Cognitive Dysfunction Syndrome in Cats

What is Cognitive Dysfunction in Cats?

Sixteen years ago when I left my residency and started out as a newly minted neurologist, feline cognitive dysfunction syndrome (CDS) was not on my radar. That has changed. As we learn more about aging in cats, it has become a more widely recognized disease by yours truly, as well as many of you in practice. If you're like me and need a Tidbit-Tuesday style refresher...read on!

What is cognitive dysfunction syndrome?
Cognitive dysfunction syndrome (CDS) is a term used to describe deterioration of mental capabilities associated with age.  Clinical signs referred to cognitive dysfunction can also be associated with other age-related illnesses (e.g. osteoarthritis, structural intracranial disease such as neoplasia, or cardiovascular disease). See table 1 for an outline of behavior changes seen in cats with CDS.
The underlying etiology of CDS is yet unknown. Causes such as oxidative stress/damage, neurodegeneration  and vascular changes are among the leading hypothesis for human and canine CDS, and therefore suspected to be similar in feline CDS.  Deposits of extracellular B-amyloid and intracellular accumulation of microtubule-associated protein tau have been seen in human patients with cognitive dysfunction. Similarly,  B-amyloid deposits and increased tau have been detected in aged cats with cognitive decline, however the significance remains unclear. 

What are the clinical signs of cognitive dysfunction in cats?
There is a handy article, recently published in the Veterinary Clinics of North America by Dr. Miele and associates that echos what others have been reporting in a very concise little table. (See reference at bottom) I have replicated this table, with a few modifications, here. Note: There are other signs such as decreased appetite or thirst, that don't usually drive an owner or veterinarian to seek consultation from a neurologist so I haven't included them here. 

Table 1: Clinical behavioral changes associated with CDS in cats.Increased vocalization, especially at nightAltered social interaction and relationships, either with other or other pet. Altered sleep/wake patterHouse soilingSpatial Disorientation or confusion (i.e. forgetting the location of the litter box)Temporal disorientation (i.e. forgetting if they have been fed)Altered activity (i.e. aimless wandering)AnxietyLearning and memory dysfunction
How is CDS in cats diagnosed?
Oh, this is as tangled of a web as the tau proteins we chase. (A little CDS humor here...you see the tau proteins can cause the "tangles" seen in human CDS.). Currently, the diagnosis is made by ruling out structural brain disease and systemic causes for disease. This may include complete blood count, full biochemistry panel including thyroid screening, urinalysis, chest radiographs, blood pressure assessment, brain MRI and possibly spinal tap. Imaging changes associated with canine CDS include increased depth of the sulci, dilation of ventricles secondary to neuronal loss (called ex vacuo hydrocephalus) and a measurably small interthalamic adhesion. Exclude everything else, and it's probably CDS.

How can we help these cats age easier?
Currently, there are no proven treatments for feline CDS.  The addition of antioxidants (B vitamins, vitamin C, other) as well as fish oil were evaluated for use in cats in one study and showed promise. The use of S-adenosyl-L-methionine (SAMe) has been recommended for cats based on a study that identified improved performance on cognitive testing. This study only found significant improvement in cognitive function testing in the least affected cats. In addition to medical management, environmental management with ready access to food, water, litter box and areas of comfort (beds, hiding spots) is recommended. Environmental stimulation with low impact toys, or bird feeders in which the cat can choose to ignore any activity if they do not feel inclined to engage, are recommended. Finally, focused veterinary visits can be important for cat owners to feel supported through the aging process. Focus your exam specifically evaluating body weight, urine production (to assess for signs of dehydration), behavior changes and mobility.This may help detect signs earlier in the course of disease and to identify concurrent morbidity that may contribute to, or be confused with, cognitive dysfunction.

Did I forget anything? Most of you treat and see this more than I do. What do you see in practice? What have you used (successfully, or not) for treatment? Please reach out - I want to hear your perspective!

Reference:
Miele A, Sordo L, Gunn-Moore DA. Feline Aging: Promoting Physiologic and Emotional Well-Being. Vet Clin North Am - Small Anim Pract. 2020;50(4):719-748. 

What Do You Do With a Confused Cat?

What do you do with a confused cat?

Sigalment: 12 year old FS Domestic short-haired cat
History: 2-3 week history of seeming "confused", and a recent onset of circling right more than left. These very astute owners observed the cat seemed to walk into a room, forget why it entered, stand there, and then leave again. Additionally, she wasn't as bright as is typical for this indoor-outdoor Wisconsin cat. Birds would land on the feeder outside of the window and she appeared uninterested. 
Physical examination: Normal TPR, normal exam. This was a remarkably fit cat for her age!
Neurologic examination:
Mentation: Obtunded
Cranial nerves: absent left menace response, normal PLR and normal menace response on the right. The cat was less responsive to facial stimulation on the left lip but did respond to hemostat pinch. All other cranial nerve exam findings were within normal limits. 
Gait: Ambulatory with mild proprioceptive ataxia and occasional circling right
Postural reactions: absent tactile placing left pelvic limb, intermittent on left thoracic limb, normal on right thoracic and pelvic limbs. 
Spinal reflexes: normal all limbs, and c. trunci

Okay..take a moment and put all of that together in your mind. I'll take this moment to remind you that my next Webinar is on Wednesday July 15th (TOMORROW) and we'll be talking about lesion localization. If you're interested in joining me to practice on cases just like this please go to https://barnesveterinaryservices.com/ce-opportunities and sign up!

Back to this case. How did you do? Here is how I would talk myself through this one...
1. The cat has a change in mentation..the problem MUST be intracranial.
2. There is a menace deficit - the affected parts could be cranial nerve 2, forebrain or cranial nerve 7. 

• 2a. PLR is normal (this is cranial nerve 2, midbrain and cranial nerve 3) so we can eliminate cranial nerve 2 as a possible cause of the menace deficit. 

• 2b. The cat did not have any noted change to motor of the face (run by cranial nerve 7), so we can eliminate cranial nerve 7 as a cause for the menace deficit. 

• 2c. Finally, one must remember that the menace response crosses and enters the opposite side forebrain so, since we have narrowed the problem down to the forebrain we then must comment that it is the RIGHT forebrain we are concerned about

3. Circling is either a vestibular or forebrain sign. This cat did not have evidence of vestibular disease so we could consider this another forebrain sign. Animals circle towards their lesion, thus supporting a RIGHT forebrain lesion. 

So far, so good?

4. Tactile placing goes from the toes, up the ipsilateral spinal cord, brain stem (crossing at the midbrain) and enters the opposite side forebrain. Voila! We don't have any evidence of spinal cord disease, or brain stem disease in this cat (no cranial nerve deficits) so this also suggests a RIGHT forebrain lesion. 

What about that sensory deficit on the cranial nerve exam? This actually suggests a proprioceptive change to the face! This finding might be the only finding we didn't routinely teach in veterinary school because it's an oddity. But, it is a crossing tract and reflects forebrain disease. 

So, what lesion localization did you come up with? Scroll to the bottom to see if you are correct.

Diagnosis
We diagnosed a brain tumor on MRI (see image above) and took this kitty to surgery. The mass was removed entirely, and was eventually diagnosed as a meningioma. Meningiomas are locally invasive, rarely spreading, intracranial tumors in cats. With complete surgical resection no additional treatment is needed! The cat went back to her normal personality, stopped circling, and regained vision in the left eye post operative (by the 1 month recheck...not immediately). Pretty cool stuff, huh!?

I hope you have a safe and fun week. Keep those consults coming and I hope to see you at the Webinar tomorrow!

Answer: RIGHT forebrain. 

Portosystemic Shunts and Their Effect on the Nervous System

Portosystemic Shunts and Their Effect on the Nervous System

Portosystemic shunts (PSS) are common in small breed dogs and surgical correction is commonly recommended. However, there is concern about neurologic signs peri-operative for these patients. Some develop seizures, mentation changes, and other neurologic signs before shunt attenuation while others do not show signs until after shunt attenuation. Sadly, the presence of neurologic signs is a poor prognostic indicator according to many studies. One recent study looked for prognostic indicators in dogs that develop seizures post attenuation (PAS) within 7 days of surgery.  I hope you'll find the study as interesting as I did!

Study Design

This was a retrospective study including 93 dogs from 14 different institutions. 53% of dogs received prophylactic levetiracetam. There were lots of different small breeds with a median age of 34 months (range 5-124 months). 

Results

• 17.3% of the dogs had experienced at least 1 seizure prior to surgery.

• Interestingly, 78% of the dogs had exhibited neurologic abnormalities including those with seizures.

• Only 30% of dogs with PAS survived to 30 days. Yikes.

• More often those with focal seizures survived, compared to dogs with generalized seizures.

• Sadly, the most common reason for euthanasia following the shunt was the presence of uncontrolled seizures. 

Key Points

According to their multivariate analysis the only two factors associated with short term survival were 1) having a history of seizures PRIOR to shunt correction (p=.004) and 2) the development of focal PAS (p=.0003). That's it! 

So, what do we tell our clients? Well, for starters..they need to know that these pets are are risk of developing seizures even if they DON'T have surgery. But, according to this study if they do elect surgery, the development of generalized seizures is a poor prognostic indicator. 

This article was packed with other data so if you want to read the entire thing please reach out and let me know. 

Reference:
Mullins RA, Sanchez Villamil C, Selmic LE, et al. Prognostic factors for short term survival of dogs that experience post attenuation seizures after surgical correction of single congenital extrahepatic portosystemic shunts: 93 cases (2005-2018) Vet Surg.2020; 49:958-970.


That's it for now! I'm maintaining curbside service for the summer and am starting to widen my travel radius again. Please reach out if I can asist with a case. Stay safe, stay healthy!

Prevalence of Idiopathic Epilepsy in Dogs

Idiopathic Epilepsy Update!

A recent article out of the Vet Record by Dr. Rachel Hall and colleagues outlines the prevalence of idiopathic epilepsy and structural epilepsy in dogs.* I found this a very interesting read, packed with useful information so I thought I'd pass along a bit (get it?) of it to you!

Study Design and Points Worth Noting

• This is a retrospective study based out of the UK. 

• 900 cases with MRI, a neurologic examination and medical record history were included. (wow!)

• Structural epilepsy is defined as a seizure disorder secondary to an identifiable structural cause. Examples include neoplasia, meningoencephalitis, hydrocephalus, etc.

• Idiopathic epilepsy is defined as the lack of identification of a structural abnormality in a pet with 2 or more discrete seizures. 

• Small (< 10 kg), medium (10-20 kg) and large breed (>20 kg) dogs were represented in approximately the same percentage in this study.

Results of Interest (there are a lot of interesting results in this study!)

• About 50% of the dogs were between 6 months and 6 years old, and 50% were > 6 years old. 

• About half of the dogs had structural epilepsy based on abnormal MRI findings

• The other half of dogs had no significant findings on MRI and the majority were classified as having idiopathic epilepsy. (The others had toxin and metabolic disease diagnosed).

  • Prevalence of idiopathic epilepsy in dogs in the UK? 50%!

Okay, fine (you might think) how does knowing the prevalence of idiopathic epilepsy in dogs in the UK help me?

I'm glad you asked...

• Idiopathic epilepsy was the leading diagnosis for dogs between 7 months and 6 years old. Inflammatory brain disease was second.

  • Take away point? Meningoencephalitis is NOT rare! Oh, and idiopathic epilepsy is most common in the group of dogs we thought it would be most common.  

• Idiopathic epilepsy was also the leading single diagnosis (34%) for dogs over 6 years of age. HOWEVER when they combined all types of neoplasia together into one group they found 43% of dogs over 6 years of age had neoplasia making it the leading singe diagnosis in this group.

  • Take away point? Read that sentence above again! I considered making this TidBit Tuesday a one line update because it's so critical to make sure we don't forget that "old" dogs can actually have idiopathic epilepsy!

  • Also, dogs over 6 years of age had structural epilepsy more often than idiopathic epilepsy if all causes for structural epilepsy were combined. (Not surprising, I know.)

What do you do with this information?

Do a neuro exam on every patient with a seizure history!

• If the exam is NORMAL, include idiopathic epilepsy on the differential diagnoses list, regardless of age. 

• If the exam is ABNORMAL, include causes for structural epilepsy on your differential diagnoses list, regardless of age.

Thanks for reading - I hope you have a great week!

Reminder! Upcoming Webinar "The Neurologic Exam for the Busy Vet" on Wednesday May 27th 12-1pm and repeated 7-8 pm.
Check out my website at www.barnesveterinaryservices.com for details and registration.

* Hall R, et al. Estimation of the prevalence of idiopathic epilepsy and structural epilepsy in a general population of 900 dogs undergoing MRI for epileptic seizures. Vet Record 2020.