Clarifying Block Anatomy and Technique in a Trial of Modified Intercostal Nerve Block versus Erector Spinae Plane Block for Modified Radical Mastectomy [Letter]

Dear editor

We read with interest the randomized trial by Da et al comparing modified intercostal nerve block (MINB) with erector spinae plane block (ESPB) for modified radical mastectomy.1 The anatomical distinction between MINB and the more familiar deep serratus anterior plane block deserves clarification. The methods place the MINB needle tip deep to the external intercostal muscle, whereas Figure 1 in Da et al1 depicts injectate both within the intercostal space and deep to the serratus anterior muscle. Could the authors specify the final needle tip position relative to these structures, explain how MINB differs from a deep serratus anterior plane injection, and identify its proposed additional coverage? In particular, was blockade of the intercostal nerve trunk demonstrated, or is the expected effect primarily on its lateral cutaneous branches?2 Figure 1 in Da et al1 illustrates MINB alone; representative ESPB images, if available, would help readers compare needle placement and observed spread.

Both blocks were assessed by cold sensation over T2–T6 at 15 minutes, with coverage of fewer than three dermatomes defined as incomplete. Reporting the dermatomes blocked in each group, together with the precise testing sites on the lateral chest wall, axilla, and anterior or parasternal chest wall, would help determine whether the same success threshold represented comparable coverage of the operative field. The intervals from injection to assessment, induction, and incision would also help interpret any difference in onset. Separately, the statistical analysis and flow diagram state that no patient was excluded after randomization, whereas the limitations section states that patients with unsuccessful sensory blocks were excluded. We would appreciate clarification and, if appropriate, correction of that statement.

Both blocks were performed with patients in the lateral position, but the position maintained after injection and the position during sensory testing are not specified. When were patients repositioned for surgery, and was this interval comparable between groups? This matters when interpreting early block distribution, as postoperative position has been associated with differences in sensory spread after ESPB, although not necessarily with differences in analgesic outcomes.3 The MINB needle is described as advancing in a caudal direction, while the corresponding cranio-caudal trajectory for ESPB is not reported. Please clarify the probe orientation, skin entry site, needle advancement and final tip direction for ESPB, and whether cranial and caudal injectate spread was observed in either group. These details would make the procedures easier to reproduce and their differing sensory coverage easier to interpret.

Disclosure

The authors report no conflicts of interest in this communication.