Early detection of subclinical neuropathy and its evolution in newly diagnosed patients of leprosy started on multidrug therapy.

Background: Early detection of nerve impairment and its progression is critical in all leprosy cases, regardless of spectrum and treatment. This study aims to identify subclinical neuropathy at presentation in newly diagnosed leprosy patients and to monitor its progression after initiating multidrug therapy (MDT) using a combination of clinical nerve palpation, small fibre neuropathy tests (e.g. vibration, temperature, touch, pain, sweat), monofilament testing (MFT), voluntary muscle testing (VMT) and nerve conduction studies (NCSs).

Methods: We studied 38 nerves among 19 patients and followed them for 12 months to assess neuropathy progression. Nerve palpation was evaluated clinically at baseline, while MFT was performed on the ulnar, median and posterior tibial nerves at baseline and 1 y. VMT and NCSs were conducted at both baseline and 12 months. Small fibre neuropathy was assessed using temperature (test tube), vibration (vibration perception threshold), sweating (starch iodide test) and pain responses at baseline.

Results: Among the study cohort, 52.6% had borderline tuberculoid leprosy, followed by lepromatous leprosy (31.5%). Seven patients (36.8%) presented with a reaction at baseline. Major nerve trunks that were thickened included the ulnar nerve (52.6%) and common peroneal nerve (31.6%). Five patients had normal NCSs at baseline and 14 (73.4%) had abnormalities at baseline through NCSs and MFT. Thickened nerves had decreased nerve conduction and amplitude at baseline and more in the lepromatous spectrum. When they were followed up, two patients improved, five had no change and seven worsened from baseline in the NCSs. One patient had an abnormal NCS when followed up from the normal baseline NCS. The pattern of neuropathy was predominantly axonal and two of them were mixed (both axonal and demyelinating). MFT, compared with NCSs, was found to help detect both small and large fibre involvement.

Conclusions: A combination of clinical tests and periodic NCSs is essential for detecting the progression of leprosy neuropathy. Neuropathy continued to progress despite 1 y of MDT, particularly in patients with early involvement at baseline.