|Primary Orthostatic Tremor In Great Danes
Primary Orthostatic Tremor In Great Danes (General Information Sheet)
John Rossmeisl Jr., DVM, MS, DACVIM and Laurent Garosi DVM, DECVN, MRCVS
Primary OT is recently recognized neurologic disease of Great Danes that causes dramatic tremors that are visible only when the animal is standing. The tremors typically begin in the lower aspects of the legs, but can also involve the muscles of the head and face. The tremors are usually first apparent at a young age (1-2 years), and the tremors are unique in that affected dogs often appear reluctant to lie down and demonstrate what appears to be a constant “shivering” while standing suggestive almost of an involuntary dance. OT is different from other causes of tremors in that the tremors that are characteristic of the disease completely disappear when the dog walks, runs, leans against an object, or lies down.
OT has been previously mistaken for other diseases known to affect Great Danes that can cause tremors including Wobblers disease, Addison’s disease, and cerebellar disease to name a few. At this time, about a dozen Great Danes in both the United States, Canada, and the United Kingdom have been identified with OT. With the information currently available, affected dogs do not appear to be related, but a pedigree analysis has not yet been completed. Currently, the cause of OT in humans and Great Danes is unknown. The general belief is that OT is mediated by an abnormal neuronal circuit in the subcortical areas of the brain. The identification of spontaneous OT in dogs provides a unique research opportunity that may be beneficial to our continued understanding of the cause and eventual treatment of this disease in people and dogs.
Great Danes with OT appear otherwise healthy on physical examination, and generally do not have any significant abnormalities that are detectable on routine blood tests, radiographic examinations, spinal fluid analysis, and even have normal MRI examinations of their brains. There are several tests that can be relatively easily performed by a veterinarian that will further support a diagnosis of OT in a Great Dane with similar clinical signs to those described above. These include:
The tremors can be totally abolished when a standing dog is lifted off of the ground;
When a stethoscope is applied to a tremoring muscle, a sound resembling a distant helicopter rotor can be heard.
Definitive diagnosis of OT requires documentation of the characteristic tremor pattern during a conscious electromyographic (EMG) examination. EMG examinations are services offered by most veterinary neurologists.
The ideal medical treatment for canine OT is unknown at this time. However, the anticonvulsant drug phenobarbital has been shown to decrease the severity of the tremors, at least temporarily, in several affected dogs. Although insufficient data currently exists to make a definitive statement regarding the long-term prognosis associated with OT in Great Danes, it appears to be a disease that can be chronically managed with medication, although the tremors may increase in severity in some dogs over periods of months to years despite escalations in drug therapy.
The original description of OT in Great Danes is available through the Journal of Veterinary Internal Medicine website: www.jvetintmed.org
John H. Rossmeisl, Jr., DVM, MS, DACVIM
Additional information regarding affected Great Danes in the UK and Europe can be obtained through:
Laurent S. Garosi, DVM, DECVN, MRCVS
Permission to reprint as submitted for educational purposes is given.