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Steroid-responsive meningitis-arteritis (SRMA) was initially referred to as beagle pain syndrome. It was first identified in young laboratory Beagles that demonstrated clinical signs of lameness, pain, and fever. The condition has also been known by several other names, including juvenile polyarteritis syndrome, necrotizing vasculitis, panarteritis, and polyarteritis, amongst others.
The term SRMA is currently the most universally accepted name, as it refers to not only the underlying pathology (i.e., inflammation of the meninges and their associated arteries) but also the most widely used treatment and its success in managing this disease. The condition has also since been described in various other breeds of dogs, making the term “beagle pain syndrome” no longer appropriate. Learn more about SRMA and its signs and causes below.
What Is Steroid-Responsive Meningitis-Arteritis?
SRMA is an immune-mediated disease that some consider to be the most frequently diagnosed inflammatory disorder involving the central nervous system (CNS) in dogs. Two different forms of SRMA have been documented: acute and chronic.
As alluded to above, the name of this syndrome gives some valuable clues as to what pathology is involved. The disease is characterized by inflammation involving the meninges and associated arteries, along with evidence of this inflammation within the cerebrospinal fluid (CSF).
Most studies on SRMA have not identified a sex predilection; in other words, males and females appear to be at similar risk, although one study did report a higher prevalence in male dogs. Typically, the condition is identified in dogs under 2 years of age (95% of cases), with the peak prevalence between 6 and 18 months. There have, however, been reports of SRMA in dogs as young as 3 months and as old as 9 years.
What Are the Signs of Steroid-Responsive Meningitis-Arteritis?
Acute SRMA
The clinical signs seen can vary depending on the form of the disease present. Typically, the acute form is characterized by neck pain and rigidity or stiffness, which can be intermittent, along with a fever (and associated lethargy). Many dog owners describe the signs as having a waxing and waning course—this is important to appreciate, given that when presented for examination at a veterinary clinic, dogs with SRMA may not be exhibiting all or even any of the signs commonly seen with this disease. For instance, while fever is common in dogs with SRMA, a normal temperature cannot rule it out as a potential diagnosis in a dog with concurrent neck pain, stiffness, and lethargy.
Chronic SRMA
The chronic form, which is considered less common, may also demonstrate signs seen with the acute form; however, it usually involves repeated episodes of neck pain accompanied by additional neurological deficits (e.g., weakness and an uncoordinated gait). These deficits are consistent with a spinal cord or multifocal neurological disorder and represent an extension of the inflammation from the meninges to adjacent structures (i.e., the spinal cord (myelitis) and the brain (encephalitis)).
Chronic lesions can include meningeal fibrosis (or scarring) and arterial stenosis (narrowing of arteries), which can obstruct normal CSF flow and even occlude vessels, respectively. Such lesions can lead to ischemia of the CNS parenchyma and the other neurological deficits described above. Thus, it can be difficult to distinguish the chronic form of SRMA from the more commonly identified meningoencephalitis of unknown etiology.
Other Signs and Diagnosis
Interestingly, various cardiac changes have also been identified in dogs with SRMA. In one population of 14 dogs, such changes were considered common. In humans, the co-occurrence of cardiac disease in patients with inflammatory CNS disease is well-described. While most cardiac changes identified in dogs with SRMA appear to resolve with steroid therapy, further research is required to determine if cardio-supportive treatment is necessary to avoid potential complications.
There is currently no definitive test for SRMA in a living dog. Thus, a diagnosis involves consideration of several variables, such as history and clinical signs, physical examination findings (e.g., neck pain and fever), the presence of nonspecific findings on laboratory work (blood and CSF), and excluding other potential diagnoses that can present similarly (e.g., infectious diseases, particularly in young dogs, and meningoencephalitis of unknown etiology or even neoplasia in older dogs).
What Are the Causes of Steroid-Responsive Meningitis-Arteritis?
The exact underlying cause is currently unknown. However, SRMA is understood to be an immune-mediated disease involving abnormal and dysregulated immune responses directed toward the central nervous system of specific breeds of dogs.
The reason or trigger/s behind such a response remains to be determined. No studies have identified an environmental, infectious, or neoplastic (cancerous) trigger for this disease. There is also no relationship between vaccination and the development of SRMA in dogs.
How Do I Care for a Dog With Steroid-Responsive Meningitis-Arteritis?
As the name suggests, treatment of this condition involves using steroids (otherwise known as corticosteroids or glucocorticoids) such as prednisone or prednisolone. Generally, dogs with SRMA are treated with prolonged courses of steroids, starting at immunosuppressive dosages and gradually tapering the dose (until the drug can be safely discontinued) over approximately 6 months. Such courses have proven excellent in achieving remission, with some studies reporting success in up to 98.4% of cases. Most dogs show clinical improvement within 2 days of starting steroid therapy.
Relapse
Unfortunately, in many dogs, this remission appears to be short-lived. Relapse rates range from anywhere between 16% and 47.5%. Relapses are believed to result from either inadequate dosage or an inappropriate or insufficient duration of treatment. Some authors have also proposed that certain dogs may be insensitive to steroids, as documented sporadically in humans undergoing treatment for various immune-mediated diseases. It has also been hypothesized that inadequate treatment leads to the development of the chronic form of SRMA.
Predicting which dogs will relapse and when is a problem that has prompted much research. Unfortunately, a predictive marker remains elusive, and relapses have been reported both during treatment and following cessation of therapy with steroids. Most cases that relapse experience one or two relapse episodes; however, although uncommon, some dogs have been noted to have three or even four relapses.
It may also be the case that certain breeds are more likely to suffer a relapse, with one study describing such a finding in Beagles and Bernese Mountain dogs. Older dogs appear less likely to relapse, with apparent resistance to recurrence of signs after approximately 2 years of age being described by some authors.
Not only has this high relapse rate prompted much investigation into a possible predictive marker, but it has also led to studies looking at the use of additional drugs in managing relapses to hopefully prevent further relapse. This is not surprising, given the multiple immunosuppressive drugs available in veterinary medicine and the somewhat common practice of using multimodal therapy to manage cases of inflammatory CNS disease in dogs.
One study looked at cytosine arabinoside, a chemotherapeutic, to help address such issues. While this addition did result in remission of signs in 10 out of 12 dogs, side effects and adverse events associated with its inclusion were identified in all 12 dogs, many requiring additional measures to manage these adverse events.
It is also worth mentioning that prolonged courses of steroids in dogs have also been associated with mild side effects, the most reported being diarrhea. These adverse effects are dose-related and therefore tend to be more apparent earlier in the treatment course, and large-breed dogs are also more susceptible.
Other Treatment Options
Another potential therapeutic option for dogs with SRMA is targeting the endocannabinoid system (e.g., using derivatives of Cannabis sativa). Endocannabinoids have proven helpful in immunomodulation, neuroprotection, and helping control inflammatory disorders of the CNS. A recent study showed upregulation of specific endocannabinoid receptors in dogs with SRMA, suggesting that targeting the endocannabinoid system may help manage dogs with SRMA.
What Is the Prognosis for a Dog With Steroid-Responsive Meningitis-Arteritis?
The prognosis varies depending on the form of SRMA a dog is diagnosed with. The acute form, especially in young dogs, generally has a good to even excellent prognosis with early implementation of steroid treatment.
In contrast, the chronic form usually has a more guarded prognosis and requires more aggressive and long-term therapy.
Frequently Asked Questions (FAQs)
What Breeds of Dogs Get SRMA? Does It Only Occur in Beagles?
While SRMA, formerly known as beagle pain syndrome, was first identified in Beagles, several other breeds have since been recognized as predisposed to this condition. Such breeds include Beagles, Bernese Mountain dogs, Border Collies, Boxers, Golden Retrievers, Jack Russell Terriers, Weimaraners, Whippets, and Wirehaired Pointing Griffons. Notably, no differences in disease severity, diagnostic findings, or even outcome have been recognized across predisposed breeds.
Is SRMA Contagious?
No. SRMA is an immune-mediated disease that stems from an abnormal immune response within the body. In the case of SRMA, this response is directed toward or against the meninges (the membranes that line the brain and spinal cord) and associated arteries. No underlying triggers have been identified that could lead to the abnormal immune response and clinical signs seen in dogs with SRMA.
Conclusion
In summary, SRMA is a common immune-mediated disorder identified in several dog breeds (not just the Beagle), particularly young dogs. Two forms of the disease have been well-described, and the clinical signs and prognosis differ. Treatment of dogs with SRMA is centered on using corticosteroids such as prednisone, which are highly effective in achieving remission of clinical signs, especially in dogs with the acute form of the disease. Unfortunately, relapse is very common and necessitates close monitoring in all dogs with a history of SRMA for the recurrence of signs and subsequent rapid re-implementation of steroid therapy.
Featured Image Credit: yangtak, Shutterstock