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Dermatomes

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Dermatomes

The term “dermatome” comes from the Greek derma (“skin”) and tome (“cutting” or “thin segment”).[1] A dermatome is an area of skin supplied by sensory (afferent) fibres from the dorsal root of a single spinal nerve.[2][3] The dorsal root is the part of the spinal nerve that carries sensory information from the periphery into the spinal cord.[2][3]

Spinal nerves arise at different levels of the spinal cord (e.g., C3 and C4). Their ventral rami may contribute to nerve plexuses, such as the brachial and lumbosacral plexuses, where fibres from adjacent roots intermingle to form peripheral nerves, or follow a segmental distribution without forming a plexus, such as the thoracic intercostal nerves.[4] A single nerve root can therefore supply more than one peripheral nerve.[5]

Thirty dermatomes are conventionally described: seven cervical (C2–C8; C1 has no cutaneous dermatome), twelve thoracic, five lumbar, five sacral and one coccygeal.[5] The International Standards for Neurological Classification of Spinal Cord Injury (ISNCSCI) tests a standardised subset of 28 (C2 to S4–5, with S4–5 taken as one level).[6] Each dermatome is supplied by the dorsal root of a single spinal nerve. Dysfunction or damage to a spinal nerve root from infection, compression, or traumatic injury can trigger symptoms in the corresponding dermatome.[1][2][7]

[8]
[9]
Table 1. Dermatomes[2][5][6][10][11]
Nerve Root Dermatome
Cervical C2 Supply Skin of Neck Posterior aspect of the head (occiput), including the angle of mandible
C3 Entire neck: anterior neck, posterior aspect of upper neck and head, and supraclavicular fossa
C4 Shoulder area, skin of infraclavicular fossa and posterior lower neck
C5 Supply the Arms  Lateral aspect of the upper arm (deltoid area), at and above the elbow
C6 Forearm and radial side of the hand, to thumb and index finger
C7 Central aspect of posterior forearm to the middle finger
C8 Ulnar side of the forearm and hand, to the little finger
Thoracic T1 Medial side of forearm and distal arm, to base of little finger
T2 Supply the Trunk Medial and proximal aspects of the arm to the medial elbow, continuing into the axilla (pectoral and midscapular areas)
T3 - 6 Upper Thorax: T3 at the level of the lower axilla, T4 nipple line, T5 just inferior to the nipple, T6 xiphoid process
T5 - 7 Costal Margin: T5 just inferior to the nipple, T6 xiphoid process, T7 midway between T6 and T8
T8 - 12 Abdomen and Lumbar Region: T8 and T9 evenly distributed between T7 and T10, T10 umbilicus, T11 between T10 and T12, T12 just superior to the pelvic girdle (inguinal ligament)
Lumbar L1 Back (lateral to the L1 vertebra), wrapping anteriorly to the groin and pelvic girdle area overlying the inguinal canal
L2 Supply Skin of Legs Front of thigh, inferior to the inguinal canal, to knee
L3 Anterior thigh and knee, extending down the medial aspect of the thigh and lower leg (evenly spaced between L2 and L4)
L4 Lateral thigh curving to the medial leg; knee, medial leg, dorsum of foot, medial surface of big toe, medial malleolus
L5 Posterolateral thigh wrapping anteriorly at the knee to the anterolateral leg; dorsal and plantar aspects of the foot, lateral surface of big toe, and toes 2, 3 and 4
Sacral S1 Sole and plantar surface of the toes, spreading up the posterior leg; lateral heel and lateral foot
S2 Posterior thigh and leg, popliteal fossa
S3 Perineum Genital region; ischial tuberosity
S4-S5 Perineal region (S4); skin adjacent to the anus (S5)
Coccygeal The dermatome corresponding with the coccygeal nerves is located on the buttocks, in the area directly around the coccyx.
Anterior and posterior body outlines divided into shaded bands, each labelled with a spinal nerve level to show dermatome distribution from the neck to the feet.
Figure 1. Dermatome map from Grant’s An Atlas of Anatomy (1962), showing the segmental distribution of cutaneous innervation by spinal nerve level on the anterior and posterior body surface

History

Origin of the Concept

[12]


The idea of dermatomes originated from initial efforts to associate anatomy with the physiology of sensation.[13] Multiple definitions of dermatomes exist, and several maps are commonly used.[2] Although they are valuable, dermatomes vary significantly between maps and even among individuals,[13] with some evidence suggesting that current dermatome maps are inaccurate and based on flawed studies.[3] [14]

Two primary dermatome maps have traditionally been recognised in clinical practice.[3] [14] The first is the Keegan and Garrett map (1948), which illustrates dermatomes in alignment with the developmental progression of the limb segments.[15] The second is the Foerster map (1933).[16] Foerster used rhizotomy, the surgical section of dorsal nerve roots, to study sensory loss in individual dermatomes, and his work became the foundation of modern dermatome maps.[16][2] Keegan and Garrett later refined these maps by examining the segmental distribution of cutaneous nerves in the limbs.[15][2] The Foerster map is featured in the American Spinal Injury Association Impairment Scale (ASIA Scale) for assessing spinal cord injury.[2] Lee et al. (2008) systematically reviewed the evidence behind published dermatome maps.[3] They concluded that existing maps were unreliable, as they rested on methodologically weak studies, and proposed a new evidence-based map of tactile dermatomes.[3]

Controversies

Published dermatome maps differ because they were derived using different methods, and textbook versions are inconsistent.[14][17] Lee et al. also highlighted that dermatomes overlap and vary between individuals, and argued that this deserves greater emphasis in teaching and practice.[3] The Foerster and Keegan and Garrett maps both remain in common use,[2] and dermatomes also vary between individuals, with overlap that is greater for light touch.[18] Clinicians should therefore use one map consistently, state which map they used, and interpret dermatomal findings alongside myotomes and reflexes.

Purpose

Testing of dermatomes is part of the neurological examination.[10] 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.[10][6]

Technique

Dermatome testing is ideally done with a pin and cotton wool.[6] 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 bilaterally.

  • Light Touch Test - Light Touch Sensation - Lightly touch the skin with cotton wool [6]
  • Pin-prick Test - Pain Sensation - Gently touch the skin with the pin and ask the patient whether it feels sharp or dull[6]

[19]


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.[17]

Adjacent dermatomes overlap substantially, so injury to a single dorsal root does not cause complete loss of sensation in the corresponding area of skin.[2] This overlap is greater for light touch, pressure and vibration than for pain and temperature.[20] Pain (pin-prick) testing therefore provides a more precise assessment of segmental nerve injury than testing with light touch, pressure or vibration.[20]

Scoring

The ISNCSCI tests light touch and pin-prick sensation at a standardised key sensory point in 28 dermatomes (C2 to S4-5) on each side of the body.[6] Each point is scored 0 (absent), 1 (altered) or 2 (normal), or “NT” if not testable. The sensory level is the most caudal dermatome with intact sensation. Sensation at S4-5 is key to distinguishing complete from incomplete injury.[6] See the ASIA page for full scoring and classification.

Clinical Significance

Dermatomes are important because they can help to assess and diagnose a variety of conditions.[2] Dermatomal testing helps clinicians localise the level of a neurological lesion.[2] Sensory loss in a single dermatomal distribution suggests nerve root involvement (radiculopathy), whereas loss in a peripheral cutaneous nerve distribution points to a peripheral nerve lesion.[18] Distinguishing between the two supports clinical reasoning and assessment. Findings are interpreted alongside myotomes and reflexes rather than in isolation. In spinal cord injury, dermatomal testing determines the sensory level and contributes to injury classification and prognosis.[6] A dermatomal rash or pain pattern can also support the diagnosis of herpes zoster.[21][22] Dermatomal assessment is relevant in conditions such as:

Red Flags

Some sensory findings need urgent medical referral rather than routine management:[24]

Although some of these features are not routinely examined in an outpatient assessment, it is important to ask about them in the subjective history to help identify serious pathology early and ensure timely referral.

Summary of the Page

Dermatomes are areas of skin supplied by afferent fibres from a single dorsal spinal nerve root. Testing with light touch and pin-prick, compared bilaterally, helps clinicians localise a lesion to a nerve root or spinal cord level, and the ISNCSCI standardises this at 28 key sensory points. Dermatomes overlap and vary between people, and published maps disagree, so clinicians should use one map consistently and interpret findings alongside myotomes and reflexes. Sensory changes such as saddle anaesthesia or rapidly progressing loss are red flags requiring urgent medical referral.

References

  1. ↑ 1.0 1.1 De Luigi AJ, Fitzpatrick KF. Physical examination in radiculopathy. Physical Medicine and Rehabilitation Clinics. 2011 Feb 1;22(1):7-40.
  2. ↑ 2.00 2.01 2.02 2.03 2.04 2.05 2.06 2.07 2.08 2.09 2.10 2.11 2.12 Rajendran B, Yunos MA, Nagalinggam H, Aziz ML, Abdullah JM. Surface Anatomy and Sensory Evaluation of Dermatomes: A Guide for Residents. The Malaysian Journal of Medical Sciences: MJMS. 2025 Feb 28;32(1):169.
  3. ↑ 3.0 3.1 3.2 3.3 3.4 3.5 3.6 Lee MW, McPhee RW, Stringer MD. An evidence‐based approach to human dermatomes. Clinical Anatomy: The Official Journal of the American Association of Clinical Anatomists and the British Association of Clinical Anatomists. 2008 Jul;21(5):363-73.
  4. ↑ Homma S, Shimada T, Wada I, Kumaki K, Sato N, Yaginuma H. A three-component model of the spinal nerve ramification: Bringing together the human gross anatomy and modern Embryology. Frontiers in Neuroscience. 2023 Jan 16;16:1009542.
  5. ↑ 5.0 5.1 5.2 Standring S, editor. Gray's Anatomy E-Book: Gray's Anatomy E-Book. Elsevier Health Sciences; 2021 May 22.
  6. ↑ 6.0 6.1 6.2 6.3 6.4 6.5 6.6 6.7 6.8 Rupp R, Biering-Sørensen F, Burns S, Franz S, Furlan JC, Guest J, Jones L, Kirshblum S, Krassioukov A, McClure I, Rodriguez G. International Standards for Neurological Classification of Spinal Cord Injury: 2026. Topics in Spinal Cord Injury Rehabilitation. 2026;32(4):141-68.
  7. ↑ 7.0 7.1 Soar H, Comer C, Wilby MJ, Baranidharan G. Lumbar radicular pain. BJA education. 2022 Sep 1;22(9):343-9.
  8. ↑ Sam Webster. Upper limb dermatomes. Available from: https://www.youtube.com/watch?v=joiuWmTeN0Y [last accessed 15/10/2026]
  9. ↑ Anatomy and Physiology by M. Roehrs. Dermatomes. Available from: https://www.youtube.com/watch?v=CYZBH6NX8wg [last accessed 15/10/2026]
  10. ↑ 10.0 10.1 10.2 10.3 Rupp R, Biering-Sørensen F, Burns SP, Graves DE, Guest J, Jones L, Read MS, Rodriguez GM, Schuld C, Tansey-Md KE, Walden K. International standards for neurological classification of spinal cord injury: revised 2019. Topics in spinal cord injury rehabilitation. 2021 Mar 1;27(2):1-22.
  11. ↑ David J. Magee. Orthopedic Physical Assessment. 6th edition. Elsevier. 2014.
  12. ↑ ashraf yunos. MJMS Neurology Examination (Neurosurgery) - Surface Anatomy of Dermatome: A Guide For Resident. Available from: https://www.youtube.com/watch?v=7frtOoeppuo [last accessed 25/10/2026]
  13. ↑ 13.0 13.1 Apok V, Gurusinghe NT, Mitchell JD, Emsley HC. Dermatomes and dogma. Practical neurology. 2011 Apr;11(2):100-5.
  14. ↑ 14.0 14.1 14.2 Downs MB, Laporte C. Conflicting dermatome maps: educational and clinical implications. journal of orthopaedic & sports physical therapy. 2011 Jun;41(6):427-34.
  15. ↑ 15.0 15.1 Keegan JJ, Garrett FD. The segmental distribution of the cutaneous nerves in the limbs of man. The Anatomical Record. 1948 Dec;102(4):409-37.
  16. ↑ 16.0 16.1 Foerster O. The dermatomes in man. Brain. 1933 Mar 1;56(1):1-39.
  17. ↑ 17.0 17.1 O'sullivan SB, Schmitz TJ, Fulk G. Physical rehabilitation. FA Davis; 2019 Jan 25.
  18. ↑ 18.0 18.1 Robblee J, Katzberg H. Distinguishing radiculopathies from mononeuropathies. Frontiers in Neurology. 2016 Jul 13;7:111.
  19. ↑ lcdpt2015. Dermatome Screening Jon, Drew, Juliana. Available from: https://www.youtube.com/watch?v=ETvKVAYxKO0 [last accessed 15/10/2026]
  20. ↑ 20.0 20.1 Khoo YH, AbdullAh JM, IdrIs Z, GhAnI AR, Halim SA. Dorsal column bedside examination test: tips for the neurosurgical resident. The Malaysian Journal of Medical Sciences: MJMS. 2023 Apr 18;30(2):172.
  21. ↑ 21.0 21.1 Centers for Disease Control and Prevention (CDC). Clinical Features of Shingles (Herpes Zoster) [Internet]. CDC; 2024
  22. ↑ Aurangzeb A, Chong EY, Yuen PW, Koh DT, Kuo CL. Case Report of Herpes Zoster Infection of the Cervical Dermatome–A Rare Cause of Acute Shoulder Pain. Journal of Orthopaedic Case Reports. 2024 Aug;14(8):89.
  23. ↑ Schmid AB, Fundaun J, Tampin B. Entrapment neuropathies: a contemporary approach to pathophysiology, clinical assessment, and management. Pain reports. 2020 Jul 22;5(4):e829.
  24. ↑ 24.0 24.1 Finucane LM, Downie A, Mercer C, Greenhalgh SM, Boissonnault WG, Pool-Goudzwaard AL, Beneciuk JM, Leech RL, Selfe J. International framework for red flags for potential serious spinal pathologies. journal of orthopaedic & sports physical therapy. 2020 Jul;50(7):350-72.
  25. ↑ 25.0 25.1 Conte A, Jain R, Lingham A, Mueller M. Cauda Equina Syndrome—A 2025 Narrative Review. British Journal of Hospital Medicine. 2026 Apr 16;87(4).
  26. ↑ Wang Q, Hou G, Wen M, Ren Z, Duan W, Lei X, Yao Z, Zhao S, Ye B, Tu Z, Huang P. How to assess the long-term recovery outcomes of patients with cauda equina syndrome before surgery: a retrospective cohort study. International journal of surgery (London, England). 2024 Mar 19;110(7):4197.
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