Hypothyroid-associated neurologic signs in dogs - Veterinary Medicine
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Hypothyroid-associated neurologic signs in dogs
Explore three cases of dogs with neurologic signs that were found to have hypothyroidism, and see when you should test for this disease in your patients with neuromuscular signs.


Treatment and follow-up

Supplementation with levothyroxine (0.02 mg/kg orally twice daily) was initiated. The dog experienced improvement of the vestibular dysfunction and the facial paralysis over the next seven days. However, the owner reported that the dog was restless, as evidenced by frequent pacing and reluctance to sleep. A total T4 concentration was rechecked because of the suspicion of oversupplementation, and the concentration was elevated (7.1 g/dl; reference range = 1 to 4 g/dl). Consequently, the dose of levothyroxine was reduced by 50%.

Three days after the dose reduction, the facial paralysis returned, and an intermediate dose of levothyroxine supplementation was instituted. The clinical signs of facial paralysis and vestibular ataxia resolved.

The patient had follow-up blood work performed by the referring veterinarian; results were not available, but recorded personal communication with the owner revealed that the dog was doing well on the intermediate dose. In this patient, a reduced initial dose of 0.1 mg/kg twice daily might have avoided the clinical signs of hyperthyroidism.

Based on results of the thyroid testing, lack of other disease processes that could explain dysfunction of cranial nerves VII and VIII, and response to thyroid hormone supplementation, hypothyroid-induced cranial neuropathy was presumptively diagnosed.

Case 3: A tetraparetic and ataxic rottweiler

A 10-year-old spayed female rottweiler was presented to Red Bank Veterinary Hospital for evaluation of acute tetraparesis and ataxia.

Physical and neurologic examinations

Physical examination abnormalities were limited to the nervous system. The dog's body condition score was 5/9, subjectively.

On neurologic examination, the dog's mentation was normal. The dog walked with a tendency to lean and fall to the right. Additionally, there was a left-sided dysmetria primarily evidenced by an over-reaching of the left limbs and excessive flexion of the carpus. There were left-sided postural reaction deficits. Spinal reflexes were normal. There was thoracic limb extensor rigidity. A cranial nerve examination revealed a right-sided head tilt. No abnormal nystagmus or strabismus was present.

The remainder of the cranial nerve examination findings were normal.

Differential diagnoses

The neuroanatomic diagnosis was consistent with a left-sided paradoxical central vestibular dysfunction. Differential diagnoses included ischemic infarction, neoplasia, infectious disease (e.g. Neospora caninum or Toxoplasma gondii infection), a noninfectious inflammatory disease such as granulomatous meningoencephalitis, and trauma. The latter seemed unlikely given the lack of history of any traumatic event.


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