Recently, we saw a mixed Boxer male dog that was presented due to abnormal head movements. His owner was very concerned as he had noticed that these symptoms showed increasing frequency. The dog was otherwise normal.
Please look at the following video and we will thereafter discuss which is this dog disease.
Has everyone seen the video?
What is a tremor?
Tremor is an involuntary, rhythmic oscillation of a body part that results from alternating contraction of antagonist muscles. Tremors can be localized or generalized.
What is this dog´s disease?
In this case, the dog shows intermittent head tremors. It is very important to stress that these intermittent head tremors are restricted to the head.Tremors can consist of either up and down (like shaking the head “yes”) or back and forth (like shaking the head “no”) motions.
They seem to start and stop spontaneously, but dogs may be momentarily distracted during the episode by directing their attention to something.
There are no retrospective or prospective publications and much of what is known about the disorder has been passed down from neurologist to neurologist or from vet to vet.
There have been at least 3 theories as to the origin of the tremors.
They may represent a focal seizure discharge.
They are a form of dyskinesia or a spontaneous discharge from the basal nuclei which are involved in patterned motor activity.
They may be an abnormality of the stretch mechanism and the proprioceptive pathway of the head (trigeminal nerve). this theory may explain why the head tremors temporarily stop when their attention is diverted i.e. when they are directed to look at you or something else, the neck muscles tense which may release the stretch mechanism that is provoking the tremors.
Thus far, patients presenting intermittent head tremors have not developed any other neurological deficits and generalized seizure activity has not been reported.
How can we make the diagnosis?
Diagnosis is possible by symptoms and considering that some breeds are predisposed: Boxer, Dobermann, English bulldog, Labrador retriever,Bassett hound, Great Dane, Malamute.
Head bobbing does not only affect pure bred dogs. It is possible to see it in some of the mixed breeds that have one of the breeds with tremors in them.
Diagnostic evaluations, including MRI and spinal fluid analysis results, are typically normal. Nevertheless, if the dog develops any persistent neurological deficits, then a thorough workup would be in order.
Differential diagnosis must include causes of encephalitis, hypocalcemia and toxicities (hexachlorophene, metaldehyde, mycotoxins, organophosphates).
Is there a treatment?
No treatments have been recognized as universally beneficial to date. The tremors are not life-threatening and may be more of a nuisance to the owner than to the patient. The response to antiepileptic drugs has been mixed.
So we decided not to treat the dog and follow his behaviour.
To date, the disease has not worsened and as time goes by, the owner is confident that it will not progress.
It is however important to distinguish, should you have a Google search, Intermittent head tremors from Idiopathic tremor syndrome (“white shakers”).
Spontaneous generalized tremors (vs tremors restricted to the head) have been recognized in dogs, most commonly small breeds with white hair coats (e.g., Maltese, West highland white terriers). This syndrome can also occur in other breeds without white hair coats. Affected dogs are typically 6 months to 5 years old. There is an abrupt onset of a mild to severe generalized, high frequency tremor, affecting the limbs, trunk, and head. The tremor is worse with excitement and absent during sleep. Other neurological deficits are uncommon but may include seizures, vestibular dysfunction, and weakness.
Cerebrospinal fluid analysis typically shows a mild increase in leukocytes, mostly mononuclear cells. Other diagnostics, including test for infectious diseases, are normal. Treatment consists of immunosuppressive doses of prednisone (2-4 mg/kg/day). Signs typically resolve within one week, and the dose is gradually tapered over the ensuing 2 to 4 months. Relapse can occur if treatment is stopped too soon. This is treated with a second course of prednisone. The long-term prognosis is good. The cause of this syndrome is unknown, but the inflammatory CSF and the response to corticosteroids suggest an inflammatory, possibly immune-mediated, disorder.
Hope this helps,
David Prandi Chevalier