“Good” Leg and a “Bad” Leg
Dr. Bruno’s Original Post: It’s well-known that “good” limbs, those thought to be unaffected by polio, commonly show electromyography (EMG) evidence of prior poliovirus damage. A large study from India brings home this point.(1)
EMGs were performed on all four limbs (not something we recommend) in 116 polio survivors. In 42% of limbs that survivors said were “unaffected by polio,” EMG revealed evidence of poliovirus damage. On manual muscle testing, 26% of the "unaffected" muscles with poliovirus damage on EMG had decreased strength.
This study is a reminder that "non-paralytic" polio (NPP) wasn't necessarily “damage free” polio. For example, it was reported in 1953 that 39% of those diagnosed with NPP had measurable weakness on manual muscle testing in at least one muscle group. A 1954 paper - “The Infrequent Incidence of Nonparalytic Poliomyelitis” - documented that 89% of polio survivors who were acutely "persuasively nonparalytic" had "very definite muscle weakness" as long as three years after the diagnosis of NPP.
So, it should be no surprise that more recent studies have documented late-onset weakness and fatigue in NPP survivors. A study of 828 polio survivors found new muscle weakness and fatigue, respectively, in 38% and 34% of those who had been paralyzed and in 14% and 21% of those diagnosed with NPP.
What’s more, study of 34 sets of twins found PPS symptoms in 71% of the twins who had had paralytic polio and "PPS-like symptoms" in 42% who had had no symptoms of paralysis. (2)
I wasn’t surprised when Post-Polio Institute patients would report that their "good" (unaffected) muscles were becoming weaker while their obviously polio-affected muscles were not. Taken together, the studies above are reminders that overworking your “unaffected good muscles” could make a good limb turn ”bad".
For more information, please look under the subjects of “Fatigue” and “Poliovirus” in the Index of the Encyclopedia of Polio and PPS.
References:
(1) Ann Indian Acad Neurol. 2016; 19(1): 44–47)
(2) Bruno, RL. Paralytic Versus "Non-Paralytic" Polio: A Distinction without a Difference? Am J Physical Med Rehabil, 2000; 79: 1-9.)