Pathology of the flexor tendon sheath in the spontaneous carpal tunnel syndrome.

The histological features of the flexor tendon sheath in the spontaneous carpal tunnel syndrome were studied. The main differences between our findings and previous studies were twofold. Firstly a striking absence of inflammation in our material and secondly the diversity of the pathological changes encountered--alterations in the connective tissue especially the collagen; proliferation with thickening of the tissues of the tendon sheath; fibrosis; amyloid deposition; oedema; vascular lesions including thickening of vessels walls, intimal hyperplasia, and thrombosis; and a foreign body giant cell reaction. Although the lesions described here may not be significant in every case in which they are encountered, they do appear to support the view that pressure in the carpal tunnel and ischaemia are the important factors in a majority of cases of the spontaneous carpal tunnel syndrome.