Carpal tunnel syndrome. Anatomical and clinical correlations and morphological and ultrastructural aspects of the tenosynovial sheath.

: Specimens of tenosynovial sheath in 80 patients affected with carpal tunnel syndrome were studied histologically and by ultrastructural methods. The specimens were obtained from patients who had been submitted to decompression with neurolysis of the median nerve and synovectomy of the flexor tendons. They were divided into two groups. The first group, consisting of patients with irritative or compressive symptomatology of recent occurrence, presented thickened and oedematous synovial sheaths, with histological inflammatory features and deposits of Types 1 and 2 collagen in the perivascular and interstitial sites. Ultrastructural analysis revealed deficits in the synovial sheath cells in addition to interstitial collagen deposits. The second group of longstanding carpal tunnel syndrome with severe signs of compression presented diffuse thickening of the sheaths, with extensive fibrosis associated with hyalinosis, and Type 3 collagen deposit which at times was amyloid. It is suggested that thickening of the synovial sheaths in carpal tunnel syndrome occurs in successive stages of a proliferative nature and successively of a regressive type, with extensive fibro-hyalinosis.