Evidence of Innervation in Talc-Induced Pleural Adhesions

Abstract

To conduct a detailed morphologic and ultrastructural study of pleural adhesions following talc pleurodesis. Talc with a main particle size of 8.36 +/- 0.2 mum (mean +/- SEM) and at a dose of 200 mg/kg in a 2-mL slurry was instilled via a small catheter into the pleural cavity of 10 male rabbits. Five rabbits were killed at 1 week, and five rabbits were killed at 1 month after instillation. At autopsy, after macroscopically observing the pleural cavity, adhesions were excised from opposing pleural surfaces and processed for histopathologic, immunocytochemical, and ultrastructural study. At 1 week, all adhesions examined were mesothelium-covered fibrovascular bands containing well-developed blood and lymphatic vessels establishing a structural continuity between both pleural layers. Nerves were present in adhesions from 20% of the rabbits. They consisted of a single fascicle containing 5 to 20 thin myelinated axons of various diameters (1 to 6 microm) uniformly distributed throughout the nerve section. The anatomic location of the adhesion did not appear to influence its overall morphology. As early as at 1 week, adhesions are well-formed structures more resembling newly formed pleural tissue than a simple scar. Nerve fibers in pleural adhesions are reported for the first time, which suggests that these adhesions are potentially capable of conducting pain stimuli. Further studies are required in order to confirm our results in human pleural adhesions.