We thank Drs. Pandit, Dorje, and Satya-Krishna for their encouraging comments on our article.1From the anatomical angle, we support the suggestion regarding proper nomenclature of the various anesthetic blocks,2but we are concerned about what anatomical landmark could be used to demarcate a “superficial” and an “intermediate” cervical plexus block. We understand that a superficial block in clinical practice involves making an injection in the subcutaneous layer, whereas an intermediate injection is intended to be placed just deep to the sternocleidomastoid muscle.2From an anatomical viewpoint, if the investing fascia does not exist, we suggest that the location of the intermediate injection may be imprecise.
The pattern or configuration of connective tissue is much more complex than our previously held view.1,3In addition to the investing layer of deep cervical fascia, two anatomical points should also be considered when testing the hypothesis raised in the letter of Pandit et al.
One is the muscular and aponeurotic fibers of platysma. As shown in figure 5 of Nash et al. ,1these fibers cover the anterior and lateral cervical regions, are layered, and often mimic the investing layer of deep cervical fascia (also see fig. 4C of Nash et al. 1). So it may be possible to achieve the functional result predicted by Pandit et al. in their letter, despite the anatomical absence of the investing fascia. Zhang and Lee3also revealed that there is no aggregation of fibrous connective tissue connecting the sternocleidomastoid and trapezius muscles, but skin ligaments are visualized between the muscles (fig. 2b of Zhang and Lee). The structure, arrangement, and density of the skin ligaments vary greatly through the body4and could mimic the behavior of a fascia. Therefore, a number of clinical and anatomical questions must be further investigated.
*University of Otago, Dunedin, New Zealand. email@example.com