Evaluation of Transcranial Magnetic Stimulation for Detecting Subclinical Neuroplastic Changes in Newly Diagnosed Leprosy Patients without Peripheral Neuritis

Purpose.

Leprosy is a chronic infectious disease predominantly affecting peripheral nerves, often leading to sensory and motor deficits. Early detection of neuroplastic changes before clinical manifestations may improve diagnosis and rehabilitation. Transcranial magnetic stimulation (TMS) is a non-invasive tool capable of assessing corticospinal excitability and detecting subclinical central nervous system involvement.

Material & Methods.

A cross-sectional study was conducted involving 51 newly diagnosed leprosy patients aged 18–45 years without clinical signs of peripheral neuritis and 51 age- and sex-matched non-leprosy (healthy) controls. Resting motor thresholds and motor evoked potential (MEP) amplitudes were measured bilaterally in four hand muscles: the first dorsal interosseous, abductor pollicis brevis, extensor pollicis brevis, and abductor digiti minimi, using TMS and electromyography.

Results.

Leprosy patients exhibited significantly elevated motor thresholds across all examined muscles compared with controls (e.g., right first dorsal interosseous mean threshold 65.2 vs. 55.1, p<0.0001). Concurrently, MEP amplitudes were markedly reduced in the leprosy group (e.g., right abductor pollicis brevis 36.75 vs. 74.35, p<0.0001), indicating decreased corticospinal excitability and early neuroplastic changes despite absence of clinical peripheral neuritis.

Conclusions.

TMS may detect early subclinical corticospinal pathway dysfunction in newly diagnosed leprosy patients without peripheral neuritis, highlighting its potential as a sensitive diagnostic and monitoring tool for neuroplastic alterations in leprosy.