To the Editor:—
Nash et al. 1provide some fascinating anatomical data, based largely on plastination techniques and confocal microscopy, to suggest that the investing layer of cervical fascia may not exist. We write first to correct some of their assumptions related to our previous anesthetic work and second to crystalize a general hypothesis that stems from their conclusion.
Nash et al. 1state in their opening paragraph that the previous work of Pandit et al. 2concluded that the “superficial cervical plexus block” injection should be placed superficial to the investing layer. In fact, the study of Pandit et al. 2(in preserved cadavers) concluded that only an injection deep to the putative investing layer would enable the injectate to spread beyond the prevertebral fascia. Pandit et al. 2observed that a strictly superficial injection did not spread beyond the subcutaneous layers. The implication was that a purely superficial or subcutaneous injection would be clinically ineffective. It was this that led to the suggestion that an injection just deep to the so-called investing fascia should be properly termed an intermediate cervical plexus block,3whereas an injection deep to the prevertebral fascia should be termed a deep block.4
The conclusion of Nash et al. 1(which we find anatomically persuasive) that the investing fascia does not exist not only raises further problems for proper nomenclature of the various anesthetic blocks, but also leads to a specific hypothesis.
If the result of Nash et al. 1is correct and the investing fascia does not, in fact, exist, the clinical efficacy of a subcutaneous injection should be as effective as an intermediate injection below the putative investing fascia. If, however, the result of Pandit et al. 2is correct, the intermediate injection should be more effective clinically than the subcutaneous injection. We are currently investigating this hypothesis in a clinical study and hope to report our results soon.
Although it might be supposed (as a matter of prejudice) that we hope our own results are correct and that “intermediate” injections prove to be more effective than simple subcutaneous ones, it would actually be desirable for overall patient care if the more superficial injections were found to be equally effective. As we have observed elsewhere, safety is increased by more superficial, as opposed to deep, injections.5,6
In summary, Nash et al. 1have offered some truly exciting anatomical data on which to formulate an important clinical question.
*John Radcliffe Hospital, Oxford, United Kingdom. jaideep.pandit@physiol.ox.ac.uk
