Metastatic disease of the paraspinal muscles: electromyographic and histopathologic correlation in early detection

Electromyographic examination may demonstrate severe segmental compromise of the posterior primary ramus and relative sparing of the anterior ramus as the earliest objective evidences of spinal and paraspinal metastases. Antecedent studies, including roentgenographic, radioisotopic and neurologic investigations, are often initially normal, failing to reveal the underlying cause of the progressive back pain. The present report demonstrates metastatic spread both through the paravertebral venous plexus and by direct extension in contiguous muscle. In this special instance, segmental 4+ fibrillations in the paraspinal muscles are electrophysiologic manifestations of a local, active process of denervation rather than a remote effect of the malignant disease, as has been suggested by others.