The Curious History of the External Petrosal Nerve: Did Citations Replace Observations?

Why clinicians should know about it

• Picked for Anatomy (paper of the day, 31 October 2026): Evidence-based reassessment of a disputed cranial nerve structure

Abstract

Anatomical knowledge is founded on repeated observation, independent verification, and transmission through authoritative texts. Although this process typically strengthens scientific understanding, transmission through textbooks may occasionally perpetuate observations that have not undergone sustained empirical confirmation. The external petrosal nerve (EPN) provides an unusually well-documented historical example of this phenomenon. Primary and secondary sources pertaining to the EPN published between 1834 and 2026, including original German and Latin sources, were critically examined. Historical accounts were compared with modern anatomical, embryological, histological, and microsurgical investigations of the facial nerve and middle cranial fossa. The modern concept of the EPN can be traced directly to Friedrich Bidder's original description published in 1836. Although several of Bidder's contemporaries questioned his interpretation, the structure continued to be described in anatomical textbooks and review articles for nearly two centuries, including recent editions of Gray's Anatomy. In contrast, none of the anatomical atlases we searched, and none of the twentieth- or twenty-first-century anatomical investigations reviewed, provided firm independent evidence supporting the EPN as a distinct anatomical structure. The historical record suggests that acceptance of the EPN resulted primarily from repeated citation rather than independent anatomical verification. Beyond reassessing the anatomical status of the EPN, this study illustrates how scientific authority may accumulate through successive secondary sources despite limited primary evidence. The EPN provides an instructive case study in evidence-based anatomy and highlights the importance of periodically re-examining accepted anatomical observations.

Abstract as published, via PubMed.