Telling the difference between brain tumor ataxia and potassium bromide ataxia in dogs
Is there a difference between the ataxia caused by potassium bromide, and the ataxia caused by a brain tumor in dogs?
If you clicked on this article, you already know why your dog is taking potassium bromide: to help prevent seizures from your dog’s brain tumor.
My parents’ dog was diagnosed with a brain tumor and put on potassium bromide for seizure control.
Potassium bromide may cause a side effect called ataxia, a drunken-like or staggering, off-kilter gait.
The chemical can also cause hind leg weakness (paresis). Both side effects may come and go (as in our dog), but may also be persistent, depending on patient tolerance and dose.
A brain tumor in a dog can also present with these signs.
Is there a way to tell the difference between the ataxia caused by a progressing brain tumor in a dog, and the ataxia caused by chronic use or increased dosage of potassium bromide?
“I agree both types of ataxia can look similar; however, there are a few clues that can help differentiate,” says Dr. Peter Gordon, DVM, Dipl. ACVIM (Neurology), with Boundary Bay Veterinary Specialty Hospital in Langley, British Columbia.
“Firstly, which limbs are involved?
“Unilateral brain tumors will often create proprioceptive deficits on one side of the body, since the right cerebral hemisphere controls the left limbs, and the left hemisphere controls the right.
“If the tumor is localized to one hemisphere, as it often is, the deficits will be on one (opposite) side of the body.”
Our dog had been on potassium bromide for about seven weeks before he suddenly took a turn for the worse.
The dog’s hind leg weakness became more pronounced, and I noticed a more pronounced drunken gait that came and went.
It was difficult to tell, however, if the weakness or tipsy-topsy gait was affecting only one side of the dog’s body.
Several times the dog outright plopped down on all fours as though suddenly losing strength, and just lie there — in locations he normally didn’t lie in.
During the dog’s rapid decline, in the middle of frenetic pacing, he suddenly plopped down and then struggled for several minutes to get up on his hind legs; I could clearly see it was a hind leg problem, but maybe it wasn’t and it just seemed that way.
Keep in mind that there was no reason why the potassium bromide would have, after all this time, suddenly caused this kind of difficulty getting up on all fours.
Dr. Gordon continues, “Since a drug side effect would be systemic and not limited to just one half of the body, hemi-paresis or proprioceptive deficits that are limited to one side point more towards tumor progression.”
In the days of the dog’s decline, I noticed that he somewhat staggered leftward, as though tipsy from alcohol, and made contact with the left side of his body into the washing machine.
The brain tumor was on the right side of the dog’s brain. I also noticed that other staggering episodes were leftward as well.
“Secondly, the patient’s previous treatment history can be helpful,” says Dr. Gordon.
“If the patient has been treated successfully with bromide for an extended period of time and the dose has not been increased, it would be very unusual for ataxia to develop that far down the road.”
Our dog was on a stable dose of potassium bromide.
“A blood bromide level can also be tested to see how much bromide is in the blood.
“If it is within an accepted therapeutic range that seems too low for the degree of ataxia, again tumor progression would seem more likely.
“Finally, if there is any further question as to the role the bromide is playing in the clinical picture, it can be diuresed (removed) from the body by flushing the system with intravenous fluids.
“Whatever ataxia remains after 24 hours of diuresis would be the result of disease.”
We didn’t have this done, but I just knew that the brain tumor was progressing, and that it was time to stop blaming our dog’s increased episodes of loppy gait and apparent hind leg weakness on the potassium bromide.
My perception that this was a hind leg weakness, rather than a weakness/clumsiness on one side of the body (left rear leg and left front leg), may have been tainted by my layman’s hope that “Hey, this is just ataxia from the potassium bromide,” rather than from an advancing brain tumor.
It’s also difficult for an untrained eye to discern exactly which limbs in a dog are compromised.
Dr. Gordon adds that cessation of potassium bromide may result in resumption of seizures.
Diureses of potassium bromide should always be done by your dog’s treating medical professionals in a well-monitored environment.
If you’re unable to tell what’s causing your dog’s ataxia — potassium bromide or brain tumor — bring this up to your veterinarian, rather than trying to fool yourself that after many, many weeks, the salt solution is still causing the ataxia or even causing more ataxia.
