2006 ACVIM Abstracts 

Chinooks

ABSTRACT #87 
CHARACTERIZATION AND MODE OF INHERITANCE OF AN 
EPISODIC DYSKINESIA IN THE CHINOOK DOG. RA Packer1,DP 
O’Brien1, JR Coates1, GS Johnson2. 1Department of Veterinary Medicine 
and Surgery, University of Missouri, Columbia, MO; 2Department of 
Veterinary Pathobiology, University of Missouri, Columbia, MO. 

Episodic dyskinesias (EDs) are episodes of abnormal movement or tone 
distinguished from seizures by the character of the episode and a lack of 
seizure activity on ictal EEG. We report a familial ED in Chinook dogs. 

Pedigrees and medical histories were reviewed for 289 Chinooks. A family 
of 173 dogs was used for analysis. Episodes were classified as seizures, ED, 
or unknown based on the owner’s description or videotapes, and segregation 
analysis performed. 

ED was identified in 32 dogs and characterized by inability to stand or 
ambulate, head tremor, and involuntary flexion of one or multiple limbs, 
without loss of consciousness or autonomic signs. Episode duration was 
variable, ranging from seconds to hours. Interictal EEGs recorded on two 
dogs with ED were normal. Four dogs had generalized tonic-clonic seizures, 
3 had ED and generalized tonic-clonic seizures, and 10 had episodes of 
undetermined type. 

ED segregation was consistent with an autosomal recessive trait. There 
was no sex predilection, and affected individuals were born to unaffected 
parents. In litters where status of littermates was known, 23.7% of offspring 
were affected (23 out of 97 individuals). Linkage analyses are currently 
underway. 

This movement disorder is prevalent in the Chinook breed. The episodes 
are most likely an ED of basal ganglia origin, but atypical seizures and 
muscle membrane disorders remain possible etiologies. The generalized 
seizures may be a variant phenotype of the same mutation that results in the 
ED, or the two syndromes may be independent.