Brain Tumor, Head Injury

by Roy F. Dvorak


A brain tumor is an abnormal growth in the brain. There are two types of tumors: primary and metastases. Primary tumors grow from tissues in the brain and their cause is unknown. Metastases are spread via the bloodstream from tumors in other places in the body. A tumor may be malignant. A tumor may also put pressure on the brain as it grows. Pressure on the brain tissue in the area of the tumor may cause:

  • loss of vision
  • motor coordination
  • seizures

Malcolm B. Willis and other noted authors state that a brain tumor is an “intracranial” cause of seizures. A tumor will probably occur in an older dog and “may leave the dog with a weak or paralyzed limb . . .”. According to the Dog Owner’s Home Veterinary Handbook, brain tumors occur in older dogs over 5 years of age. The MRI (magnetic resonance imaging) that we had performed on Korie would have shown a brain tumor; it did not. The MRI and CAT (computed axial topography) are the two most useful diagnostic tests to show brain tumors. Of all canine tumors reported, the brain tumor only accounts for 3.0% of these, a very small percentage. Over time, the tumor would grow and seizures would continue to occur and the anticonvulsant medications would not control the seizures caused by a tumor.

An injury to the skull would require a significant impact to cause an intracranial disturbance. If such an event did occur, then the seizures will not be observed immediately. The dog would not have seizures until weeks or even months after the event. If such an impact did occur, then the MRI would show an “abrasion” on the skull; it did not. The anticonvulsant drugs would not be effective against a skull injury. Since Korie’s last set of cluster seizures occurred in January 1997, we can safely say that her seizures are not due to a brain tumor or head injury. Korie’s MRI showed NO evidence of a brain tumor or skull injury or any other abnormality.

We have had Standard Schnauzers at our home for over 14 years and have had several rescue dogs too. In 14 years we have had ample opportunity to study them and their habits and mannerisms. We will admit that Korie is the smartest Standard that we have ever seen at our Schnauzer home.

Of all the text books that we have, only the one by Oliver and Lorenz discusses the neurologic exam. In their text, Handbook of Veterinary Neurology they devote their first chapter to the discussion of the neurologic examination. In lay person’s terms, the neurologic exam evaluates how the nerves of the limbs are “talking” or communicating to the central nervous system and the brain and how the brain is responding. The examination is divided into 6 parts:

  • observation
  • palpitation
  • postural reactions
  • spinal reflexes
  • cranial nerves
  • sensation

Dr. Luttgen performed the neurologic examination prior to Korie’s MRI and spinal tap. She repeated the postural reaction portion of examination for us to include on - Korie's video.

In the observation portion, the examiner notes the posture and movement of the dog. This can be done while the dog is allowed to roam and sniff around the doctor’s office. In the palpitation portion, the examiner notes the muscle tone and size. They also check for any abnormalities in the skin and skeletal system. In the postural reaction portion, the examiner evaluates the responses that maintain the dog’s posture. We included a portion of this examination in Korie’s video when Dr. Luttgen turned Korie’s paw to the sky. She also forced Korie to hop on two legs on one side of her body. In the spinal reflex portion of the examination, the examiner evaluates the integrity of the sensory and motor components of the reflex arc. An example of the reflex arc in humans, is the reaction of tapping the tendon below the knee cap. The impact of the small mallet causes the lower leg to jerk. The reflex arc is the path that the nerve signal takes from impact at the knee to the brain, and then the brain sends the signal to the lower leg to somewhat kick. In the cranial nerve portion of the examination, the examiner notes the position of the head, notes the symmetry of the eyes and the pupils, notes the reactions of the nose when touched, evaluates the mucous membranes of the mouth and tonsils, the symmetry of the tongue, etc. Finally, in the sensation portion of the examination, the examiner evaluates the dog’s response to pain based on the stimulus of the other tests.

Korie’s neurological examination did not indicate any abnormalities in her nervous system. It also indicated that there was no interference in her nervous system signals from her external sensors to her brain. This implies that she has no tumor in her brain or on her spinal cord that may inhibit any normal behavior or cause any abnormal behavior, i.e., seizures. This is additional evidence that allows us to safely state that her seizures are not due to a brain tumor or head injury or any other abnormality of this kind.

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