Hypothyroid-associated central vestibular disease in 10 dogs: 1999-2005.
BACKGROUND
With the exception of myxedema coma, central nervous system signs are rare in hypothyroid dogs.


OBJECTIVE
Central vestibular dysfunction is a possible and reversible manifestation of hypothyroidism.


METHODS
Medical records of dogs with vestibular dysfunction and hypothyroidism were reviewed. Of 113 records identified, 10 dogs with at least 2 concurrent clinical neurologic abnormalities localizable to the central vestibular system were included.


METHODS
Retrospective, descriptive study.


RESULTS
Median age at diagnosis was 7 years (range, 5-10 years). All dogs were referred for progressive neurologic disease. Lesions were localized to the myelencephalic region in 5 dogs and to the vestibulocerebellum in 5 dogs. Two dogs had evidence of multifocal intracranial disease. Non-neurologic physical abnormalities suggestive of hypothyroidism were absent in 7 of 10 dogs. Hypercholesterolemia was the only consistent clinicopathologic abnormality detected, and was present in 7 of 10 dogs. All dogs had total thyroxine (TT4) and free thyroxine (fT4) concentrations below reference ranges, and 9 of 10 had increased TSH concentrations. Intracranial imaging studies were normal in 5 of 8 dogs, and identified lesions consistent with infarctions in 3 of 8 dogs. Albuminocytologic dissociation was detected in 5 of 6 CSF analyses. Brainstem auditory-evoked responses disclosed prolonged wave V latencies in 3 of 4 dogs tested. No other causes of central vestibular dysfunction were identified during other diagnostic investigations. The median time from initiation of treatment to clinical improvement was 4 days. Vestibular signs resolved in 9 of 10 dogs within 4 weeks.


CONCLUSIONS
Although the pathogenesis in dogs without evidence of infarction is unknown, central vestibular dysfunction appears to be a rare but reversible neurologic sequelae of hypothyroidism.
Higgins
Michael A
MA
Department of Small Animal Clinical Sciences, Virginia-Maryland Regional College of Veterinary Medicine, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061, USA.
Rossmeisl
John H
JH
Panciera
David L
DL
D000818:Animals; D004283:Dog Diseases / Q000097:blood* / Q000188:drug therapy / Q000473:pathology; D004285:Dogs; D016057:Evoked Potentials, Auditory, Brain Stem; D005260:Female; D006937:Hypercholesterolemia / Q000150:complications / Q000473:pathology / Q000662:veterinary; D007037:Hypothyroidism / Q000150:complications / Q000188:drug therapy / Q000473:pathology / Q000662:veterinary*; D008297:Male; D012189:Retrospective Studies; D013960:Thyroid Function Tests / Q000662:veterinary; D013972:Thyrotropin / Q000097:blood*; D013974:Thyroxine / Q000097:blood* / Q000627:therapeutic use; D016896:Treatment Outcome; D015837:Vestibular Diseases / Q000188:drug therapy / Q000209:etiology / Q000473:pathology / Q000662:veterinary*; D014724:Vestibular Function Tests / Q000662:veterinary
D013972:Thyrotropin; D013974:Thyroxine