Cranial Nerve Zero (CN0), True or Fiction: A Comparative Review Study on Cranial Nerves with Emphasize on CN0 Anatomy and Function

Abstract

Context: Cranial nerves are integral components of the central nervous system in vertebrates. Throughout history, from the pre-Hippocratic era to 18 ADS, anatomists have debated the existence and classification of human cranial nerves. This review explores the evolution of understanding regarding cranial nerve anatomy and nomenclature. Evidence Acquisition: The literature was examined through three separate historical phases: The early macroscopic phase, the microscopic phase, and the ontogenetic and geno-architectural phase. Important contributions from prominent individuals, especially during the Galenic period, were evaluated to grasp the historical background of cranial nerve categorization. Results: The analysis revealed persistent disagreements regarding the number of cranial nerves. While contemporary anatomy recognizes 12 pairs, recent discussions have introduced the concept of a zero-numbered cranial nerve (CN0/13), further complicating the classification. Conclusions: The ongoing debate about the number of cranial nerves underscores the complexities of anatomical classification. This review highlights the need for continued research and dialogue within the anatomical community to resolve these longstanding discrepancies.