Internal Shivering
Question: I have been experiencing a lot of internal shivering. It used to wake me up at night but now is coming and going throughout the day as well. The problem seems to stem from my spine between and just below my shoulder blades, could this be something to do with my weakened respiratory and diaphragm muscles.
Dr. Bruno’s Response: The first step to find a cause for shivering is to make sure nothing is going on, like an infection or thyroid abnormality.
That said, I have heard over the years from a number of polio survivors reporting “internal shivering”. Your experience is probably not related to respiratory or diaphragm muscles. And it makes sense that you feel the shivering below your shoulder blades since it is your core muscles, especially in the lower chest, and also leg muscles that are the primary shivering muscles.
Remember the form and function of shivering: rhythmic contraction of muscles to generate heat and help you stay warm. Polio survivors should shiver more easily because poliovirus-damage opens skin blood vessels, allowing hot blood to flow to the skin surface, dump heat into the environment and drop your core body temperature.
There may also be a brain reason for polio survivors to shiver more easily. The "shivering center" in the brain (the posterior hypothalamus) was consistently damaged by the poliovirus, possibly making polio survivors more sensitive to being even slightly cold (for example not being warm enough in bed) and therefore shivering more easily.
Speaking of being in bed, many polio survivors have reported internal shivering in the early morning while they’re still in bed, shivering sometimes waking them from sleep. Sleepy-time shivering may have to do with your circadian body temperature rhythm. By early morning your core body temperature is at its nadir, about 3°F lower than usual, a temperature drop possibly triggering shivering.
A drop in core body temperature also may be one of the factors responsible for shivering associated with anesthesia. Studies have reported shivering in as many as 65% of non-polio survivors after general anesthesia and up to 33% after epidural/spinal anesthesia. Shivering after anesthesia is why we recommend all polio survivors’ physicians order a heating device called a "Bair Hugger" (www.bairhugger.com/3M/en_US/bair-hugger-us/) postoperatively to prevent both discomfort and shivering- caused postoperative problems.
Preventing Complications in Polio Survivors Undergoing Surgery (or) Receiving Anesthesia
For more information about temperature regulation in polio survivors, look for the topic of Temperature in the Index of the Encyclopedia of Polio and PPS