ELECTRON MICROSCOPIC STUDY OF STAPEDIUS TENDON IN OTOSCLEROSIS

Abstract

Objective: This study was undertaken to study the ultrastructural alterations of stapedius tendon in otosclerosis compared to normal control case. Methods: Human stapedius tendon from 10 otosclerotic patients and 5 posl-monem normal (non otosclerotic) cases were studied using transmission electron microscope. Results: Tendocytes of control cases showed dense clumped heterochromatin and indistinct nucleoli. They assumed a stellated morphology and showed abundant cytoplasm with organelles and inclusions. They gave rise to fine cytoplasmic processes, which ended up with collagenic aggregates .9/ different sizes. The extracellular matrix of control cases consisted of amorphous .ground substance, collagenic fibrils, aggregates and elastin. Collagenic bundles ran in different directions. Collagenic aggregates assumed mostly rounded profiles. Fibril diameter rangedfrom 35-65 nm. in otosclerosis; tendocytes were compressed and parallel to each other and to the surrounding collagenic fibrils and aggregates. They were elongated or spindle-shaped. Their processes were retracted except for a few fine long processes at cell poles. Their cytoplasm was withdrawn, minimized and compressed in-between dense collagenic bundles showing no obvious organelles or inclusions. They displayed a strict parallel orientation along the tendon axis. CytoplasmiC processes of otosclerotic tendocytes had partitioned the newly formed collagenic fibrils into rounded and mostly elongated aggregates. Tendonous components in otosclerosis were not evenly distributed and showed a heterogeneous character and a.reduction of the elastin content. Fibril diameter was reduced 10 30-50 nm. Otosclerosis induced these ultrastructural changes probably due to tendon immobility. Conclusions: The histopathological changes raf..:ing place in otosclerosis are not only confined to bone but also a substantial ultrastructural alteration is affecting the tendon of stapedius as well, propably due to tendon immobility.