Palsy is a general term that describes uncontrollable tremors in one or more parts of the body, sometimes accompanied by partial or total paralysis. The etiology of human and canine palsy is not exactly the same, but dogs can experience palsy for a number of reasons. The condition can be idiopathic, meaning there is no known cause, or can be symptomatic of an underlying condition.
Idiopathic Head Tremors
Some dogs develop a condition wherein their heads bob up and down or side to side. The tremors are idiopathic, meaning there's no known medical cause or underlying condition. The condition does not respond to seizure medication, but the tremoring appears to subside as the dog ages. The best way to alleviate an episode is to get your dog to focus his attention on a snack or a toy.
Facial paralysis is common in middle-age and senior dogs. While in humans facial paralysis is often symptomatic of a stroke, in dogs it's generally the result of nerve damage. Dogs with facial paralysis typically present drooping on one side of the face, excessive drooling and the inability to blink or chew food on the affected side. The most prevalent cause of facial paralysis is idiopathic, which is similar to a disorder in humans called Bell's palsy. Other causes include severe ear infections, polyneuropathy and brain disorders, but these usually present other symptoms.
Intention tremors occur when a dog focuses his attention on a task such as eating or chasing a ball. Similar to those seen in humans with Parkinson's disease, they typically present in the head and neck, and they completely disappear during rest or sleep. Intention tremors in dogs are generally associated with cerebellar disease, damage or infection.
Generalized or whole body tremors generally occur secondary to an underlying condition, disease process or intoxication. Causes of generalized tremors include the ingestion of household toxins or toxic plants, epilepsy, hypoglycemia, hypocalcemia, congenital myelination disorders, bacterial or viral infections, central nervous system disorders, hyper- or hyponatremia, or nonsuppurative meningoencephalomyelitis, also called white shaker dog syndrome because it's more prevalent in small white dogs.
Dogs who have recovered from distemper may suffer from distemper myoclonus later in life. It presents as involuntary, rough, rhythmic contractions in one muscle, part of one muscle or in a group of muscles. The condition does not respond to seizure medications, but some success has been seen with onabotulinumtoxinA injections. The prognosis for distemper myoclonus is mixed; some dogs are able to live with the disorder, while others are so disabled that some veterinarians recommend euthanasia.
If your dog presents with tremors, he should be examined by a veterinarian. The cause may be benign; your dog may simply be cold, fatigued or frightened. However, it's important to rule out a serious condition before it's allowed to progress. Your veterinarian will typically perform a battery of tests including X-rays, a CT scan, an MRI, a cerebrospinal fluid tap, an electromyogram, urinalysis, an electrolyte panel, a complete blood count and a biochemistry profile. Once the test results are assessed, your veterinarian will be able to determine whether the tremors are idiopathic or if an underlying condition requires further treatment.