Trochlear nerve: Celebrating 500 years of description

Résumé

The history of the description and classification of the cranial nerves has paralleled the development of anatomy and its role in providing rationality to medicine. About five hundred years ago, the “Anatomical Notes by the Great Alexander Achillinus of Bologna” (1520) provided the first description of the trochlear nerve. In this article, we review the most important macroscopic achievements through different epochs and pioneers such as Herophilus of Chalcedon, Galen of Pergamon, Andreas Vesalius, Bartolomeo Eustachi, Realdo Colombo, Gabriele Falloppio, Antonio Molinetti, Caspar Bartholin, Thomas Willis and Samuel Thomas von Soemmerring. Each of them contributed to a better understanding of the cranial nerves as we know today. Galen's classification was enduring through his seven pairs of cranial nerves. Realdo Colombo coined the name pathetic nerve or nervus oculorum pateticos to the trochlear nerve in 1559, and Molinetti, nervus trochlearis, in 1669. The term trochlear nerve is derived from the Latin word pulley, trochlea, as it innervates the superior oblique muscle that ends in a tendon that bends through a pulley of connective tissue. Besides description and naming, the inclusion into current cranial nerve classification system and how such knowledge applies to current microsurgical understanding is also discussed.