Steroid Responsive Meningomyelitis

Case Report
Catherine Sohn, DVM

Reviewed by
TODD DEPPE, DVM, DACVIM

Signalment
Jodi Wrin
4 year old Female, Spayed
Australian Shepherd

Fig 1: Prior to neurological signs, portrait
of Jodi Wrin.

History
Jodi presented to VMSG for an acute onset of progressive ataxia. Five days prior to presentation, Jodi was in agility training class and practicing on an A-frame. When she reached the top of the A-frame, she collapsed in the hind limbs but remained ambulatory through the rest of the event. The next day she was stiff and sore. Over the next few days, she began dragging her hind limbs, and her motor function became weak. She also became more painful. Administration of 50 mg Deramaxx SID did not reduce nor resolve her clinical signs. She had not been observed urinating since one day prior to presenting. Jodi has no other prior medical history.

Clinical Exam
Upon presentation, Jodi had absent conscious proprioception, weak motor function, and normal to increased spinal reflexes in both hind limbs. She had a moderately distended, easily expressible urinary bladder and intact anal tone. She was mildly ataxic in her thoracic limbs with mildly brisk spinal reflexes. She was mildly painful on palpation of her spine at L3-L4 and the lumbosacral junction. She had an absent panniculus response on the left side up to T13-L1, and the reflex was intact on the right. Over the next couple of days of hospitalization, Jodi’s neurological condition continued to slowly progress. Jodi became weaker in her thoracic limbs, lost conscious proprioception in all four limbs, and completely lost motor in her rear limbs. A urinary catheter was placed due to the inability to express her bladder.

Diagnostic Imaging
A CT-scan and myelogram were conducted, and both were negative for any evidence of disk disease. Abdominal ultrasound was negative for any evidence of neoplasia or other abnormalities.

Pathology/Laboratory Tests
A CBC, serum chemistry, and urinalysis were unremarkable except for a mild lymphopenia and eosinopenia. A CSF tap was conducted, and the analysis revealed a nucleated cell count of 120 cells/ul and a protein count of 915.3 mg/dL. A differential of the cellular make up of the CSF showed 94% small mature lymphocytes, 4% monocytoid mononuclear cells, and 2% neutrophils. This type of cell population is termed lymphocytic pleocytosis and indicates a non-specific immunostimulation. To determine if the immunostimulation was due to an infectious cause, numerous infectious disease panels were conducted. CSF culture did not grow or isolate any organisms. A tick panel for Ehrlichia canis, Lyme, and Rocky Mountain Spotted Fever was negative. A Neospora IFA and Toxoplasma IgG and IgM ELISA were negative. A Cryptococcus antigen titer and Cocciodioides antibody screen and titer were negative as well. No histopathology has been submitted to date.

Diagnosis
Due to her young age, the progressive nature of her neurological deterioration, and exclusion of other disease processes, steroid-responsive, immune-mediated meningomyelitis was diagnosed. Classically, steroid responsive meningomyelitis is a diagnosis of exclusion. It is important to rule out infectious agents before long-term immunosuppressant agents are used. Another differential diagnosis is small cell lymphoma, which can cause similar clinical and CSF findings. Additional diagnostic imaging (i.e. thoracic radiographs) and immunophenotying of the CSF lymphocytes would have been valuable for further work up of this differential.

Treatment/Management
After CSF was collected for analysis and aerobic/anaerobic culture, Jodi was administered Baytril 5 mg/kg SID and clindamycin 12 mg/kg BID. Due to recent Deramaxx administration, she was also started on misoprostol 100 mcg BID for enhanced gastrointestinal protection when prednisone is administered. Two days following presentation, Jodi’s neurological signs continued to progress. Although her infectious diseases tests were still pending, prednisone with her antibiotic therapy was initiated. Initially, oral prednisone was started at 0.5 mg/kg/day, and then increased to 1 mg/kg BID after her infectious disease test results were negative. Within 24 hours of starting the prednisone therapy, Jodi’s neurological decline halted and began progressively improving. The day she was discharged, one week after starting prednisone, Jodi could walk and urinate voluntarily.

Prognosis
At Jodi’s one week recheck, she showed great improvement, but was still ataxic in her hind limbs and had delayed conscious proprioception in her hind limbs. Her prednisone dose has been tapered down slowly. No other immunosuppressants, such as cyclosporine or azathioprine, were needed. At Jodi’s 1 month recheck, she showed only mild ataxia with a long-strided pelvic limb gait. Over the next few months, Jodi’s prednisone dose will be slowly tapered and, hopefully, can be discontinued altogether without recurrence of disease.

Discussion
Steroid-responsive meningomyelitis typically afflicts dogs under the age of 2. Medium and large breed dogs tend to be predisposed. Unfortunately, in most cases of steroid-responsive CNS syndromes, the cause remains unknown. CSF commonly reveals an increase in inflammatory cells, but is rarely pathognomonic. Diagnostic imaging is valuable but does not provide a definitive diagnosis, often revealing non-specific changes supportive of, but not diagnostic for, inflammation. A biopsy is commonly the most important means of gaining a diagnosis, unfortunately only a few facilities (i.e. UC-Davis) presently conduct this service. Neurological improvement with corticosteroid therapy can be seen in 72 hours. Resolution or improvement of clinical signs with immune-suppressant therapy is supportive of a diagnosis of immune-mediated meningomyelitis.

References

1. Clemmons RM. University of Florida Veterinary Medicine Web site. Quadriparesis and quadriplegia. Available at: http://neuro.vetmed.ufl.edu/neuro/quadriparesis/quad2.htm, Accessed May 29, 2008.
2. Levine JM, Bergman RL, Coates JR, Shelton GD. Myasthenia gravis and hypothyroidism in a dog with meningomyelitis. J Am Anim Hosp Assoc 2005; 41:247-251.
3. Oliver JE, Lorenz MD, and Kornegay JN. Handbook of veterinary neurology. 3rd ed. Philadelphia: Saunders, 1997.
4. Platt SR. Inflammatory central nervous system disease of the dog. World Small Animal Veterinary Association World Congress Proceedings, 2006.