Dermatomes: Foerster/Keegan and Garrett map - Anterior (Latin)

The Foerster (right) and Keegan and Garrett (K&G; left) dermatome maps of the ventral surface of the body side by side. There are three dermatomes of the face, V1, V2 and V3, which are innervated by the three branches of the n. trigeminus (CN V), and have a similar distribution in both dermatome maps. A slight difference between the two maps is seen in the neck (collum) and shoulder region (regio deltoidea), which on the Foerster map, are represented as C3 and C4 dermatomes, while on the K&G map, as C3, C4, C5 dermatomes, with C5 extending into the central arm (brachium) and forearm (antebrachium) region. In the Foerster map, C4, C5, C6 cover the lateral-most aspect of the shoulder (omos), arm, forearm and thumb (pollex) respectively, while all of these regions are represented by only C6 in the K&G map. In both maps, the central aspect of the palm (palma) and middle finger (digitus medius manus) represent the C7 dermatome, while C8 covers the ulnar side of the forearm, hand (manus) and little finger (digitus minimus manus), as well as the ring finger (digitus anularis) in the K&G map. On the Foerster map, T1 extends to the medial aspect of the forearm and distal arm, while T2 covers the medial and proximal aspect of the arm continuing into the axilla and upper pectoral region (regio pectoralis). On the K&G map, however, the medial and proximal aspect of the arm represents the C8 dermatome, while T1 covers the upper pectoral region and extends over the central arm and forearm regions.Dermatomes of the thorax and abdomen arise from T2-T12 spinal nerves and have a fairly similar segmental pattern of distribution on both maps. T2-T9 are nearly horizontal lines and are quite evenly spaced. T4 lies at the level of the nipple (papilla mammaria) and T10 at the level of the umbilicus. T10-T12 have their lower borders dipping inferiorly, a feature which is more pronounced on the K&G map.There is some significant variation between both dermatome maps in the lower limb. The K&G map shows a spiral and sequential arrangement of the dermatomes from L1-S1, whereas the Foerster map exhibits a more segmental distribution. The anterior thigh (regio anterior femoris) is covered by the L2 and L3 on the Foerster map, with the addition of the L4 dermatome in the K&G map. The anterior leg (regio anterior cruris) on both maps is covered by L4, L5 and S1 dermatomes. In both maps, S1 dermatome has a fairly similar distribution, covering the malleolus lateralis, lateral margin of foot (margo lateralis pedis), heel (calx), and little toe (digitus minimus pedis). S2 and S3 dermatomes cover the perineal area (regio perinealis) and genitals in both maps.