MSFinals-3102

A 32-year-old woman complains of numbness and ‘pins and needles’ in her left leg that has been present for 48 h after a long flight. On examination, there is reduced sensation to light touch at the lateral aspect of her left thigh, extending from the iliac crest to the knee. There is no distal sensory loss. There is preserved motor function through all muscle groups of the affected limb. There is no weakness or sensory change in the opposite limb.
What is the most likely anatomical source for this woman’s presentation?