How a Medical Student’s Cranial Nerve Numbering System Led to Widespread Inaccuracies in Modern Anatomical Illustrations
Eduardo C. Corrales, MD, for the Otolaryngology Historical Society In 1778, Thomas Soemmerring, a 23-year-old medical student in Goettingen, Germany, described in his dissertation the cranial nerve numbering (I–XII), which remains in common use today. His system was based on the rostro-caudal exit points of the nerve roots from the brain. Limited by naked eye observation and poor preservation, errors were made in the rank order. The abducens nerve (VI) actually exits in the groove between the pons and medulla just rostral to the glossopharyngeal nerve (IX) and well caudal to the facial (VII) and audiovestibular nerves (VIII). To further complicate things, modern microscopic observation shows the facial nerve actually exits the pons caudal to the audiovestibular nerve. The weight of authority of this classical numbering system led generation after generation of textbook authors and their illustrators to distort human anatomy to fit with the traditional rank order. Depictions of the ventral surface of the brain and brainstem, with rare exceptions, show the exit order of abducens-facial-auditory-glossopharyngeal rather than the anatomically correct auditory-facial-abducens-glossopharyngeal. For more than 200 years, drawings have been distorted to make anatomy conform to the universally accepted numbering system. Early in medical school, physicians are taught that there is nothing left to be discovered in gross anatomy. The numbering system has been impressed upon beginning medical students, often memorized with the aid of colorful mnemonics, and thus becomes deeply engrained. In a culture that routinely questions the validity of scientific principles, physicians tend not to doubt the correctness of a well established truth such as the numbering of the cranial nerves. While it is always difficult to go against entrenched dogma, it is worth noting that legions of anatomists chose to alter reality rather than rise to this challenge. This article is based on the paper, co-authored by Robert K. Jackler, MD, and Albert Mudry, MD, PhD, and presented by Dr. Corrales at the Otolaryngology Historical Society meeting, September 10, 2012. If you are interested in presenting at the next OHS meeting, Vancouver, BC, Canada, September 30, 2013, email museum@entnet.org.To join the society or renew your membership, please check the box on your Academy dues invoice or email Catherine R. Lincoln, CAE, MA (Oxon) at clincoln@entnet.org or call 1-703-535-3738.
In 1778, Thomas Soemmerring, a 23-year-old medical student in Goettingen, Germany, described in his dissertation the cranial nerve numbering (I–XII), which remains in common use today. His system was based on the rostro-caudal exit points of the nerve roots from the brain.
Limited by naked eye observation and poor preservation, errors were made in the rank order. The abducens nerve (VI) actually exits in the groove between the pons and medulla just rostral to the glossopharyngeal nerve (IX) and well caudal to the facial (VII) and audiovestibular nerves (VIII). To further complicate things, modern microscopic observation shows the facial nerve actually exits the pons caudal to the audiovestibular nerve.
The weight of authority of this classical numbering system led generation after generation of textbook authors and their illustrators to distort human anatomy to fit with the traditional rank order. Depictions of the ventral surface of the brain and brainstem, with rare exceptions, show the exit order of abducens-facial-auditory-glossopharyngeal rather than the anatomically correct auditory-facial-abducens-glossopharyngeal. For more than 200 years, drawings have been distorted to make anatomy conform to the universally accepted numbering system.
Early in medical school, physicians are taught that there is nothing left to be discovered in gross anatomy. The numbering system has been impressed upon beginning medical students, often memorized with the aid of colorful mnemonics, and thus becomes deeply engrained.
In a culture that routinely questions the validity of scientific principles, physicians tend not to doubt the correctness of a well established truth such as the numbering of the cranial nerves. While it is always difficult to go against entrenched dogma, it is worth noting that legions of anatomists chose to alter reality rather than rise to this challenge.
