NEUROMUSCULAR CASE OF THE MONTH - JUNE 2005

Tetraparesis in a 9 year old mix breed dog
Contributed by Dr. Michael Wolf
Animal Neurology Center, Canton, MI

Clinical History
This 9 year old mixed breed MC dog presented for a 1 month history of tetraparesis progressing to tetraplegia. Treatment prior to presentation included a tapering dose of prednisone.

Fig. 1

Physical and Neurological Examination
No specific abnormalities were detected on physical examination and vital signs were normal. On neurological examination, the dog was alert and responsive, but was unable to stand or support weight unassisted. Spinal reflexes were depressed (0-1+) and a panniculus reflex was not present. Right sided facial nerve paralysis and left sided facial nerve paresis was present with remaining cranial nerves appropriate. Pain perception was present without spinal hyperesthesia. A neuromuscular disease was suspected and differentials included neuropathies, myopathies, or disorder of neuromuscular transmission.

CBC and serum chemistry profiles – No abnormalities (cholesterol not included)
Thoracic radiographs – No evidence of esophageal dilatation, mass lesions or metastatic disease
Tensilon Test – Negative
Acetylcholine receptor antibody – 0.07 nmol/l (canine reference <0.6 nmol/l)
Creatine kinase – Within reference range
Cerebrospinal fluid analysis – No abnormalities
Thyroid – Performed at Michigan State University. Results confirmed a diagnosis of hypothyroidism associated with lymphocytic thyroiditis.

            TT4 – 2                                                (15/67 nmol/l)
            TT3 – 0.0                                             (1.0-2.5 nmol/l)
            FT4 – 5                                                (8-26 pmol/l)
            FT3 – 3.3                                             (4.5-12.0 pmol/l)
            T4 Autoantibody – 8                            (<20)
            T3 Autoantibody – 24                          (<10)
            TSH – 61                                             (0-37 mU/L)
            Thyroglobulin Autoantibody – 97          <20 negative
                                                                       20-35% inconclusive
                                                                       >35% positive

Electrodiagnostic Testing
Declined by owner

Muscle and Nerve biopsy
No specific abnormalities identified within either the muscle or nerve biopsies

Conclusion
Following collection of muscle and nerve biopsy specimens, the dog was started on thyroid supplementation. A marked improvement was noted within just a couple of weeks and the dog was again walking. This case is a good example of muscle weakness and hypothyroidism in a senior dog and emphasizes the importance of thyroid testing in any middle-aged or older dog. Muscle weakness, stiffness, and myalgia can all be early clinical signs of an endocrine disorder, with or without the “classical” clinical signs.

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