The impact of using transcutaneous nerve mapping as an adjunct to ultrasonography for lateral femoral cutaneous nerve block amongst post graduate trainees: a randomized control study.

Background: Lateral femoral cutaneous nerve block is an effective treatment for meralgia paresthetica refractory to pharmacological therapy. Use of ultrasound has increased the success rate of the block. However, because of steep learning curve and anatomical variations in nerve morphology, the success rate varies amongst doctors. Recently, transcutaneous nerve mapping has been used for non-invasive localization of superficial nerves.

Methods: Study was conducted to compare the efficacy of Lateral femoral cutaneous nerve block in patients of meralgia paresthetica by post graduate trainees in pain medicine. Fifty patients were randomly divided into two equal groups. Group U (N.=25) received a block using ultrasound alone, while patients in group TU (N.=25) received block using ultrasound combined with transcutaneous nerve mapping. The efficacy of the block was compared in terms of Neuropathic Pain Symptom Inventory scores, Global Pain Scale score, requirement of rescue analgesics and complication.

Results: Both NPSI and GPS scores decreased over time, indicating pain improvement in both the groups. Group 'TU' consistently showed lower scores at all time points, suggesting a better response to treatment in terms of both neuropathic and global pain relief. The difference between groups became more prominent over time, particularly after two weeks for NPSI and six weeks for GPS. These findings indicate that Group TU had a more significant and sustained pain reduction compared to Group U.

Conclusions: Ultrasound guided Lateral femoral cutaneous nerve block combined with transcutaneous nerve mapping resulted in significantly better reduction in pain scores in meralgia paresthetica.