Is it a Shiver or a Seizure?

A dog’s unusual movements may or may not be a cause for concern.

A dog’s body temperature is higher than ours—around 100-102 F—but that doesn’t mean they won’t get cold, or shiver from time to time, especially in winter. But when is it just a shiver, and when is it something more concerning, like a seizure? And what is a tremor? Are these also symptoms to watch for?
We spoke to SAGE Neurologist Vivian Lau about the differences between these distinct physiological triggers.

What is a shiver? What is a seizure?

Shivering is a way to help your dog raise their body temperature and warm up. Dogs may shiver when they’re cold, as well as when they’re nervous or fearful. Some medical issues can also cause your dog to shiver, or tremble, such as tremorgenic mycotoxins (usually from ingestion of garbage or compost) or certain electrolyte imbalances, which could make muscle twitches easier to elicit.
A seizure, on the other hand, is a symptom of a problem affecting the forebrain. A seizure could be caused by a range of potential triggers that are inside or outside the brain. Those triggers could include:

  • Metabolic issues
  • Electrolyte abnormalities
  • Brain tumors
  • Strokes
  • Trauma
  • Inflammatory conditions (either infectious or non-infectious)

Dogs are also prone to “meningoencephalitis of unknown origin” (MUO) which can cause seizures, Dr. Lau says. This is an umbrella term encompassing groups of non-infectious and non-contagious inflammatory disorders of the brain that are believed to arise from an overactive immune system. Toy dog breeds, such as Maltese and Yorkshire Terriers, and other breeds such as French bulldogs and Pugs, have a higher incidence of meningoencephalitis of unknown origin. Researchers have still not discovered the exact cause of the condition (hence the “unknown origin” part of the name) and the causes may be a combination of both genetics and environmental factors. Dr. Lau notes that most dogs who suffer from these inflammatory conditions tend to respond well to immune suppressant medications and anti-seizure medications as a long-term treatment.

How can you tell the difference?

You can alleviate a shiver caused by cold by helping your dog warm up, or you can move them away from whatever appears to be making them nervous or excited. And, if your dog is shivering, you should be able to interact with him and talk with him. Generalized seizures, on the other hand, affect the whole body and dogs can become unresponsive. Seizures can last about 1 to 2 minutes; if they last longer than 5 minutes, they are considered a medical emergency. Capture the seizure on video if you can—this is tremendously helpful to veterinarians who will try to piece together the cause of the seizure.
Primary care veterinarians can order blood work to assess whether electrolyte imbalances or low blood sugar could have caused the seizure. If there is not an obvious metabolic cause for the seizure, a patient can be referred to a veterinary neurologist where other recommended diagnostic tests could include an MRI to rule out tumors, strokes, trauma or other structural causes of seizures. Neurologists often combine MRI with a spinal tap to help diagnose common inflammatory conditions such as MUO or infectious meningitis, which is more rare in dogs.

What is a tremor?

Dr. Lau says many pet owners ask her about tremors. A tremor is usually indicated by rhythmic muscular contraction and relaxation of specific muscle groups (either localized to just the hind limbs or just the head and neck); they are mostly benign but can be indicative of more serious problems affecting specific areas of the brain (the cerebellum) or metabolic disease. One of the most common tremors is the benign idiopathic rapid postural tremor, which typically occurs when a dog is standing, but stops when they are sitting or lying down. Older dogs tend to experience these tremors more than younger dogs. As with seizures, Dr. Lau recommends pet owners film the tremors to help their veterinarian assess the cause and any treatments.

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