Acta Scientiae Veterinariae, 2016. 44(Suppl 1): 150
Rafael Oliveira Chaves , Bruna Copat , João Pedro Scussel Feranti , Dênis Antonio Ferrarin, Marcelo Luis Schwab , Luciana Schneider , Raqueli Teresinha França & Alexandre Mazzanti
Secondary neurological disorders to hypothyroidism are unusual in dogs, especially when compared with other
clinical signs, such as lethargy, weight gain and dermatological alterations. When manifested, these signals refer to the
peripheral or central nervous system and the most common include: vestibular disease, seizures, laryngeal paralysis, polyneuropathy
and paralysis of the facial nerve. Several reports of neurological disorders associated with hypothyroidism are
found in literature. In the national literature, however, there are few reports on the subject. Thus,
the aim of this study was to report a case of facial paralysis associated with hypothyroidism in a dog.
A 7-year-old canine, male boxer, was referred to the Veterinary Medical Teaching Hospital of the
UFSM with a history of difficult water and food intake and asymmetry of the face for seven days. On neurological examination,
the animal was alert and with normal locomotion, postural reactions and segmental reflexes. In
the evaluation of the cranial nerves, there was a menace response absent the right side, however with preserved vision. There was palpebral and lip ptosis of the right side and absence of palpebral reflex on the same side. The diagnosis of facial paralysis associated with hypothyroidism was based on the history, clinical and
neurological examination findings, laboratory assessment of thyroid function by observing low serum free T4 and high
concentrations of TSH, the therapeutic response after supplementation levothyroxine sodium, and exclusion of other possible
causes, such as otitis interna and traumatic. The pathogenesis of this change associated with hypothyroidism is not
completely understood, although it is believed that cranial nerve paralysis (trigeminal, facial and vestibulocochlear) may
result from the resulting compression of myxedema deposit nerve or in the tissues of the head and neck, demyelination
caused by disordered metabolism of Schwann cells, decreased blood perfusion of the inner ear secondary to hyperlipidemia
and increased blood viscosity or metabolic defects ranging from change in axonal transport to severe axonal loss. Treatment
consists of supplementation of levothyroxine and most dogs with neurological disorders associated with hypothyroidism
will present partial or total improvement of clinical signs between two and four months, generally being observed improvement
within the first week of treatment. In the dog this report, after the beginning of treatment, improvement was observed
partial and total clinical signs in 15 and 32 days, respectively. Therefore, with appropriate treatment, hypothyroidism is a
disease with an excellent prognosis. The report brings to clinical relevance, the importance of hypothyroidism in the differential
diagnosis of facial paralysis in dogs with face asymmetry history, the laboratory evaluation of thyroid function
and response to therapy with levothyroxine sodium supplementation essential for definitive diagnosis
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