Electromyography (EMG) along with nerve conduction studies comprise electrodiagnostic testing, which is critical for accurate diagnosis of many nerve and muscle diseases. It is usually done by a neurologist or physiatrist. EMG involves inserting very thin needles into muscles in order to record and analyze their electrical activity when the muscle is at rest and when it contracts. It is typically abnormal in muscles of polio survivors that had former nerve loss. Nerve conduction studies involve measuring the speed that a nerve impulse travels down a peripheral limb nerve, and they are expected to be normal in a polio survivor without other abnormal nerve conditions.
EMG can be used to confirm a history of paralytic polio if there is doubt about the diagnosis (see Diagnosis, Post-Polio Syndrome). It can be helpful in the assessment of nerve loss in individual muscles for the purpose of planning focused strengthening exercises. It is also used to be certain that other diseases are not causing or co-existing with post-polio syndrome (Peach, 1997). EMG is not a reliable test to establish a diagnosis of PPS or to monitor progression. Studies have also not shown EMG to be reliably different in limbs of survivors who are weakening from accurately diagnosed PPS and those who are stable (Cashman et al, 1987; McComas et al, 1997).
References
Cashman, N.R., Maselli, R., Wollman, R.L., Ross, R., Simon, R., & Ante!, J.P. (1987). Late denervation in patients with antecedent paralytic poliomyelitis. New England Journal of Medicine, 317, 7-12.
McComas, A.J., Quartly, C., & Griggs, R.C. (1997). Early and late losses of motor units after poliomyelitis. Brain, 120, 1415-1421.
Peach, P. (1997). EMG: What, why, and why not. Polio Network News, 13(4), 1-2.