US and MR imaging of peripheral nerves in leprosy

Objective. To analyze peripheral nerves with ultrasonography (US) and magne tic resonance imaging (MR) in leprosy and assess the role of imaging in lep rosy patients. Design arm patients. Fifty-eight nerves with abnormal clinic al features or electromyograms were examined in 23 leprosy patients by mean s of gray-scale US, Doppler US and MR imaging. Image analysis included: mea surement of nerve cross-sectional area; assessment of nerve structure and M R signal intensities; identification of nerve compression within osteofibro us tunnels; detection of endoneural color flow signals and Gd-DTPA enhancem ent. Correlations were made with clinical findings and a control group of 2 0 subjects. Fourteen nerves in active reversal reaction were followed up af ter therapy. Results. Leprosy nerves were classified into three groups based on imaging appearance: group I consisted of 17 normal-appearing nerves; group II, of 3 0 enlarged nerves with fascicular abnormalities; group III, of 11 nerves wi th absent fascicular structure. Group II nerves were from patients subjecte d to reversal reactions, 75% of patients with group III nerves had a histor y of erythema nodosum leprosum. Nerve compression in osteofibrous tunnels w as identified in 33% of group II and 18% of group III nerves. Doppler US an d MR imaging were 74% and 92% sensitive in identifying active reactions, ba sed on detection of endoneural color flow signals, long T2 and Gd enhanceme nt. In 64% of cases, follow-up studies showed decreased color flow and Gd u ptake after steroids and decompressive surgery. Conclusion. US and MR imaging are able to detect nerves abnormalities in le prosy. Active reversal reactions are indicated by endoneural color flow sig nals as well as by an increased T2 signal and Gd enhancement. These signs w ould suggest rapid progression of nerve damage and a poor prognosis unless antireactional treatment is started.