Mnemonics - Dermatomal distribution easiest way to remember Hey people, I don't know if you struggled remembering the dermatomal distribution but I always had a tough time with it. Starting off: The sensory distributions always overlap with the adjacent ones. So there is no hard and fast rule. The zones that have sole supply from one nerve are known as Autonomous Sensory zones. Which are helpful in identifying the nerve lesion. C1 segment has no sensory supply, only motor supply. Face is supplied by the Trigeminal's branches. It covers the part from the edges of the mandible to the front of the ear and above till vertex. Mandibular (V3) obviously supplies the mandible with some upward continuation. Maxillary (V2) obviously maxilla part excluding the dorsal ridge of the nose. Ophthalmic (V1) obviously the eye part and ridge of nose till the vertex. Cervical roots Above Posteriorly from the vertex and Anteriorly from the border of the mandible. C2- Supplies an area that looks like a helmet with a strap to be tied below the chin C4- Neck Lace. C3 is the area between those two C5 covers Ant chest and continues into the arm till wrist. On the Ant chest from C5 we DIVE to T1. Saying C5 and T1 are continuous. Hence they also continue into the arm and supply Ant part of arm and forearm till the wrist with C5 above and T1 below when arms are extended. Thumb is C6. Always remember this. C6 also supplies a part of the index finger. Join thumb and index with tips(looks like a 6) The next ones are in continuation. Index and Middle C7. Ring and Little C8. The Posterior part of the arm and forearm also can be made out. Thumb is C6 so Laterally C6. Index and Middle C7 so middle of Forearm and Arm C7. Medially C8 similarly. Thoracic roots The entire area supplied by these roots make the letter T. The limbs of T are the topmost, so obviously is supplied by T1. T4 is the level of Boob (Nipple) T10- Belly ButTEN (Umbilicus) Lumbar roots Supplies the Legs and Loin. L1- 1nguinaL Area ( Inguinal Area Is L1) L4- Knee L5- Middle part of the supply of Sole of the foot is somewhat triangular. Like an inverted V. Roman for 5. On the dorsal aspect of the foot S5 supplies the middle three toes. The Great toe is supplied by L4. (Remember The Great Fire(4) of London) All segments are parallel to the Inguinal ligament Sacral roots The sacral supplies start off on the sacral area which do so in a concentric fashion. S1 to S5 out to in. S5 being the anus. S4 is the perianal area. S2 and S3 are FREE and roam down the perineum and supply the genital area as well. S1 and S2 go down on the post aspect of the leg till the foot. As they continue down and S1 being above S2, S2 obviously will be lateral and end up supplying the lateral aspect of the foot and the little toe. Little toe is smallest of the lot (1). So the foot is supplied by L4 L5 S1. This representation blew my mind away. Finally it all made sense. If somebody doesn't believe in The Thoery of Evolution show them this. Hope I've made it easier for you. Read it out 2-3 times and picturise it on yourself and you're sure to not forget it for a long time. Thats all -Ved Source
