Electromyographic abnormalities following myelography.

Electromyographic (EMG) abnormalities were found in 13 of 32 patients with previously normal studies following myelography. These abnormalities usually developed by the first day after myelography and resolved by the fourth day. The changes were evenly divided between those restricted to a single paraspinal muscle level, thus mimicking the frequent findings in radioculopathy, and those present bilaterally and at multiple levels. We were unable to correlate these EMG changes with the clinical status of the patient or with events occurring at myelography. Thus, the performance of EMG within four days following myelography can lead to false-positive results if paraspinal muscle EMG abnormalities are used as the diagnostic criteria.