Tumors in Dogs

MENINGIOMA: A DIAGNOSIS WITHOUT CLEAR DIRECTION

Kayla, a 6-year-old spayed female German Shepherd owned by a local veterinarian, presents with a history of recent onset seizures. Although Kayla shows no other signs and her neurologic examination is otherwise normal, a prefrontal meningioma is certainly a consideration. MRI confirms this diagnosis within a few days, and Kayla heads to the surgery table. The tumor is approached through her frontal sinus and a large portion of her right olfactory tract is removed so that there are clean margins. Kayla’s recovery is uneventful and she goes on to run, play and be the wonderful family member she was before this ordeal first started. She never has another seizure and she lived for three years eventually succumbing to suspected tumor regrowth at the age of nine.

Of course, we best remember our successes, but the decision making process surrounding this most common of brain tumors is not so straightforward.

At least 85% of the older dogs that we see with recent onset seizures have a brain tumor. The vast majority of those are meningiomas and those patients that present without other neurologic signs, are most likely to have a prefrontal neoplasm that must be irritative but not affecting critical neural pathways. Most of these dogs present with seizures. These seizures can most often be terminated in the short-run with corticosteroids.

We know that the Golden Retriever is over represented with this particular neoplasm and more often than not, their meningiomas are in this prefrontal location. Although brachycephalic breeds have a higher incidence of brain tumors, they do not often have meningiomas. Boxers often present with brain tumors at a younger age (five to eight years) and typically present with additional signs of intracranial dysfunction such as “head-pressing”, circling, compulsive pacing and behavioral changes as well as seizures.

Although all meningiomas arise from arachnoid cells, there are several types of meningiomas. It is difficult to distinguish between them based upon MRI findings. In cats, meningiomas tend to compress the brain as they grow and their growth is assumed to be quite slow because the severely compressed cortex looks rather healthy once the neoplasm is removed. In dogs, it is far more likely that the meningioma will actually invade the brain tissue itself and for that reason, the tumor is often much more difficult to remove. Although we often state that canine meningiomas are slow growing, the evidence that this is true is anecdotal at best.

As in all things oncologic, there are several treatment options available. Radiation, as the sole therapy, has limited use with this particular tumor type in my opinion. In the few that I have followed, radiation shrinks the tumor somewhat (about 10%) and then it begins to grow again within a very short period of time.

We have placed dozens of dogs on CCNU using a modification of the protocol first described by Dr. Lisa Fulton and me in 1982. Whether this is a good primary protocol is unknown. We do not have any cases where there is a biopsy diagnosis and a follow-up autopsy that shows there is complete tumor remission. Nor, do we have any cases where the follow-up MRI shows complete regression of the tumor. We do, however, have numerous cases that have survived for the entire treatment course of twelve months and beyond. We have a handful of cases where the owner reports modest to complete recovery but, when the MRI’s were repeated, the tumor is unchanged or mildly smaller in size.

Surgical excision of this neoplasm is quite popular among those neurologists that perform surgery. Wide excision, with tumor-free margins, should theoretically be curative. This has not turned out to be the case and in several patients tumor re-growth has been discovered at some distance from the original surgical site. Whether this represents seeding from the original surgical removal, or is the result of the meningeal tissue being specifically prone to forming tumors at this time in the animal’s life, is totally unknown. An even more bothersome aspect of these meningeal re-growths is that the tumor can re-grow at a truly impressive rate. We have removed neoplasms that are only 1 cm3 in volume and tumor re-growth twelve weeks later reveals a neoplasm at the surgical site that is ten times larger. Does this reflect an enhanced growth rate related to some factor involved in the original surgery or was this a fast-growing neoplasm from the onset? These questions remain unanswered.

Over the years and after hundreds of meningioma surgeries, I, in conjunction with the neuropathology department at The University of Pennsylvania, have gone back over dozens of meningiomas to see if there is some association between the behavior of the neoplasm and the histopathologic type of meningioma removed. To date, no hint of an association has been discovered. It is quite remarkable that a meningioma in the same location, presenting with the same clinical signs and the exact same MRI findings, is likely to be one of several different types of meningiomas recognized by the WHO (World Health Organization). The WHO recognizes nine different types of meningioma.
1) Meningotheliomatous
2) Fibrous
3) Transitional
4) Psammomatous
5) Angiomatous
6) Papillary
7) Granular Cell
8) Myxoid
9) Anaplastic

We have also seen no correlation between tumor size and the success rate of any of the treatments. This surprisingly includes cases involving the surgical removal of very large tumors sometimes yielding the best patient response and longest survival times.

We currently are following an 11 year old, German Shepherd that presented with a single generalized seizure. An MRI revealed a pea-sized prefrontal meningioma-like lesion. We discussed surgical removal, but the owner elected to wait and see what happens without treatment of any kind. We repeated the MRI on this dog six months later and the tumor was unchanged in every way. We hope to follow this dog with additional MRI studies and are hopeful that, ultimately, the diagnosis will be confirmed on autopsy.

We have a handful of dogs whose tumor was removed a second time, after confirming they have regrown. We have had a small number of owners ask that radiation or chemotherapy be performed on animals that have had a surgical excision. It is hard to know the impact of these follow-up treatments, when we include a substantial population whose tumor never returns once it is removed. A corollary to this includes the fact that on presentation, the average age of these dogs is ten and they therefore may succumb to other age-related diseases before we actually know how the tumor or the surgical site might behave.

With all of this experience and with so few really dependable facts, the discussion with the pet owner about their best choices is both challenging and extensive. As with any treatment plan, the veterinarian wants to know the percentages when discussing complications and successful outcomes with the client. Although our experience in treating prefrontal meningiomas at VRA extends over three decades and includes hundreds of cases, dependable facts that apply to this very common brain neoplasm have neither surfaced in our collective literature nor our collective experience.

Categories: Canine Brain Tumor Surgical Considerations

Video Blog: Dog Rehab with Bear Bells Exercise

This exercise has this strange name because of the device we used to use to reinforce this exercise. Bear bells are Velcro straps with a free hanging bell attached that one can obtain from any camping store. They are to be placed on one's backpack when one is in the Bear Country so the Bear can hear you coming. This encourages the Bear to leave before you reach them or if the Bear is hungry get out the condiments before you reach them. In the same way, we can use this contraption as a therapy device!  

A strap-like device that is placed above the hock or "ankle" in the dog will generally get their attention and they will start lifting the limb higher in the leg with the strap. In dogs that drag their toes this encourages them to lift their limbs higher and we often can retrain them to have a better less traumatic gait. In our experience, the bell sound which was supposed to reinforce the change in gait doesn't seem to have much effect on most dogs and the bell itself seems unnecessary.

We commonly use Velcro straps that are readily available and also find that pony-tail scrunchies are excellent for this exercise. There are a large number of variations on how to use these straps and scrunchies, and we recommend that our rehab specialists try variations on your dog till we find the most effective method. Bear Bells is an extremely common home exercise that we recommend.

Categories: Rehab Exercises

Video Blog: Tail Pull Rehab Exercise for Dogs

As some dogs age they have a tendency to have entrapment of their nerve roots at the caudal spinal canal above their tails. Dogs who are afflicted with this problem may be predisposed to this condition because their spinal canals are particularly narrow at that level. Although this condition represents quite a number of various degenerative changes, these dogs are commonly lumped into the category of Cauda Equina Syndrome. Cauda Equina literally means horses' tail and the end of the spinal canal with its many nerve roots looks very much like a horse's tail. The presentation for this condition is quite variable. Hindlimb lameness or gait abnormalities as well as a weak tail and sometimes a loss of control over urine and stool are most common.

The surgical treatment for this condition has been well described and has a high rate of success, but since many of these dogs are older, a more conservative approach is desirable. Several years ago it was noted in cadavers that when the hind limbs of dogs were pulled forward that the entire lower spinal cord and roots moves as much as three-quarters of an inch. This should come as no surprise to any one who has tried sitting in a chair with their head tucked down against their chest knows that with a straight leg lift one can feel the tug on the spinal cord from one end to the other.

Several years ago in response to this information we initiated conservative treatment for Cauda Equina Syndrome with aggressive tail manipulation. To our surprise we determined that we were experiencing about a 75% improvement rate in cases.

Although the success of this therapy seems to require aggressive manipulation that really should be performed by our rehab therapists on a regular basis, our home program includes straight tail pulls performed by the owner (see the attached movie).

Sit behind the dog and place a hand on the caudal "points" of your dog's pelvis (the ischia) on each side of the anus and pull for five to 10 seconds straight back with quite a bit of force. This should not be painful and should be repeated 4-5 times per session and 3-4 sessions per day is recommended.

Categories: Rehab Exercises

Video Blog: Exercises for Dogs with Spinal Problems

Cookie Stretches are one of the best exercises for dogs with spinal problems who are not experiencing acute pain or clinical signs. It has been well documented in man that these kinds of stretching exercises decrease the incidence of back and neck problems and the hope is that those results will carry over to our canine friends.

To start Cookie Stretches one stands behind the patient and stabilizes their pelvis. The idea is to prevent the dog from actually turning and rather stretch the back and neck tissues themselves. Once the pelvis is stable then the dog is encouraged to take a treat from one side then the other in a slow alternating manner. Dogs with back and neck problems will have very little mobility and will not be able to reach all the way back to their hips or tail but with time most dog's flexibility increases quite dramatically.

This is an excellent exercise to perform first thing in the morning before your dog goes out into the yard or for his first walk. As with most rehab exercises, it is best to perform this activity for a short period of time, i.e. a couple of minutes, rather than setting aside a long period of time considering the nature of the dog's attention span. Likewise these exercises are best performed multiple times per day rather than attempting a long single session per day.

Once a significant amount of flexibility is attained, more advanced stretching can be attempted including activities like "sit-ups" and stretching by moving the head through various planes not just side to side.

Categories: Rehab Exercises

Video Blog: Sit to Stand Exercise for Dogs

The "Sit To Stand" exercise is one of the most common exercises that we give to our dog owning clients. In so many cases we are working with dogs that have hindlimb weakness. This exercise can be compared to weight-lifting exercises to buiold strength.

The dog is positioned head away from the owners body with the owner kneeling or crouching over the dog. The hind limbs are squared up so that the paw's position on the ground is directly under the dog's hip joints. In small dogs the thumbs are placed over the tops of the pelvis and the pinkie fingers are placed behind the knees. Pressure is placed downward over the pelvis at the same time that the pinkies are pressing on the backs of the knees. This forces the dog to squat and the resistance the dog places against this movement tires the muscles used in standing. Three or four sqats is the correct number to start with and one quickly gets a feel for the number that is takes to tire these muscles. Like most rehab exercises, this one should be performed 3-4 times per day and shouldn't take more than a few minutes each time. Working on this exercise for a longer period of time is counterproductive.

In smaller dogs it often helps to put your "Pinkie" behind the knee to get the stifle (knee) to flex while pushing on the pelvis (hip bones).



In larger dogs it is not possible to position ones Pinkie properly and some pressure can be exerted behind the hamstring muscles. In very large dogs it is often necessary to place one's shoulder over the pelvis to produce enough downward force to cause a squat.

Categories: Rehab Exercises