Dermatome (anatomy)

Dermatome
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 [ edit on Wikidata]

Last updated January 04, 2024

A dermatome is an area of skin that is mainly supplied by afferent nerve fibres from the dorsal root of any given spinal nerve.^[1]^[2] There are 8 cervical nerves (C1 being an exception with no dermatome), 12 thoracic nerves, 5 lumbar nerves and 5 sacral nerves. Each of these nerves relays sensation (including pain) from a particular region of skin to the brain.

Along the thorax and abdomen, 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 single nerve is called a peripheral nerve field.

The word dermatome is formed from Ancient Greek δέρμα 'skin, hide' and τέμνω 'cut'.

Clinical significance

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 related nerve root. Examples include somatic dysfunction of the spine or viral infection. Certain skin problems tend to orient the lesions in the dermatomal direction.

In referred pain, sensory nerve fibers such as that from dermatomes may come together at the same spinal cord level as the general visceral afferent fibers such as that from the heart. When the general visceral sensory fiber is stimulated, the central nervous system does not clearly discern whether the pain is coming from the body wall or from the viscera, 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 both chickenpox and shingles), 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

Following is a list of spinal nerves and points that are characteristically belonging to the dermatome of each nerve:^[4]

C2 – At least one cm lateral to the occipital protuberance at the base of the skull. Alternately, a point at least 3 cm (1.2 in) behind the ear.
C3 – In the supraclavicular fossa, at the midclavicular line.
C4 – Over the acromioclavicular joint.
C5 – On the lateral (radial) side of the antecubital fossa, just proximally to the elbow.
C6 – On the dorsal surface of the proximal phalanx of the thumb.
C7 – On the dorsal surface of the proximal phalanx of the middle finger.
C8 – On the dorsal surface of the proximal phalanx of the little finger.
T1 – On the medial (ulnar) side of the antecubital fossa, just distal to the medial epicondyle of the humerus.
T2 – At the apex of the axilla.
T3 – Intersection of the midclavicular line and the third intercostal space
T4 – Intersection of the midclavicular line and 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 the xiphoid process.
T6 – Intersection of the midclavicular line and the horizontal level of the xiphoid 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 the umbilicus.
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 the inguinal 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 the medial epicondyle of the femur.
L3 – At the medial epicondyle of the femur.
L4 – Over the medial malleolus.
L5 – On the dorsum of the foot at the third metatarsophalangeal joint.
S1 – On the lateral aspect of the calcaneus.
S2 – At the midpoint of the popliteal fossa.
S3 – Over the tuberosity of the ischium or intragluteal fold
S4 and S5 – In the perianal area, less than one cm lateral to the mucocutaneous zone

Following is a list of cranial nerves responsible for sensation from the face:

Additional images

Diagram of segmental distribution of the cutaneous nerves of the right upper extremity
Lower limb
Foot
Major dermatomes and cutaneous nerves (anterior view)
Major dermatomes and cutaneous nerves (posterior view)

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A spinal nerve is a mixed nerve, which carries motor, sensory, and autonomic signals between the spinal cord and the body. In the human body there are 31 pairs of spinal nerves, one on each side of the vertebral column. These are grouped into the corresponding cervical, thoracic, lumbar, sacral and coccygeal regions of the spine. There are eight pairs of cervical nerves, twelve pairs of thoracic nerves, five pairs of lumbar nerves, five pairs of sacral nerves, and one pair of coccygeal nerves. The spinal nerves are part of the peripheral nervous system.

In human anatomy, the ulnar nerve is a nerve that runs near the ulna bone. The ulnar collateral ligament of elbow joint is in relation with the ulnar nerve. The nerve is the largest in the human body unprotected by muscle or bone, so injury is common. This nerve is directly connected to the little finger, and the adjacent half of the ring finger, innervating the palmar aspect of these fingers, including both front and back of the tips, perhaps as far back as the fingernail beds.

In neuroanatomy, the trigeminal nerve (lit. triplet nerve), also known as the fifth cranial nerve, cranial nerve V, or simply CN V, is a cranial nerve responsible for sensation in the face and motor functions such as biting and chewing; it is the most complex of the cranial nerves. Its name (trigeminal, from Latin tri- 'three', and -geminus 'twin') derives from each of the two nerves (one on each side of the pons) having three major branches: the ophthalmic nerve (V₁), the maxillary nerve (V₂), and the mandibular nerve (V₃). The ophthalmic and maxillary nerves are purely sensory, whereas the mandibular nerve supplies motor as well as sensory (or "cutaneous") functions. Adding to the complexity of this nerve is that autonomic nerve fibers as well as special sensory fibers (taste) are contained within it.

<span class="mw-page-title-main">Lesser occipital nerve</span> Nerve of the head and neck

The lesser occipital nerve is a cutaneous spinal nerve of the cervical plexus. It arises from second cervical (spinal) nerve (C2). It innervates the skin of the back of the upper neck and of the scalp posterior to the ear.

The cubital fossa,chelidon, grivet or inside of elbow, is the area on the anterior side of the upper part between the arm and forearm of a human or other hormid animals. It lies anteriorly to the elbow when in standard anatomical position.

The lumbar plexus is a web of nerves in the lumbar region of the body which forms part of the larger lumbosacral plexus. It is formed by the divisions of the first four lumbar nerves (L1-L4) and from contributions of the subcostal nerve (T12), which is the last thoracic nerve. Additionally, the ventral rami of the fourth lumbar nerve pass communicating branches, the lumbosacral trunk, to the sacral plexus. The nerves of the lumbar plexus pass in front of the hip joint and mainly support the anterior part of the thigh.

The lateral cutaneous nerve of the thigh is a cutaneous nerve of the thigh. It originates from the dorsal divisions of the second and third lumbar nerves from the lumbar plexus. It passes under the inguinal ligament to reach the thigh. It supplies sensation to the skin on the lateral part of the thigh by an anterior branch and a posterior branch.

<span class="mw-page-title-main">Medial cutaneous nerve of forearm</span>

The medial cutaneous nerve of the forearm is a sensory branch of the medial cord of the brachial plexus derived from the ventral rami of spinal nerves C8-T1. It provides sensory innervation to the skin of the medial forearm and skin overlying the olecranon. It descends through the (upper) arm within the brachial fascia alongside the basilic vein, then divides into an anterior branch and a posterior branch upon emerging from the brachial fascia; the two terminal branches travel as far distally as the wrist.

<span class="mw-page-title-main">Supraclavicular nerves</span>

The supraclavicular nerve is a cutaneous (sensory) nerve of the cervical plexus that arises from the third and fourth cervical (spinal) nerves. It emerges from beneath the posterior border of the sternocleidomastoid muscle, then split into multiple branches. Together, these innervate the skin over the shoulder.

A nerve root is the initial segment of a nerve leaving the central nervous system. Nerve roots can be classified as:

The saphenous nerve is the largest cutaneous branch of the femoral nerve. It is derived from the lumbar plexus (L3-L4). It is a strictly sensory nerve, and has no motor function. It commences in the proximal (upper) thigh and travels along the adductor canal. Upon exiting the adductor canal, the saphenous nerve terminates by splitting into two terminal branches: the sartorial nerve, and the infrapatellar nerve. The saphenous nerve is responsible for providing sensory innervation to the skin of the anteromedial leg.

Hypoesthesia or numbness is a common side effect of various medical conditions that manifests as a reduced sense of touch or sensation, or a partial loss of sensitivity to sensory stimuli. In everyday speech this is generally referred to as numbness.

Cutaneous innervation refers to an area of the skin which is supplied by a specific cutaneous nerve.

The posterior branches of thoracic nerves branch from the dorsal rami of the thoracic nerves.

The following outline is provided as an overview of and topical guide to human anatomy:

The following diagram is provided as an overview of and topical guide to the human nervous system:

References

↑ Kishner, Stephen. "Dermatomes Anatomy" . eMedicine. Medscape. Retrieved 2013-10-09.
↑ "dermatome". The Free Dictionary by Farlex, Medical dictionary. Archived from the original on 2017-09-16.
↑ "Referred Pain". Physiopedia. 2019-02-02. Archived from the original on 2019-05-21. cited van 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 from the original (PDF) on 2016-03-04.

External links

3D Dermatomes Web App, Instamedic
Hand kinesiology at the University of Kansas Medical Center
Diagram of "Adult Dermatome", The New York Times

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[1] Kishner, Stephen. "Dermatomes Anatomy" . eMedicine. Medscape. Retrieved 2013-10-09.

[2] "dermatome". The Free Dictionary by Farlex, Medical dictionary. Archived from the original on 2017-09-16.

[3] "Referred Pain". Physiopedia. 2019-02-02. Archived from the original on 2019-05-21. cited van Cranenburghauthors, B. (1997). SCHEMA'S FYSIOLOGIE. Maarssen: Elsevier/De Tijdstroom. pp. 53, 65, 70.

[4] "International Standards for the Classification of Spinal Cord Injury - Key Sensory Points" (PDF). American Spinal Injury Association. June 2008. Archived from the original (PDF) on 2016-03-04.

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