Sonographic pattern of median nerve enlargement in Hansen's neuropathy

Median nerve enlargement in leprosy seems to be more proximal than in carpal tunnel syndrome (CTS), but this feature has not been studied systematically. The aim of the study was to compare the sites of median nerve enlargement in patients with leprosy with that of patients with CTS.

Transverse sections of the median nerve were recorded from wrist to the mid-forearm (at distal wrist crease and at 2-cm: M1, 4-cm: M2, 6-cm: M3, 8-cm: M4 and 10-cm: M5, proximal to the distal wrist crease in the forearm) in patients with leprosy, CTS and healthy subjects using high-resolution ultrasound.

Twenty-six patients each with leprosy and CTS were compared with healthy controls. Patients with leprosy included 6 (23.1%), 7 (26.9%), 7 (26.9%) and 6 (23.1%) patients with borderline tuberculoid, borderline-borderline, borderline lepromatous and lepromatous leprosy, respectively. Cross-sectional area (CSA) of median nerve was increased in all patients with leprosy as compared to healthy controls at all points of measurement. CSA was higher among patients with leprosy as compared to CTS at all points except at the wrist. In patients with leprosy, the maximal enlargement was noted 2-cm (M1) proximal to the wrist crease with gradual tapering of the CSA proximally (p < .05). In contrast, in patients with CTS the median nerve was maximally enlarged at the distal wrist crease (p<.05).

Median nerve enlargement 2-cm proximal to the distal wrist crease distinguishes leprosy from CTS. This important discriminating sign can be used at point-of-care to identify patients with leprosy.