SPINAL CORD DISEASES IN CATS

Drs. Randy Cross, DVM and Jay McDonnell, DVM, MS, Diplomate ACVIM (Neurology)

Spinal cord diseases in cats can be incredibly frustrating. The adventure starts with the uncooperative patient, winds its way through the dreaded neurologic examination interpretation, and ends in the sea of diseases that could be causing the clinical signs. It’s not easier for a board certified neurologist, but there are some things that we can share that might be helpful.

Tips on neurologic examination in cats

Cats essentially say, “I don’t want to play your game and I am not going to participate.” However, there are ways to get them to participate without their knowledge or even with their cooperation. If you need some reminders on the neurological examination, please see, “The Neurological examination of the cat” by Laurent Garosi in the Journal of Feline Medicine and Surgery, 2009 Volume 11. We would like to emphasize a couple of key points:

1. Gait Analysis – This is incredibly important in cats. Since time is always crucial, let the patient walk around the room while you are getting the history from the owner. Break the cat down into three segments, the head, thoracic limbs and pelvic limbs with tail. Evaluate each one separately then try to put it all together. Don’t forget to watch the movement of the tail: Does it drag or does it appear to be straight up as if to aid with balance, as in a vestibular cat?

2. Postural Reactions – In our experience, cats hate hopping and don’t like when you touch their feet. The best tests to perform are wheelbarrowing, extensor postural thrust and, especially, tactile placing using a table. Consistency is key in cats as one abnormal extensor postural thrust among four normal attempts means little.

3. Cranial Nerves – In addition to routine tests, remember to perform a fundic exam. Since infectious disease is one of the most common causes of spinal problems in cats, this test can be extremely helpful.

4. Spinal Reflexes and Appendicular Tone/Muscle Size – These tests are best performed with the patient lying in dorsal recumbency between your legs or by having a technician hold the cat so the pelvic limbs dangle for examination.

5. Spinal Pain – This should always be saved for last in cats, since their fuse can be short. It is important to ask the owner how the pet reacted to being touched on the back in the past. Many cats are merely hyperreactive and not necessarily hyperesthetic to thoracolumbar spinal palpation.

6. Orthopedic Versus Neurologic Disease – The more predictable an abnormal movement is, the more likely the cause is orthopedic. Cats that hold their limbs up are more likely to have orthopedic disease. Cats with difficulty holding their heads up usually have a neurologic disease.

Remember, the neuroanatomic localization is important because once you have it, you can utilize textbooks to help with your differential list. If you are uncertain where the problem is occurring, this is the time to refer. Localizing the problem correctly guides appropriate diagnostics, saves time and mitigates owner frustration.

Once you have your neuroanatomic localization, you can now consider the most likely differentials. There are a couple ways to look at this: first, based on categories (from most to least likely):

1. Infectious/Inflammatory

2. Neoplasia

3. Traumatic (including fracture, luxation, and Intervertebral Disc Disease)

4. Congenital/Inherited Disease (i.e., Storage Disease)

5. Vascular Disease

Or based on individual diseases:

1. Feline Infectious Peritonitis

2. Lymphosarcoma

3. Vertebral Tumors (with osteosarcoma most frequent)

4. Traumatic (fractures and luxations)

5. Vascular Disease

Or based on age:

Prevalence < 2 years old 2-8 years old >8 years old

1 Feline Infectious Peritonitis Feline Infectious Peritonitis Vertebral Neoplasia

2 Storage Disease Lymphosarcoma Vascular Disease

3 Bacterial Vertebral Neoplasia Lymphosarcoma

4 Trauma Cryptococcus Other Neoplasia

5 Lymphosarcoma Intervertebral Disc Disease Intervertebral Disc Disease

Using your history, clinical signs, and some of the disease prevalence guidelines, you can come up with your differentials. Here is some information on feline diseases you might not be as familiar with.

• Intervertebral Disc Disease: Yes, this happens in cats too. Discs are usually thoracolumbar or lumbosacral. If you have a cat with a cervical localization, disc disease should be removed from consideration. The average age is around 8-10 years old. Back pain, pain on tail manipulation and paraparesis/plegia are very common. Prognosis is the same for cats as with dogs: In general, if sensation remains intact and surgery is performed, a favorable outcome is ~90%.

• Vascular Disease: Interestingly, on many necropsies, multiple levels of the spinal cord are often affected. The cervical region appears to be a common location. These cats often have difficulty holding their heads up, along with tetraparesis/plegia and increased appendicular tone/reflexes. Fibrocartilaginous embolisms from the nucleus pulposus occur infrequently in cats, so a concerted effort should be made to look for other causes of vascular disease (hyperthyroidism, renal disease, heart disease, chronic pancreatitis, coagulopathy, diabetes mellitus, etc.). The prognosis for many cats is similar to dogs with vascular lesions if the underlying cause can be addressed; a favorable outcome is achieved in about 75%. Remember, these are vascular lesions of the spinal cord, and not the same as feline aortic thromboembolism, which carries a much worse prognosis overall (~25% favorable outcome).

• Neoplasia: Lymphosarcoma is the most frequent tumor affecting cats, representing up to 40% of all spinal tumors. The next most frequent tumor is osteosarcoma. The thoracolumbar and lumbosacral spinal cord is often affected. Pain is not a consistent feature of their examinations and clinical signs are more often symmetric. Younger cats are significantly more likely to have lymphosarcoma than other tumors and they test positive for FeLV in ~50% of cases. The prognosis for lymphosarcoma is poor to grave. Spinal cord meningiomas are infrequently seen, but prognosis for return to function and two year survival is good.

Overall, here are some helpful hints for when you should refer to a neurologist:

1. Persistent pain despite appropriate pain medications

2. Non-ambulatory status for more than one day

3. Plegia in any limb

4. Relapse or progression of the clinical signs with appropriate rest and medications (failure of medical treatment)