A 46-year-old man experiences burning pain in his left thigh and leg. The next day, he notices groups of erythematous, tender, fluid-filled vesicles in the painful region. The lesions gradually crust over the next several days as shown in the exhibit.

Which of the following dermatomes are most likely involved in this patient's disease process?

Question

A 46-year-old man experiences burning pain in his left thigh and leg. The next day, he notices groups of erythematous, tender, fluid-filled vesicles in the painful region. The lesions gradually crust over the next several days as shown in the exhibit.

Which of the following dermatomes are most likely involved in this patient's disease process?

Quizplus · Accepted Answer

11ec160b_35b1_d1b7_9249_6926fda71a09_MD0001_00 This patient has single and grouped vesicles in various stages of ulceration and crusting, which is consistent with herpes zoster (ie, shingles). Following primary VZV infection (ie, chickenpox), the virus migrates via sensory nerves to the dorsal spinal ganglia, where it lies dormant for years. Reactivation of the virus typically occurs in a single (or multiple-adjacent) ganglion. This causes hemorrhagic inflammation involving the entire peripheral nerve associated with that ganglion and eruption of a painful, vesicular rash on the skin supplied by that sensory nerve (ie, dermatome). This patient's vesicular rash primarily involves the anteromedial thigh and medial leg, which is consistent with the dermatomal distribution of L3 and L4. (Choice A) The L1 dermatome is at the level of the inguinal ligament. The L2 dermatome covers the upper anteromedial thigh but does not extend downward into the leg. (Choice C) The L5 dermatome covers the lateral thigh and anterolateral leg along with the dorsum/sole of the foot. The S1 dermatome includes the posterior thigh and leg and the lateral portion of the foot. (Choice D) The S2 dermatome supplies portions of the posterior thigh and leg as well as the perineum. S3 primarily supplies the perineum. (Choice E) Primary VZV infection (ie, chickenpox) produces a generalized vesicular rash. However, reactivation typically occurs in a single (or multiple-adjacent) spinal ganglia, leading to a rash confined to the distribution of those nerves (ie, dermatome). Educational objective: Herpes zoster reactivation typically occurs in a single or multiple-adjacent dorsal spinal ganglia, leading to a vesicular rash in a dermatomal distribution. The L3 and L4 dermatomes supply the anteromedial thigh and medial leg.

A 46-Year-Old Man Experiences Burning Pain in His Left Thigh