The 2016 scientific paper
Paroxysmal Dyskinesia in Norwich Terrier Dogs
Movement Disorders Clinical Practice, 2016
Luisa De Risio, DVM, MRCVS, PhD, Dipl ECVN, Oliver P. Forman, PhD, Cathryn S. Mellersh, PhD, Julia Freeman, BSc
surveyed Norwich Terriers in the United Kingdom and expresses the opinion that the episodes are a form of paroxysmal dyskinesia. From the paper:
Paroxysmal dyskinesias (PxDs) are a heterogeneous group of disorders in humans and animals characterized by recurrent episodes of sudden, abnormal, involuntary movements of variable duration.
The episodes [of the dogs in the study] were characterized by sustained muscular hypertonicity in the pelvic limbs, lumbar region, and thoracic limbs, impairing posture and locomotion without loss of consciousness. ... Episode duration generally was from 2 to 5 minutes ... The majority of affected dogs were related.
It is unlikely that the paroxysmal disorder described in the [Norwich Terrier] dogs in this study represents a form of epilepsy, considering the episode phenomenology (e.g., normal level of consciousness and awareness, lack of autonomic signs, the tendency to continue performing certain activities during the episode, and the absence of postictal signs), the similarities with PxDs in other canine breeds, the lack of response to antiepileptic drugs commonly used in canine epilepsy, and the absence of electroencephalogram (EEG) abnormalities in the 2 tested dogs.
However, differentiation between PxD and epilepsy can be very challenging,...The stereotyped licking movements movements (observed in 38% of [the Norwich Terrier] dogs in this study) can occur in epileptic patients.
Clearly more research needs to be done and better diagnostic tests developed. Currently all we have are the opinion of canine neurologists based upon videos of episodes provided by owners.
While not trying to minimize this health problem, in terms of the dog's quality of life, these episodes seem to be more distressing to the owners than to the dog (although the dog clearly knows that something is wrong). The episodes are over in a few moments, and no surgical intervention is necessary (as is frequently the case for UAS and liver shunts).
Here are several videos of episodes.
The following DNA tests were performed - for research purposes - but did not reveal any mutations. (The tests reported "clear" or "normal".)
Last updated 20160831.