NEUROMUSCULAR CASE OF THE MONTH - SEPTEMBER 2002

Acute Demyelinating Polyneuropathy in
an 8 year old MC Labrador Retriever Mix
Contributed by Dr. Mark Kent
University of Georgia
Athens, GA


Clinical History
During the four months prior to presentation, Shadow had 3 episodes of small bowel diarrhea. Each time he was treated empirically. The last episode was 3 weeks prior to presentation. A fecal culture was performed which grew Clostridium perfringens.  Ampicillin (28mg/kg BID), Metronidazole (28mg/kg) BID, Metoclopramide (unknown dosage), and Clomipramine (unknown dosage). Episodes would last approximately 24 hours. One day prior to presentation, Shadow developed pelvic limb paresis which progressed to the point of being unable to ambulate with the pelvic limbs (Go to video clip).  Dexamethasone (unknown dosage) was prescribed by the referring veterinarian. The owner reported a normal activity level prior to developing paresis. Shadow’s appetite remained normal however he had lost approximately 15-20 pounds of body weight. There was no change in his bark. There was no report of vomiting, regurgitation, coughing, sneezing, polydypsia, polyuria.

Physical and Neurological Examination
No abnormalities detected on routine physical examination. Mentation was normal. The dog had tetraparesis but was ambulatory with assistance. Postural reactions were abnormal in all 4 limbs and spinal reflexes were reduced in the thoracic limbs and absent (patellar and cranial tibial) in the pelvic limbs (Go to video clip). Reduce muscle tone was noted. Cranial nerves and sensory evaluations were all normal. The neuroanatomic localization was consistent with generalized lower motor neuron disease. Over the subsequent 48 hours, paresis developed in the thoracic limbs, the dog became tetraparetic and was unable to ambulate.

Diagnostic Testing
CBC – No abnormalities
Serum Chemistry Profile – Mildly elevated alkaline phosphatase, ALT, glucose, magnesium, total bilirubin, and cholesterol
Creatine kinase – 16, 033 U/L (reference range 63-350); repeated 24 hours after initial measurement 3,354 U/L.
Urinalysis – No abnormalties
CSF analysis – No abnormalities on routine analysis. On cytospin preparation 29 lymphocytes and 19 mononuclear cells were identified.

Electrodiagnostics
Electromyography: No spontaneous activity was observed.
Motor nerve conduction velocity: There was an increased latency, decreased amplitude, and dispersion in tibial and ulnar nerve CMAP with decreased conduction velocity.


Ulnar Nerve



Tibial Nerve

Muscle and Nerve Biopsy
No abnormalities were identified within the muscle biopsy. Ballooning myelin degeneration and splitting were present within the resin embedded ulnar and peroneal nerve biopsy specimens. These findings are consistent with a demyelinating neuropathy.






10 Days After Initial Presentation
No treatment was initiated. Over the course of the subsequent 10 days, there was gradual improvement back to a normal gait (Go to video clip). Postural reactions were normal although spinal reflexes were still reduced. An abscess developed in the right first digit (dewclaw) of the thoracic limb and a surgical amputation was performed. Post-operatively, electrodiagnostics were performed.  No spontaneous activity was observed on electromyography. There was still an increased latency, although improved from the previous examination, decreased amplitude, and dispersion in tibial CMAP. The MNCV was now 50 m/sec in the pelvic limb.



Conclusion
Acute demyelinating polyneuropathy. The clinical course in this dog paralled the electrodiagnostic findings. On initial presentation the dog could barely walk and the nerve conduction velocities were markedly decreased. On re-evaluation 10 days later the dog was markedly improved, similar to the improvement in conduction velocity. The dog continues to do well as of 4 months following the original episode without reoccurrence of weakness.

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