Horner Syndrome Following Intercostal Nerve Block Via an Anterolateral Approach in Breast Lumpectomy: A Prospective Nested Case-control Study.

Background: Lumpectomy is important for preventing malignant changes in benign tumors and diagnosing malignant tumors. Intercostal nerve blocks (ICNBs) are useful for breast lumpectomy as either the primary anesthetic or as an adjuvant anesthetic procedure. To our knowledge, no studies have evaluated the association between Horner syndrome and ICNB.