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NEUROMUSCULAR CASE OF THE MONTH - JANUARY 2000
Distal polyneuropathy in a "Dancing Doberman"
Contributed by Drs. Roberto Poma and Joane Parent
University of Guelph
Ontario Veterinary College
Guelph, Ontario, Canada
Clinical History
A 4.5 year old, female spayed Doberman Pincher was presented to the Ontario Veterinary College in September 1999 for hind limb
weakness of approximately two months duration. A dancing motion was described with alternating flexion and extension of the hind limbs.
The owners reported that the dog preferred to sit rather than stand, and tended to lie down for eating and drinking. A voice change was
also noted within the two weeks prior to presentation. The dog had been treated with Anafen (20 mg BID for four days) and Bufferin (350
mg BID) by the referring veterinarian with no improvement.
Physical and Neurological Examination
No significant abnormalities were present on general physical examination. The dog was bright, alert and responsive with a normal
cranial nerve examination. Bilateral hind limb weakness was present with flexion and extension of both limbs in a dancing motion (See
video segment) and a preference to sit rather than stand. The front limbs had a short, stiff gait. Neither ataxia or proprioceptive
positioning deficits were detected. Spinal reflexes were decreased in all limbs and there was a decreased perineal reflex. No back
or neck pain was elicited on palpation.
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Diagnostic Tests
Routine laboratory tests
CBC and serum chemistry evaluation (including CK) - no abnormalities
Thyroid evaluation - Free T4, Total T4, and cTSH within the reference range
Survey radiographs of the cervical and lumbosacral spine - no abnormalities
Electromyography - Fibrillation potentials and positive sharp waves were present in the distal muscles of both hind limbs
(gastrocnemius, cranial tibial, and interosseous muscles) and front limbs (extensor carpi radialis, flexor carpi ulnaris,
and interosseous muscles). The motor nerve conduction velocity could not be determined.
Muscle and Nerve Biopsies - A fresh, frozen muscle biopsy was evaluated from the cranial tibial muscle of the left hind limb.
There was a moderate variation in myofiber size with atrophic fibers having an anguloid-angular shape (Fig. 1) and of both
fiber types (Fig. 2; type 1 fibers dark, type 2 fibers light, type 2C fibers intermediate). An increased population
of type 2C fibers was present. Fiber type grouping was not observed. Intramuscular nerve branches were moderately depleted
of myelinated nerve fibers (not shown). The pathological changes within the muscle biopsy were consistent with denervation.
A fixed biopsy was also evaluated from the peroneal nerve in resin embedded sections (Fig. 3). The nerve biopsy demonstrated
moderate depletion of large myelinated nerve fibers, and active axonal degeneration with myelin ovoids and foamy macrophages
within the endoneurium. |
Figure 1. Cranial
tibial muscle (H&E stain)
Figure 2. ATPase pH 4.3;
cranial tibial muscle
Figure 3. Toluidine blue-acid fuschin; peroneal nerve |
Conclusion
The neurologic, electromyographic, and histological evaluations in this dog supported a disorder of the peripheral nervous system
with most marked involvement of the distal limb muscles. The voice change also indicated possible involvement of cranial nerves IX
and X. The dog was again evaluated approximately 2 months after the initial presentation. The gait was similar to that shown in the
video clip; however, the front limbs also showed a dancing motion similar to that of the rear limbs when standing or walking. It was
felt that the dog was progressively deteriorating.
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