Osteoid osteomas stained with the Bielschowsky axon stain, demonstrated nerve fibers within the matrix of the nidus in sixteen of eighteen lesions studied. These fibers were associated with blood vessels and were found in greatest abundance adjacent to arterioles. Routine hematoxylin and eosin stains failed to reveal these fibers. Similar but less prominent findings were evident in two of the three osteoblastomas studied.
The pain of these lesions may be mediated by the autonomic nervous system via these nerve fibers. It is postulated that tue neural elements demonstrated are sensitive to changes in vascular pressure.