Page 305 Guide to Pain Management in Low-Resource Settings

Chapter 38

Diagnostic and Prognostic Nerve Blocks

Steven D. Waldman

What are the assumptions clinical impression. Laboratory and radiological testing

underlying the use of nerve are often the next place the clinician seeks reassurance,
blocks in pain management? although the lack of readily available diagnostic testing in
the low-resource setting may preclude their use.
Fortunately, diagnostic nerve block requires
Th e cornerstone of successful treatment of the patient
limited resources, and when done properly, it can pro-
with pain is a correct diagnosis. As straightforward as
vide the clinician with useful information to aid in in-
this statement is in theory, success may become diffi cult
creasing the comfort level of the patient with a tentative
to achieve in the individual patient. Th e reason for this
diagnosis. However, it cannot be emphasized enough
diffi culty is due to four disparate, but interrelated issues:
that overreliance on the results of even a properly per-
Pain is a subjective response that is diffi cult if not
formed diagnostic nerve block can set in motion a se-
impossible to quantify;
ries of events that will, at the very least, provide the pa-
Th e pain response in humans is made up of a variety
tient with little or no pain relief, and at the very worst,
of obvious and not-so-obvious factors that may serve to
result in permanent complications from invasive surger-
modulate the patient’s clinical expression of pain either
ies or neurodestructive procedures that were justifi ed
upward or downward;
solely on the basis of a diagnostic nerve block.
Our current understanding of neurophysiological,
neuroanatomical, and behavioral components of pain is
incomplete and imprecise; and What would be a roadmap for
Th ere is ongoing debate by pain management spe- the appropriate use of diagnostic
cialists as to whether pain is best treated as a symptom nerve blocks?
or as a disease.
Th e uncertainty introduced by these factors can It must be said at the outset of this discussion, that even
often make accurate diagnosis very problematic and the perfectly performed diagnostic nerve block is not
limit the utility of neural blockade as a prognosticator without limitations. Table 1 provides the reader with a
of the success or failure of subsequent neurodestructive list of do’s and don’ts when performing and interpreting
procedures. Given the diffi culty in establishing a correct diagnostic nerve blocks.
diagnosis of a patient’s pain, the clinician often is forced First and foremost, the clinician should use
to look for external means to quantify or fi rm up a shaky the information gleaned from diagnostic nerve blocks

Guide to Pain Management in Low-Resource Settings, edited by Andreas Kopf and Nilesh B. Patel. IASP, Seattle, © 2010. No responsibility is assumed by IASP 293
for any injury and/or damage to persons or property as a matter of product liability, negligence, or from any use of any methods, products, instruction, or
ideas contained in the material herein. Because of the rapid advances in the medical sciences, the publisher recommends that there should be independent
verifi cation of diagnoses and drug dosages. Th e mention of specifi c pharmaceutical products and any medical procedure does not imply endorsement or
recommendation by the editors, authors, or IASP in favor of other medical products or procedures that are not covered in the text.