinary Medicine.
4. Manteca X, Etología clínica veterinaria del perro y del gato. 3a ed. Barcelona España: Gráfica In Multimedias S.A 1997
5. Heiblum M Trastornos geriátricos. Memorias de Etología clínica en perro y gatos; 2003 marzo 5-8; México (DF): Facultad de Medicina Veterinaria y Zootecnia UNAM, 2003:69-75
6. Landsberg G, Hunthausen W, Ackerman . Manual de problemas de conducta en el perro y el gato. Zaragoza España: Acriba S.A. 1998
7. Aminoff M, Greenber D. Neurología clínica. 3a ed. México: Manual moderno, 1998
8. University of Georgia, continuing education courses November 2001 Update on diagnosis and treatment of small animal behavior problems.