Conflicting dermatome maps: educational and clinical implications

Sensory testing is a common noninvasive method of evaluating nerve function that relies on the knowledge of skin dermatomes and sensory fields of cutaneous nerves. Research to determine the extent of the dermatomes was conducted in Europe during the late nineteenth and early twentieth centuries. Experiments performed on cadavers, monkeys, and human patients prior to 1948 resulted in the creation of similar but somewhat different dermatome maps. A radically different map with long, swirling dermatomes was produced by Keegan and Garrett in 1948. This map was derived largely by examining compression of dorsal nerve roots by vertebral disc herniation. The maps appearing in textbooks are inconsistent. Some books show a version of the early maps, some show the Keegan and Garrett map, and others show maps that are not consistent with either. The purpose of this paper is to discuss the history of dermatome maps, including the experimental procedures by which each was obtained, and to relate the early maps to those found in textbooks commonly used in healthcare education programs. The paper discusses the significance of these maps as used for clinical diagnosis and the need for further research.