Diagnostic assessment of ulnar nerve thickness in leprosy using high-resolution ultrasonography versus magnetic resonance imaging

Background: Nerve thickening in leprosy is a clinical hallmark and helps in distinguishing leprosy from other peripheral neuropathies. Traditional clinical examination via palpation is subjective and prone to variability. Imaging techniques such as High-Resolution Ultrasound (HRUS) and Magnetic Resonance Imaging (MRI) offer more objective and reliable methods for assessing nerve thickening. This study aimed to evaluate the efficacy of HRUS in comparison to MRI in detecting nerve thickening in leprosy patients.

Methods: A prospective study was conducted at a tertiary care hospital in India, involving 11 patients (22 ulnar nerves) diagnosed with leprosy. MRI was performed with a 1.5 Tesla (T) scanner, and HRUS was done using a linear array high-frequency probe (8-13 MHz). Cross-sectional areas of ulnar nerves were measured, and statistical analysis was performed using SPSS software to compare results from HRUS and MRI.

Results: MRI detected nerve thickening in 68.2% of nerves, while HRUS identified thickening in 47.6%. HRUS demonstrated a sensitivity of 57.1% and a specificity of 71.4%. Despite its lower sensitivity compared to MRI, HRUS proved valuable in confirming nerve thickening, with a positive predictive value of 80%. MRI showed superior accuracy in measuring nerve thickness.

Conclusion: HRUS, while less sensitive than MRI, shows high specificity, making it an effective tool for confirming nerve thickening, particularly in pure neuritic leprosy. It can also monitor nerve thickness changes during follow-up. Further studies using higher-frequency probes and larger sample size are recommended to optimize HRUS for routine diagnostic use.