Paravertebral muscle metastases as imaged by magnetic resonance venography: a brief report.

Paraspinal muscle metastasis as initially suggested by an electromyographic pattern of isolated posterior primary ramus denervation and subsequently confirmed by magnetic resonance imaging has been reported. However, despite widespread systemic tumor dissemination, metastases to other skeletal muscle occurs infrequently. Uniquely, the paraspinal muscles are drained by the paravertebral plexus of veins. Valveless and at very low pressures, they communicate directly by collaterals with the portal system. Valsalva maneuvers with sudden increases of pressure within the intra-abdominal and intrathoracic cavities can force venous blood from the systemic circulation into the paravertebral plexus of veins. These same venous surges potentially carry tumor emboli to the vertebrae and/or from the vertebral medulla to the adjacent paravertebral muscle by the venous communicators. The inherent increased vascularity of metastatic tumor relative to the surrounding paraspinal muscle as demonstrated by magnetic venous angiography for the first time now permits earlier confirmation and biopsy of the electromyographic-suspected metastatic lesion. In this reported instance of a magnetic resonance imaging-recognized primary lung metastasis confirmed by magnetic resonance venography, there is the future promise of identifying earlier and smaller lesions by this technique.