NEUROMUSCULAR CASE OF THE MONTH - OCTOBER 2005

Is this Neuromuscular?
Contributed by Dr. Joan Coates
University of Missouri
Columbia, MO 65211

Clinical History
A 5 year old male neutered Labrador Retriever dog presented to the emergency service at the Veterinary Teaching Hospital University of Missouri with an acute onset of difficulty walking in the pelvic limbs. There was a mild crouched gait and paresis of the pelvic limbs bilaterally with intact spinal reflexes.

Physical and Neurological Examination
On evaluation 24 hours following initial presentation, crouching worsened and proprioception was absent. Patellar reflexes were absent bilaterally and flexor withdrawal reflexes were absent in the right pelvic limb and reduced in the left. Hopping was 1+. The gait showed inability to extend the pelvic limbs. (Go to video clip). Weakness worsened with exercise. Micturition revealed the presence of dysuria, a full bladder on palpation, a weak urine stream, and there was a large amount of residual urine. Pain was elicited upon tail elevation and deep palpation of the L-S region. The neuroanatomic localization was L4-S2 with suspected femoral and sciatic nerve involvement.

Diagnostic Testing
CBC, serum chemistry profiles, urinalysis – no abnormalities found
CT of L3-S2 – revealed mineralized disc material in the spinal canal on the right side over L6-7 (Fig. 1A with contrast, 1B without contrast) 

Fig. 1A. with contrast

Fig. 1B. without contrast

Diagnosis Treatment and Outcome
Intervertebral disk disease was diagnosed at the level of L6-7and a dorsal laminectomy performed. A large amount of chalky and hemorrhaghic disk material was removed from the right side of the canal. Nerve roots appeared intact. The dog recovered well after surgery and was able to urinate on its own 2 days post-operatively. Phenoxybenzamine (10 mg SID) was administered for one week after surgery. By 4 days after surgery, the dog was able to walk with only mild ataxia and fully support its body weight.

Comments
This case could have been interpreted as a neuromuscular disorder since the dog was weak, spinal reflexes were decreased, then lost over a 24 hour period. However, loss of proprioception, hypotonic bladder and pain on tail elevation and over the L-S area are not typical of neuromuscular disease.In addition, the lesion and spinal pain were focal, making a generalized neuromuscular disease less likely. Because of compression to the pelvic nerve, there may have been weak detrusor muscle contraction which would not have been able to over ride the sphincter tone. The CT was diagnostic in this case and surgery was corrective.      

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