NEUROMUSCULAR CASE OF THE MONTH - JANUARY 2015

Stiff rigid gait in an 11 year old intact male Miniature Schnauzer
Contributed by: Dr. Elena Kabatchnick and Dr. Douglas Palma
Animal Medical Center
New York, NY

Clinical History
Yoshi, an 11 year old intact male Miniature Schnauzer was presented for a two week history of progressively stiff gait and reluctance to walk. The dog was progressively reluctant to go outdoors in the winter weather. Two weeks prior to presentation, Yoshi had been treated for suspected intervertebral disc disease of the thoracolumbar spine with tramadol, pregabalin, and strict cage rest without any improvement. The dog was also noted to have a progressive wet cough unrelated to activity, eating, or drinking

Physical and Neurological Examinations
On initial physical examination, Yoshi was quiet, alert, and mildly hypothermic with a rectal temperature of 98.9°F. On thoracic auscultation Yoshi had quiet bronchovesicular sounds, a soft wet cough, and a respiratory sinus arrhythmia. Although his heart sounds were muffled, a murmur was appreciated, but difficult to grade. Abdominal palpation revealed a tense abdomen, but was otherwise unremarkable. End stage periodontal disease and severe halitosis were noted. On further musculoskeletal and neurologic examinations the dog was observed to be quiet with an appropriate mentation. A stiff gait and contracted musculature of all four limbs, more severe in the pelvic limbs, was observed. The pet minimally bent his pelvic limbs to ambulate and thus appeared to have a pelvic limb ataxia (crossing over, narrow base stance). The gait was characterized by rigidity, stiffness, and increased muscle tone. At rest, the posture was scoliosis-like. Cranial nerves, conscious proprioception, and spinal reflexes all remained intact. A generalized myopathy was suspected.


Click on image for pretreatment video

Diagnostic Testing - Initial
1. Blood Pressure: 180 mmHg
2. Complete blood count: mild non-regenerative anemia, otherwise unremarkable
3. Chemistry: moderate hypoalbuminemia, mildly elevated BUN with a normal creatinine, mild hypochloremia, mild hyponatremia, normal CK, moderate hypercholesterolemia
4. Total T4: 0.5 ug/dL (1.0-4.0)
5. PLI: 62 ug/dL (normal)
6. 4Dx: negative
7. Urinalysis: urine specific gravity 1.034, pH 6.5, 4+ protein, 0-2 WBC, 6-10 RBC, no bacteriuria, occasional hyaline casts, 1+ calcium oxalate crystals, sperm present in sample
8. UPC: 7.9
9. Urine culture: negative
10. Abdominal ultrasound:
- Chronic renal disease with renal calculi
- Numerous cystic and proximal urethral calculi
- Prostatic mottling may be a sign of benign prostatic hyperplasia or prostatitis
- Left testicular nodule, either benign or malignant


Diagnostic Testing - Follow-up
iCa: 1.34 mmol/L (normal)
cTSH: 0.04 ng/ml (0.05-0.42)
fT4: <0.3 ng/dL (0.6-3.7), <3.9 pmol/L (7.7-47.6)

Chest radiographs: Focus of soft tissue opacity associated with the right cranial lung lobe. Because the pulmonary blood vessels and bronchus are not obscured, this may simply represent overlying mediastinal fat or a focus of fibrosis/scarring. A low-grade pneumonia is considered less likely.

First Follow-up Examination Three Weeks after Beginning Soloxine:

1. Total T4 (1 hour post 0.1 mg Soloxine): 3.2 ug/dL (1.0-4.0)
2. Chemistry: mildly improved hypoalbuminemia, high normal BUN with a normal creatinine  


Diagnosis
Suspected hypothyroidism with secondary myotonic myopathy.

Treatment and Outcome
Following the initial examination, Yoshi was started on empirical therapy for Clostridium tetani (metronidazole, diazepam) pending further diagnostics. There was no clinical response and the clinical signs remained static. Follow up testing confirmed a low total T4 in addition to low free T4 and TSH concentrations. Although TSH is often elevated in dogs with untreated primary hypothyroidism, about 25% of this population will have a normal or slightly low TSH. In lieu of further diagnostics (further infectious disease testing, ANA, muscle and nerve biopsies, CNS imaging, CSF analysis) the owner elected to begin therapy for hypothyroidism while monitoring for response. Yoshi was started on Soloxine (0.015 mg/kg PO BID) with rapid improvements in the dog's energy level and attitude within the first 24 hours and 75% improvement in the stiff contracted gait over the following week. Cold sensitivity also resolved. On recheck examination 20 days after starting Soloxine therapy, Yoshi's physical examination was much improved with a mild persistent contracture of the pelvic limb musculature and associated abnormal pelvic limb gait most noticeable on slippery surfaces (Go to post-treatment video). Total T4 was improved at 3.2 ug/dL 1 hour after the Soloxine dose. The owners declined immediate total T4 retesting at the standard 4-6 hours post Soloxine administration due to scheduling constraints, so the Soloxine dose was decreased by 25% to 0.01 mg/kg PO BID. A recheck total T4 is recommended in about 1 month and the owner was also encouraged to pursue dental intervention, further workup (abdominal radiographs) and intervention for urolithiasis, and castration for histopathology of the incidentally found testicular nodule.



 

 

 

 

 

 

 

 

 


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