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Potpourri of canine neurologic disorders: Parts I and II (Proceedings)

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Aug 01, 2008

Infraspinatus muscle contracture in the dog

History/signalment –

1. Hunting/working breeds more commonly affected.

2. Dogs are presented for a chronic, non-painful paddling gait in the affected forelimb.

3. However, there usually is a history of an acute lameness several weeks prior to the presentation in #2. This initial episode of lameness is usually associated with a period of vigorous exercise and subsides in 3-4 days.

Clinical findings –

1. Non-painful gait abnormality consisting of:
- Lateral circumduction of the limb
- Elbow being maintained in adduction throughout stride
- A carpal flip in midpoint of stride

2. Prominent scapular spine

3. While standing, elbow is adducted, shoulder is abducted, and antebrachium is rotated outwardly so that digits are pointing laterally instead of toward the front

Diagnosis –

1. By history, characteristic gait, and atrophy of the infraspinatus muscle.

2. There are no definitive tests to prove diagnosis. Ultrasound could possibly reveal hyperechoic lesions in the infraspinatus muscles.

Treatment/prognosis –

1. Surgery – tenotomy or partial tenectomy of infraspinatus tendon.

2. Dramatic improvement seen immediately post-op in 95% of the cases.

Idiopathic tremor syndrome of adult dogs (white shaker dogs)

History/signalment –

1. Age-usually young adults (9 months – 2 years)

2. Small breeds with white haircoats (esp. Maltese, West Highland White Terriers) comprise the majority of cases.

3. Acute onset of head and generalized whole body tremors.

4. Tremors are exaggerated by handling, locomotion, and excitement. They are reduced at rest and totally stop when the dog is sleeping.

Clinical/neurologic findings –

1. Generalized, rapid whole body tremors. If severe enough, the animal may have trouble with locomotion.

2. Very alert, responsive animal and generally no other neurologic deficits are seen.

3. Strength is very good.

4. Very rarely, head tilt or seizures may occur.

Diagnosis –

1. Primarily made by history, signalment, and neurologic examination.

2. Routine hematology and biochemistry are normal.

3. Cerebrospinal fluid analysis may be normal or show a mild to moderate lymphocytic pleocytosis, and protein elevations.

Differential diagnosis of tremors in adult dogs –

1. Toxicities – metaldehyde, O-Ps, chlorinated hydrocarbons, hexachlorophene, mycotoxins (aflatoxins) are a few examples.

2. Metabolic – hypocalcemia, hypoglycemia.

3. Inflammatory – non-suppurative encephalomyelitis.

Treatment/prognosis –

1. Many animals spontaneously recover over several weeks to months, but mild tremors may persist.

2. Prednisone(should be used in most cases) – 2-3 mg/kg/day divided BID for 5 days, then decreasing to alternate day therapy for another 5 days, then a phased withdrawal over 6 more weeks: this usually results in dramatic disappearance of signs. In some cases, 3-4 months of glucocorticoid therapy may be needed but usually at a decreased dose and frequency.