Histopathology of the flexor tendon sheaths and its relevance in idiopathic carnal tunnel syndrome

Compression of the median nerve in the carpal tunnel can be produced by a v ariety of factors, including fractures, metabolic disturbances, rheumatoid arthritis or anatomical anomalies. When it is not possible to identify a sp ecific cause, the term "idiopathic carpal tunnel syndrome" is used. Althoug h this disease is very common, its pathophysiology is still unclear. In the past, the presence of a chronic non-specific tenosynovitis around the flex or tendons was postulated but several investigations failed to show any inf lammatory reaction in the carpal synovium. In this study, the histology of the flexor tendon sheaths in a group of 50 patients surgically treated for idiopathic carpal tunnel syndrome (ICTS) have been investigated both from t he qualitative (histopathology) and quantitative (micrometric evaluation) p oints of view. Lack of acute or chronic inflammatory cells, connective diso rganization, and vascular modifications are the main histological findings which are present in all the specimens, regardless of the patient's age, th e duration of the sensory symptomatology or the severity of the neurologica l lesion on EMG exam. The carpal synovium in these patients appeared thicke ned when compared to the specimens obtained from the control group. However , on micrometric evaluation a relationship between synovial thickness and s everity of the symptomatology or of the EMG data was not observed. The carp al synovium in ICTS has a consistent histological appearance and is increas ed in thickness when compared with normal specimens.