Steroid Responsive Meningitis-Arteritis (SRMA)
The cause of steroid responsive meningitis-arteritis (SRMA) is unknown but is thought to be due to an autoimmune disease process causing inflammation of the meninges (the covering layer of the central nervous system) and peripheral nerve roots. It also affects arteries and tissues in many of the body’s systems.
Autoimmune disease occurs when something within the dog’s environment acts as a trigger factor, causing the immune system to become confused. This results in the immune system no longer recognising its own body parts as ‘itself’ but as foreign to the body, like bacteria. The immune system automatically mounts an attack to destroy the ‘invader’ but in reality it set to destroy part of its own body, resulting in an autoimmune disease. There are various autoimmune diseases that affect different systems of the body and SRMA is just one of these diseases. A genetic predisposition is required for a dog to develop an autoimmune disease, and is often more prevalent in certain families. Some breeds are more prone to SRMA than others, and an association with vaccination has been recorded in Weimaraners.
SRMA is a non-infectious, inflammatory disease usually affecting young animals. It can be cyclic in nature but the initial onset of the disease is usually sudden, showing symptoms such as: high temperature, neck stiffness, intense pain - especially around the neck and ears, general body stiffness, sensitive to touch and depression. Characteristically, the dog may stand with his neck stiff and held low, just below horizontal, almost as if frightened to move. Initially, a severe ear infection may be suspected, although speculative treatment with anti-inflammatory drugs and antibiotics will show no improvement in the dog’s condition.
Diagnosis is achieved by physical and neurological examination, and spinal fluid analysis, revealing elevated protein and white cells typical of central nervous system inflammation.
SRMA responds very well to immunosuppressive treatment of prednisolone (2mg/kg/day) or a combination therapy of prednisolone and azathioprine (2mg/kg/day or alternate days) reducing steroid therapy to alternate days and weaning off all treatment over a period of months. A dog on high dose steroids should be given a gastroprotectant, such as Zantac, to minimise irritation to the stomach.
The prognosis for patients with SRMA is generally very good, although relapses may occur at any time. Recovery is usually rapid and improvement can be seen with hours of giving immunosuppressive therapy, hence the name steroid responsive meningitis.
SRMA can occur with polyarthritis. The arthritis is symmetrical and non-erosive and confirmed by synoval fluid biopsy. Polyarthritis/meningitis syndrome is recognised in several larger breeds.
Clinical Immunology of the Dog & Cat by Michael J Day
Canine Medicine & Therapeutics by Neil Gorman
Clinical Medicine of the Dog and Cat by Schaer
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