Gundogs: inflammation in the nervous system

Q: My young cocker has recently been diagnosed with SRMA. Will he ever be able to join me in the beating line? ROBERT BORGON, WEST YORKSHIRE 

A: The good news is, his chances are good. SRMA, or steroid responsive meningitis-arteritis, is an immune mediated (or auto-immune) condition involving inflammation of the meninges (the membrane that covers the brain and spinal cord) and its associated arterial supply. Occasionally, SRMA is seen alongside other inflammatory conditions, such as immune-mediated polyarthritis. 

What causes SRMA? 

Despite much research, we still don’t know. The cause and mechanism of SRMA remains a mystery and no infectious or cancerous triggers have been identified. One study showed a prevalence of 0.6%, and SRMA accounted for 1.6% of neurology consultations at a UK referral hospital. It is generally seen in dogs younger than two years old, with first symptoms occurring between six and 18 months of age. It seems that the juvenile immune system produces inflammation and antibodies against a normal body protein, which is a protein expressed by the walls of the blood vessels in the meninges. There is no infection and the condition is not contagious. 

Who is affected? 

While the textbooks tend to refer to beagles, boxers, Bernese mountain dogs, Nova Scotia duck tolling retrievers, Weimaraners and English springer spaniels, most GP vets will tell you that they have seen it in nearly all breeds and in cross-breeds. Certainly, I have commonly encountered it in Border collies, whippets and cockapoos. Essentially, anyone who owns a young dog should be aware of it. 

What do we see? 

SRMA is characterised by waxing and waning episodes of severe spinal pain, usually manifested in the neck. There is a high temperature, a stiff neck and gait, reluctance to move and lethargy. Affected dogs will often scream in pain at the slightest movement (or touch) and will stand hunched and guarded, with the neck lowered. These acute symptoms can go on to become chronic, with weakness and incoordination seen. 

How is it diagnosed? 

In the old days, before relatively easy (but expensive) access to spinal taps and MRI scans, SRMA was provisionally diagnosed on the history, taking into account the clinical signs and the breed, and was confirmed by a good response to steroid medication. Where finances allowed, radiography could rule out bony issues. 

Now, routine blood samples can show an inflammatory response and blood and urine tests can rule out infection. The gold standard includes sampling of cerebrospinal fluid (CSF) under general anaesthesia and MRI (magnetic resonance imaging) scans. CSF is the normally clear fluid that circulates within the meninges and nervous system, but it will appear yellow (from bleeding) or cloudy (from an increased cell count) when SRMA is present. An increased level of IgA (an immunoglobulin) is also seen. MRI scans can demonstrate a particular pattern that is produced by inflamed meninges. 

How is it treated? 

The clue is in the name. The bedrock of treatment for SRMA is, you’ve guessed it, steroids. Corticosteroids (prednisolone), given initially at high, immunosuppressive doses then tapered, are usually effective at controlling pain within a few hours of commencing treatment. They are generally required for a few weeks and can then be stopped, although some cases relapse and require repeat courses. 

Unfortunately, side-effects (which are dose-dependent) are common, and include increased thirst and hunger (thus also urination and weight gain), lethargy, panting and increased risk of respiratory and urine infections. 

Where the response to steroids is poor, which is rare, other drugs can be helpful, such as the chemotherapeutic cytarabine, which is administered by injection, and immunomodulators, such as cyclosporine and azathioprine, which are given orally. 

Is there more? 

Of course! Recent advances in veterinary medicine have identified a marker called canine reactive protein (CRP), which is an acute phase protein that is released by the liver into the bloodstream within hours of an inflammatory reaction. Most veterinary practices now have the ability to measure CRP levels on a simple blood sample with results produced in a few minutes. 

SRMA cases show high CRP levels initially but these then drop as treatment is successful. Regular monitoring of CRP levels is a cost-effective, relatively reliable way of deciding when steroid doses can be reduced, thus limiting unwanted side-effects. 

And, finally 

To answer your question, unlike other immune-mediated conditions, most cases of SRMA resolve completely by the time a dog reaches two years of age and do not recur. Good luck in the beating line.