Does the investing layer of the deep cervical fascia exist?

Background: The placement of the superficial cervical plexus block has been the subject of controversy. Although the investing cervical fascia has been considered as an impenetrable barrier, clinically, the placement of the block deep or superficial to the fascia provides the same effective anesthesia. The underlying mechanism is unclear. The aim of this study was to investigate the three-dimensional organization of connective tissues in the anterior region of the neck. Methods: Using a combination of dissection, E12 sheet plastination, and confocal microscopy, fascial structures in the anterior cervical triangle were examined in 10 adult human cadavers. Results: In the upper cervical region, the fascia of strap muscles in the middle and the fasciae of the submandibular glands on both sides formed a dumbbell-like fascia sheet that had free lateral margins and did not continue with the sternocleldomastoid fascia. In the lower cervical region, no single connective tissue sheet extended directly between the sternocleidomastoid muscles. The fascial structure deep to platysma in the anterior cervical triangle comprised the strap fascia. Conclusions: This study provides anatomical evidence to indicate that the so-called investing cervical fascia does not exist in the anterior triangle of the neck. Taking the previous reports together, the authors' findings strongly suggest that deep potential spaces in the neck are directly continuous with the subcutaneous tissue.