Meralgia paresthetica (MP) is a purely sensory mononeuropathy of the lateral femoral cutaneous nerve (LFCN), which can mimic a high lumbar radiculopathy. Characterized by sensory disturbances and burning paresthesias in the anterolateral thigh, it is most commonly caused by nerve entrapment as the nerve exits the pelvis under the inguinal ligament. While 85% of patients have a favorable course, 15% may develop chronic intractable pain. The LFCN arises from the dorsal branches of the L2 and L3 spinal nerves and emerges from the lateral border of the psoas major, crossing the iliacus obliquely. It then passes under the inguinal ligament medial and inferior to the anterior superior iliac spine (ASIS). It eventually passes over the sartorius where it becomes more superficial to innervate the anterolateral cutaneous region from the thigh to the knee. The course of the nerve is known to be highly variable.

While treatment for MP is typically conservative, injections have been employed in recalcitrant cases with good success. Ultrasound guidance, especially given the variability of the nerve location, increases the accuracy of the injection. In this chapter, we will present an in-plane technique, short axis to the LFCN. We will also demonstrate out-of-plane confirmation. Safety considerations include an intraneural injection or injection of the vascular structures that travel with the nerve.