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Dermatome chart leg: Dermatomes – Physiopedia

Dermatomes – Physiopedia

Original Editor – Lucinda Hampton

Top Contributors

Naomi O’Reilly,

Anas Mohamed,

Lucinda hampton,

Joao Costa,

Nikhil Benhur Abburi,

Rachael Lowe,

Kim Jackson and

Blessed Denzel Vhudzijena

Lead Editors  

Contents

  • 1 Dermatomes
  • 2 History
  • 3 Purpose
  • 4 Technique
  • 5 Controversies
  • 6 Clinical Significance
  • 7 References

The term “dermatome” is a combination of two Greek words; “derma” meaning “skin”, and “tome”, meaning “cutting” or “thin segment”. Dermatomes are areas of the skin whose sensory distribution is innervated by the afferent nerve fibres from the dorsal root of a specific single spinal nerve root, which is that portion of a peripheral nerve that “connects” the nerve to the spinal cord.

Nerve roots arise from each level of the spinal cord (e. g., C3, C4), and many, but not all, intermingle in a plexus (brachial, lumbar, or lumbosacral) to form different peripheral nerves as discussed above. This arrangement can result in a single nerve root supplying more than one peripheral nerve. For example, the median nerve is derived from the C6, C7, C8, and T1 Nerve Roots, whereas the ulnar nerve is derived from C7, C8, and T1.

In total there are 30 dermatomes that relay sensation from a particular region of the skin to the brain – 8 cervical nerves (note C1 has no corresponding dermatomal area), 12 thoracic nerves, 5 lumbar nerves and 5 sacral nerves. Each of these spinal nerves roots.[1] Dysfunction or damage to a spinal nerve root from infection, compression, or traumatic injury can trigger symptoms in the corresponding dermatome. [2]

[3]

Table. 1 Dermatomes
Nerve RootDermatome
CervicalC2Supply Skin of NeckTemple, Forehead, Occiput
C3Entire Neck, Posterior Cheek, Temporal Area, Prolongation forward under Mandible
C4Shoulder Area, Clavicular Area, Upper Scapular Area
C5Supply the Arms Deltoid Area, Anterior aspect of entire arm to base of thumb
C6Anterior Arm, Radial side of hand to thumb and index finger
C7Lateral Arm and Forearm to index, long, and ring fingers
C8Medial Arm and forearm to long, ring, and little fingers
ThoracicT1Medial side of forearm to base of little finger
T2Supply the chest and abdomenMedial side of upper arm to medial elbow, pectoral and midscapular areas
T3 – 6Upper Thorax
T5 – 7Costal Margin
T8 – 12Abdomen and Lumbar Region
LumbarL1Back, over trochanter and groin
L2Back, front of thigh to knee
L3Supply Skin of LegsBack, upper buttock, anterior thigh and knee, medial lower leg
L4Medial buttock, latera thigh, medial leg, dorsum of foot, big toe
L5Buttock, posterior and lateral thigh, lateral aspect of leg, dorsum of foot, medial half of sole, first, second, and third toes
SacralS1Buttock, Thigh, and Leg Posterior
S2Supply GroinSame as S1
S3Groin, medial thigh to knee
S4Perineum, genitals, lower sacrum
CoccygealThe dermatome corresponding with the coccygeal nerves is located on the buttocks, in the area directly around the coccyx. [4][5]

The idea of dermatomes originated from initial efforts to associate anatomy with the physiology of sensation. Multiple definitions of dermatomes exist, and several maps are commonly employed. Although they are valuable, dermatomes vary significantly between maps and even among individuals,[6] with some evidence suggesting that current dermatome maps are inaccurate and based on flawed studies.[7][8]

The medical profession typically recognised two primary maps of dermatomes. Firstly, the Keegan and Garret Map (Fig.1) from 1948, which illustrates dermatomes in alignment with the developmental progression of the limb segments. Secondly, the Foerster Map from 1933, which portrays the medial area of the upper limb as being innervated by T1-T3, depicting the pain distribution from angina or myocardial infarction. This latter map is the most frequently used in healthcare and accounts for the dermatomes used in the American Spinal Cord Injury Association Impairment Scale (ASIA Scale). In recent years there have been few attempts at verifying these original dermatome maps. Lee et al conducted an in-depth review that examined the discrepancies among dermatome maps. They put forth an “evidence-based” dermatome map that combined elements of previous maps (Fig.3). Though the application of the term “evidence-based” may be somewhat questionable, their proposed map represents a systematic attempt to synthesise the most credible evidence available.[6][7]

Testing of dermatomes is part of the neurological examination. They are primarily used to determine whether the sensory loss on a limb corresponds to a single spinal segment, implying the lesion is of that nerve root (i.e., radiculopathy), and to assign the neurologic “level” to a spinal cord lesion[9].

Dermatome Testing is done ideally with a pin and cotton wool. Ask the patient to close their eyes and give the therapist feedback regarding the various stimuli. Testing should be done on specific dermatomes and should be compared to bilaterally.

  • Light Touch Test – Light Touch Sensation – Dab a piece of cotton wool on an area of skin [10]
  • Pinprick Test – Pain Sensation – Gently touches the skin with the pin ask the patient whether it feels sharp or blunt

During the review of systems, asking the patient to carefully describe the pattern or distribution of sensory symptoms (e.g., tingling, numbness, diminished, or absent sensation) provides the therapist with preliminary information to help guide the examination and to assist in identifying the dermatome(s) and nerve(s) involved.[11]

Light touch dermatomes are larger than pain dermatomes. When only one or two segments are affected, testing for pain sensibility is a more sensitive method of examination than testing for light touch.[9]

Dermatomes have a segmented distribution throughout your body. The exact dermatome pattern can actually vary from person to person. Some overlap between neighboring dermatomes may also occur. There exist some discrepancies among published dermatome maps based on the methodologies used to identify skin segment innervation.

In a clinical commentary, Downs and Laporte discuss the history of dermatome mapping, including the variations in methodologies employed, and the inconsistencies in the dermatome maps used in education and practice.[11] [[Laporte C. Conflicting dermatome maps: educational and clinical implications. journal of orthopaedic & sports physical therapy. 2011 Jun;41(6):42[12]7-34.]]

Dermatomes are important because they can help to assess and diagnose a variety of conditions. Neurological screening of dermatomes helps to assess patterns of sensory loss that can suggest specific spinal nerve involvement. For instance, symptoms that occur along a specific dermatome may indicate disruption or damage to a specific nerve root in the spine.

  • Nerve Entrapment
  • Radiculopathy
  • Spinal Cord Injury
  • Herpes Zoster [2]
  1. ↑ Wikipedia Dermatome. Available from: https://en.wikipedia.org/wiki/Dermatome_(anatomy) (last accessed 23.4.2019)
  2. 2.02.1 Medical news today What and where are dermatomes? Available:https://www.medicalnewstoday.com/articles/what-are-dermatomes (accessed 25.5.2022)
  3. ↑ M Roehrs. Dermatomes. Available from: https://www.youtube.com/watch?v=CYZBH6NX8wg&feature=youtu.be (last accessed 23.4.2019)
  4. ↑ Medical news today What and where are dermatomes? Available:https://www.medicalnewstoday.com/articles/what-are-dermatomes (accessed 25.5.2022)
  5. ↑ David J. Magee. Orthopedic Physical Assessment. 6th edition. Elsevier. 2014.
  6. 6.06.1 Apok V, Gurusinghe NT, Mitchell JD, Emsley HC. Dermatomes and dogma. Practical neurology. 2011 Apr 1;11(2):100-5.
  7. 7.07. 1 Lee MW, McPhee RW, Stringer MD. An evidence-based approach to human dermatomes. Australasian Musculoskeletal Medicine. 2013 Jun;18(1):14-22.
  8. ↑ Downs MB, Laporte C. Conflicting dermatome maps: educational and clinical implications. journal of orthopaedic & sports physical therapy. 2011 Jun;41(6):427-34.
  9. 9.09.1 Liebenson C, editor. Rehabilitation of the spine: a practitioner’s manual. Lippincott Williams & Wilkins; 2007.Available: https://www.sciencedirect.com/topics/medicine-and-dentistry/dermatome (accessed 25.5.2022)
  10. ↑ Slide share. Dermatomes and myotomes. Available from: https://www.slideshare.net/TafzzSailo/special-test-for-dermatomes-and-myotomes (last accessed 23.4.2019)
  11. 11.011.1 Susan B.O’Sullivan, Thomas J. Schmitz, George D. Fulk. Physical Rehabilitation. 6th edition. F. A. Davis Company. 2014.
  12. ↑ Downs MB, Laporte C. Conflicting dermatome maps: educational and clinical implications. journal of orthopaedic & sports physical therapy. 2011 Jun;41(6):427-34.

Dermatomes – Physiopedia

Original Editor – Lucinda Hampton

Top Contributors

Naomi O’Reilly,

Anas Mohamed,

Lucinda hampton,

Joao Costa,

Nikhil Benhur Abburi,

Rachael Lowe,

Kim Jackson and

Blessed Denzel Vhudzijena

Lead Editors  

Contents

  • 1 Dermatomes
  • 2 History
  • 3 Purpose
  • 4 Technique
  • 5 Controversies
  • 6 Clinical Significance
  • 7 References

The term “dermatome” is a combination of two Greek words; “derma” meaning “skin”, and “tome”, meaning “cutting” or “thin segment”. Dermatomes are areas of the skin whose sensory distribution is innervated by the afferent nerve fibres from the dorsal root of a specific single spinal nerve root, which is that portion of a peripheral nerve that “connects” the nerve to the spinal cord.

Nerve roots arise from each level of the spinal cord (e.g., C3, C4), and many, but not all, intermingle in a plexus (brachial, lumbar, or lumbosacral) to form different peripheral nerves as discussed above. This arrangement can result in a single nerve root supplying more than one peripheral nerve. For example, the median nerve is derived from the C6, C7, C8, and T1 Nerve Roots, whereas the ulnar nerve is derived from C7, C8, and T1.

In total there are 30 dermatomes that relay sensation from a particular region of the skin to the brain – 8 cervical nerves (note C1 has no corresponding dermatomal area), 12 thoracic nerves, 5 lumbar nerves and 5 sacral nerves. Each of these spinal nerves roots.[1] Dysfunction or damage to a spinal nerve root from infection, compression, or traumatic injury can trigger symptoms in the corresponding dermatome. [2]

[3]

Table. 1 Dermatomes
Nerve RootDermatome
CervicalC2Supply Skin of NeckTemple, Forehead, Occiput
C3Entire Neck, Posterior Cheek, Temporal Area, Prolongation forward under Mandible
C4Shoulder Area, Clavicular Area, Upper Scapular Area
C5Supply the Arms Deltoid Area, Anterior aspect of entire arm to base of thumb
C6Anterior Arm, Radial side of hand to thumb and index finger
C7Lateral Arm and Forearm to index, long, and ring fingers
C8Medial Arm and forearm to long, ring, and little fingers
ThoracicT1Medial side of forearm to base of little finger
T2Supply the chest and abdomenMedial side of upper arm to medial elbow, pectoral and midscapular areas
T3 – 6Upper Thorax
T5 – 7Costal Margin
T8 – 12Abdomen and Lumbar Region
LumbarL1Back, over trochanter and groin
L2Back, front of thigh to knee
L3Supply Skin of LegsBack, upper buttock, anterior thigh and knee, medial lower leg
L4Medial buttock, latera thigh, medial leg, dorsum of foot, big toe
L5Buttock, posterior and lateral thigh, lateral aspect of leg, dorsum of foot, medial half of sole, first, second, and third toes
SacralS1Buttock, Thigh, and Leg Posterior
S2Supply GroinSame as S1
S3Groin, medial thigh to knee
S4Perineum, genitals, lower sacrum
CoccygealThe dermatome corresponding with the coccygeal nerves is located on the buttocks, in the area directly around the coccyx. [4][5]

The idea of dermatomes originated from initial efforts to associate anatomy with the physiology of sensation. Multiple definitions of dermatomes exist, and several maps are commonly employed. Although they are valuable, dermatomes vary significantly between maps and even among individuals,[6] with some evidence suggesting that current dermatome maps are inaccurate and based on flawed studies.[7][8]

The medical profession typically recognised two primary maps of dermatomes. Firstly, the Keegan and Garret Map (Fig.1) from 1948, which illustrates dermatomes in alignment with the developmental progression of the limb segments. Secondly, the Foerster Map from 1933, which portrays the medial area of the upper limb as being innervated by T1-T3, depicting the pain distribution from angina or myocardial infarction. This latter map is the most frequently used in healthcare and accounts for the dermatomes used in the American Spinal Cord Injury Association Impairment Scale (ASIA Scale). In recent years there have been few attempts at verifying these original dermatome maps. Lee et al conducted an in-depth review that examined the discrepancies among dermatome maps. They put forth an “evidence-based” dermatome map that combined elements of previous maps (Fig.3). Though the application of the term “evidence-based” may be somewhat questionable, their proposed map represents a systematic attempt to synthesise the most credible evidence available.[6][7]

Testing of dermatomes is part of the neurological examination. They are primarily used to determine whether the sensory loss on a limb corresponds to a single spinal segment, implying the lesion is of that nerve root (i.e., radiculopathy), and to assign the neurologic “level” to a spinal cord lesion[9].

Dermatome Testing is done ideally with a pin and cotton wool. Ask the patient to close their eyes and give the therapist feedback regarding the various stimuli. Testing should be done on specific dermatomes and should be compared to bilaterally.

  • Light Touch Test – Light Touch Sensation – Dab a piece of cotton wool on an area of skin [10]
  • Pinprick Test – Pain Sensation – Gently touches the skin with the pin ask the patient whether it feels sharp or blunt

During the review of systems, asking the patient to carefully describe the pattern or distribution of sensory symptoms (e.g., tingling, numbness, diminished, or absent sensation) provides the therapist with preliminary information to help guide the examination and to assist in identifying the dermatome(s) and nerve(s) involved.[11]

Light touch dermatomes are larger than pain dermatomes. When only one or two segments are affected, testing for pain sensibility is a more sensitive method of examination than testing for light touch.[9]

Dermatomes have a segmented distribution throughout your body. The exact dermatome pattern can actually vary from person to person. Some overlap between neighboring dermatomes may also occur. There exist some discrepancies among published dermatome maps based on the methodologies used to identify skin segment innervation.

In a clinical commentary, Downs and Laporte discuss the history of dermatome mapping, including the variations in methodologies employed, and the inconsistencies in the dermatome maps used in education and practice.[11] [[Laporte C. Conflicting dermatome maps: educational and clinical implications. journal of orthopaedic & sports physical therapy. 2011 Jun;41(6):42[12]7-34.]]

Dermatomes are important because they can help to assess and diagnose a variety of conditions. Neurological screening of dermatomes helps to assess patterns of sensory loss that can suggest specific spinal nerve involvement. For instance, symptoms that occur along a specific dermatome may indicate disruption or damage to a specific nerve root in the spine.

  • Nerve Entrapment
  • Radiculopathy
  • Spinal Cord Injury
  • Herpes Zoster [2]
  1. ↑ Wikipedia Dermatome. Available from: https://en.wikipedia.org/wiki/Dermatome_(anatomy) (last accessed 23.4.2019)
  2. 2.02.1 Medical news today What and where are dermatomes? Available:https://www.medicalnewstoday.com/articles/what-are-dermatomes (accessed 25.5.2022)
  3. ↑ M Roehrs. Dermatomes. Available from: https://www.youtube.com/watch?v=CYZBH6NX8wg&feature=youtu.be (last accessed 23.4.2019)
  4. ↑ Medical news today What and where are dermatomes? Available:https://www.medicalnewstoday.com/articles/what-are-dermatomes (accessed 25.5.2022)
  5. ↑ David J. Magee. Orthopedic Physical Assessment. 6th edition. Elsevier. 2014.
  6. 6.06.1 Apok V, Gurusinghe NT, Mitchell JD, Emsley HC. Dermatomes and dogma. Practical neurology. 2011 Apr 1;11(2):100-5.
  7. 7.07. 1 Lee MW, McPhee RW, Stringer MD. An evidence-based approach to human dermatomes. Australasian Musculoskeletal Medicine. 2013 Jun;18(1):14-22.
  8. ↑ Downs MB, Laporte C. Conflicting dermatome maps: educational and clinical implications. journal of orthopaedic & sports physical therapy. 2011 Jun;41(6):427-34.
  9. 9.09.1 Liebenson C, editor. Rehabilitation of the spine: a practitioner’s manual. Lippincott Williams & Wilkins; 2007.Available: https://www.sciencedirect.com/topics/medicine-and-dentistry/dermatome (accessed 25.5.2022)
  10. ↑ Slide share. Dermatomes and myotomes. Available from: https://www.slideshare.net/TafzzSailo/special-test-for-dermatomes-and-myotomes (last accessed 23.4.2019)
  11. 11.011.1 Susan B.O’Sullivan, Thomas J. Schmitz, George D. Fulk. Physical Rehabilitation. 6th edition. F. A. Davis Company. 2014.
  12. ↑ Downs MB, Laporte C. Conflicting dermatome maps: educational and clinical implications. journal of orthopaedic & sports physical therapy. 2011 Jun;41(6):427-34.

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    Explanation and location of 30 dermatomes – Drink-Drink

    Contents

    • Dermatomes in context
      • Your spinal nerves
      • Your dermatomes is each dermatome located?
        • Cervical spinal nerves
        • Thoracic spinal nerves
        • Lumbar spinal nerves
        • Sacral spinal nerves
        • Coccygeal spinal nerves
      • Diagram of dermatomes
      • Why are dermatomes important?
      • Conclusion

      A dermatome is a skin area innervated by one spinal nerve. The spinal nerves help transmit sensory, motor, and autonomic information between the rest of the body and the central nervous system (CNS).

      Why are dermatomes important? How many are there? And where can they be found? Keep reading as we answer these questions and more.

      Dermatomes in context

      Each of your dermatomes is supplied by one spinal nerve. Let’s take a closer look at both of these components of the body.

      Your spinal nerves

      The spinal nerves are part of your peripheral nervous system (PNS). Your PNS works to connect the rest of your body to your CNS, which is made up of your brain and spinal cord.

      You have 31 pairs of spinal nerves. They form from nerve roots that branch off from the spinal cord. The spinal nerves are named and grouped according to the region of the spine they are associated with.

      Five groups of spinal nerves:

      • Cervical nerves. There are eight pairs of these cervical nerves, numbered C1 to C8. They come from your neck.
      • Thoracic nerves. You have 12 pairs of thoracic nerves, which are numbered T1 through T12. They occur in the part of the spine that forms the torso.
      • Lumbar nerves. There are five pairs of lumbar spinal nerves, labeled L1 to L5. They come from the part of the spine that forms the lower back.
      • Sacral nerves. Like the lumbar spinal nerves, you also have five pairs of sacral spinal nerves. They are connected to your sacrum, which is one of the bones in your pelvis.
      • Coccygeal nerves . You have only one pair of coccygeal spinal nerves. This pair of nerves originates in the coccyx or coccyx region.

      Your dermatomes

      Each of your dermatomes is connected to one spinal nerve. These nerves transmit sensations, such as pain, from a specific area of ​​the skin to the CNS.

      There are 30 dermatomes in your body. You may have noticed that this is one less than the number of spinal nerves. This is because the C1 spinal nerve usually does not have a sensory root. As a result, dermatomes begin with the C2 spinal nerve.

      Dermatomes have a segmented distribution throughout the body. The exact pattern of the dermatome can vary from person to person. There may also be some overlap between adjacent dermatomes.

      Since your spinal nerves exit the spine laterally, the dermatomes associated with your torso and nucleus are distributed horizontally. When viewed on a body map, they look a lot like stacked discs.

      The dermatome pattern on the limbs is slightly different. This is due to the shape of the limbs compared to the rest of the body. Typically, dermatomes associated with your limbs run vertically along the long axis of the limb, such as down the leg.

      Where is each dermatome located?

      Your dermatomes are numbered according to which spinal nerve they correspond to. Below, we describe each dermatome and the region of the body it is associated with.

      Be aware that the exact area that the dermatome can cover may vary from person to person. Some overlap is also possible. Thus, consider the diagram below as a general guide.

      Cervical spinal nerves

      • C2: mandible, occiput
      • C3: upper neck, occiput
      • C4: lower neck, upper shoulders
      • C5: collarbone, upper shoulders
      • C 6: shoulders, outer arm, thumb
      • C7: upper back, back of hand, index and middle fingers
      • C8: upper back, inside of hand, ring finger and little finger

      Thoracic spinal nerves

      • T1: upper chest and back, armpits, front of the arm
      • T2: upper chest and back
      • T3: upper chest and back
      • 90 005 T4: upper chest ( nipple area) and back

      • T5: middle chest and back
      • T6: middle chest and back
      • T7: middle chest and back
      • 90 246 T8: upper abdomen and mid back
      • T9: upper abdomen and middle back
      • T10: abdomen (navel area) and middle back
      • T11: abdomen and middle back
      • T12: lower abdomen and mid back

      Lumbar spinal nerves

      • L1: lower back, thighs, groin
      • L2: lower back, anterior and inner thighs
      • L3: 9 0247 lower back, anterior and inner thighs
      • L4: lower back, front thigh and calf, knee area, inner ankle
      • L5: lower back, front and outer calf, upper and lower foot, first four toes

      Sacral spinal nerves

      • S1: lower back, hamstring, back and inner calf, last toe
      • S2: buttocks, genitals, hamstrings and calves
      • S3: buttocks, genitals
      • S4: buttocks
      • S5: buttocks

      Coccyx-spinal nerves 90 237

      buttocks, coccyx area

      Diagram of dermatomes

      Why are dermatomes important?

      Dermatomes are important because they can help evaluate and diagnose various conditions. For example, symptoms occurring along a particular dermatome may indicate a problem with a particular nerve root in the spine.

      Examples of this include:

      • Radiculopathy. This refers to conditions in which the nerve root in the spine is compressed or pinched. Symptoms may include pain, weakness, and tingling. Pain in radiculopathies may follow one or more dermatomes. One form of radiculopathy is sciatica.
      • Shingles. Shingles is a reactivation of the varicella zoster virus (chickenpox) that is dormant in the nerve roots of your body. Shingles symptoms such as pain and rash occur along the dermatomes associated with the affected nerve root.

      Summary

      Dermatomes are areas of skin associated with a single spinal nerve. You have 31 spinal nerves and 30 dermatomes. The exact area each dermatome covers can differ from person to person.

      The spinal nerves help convey information from other parts of the body to the central nervous system.