Detection of sensory deficits in fine nerve fibres in leprosy diagnosis.

Objectives: The purpose of this study was to determine reference points for thermal perception in cutaneous lesions of leprosy, a disease caused by Mycobacterium leprae characterised by hypoesthesia in skin lesions due to nerve and Schwann cell infection. Early diagnosis is essential to control transmission and effectively treat the disease.

Methods: Quantitative thermal testing (QTT) has been proposed as a valuable tool for early detection of the disease, initiation of treatment, and monitoring of nerve damage. A thermal analyser was used to determine warm and cold perception thresholds (WPT and CPT, respectively) in skin lesions of 42 leprosy patients and 22 healthy controls.

Results: The thresholds were determined using a 0.25 cm² thermal stimulator, the method of limits, and the receiver operating characteristic (ROC) curve. Thermal thresholds were higher in patients' skin lesions compared to unaffected areas and controls. The reference points calculated for the WPT and CPT were 36.55 and 26.35°C, respectively, with high sensitivity and specificity.

Conclusion: The nerve fibres affected by leprosy caused altered thermal sensitivity in the patients' lesions, especially in warm sensation. A smaller thermal stimulator and the method of limits were effective in detecting early sensory deficits in nerve fibres, demonstrating the potential for early detection of the disease.