Category: neurological-disease-cats

Ischaemic myelopathy

Back (spinal) problems are not common in cats. If your cat has a spinal problem they may have neck or back pain or show a variety of signs including difficulty walking, jumping, using one or more legs or even complete paralysis. These signs may occur suddenly (acute spinal problem) or more progressively (chronic spinal problem).

Many different spinal problems (slipped disc, fractured spine, spinal infection, spinal tumour, ischaemic myelopathy) can cause similar signs. Ischaemic myelopathy is only occasionally seen in cats but comes on very suddenly without warning and can be very frightening. If you suspect your cat might have a spinal problem (especially an acute one) you should make sure your vet checks them over as soon as possible.

Ischaemic myelopathy is a disease of the spinal cord (myelopathy) caused by a poor blood supply (ischaemia). Like any other part of the body, the spinal cord relies on a permanent blood supply to bring nutrients and remove waste products. Arteries supply defined segments of the cord on each side. If one of these arteries becomes blocked the blood supply to a particular area of the spinal cord is shut off and this causes damage to the nerves running there.

The most common cause of blockage is a fragment of the cushion (disc) between the bones in the back. This disc is made of a tough cartilage (fibrocartilage) and so the term fibrocartilagenous embolism (literally meaning fragment of fibrocartilage blocking an artery) is often used to describe the condition. There are many theories, but no-one really knows how or why this fragment of intervertebral disc suddenly gets into the spinal cord artery. There are many other more unusual causes of blockage (a fragment of tumour or fat).

Ischaemic myelopathy is only occasionally seen in cats. This condition can cause paralysis of one back leg, both back legs, all four legs or only one side of the body (depending on which portion of spinal cord is affected). Typically, this paralysis comes on suddenly, is not painful and does not get worse with time (at least after the first 24 hours).

Other diseases that cause sudden paralysis and may be mistaken for ischaemic myelopathy include spinal fracture or dislocation (“broken neck” or “broken back”), spinal cord bruising (spinal cord contusion) caused by a road traffic accident or a bad fall. “Slipped disc” (intervertebral disc herniation) is considered rare in cats and often seen as a result of spinal trauma.

A diagnosis of ischaemic myelopathy is often made by ruling out other causes of acute paralysis (see above). For this purpose, diagnostic tests such as spinal X-rays, myelography and/or MRI scan are indicated. It is important to rule out other conditions causing pressure on the spinal cord (slipped disc or spinal fracture/dislocation) where an operation might be needed.

In most animals with ischaemic myelopathy the results of these tests come back as normal. Since your vet is relying on absence of findings on X-ray or MRI scan to make a diagnosis it is essential that the correct portion of the spinal cord is checked. Occasionally, swelling of the spinal cord can be detected on X-rays or MRI scan.

A definite diagnosis of ischaemic myelopathy and identification of its exact cause can only be made by examining the spinal cord after death.

There is no specific treatment for ischaemic myelopathy but most cats tend to recover within a few weeks provided they have retained the ability to feel pain in their feet. Good nursing care (physiotherapy, assisted walking, hydrotherapy, adequate bedding to prevent bed sores) is essential for the recovery of the animal. The recovery period may be long and require intensive nursing so can be quite expensive.

If your cat did not lose sensation in its feet then it will probably recover over a few weeks. Most cats will make a full recovery after 8 to 12 weeks but some may keep some residual deficits. In animals where there was complete paralysis, improvement may not be seen for a number of weeks and some animals may never fully recover.

Inflammatory CNS disease

Animals with brain disease may show sudden, dramatic signs and become very poorly extremely quickly. In other cases the signs are more vague and it may be some time before your vet gets to the bottom of the problem. Diseases affecting the brain are not limited to brain tumours and include conditions affecting the blood supply (stroke), causing inflammation (meningitis or encephalitis), trauma or malformation of the brain. Many of these diseases can be treated (or at least managed successfully) to give your pet a good quality of life, so it is very important that conditions are investigated and an accurate diagnosis made so that the best treatment can be given.

The central nervous system (CNS) is the control centre for the body. It is made up of the brain, spinal cord and the covering of these, the meninges. Inflammatory CNS disease is a broad term used to describe a number of conditions causing inflammation of structures in the CNS.

Depending on which part of the CNS is involved, inflammatory CNS disease can be more precisely divided into meningitis (inflammation of the meninges), encephalitis (inflammation of the brain) and myelitis (inflammation of the spinal cord). Each condition can occur on its own, but more usually the conditions occur in combination (e.g. meningo-encephalitis, meningo-myelitis).

Inflammatory CNS disease can be the result of either infectious or non-infectious disease. In humans viral and bacterial meningitis are common causes of inflammatory brain disease. In animals infectious causes are probably the least common cause of inflammatory brain disease but include a number of infectious agents such as viruses (distemper in dogs, and Feline Infectious Peritonitis [FIP] or Feline Immunodeficiency Virus [FIV] in cats), bacteria, protozoa (Toxoplasma, Neospora) or fungi.

Non-infectious inflammatory diseases are more common. Other rare non-infectious causes include precancerous changes (inflammation that will turn into cancer with time) and paracancerous disease (cancer elsewhere in the body causing a reaction in the brain).

The signs of inflammatory CNS disease depend on which part of the CNS is affected (i.e. brain, spinal cord and/or meninges).

Compared to dogs, meningitis is rare in cats. When meningitis occurs on its own, pain, stiffness of the gait, reluctance to move the neck and a hunched back are the most common signs. The signs seen with encephalitis and myelitis vary according to the part of the nervous system that is inflamed but often include seizures, head tilt, depression, neck pain and ataxia.

Unfortunately, the diagnosis of inflammatory CNS disease cannot be based solely on the signs shown by a patient. Other neurological conditions such as brain cancers, and bleeding into the brain can potentially cause similar signs. Even the most severe meningitis or encephalitis may not show up on any blood test.

Further tests are always required and special imaging studies such as a CT or MRI scan can help your vet to make a diagnosis. Collection of fluid from around the brain (cerebrospinal fluid analysis) is one of the most useful tests. This can help to confirm the presence and type of inflammation and, perhaps more importantly, tests can be carried out to look for an infection. It is rare for cerebrospinal fluid to be normal if an animal has inflammatory CNS disease.

Treatment of inflammatory CNS disease depends on the primary cause. Bacterial infections can be treated with antibiotics and other drugs may be available for fungal and viral causes. In non-infectious disease, drugs are used to try to counteract the over-excitation of the immune system. High doses of steroids (prednisolone) is the mainstay of treatment, but other powerful drugs such as azathioprine, cytarabine, mycophenolate, cyclosporin, and cyclophosphamide can also be used in combination. Once the inflammation has been controlled using high doses of medication, drug doses are slowly reduced.

The long-term aim is to take the animal off any drugs but usually a low dose of medication is needed to control the signs. Steroids have many side-effects when used in the long term and this is why your vet will try to minimise the drug dose or combine treatment with other drugs. The main risk of using the other more powerful drugs is that they can affect the bone marrow making your pet more prone to infection.

In most animals, inflammatory CNS disease can be controlled. This means that your pet can lead a normal life (although they may need to remain on medication for many months or even years). Unfortunately, a small number of animals with very severe disease may not get better despite treatment. Other animals appear to get better but experience relapses months after being taken off medication.