Adermatomeis an area ofskinthat is mainly supplied byafferent nerve fibresfrom thedorsal rootof any givenspinal nerve.[1][2] There are 8cervical nerves(C1 being an exception with no dermatome), 12thoracic nerves, 5lumbar nervesand 5sacral nerves. Each of these nerves relays sensation (including pain) from a particular region of skin to thebrain.
| Dermatome | |
|---|---|
 Dermatomes of the upper and lower limbs (modified, after Keegan, J. J., and Garrett, F. D.) | |
 Dermatomes of the upper parts of the body, displaying significant overlapping (modified, from Fender, after Foerster) | |
| Anatomical terminology |
The term is also used to refer to a part of an embryonicsomite.
Along thethoraxandabdomen,the dermatomes are like a stack of discs forming a human, each supplied by a different spinal nerve. Along the arms and the legs, the pattern is different: the dermatomes run longitudinally along the limbs. Although the general pattern is similar in all people, the precise areas of innervation are as unique to an individual as fingerprints.
An area of skin innervated by a singlenerveis called aperipheral nerve field.
The worddermatomeis formed fromAncient Greekδέρμα'skin, hide' andτέμνω'cut'.
Clinical significance
edit
A dermatome is an area of skin supplied by sensory neurons that arise from a spinal nerve ganglion. Symptoms that follow a dermatome (e.g. like pain or a rash) may indicate a pathology that involves the relatednerve root.Examples include somatic dysfunction of the spine or viral infection. Certain skin problems tend to orient the lesions in the dermatomal direction.
Inreferred pain,sensory nerve fiberssuch as that from dermatomes may come together at the samespinal cordlevel as thegeneral visceral afferent fiberssuch as that from theheart. When the general visceral sensory fiber is stimulated, thecentral nervous systemdoes not clearly discern whether thepainis coming from the body wall or from theviscera,so it perceives the pain as coming from somewhere on the body wall, e.g. left arm/hand pain, jaw pain. So the pain is "referred to" the related dermatomes of the same spinal segment.[3]
Viruses that lie dormant in nerve ganglia (e.g.varicella zoster virus,which causes bothchickenpoxandshingles), often cause either pain, rash or both in a pattern defined by a dermatome (a zosteriform pattern). However, the symptoms may not appear across the entire dermatome.
Important dermatomes and anatomical landmarks
editFollowing is a list ofspinal nervesand points that are characteristically belonging to the dermatome of each nerve:[4]
- C2– At least one cm lateral to theoccipital protuberanceat thebase of the skull.Alternately, a point at least 3 cm (1.2 in) behind the ear.
- C3– In thesupraclavicular fossa,at themidclavicular line.
- C4– Over theacromioclavicular joint.
- C5– On the lateral (radial) side of theantecubital fossa,just proximally to the elbow.
- C6– On the dorsal surface of theproximal phalanxof thethumb.
- C7– On the dorsal surface of theproximal phalanxof themiddle finger.
- C8– On the dorsal surface of the proximal phalanx of thelittle finger.
- T1– On the medial (ulnar) side of theantecubital fossa,just distal to themedial epicondyle of the humerus.
- T2– At the apex of theaxilla.
- T3–Intersectionof themidclavicular lineand the thirdintercostal space
- T4– Intersection of themidclavicular lineand the fourth intercostal space, located at the level of the nipples.
- T5– Intersection of the midclavicular line and the fifth intercostal space, horizontally located midway between the level of the nipples and the level of thexiphoid process.
- T6– Intersection of the midclavicular line and the horizontal level of thexiphoid process.
- T7– Intersection of the midclavicular line and the horizontal level at one quarter the distance between the level of the xiphoid process and the level of theumbilicus.
- T8– Intersection of the midclavicular line and the horizontal level at one half the distance between the level of the xiphoid process and the level of the umbilicus.
- T9– Intersection of the midclavicular line and the horizontal level at three quarters of the distance between the level of the xiphoid process and the level of the umbilicus.
- T10– Intersection of the midclavicular line, at the horizontal level of the umbilicus.
- T11– Intersection of the midclavicular line, at the horizontal level midway between the level of the umbilicus and theinguinal ligament.
- T12– Intersection of the midclavicular line and the midpoint of the inguinal ligament.
- L1– Midway between the key sensory points for T12 and L2.[clarification needed]
- L2– On the anterior medial thigh, at the midpoint of a line connecting the midpoint of the inguinal ligament and themedial epicondyle of the femur.
- L3– At themedial epicondyle of the femur.
- L4– Over themedial malleolus.
- L5– On thedorsum of the footat the thirdmetatarsophalangeal joint.
- S1– On the lateral aspect of thecalcaneus.
- S2– At the midpoint of thepopliteal fossa.
- S3– Over thetuberosity of the ischiumorintragluteal fold
- S4andS5– In theperianalarea, less than one cm lateral to themucocutaneous zone
Following is a list ofcranial nervesresponsible for sensation from the face:
Additional images
edit-
Diagram of segmental distribution of the cutaneous nerves of the right upper extremity -
Lower limb -
Foot -
Major dermatomes andcutaneous nerves(anterior view) -
Major dermatomes andcutaneous nerves(posterior view)
See also
editReferences
edit- ^Kishner, Stephen."Dermatomes Anatomy".eMedicine.Medscape.Retrieved2013-10-09.
- ^ "dermatome".The Free Dictionary by Farlex, Medical dictionary. Archived fromthe originalon 2017-09-16.
- ^"Referred Pain".Physiopedia. 2019-02-02.Archivedfrom the original on 2019-05-21.citedvan Cranenburghauthors, B. (1997).SCHEMA'S FYSIOLOGIE.Maarssen: Elsevier/De Tijdstroom. pp. 53, 65, 70.
- ^"International Standards for the Classification of Spinal Cord Injury - Key Sensory Points"(PDF).American Spinal Injury Association.June 2008. Archived fromthe original(PDF)on 2016-03-04.
External links
edit
- 3D Dermatomes Web App,Instamedic
- Hand kinesiology at the University of Kansas Medical Center
- Diagram of "Adult Dermatome",The New York Times