Dermatome and myotome charts
These dermatome and myotome charts list the test points used in the International Standards for Neurological Classification of Spinal Cord Injury (ISNCSCI), published by the American Spinal Injury Association (ASIA). That covers the 28 key sensory points from C2 to S4-5 and the 10 key muscles (C5 to T1, L2 to S1) with a short version of each test. The upper and lower limb reflexes are here too, with the root levels two sources give for each. Type a level such as C6, a range such as L4-S1 or a body part, or pick a body area.
Dermatome chart: ISNCSCI key sensory points
A dermatome is the area of skin supplied by the sensory fibers of one spinal nerve root. The ISNCSCI exam does not test a whole dermatome. It tests one key sensory point in each, on both sides of the body, for light touch and for pin prick. The wording in the table is ours, written from ASIA's key sensory points sheet.
| Level | Key sensory point | Body area |
|---|---|---|
| C2 | At least 1 cm to the side of the bump at the back of the skull (occipital protuberance), at the base of the skull. As an alternative, at least 3 cm behind the ear. | Neck and shoulder |
| C3 | In the hollow above the collarbone (supraclavicular fossa), on the midclavicular line. | Neck and shoulder |
| C4 | Over the acromioclavicular joint, on top of the shoulder. | Neck and shoulder |
| C5 | On the outer (radial) side of the front of the elbow (antecubital fossa), just above the elbow. | Arm and hand |
| C6 | On the back (dorsal surface) of the first bone (proximal phalanx) of the thumb. | Arm and hand |
| C7 | On the back of the proximal phalanx of the middle finger. | Arm and hand |
| C8 | On the back of the proximal phalanx of the little finger. | Arm and hand |
| T1 | On the inner (ulnar) side of the front of the elbow, just above the medial epicondyle of the humerus. | Arm and hand |
| T2 | At the top (apex) of the armpit (axilla). | Arm and hand |
| T3 | On the midclavicular line in the third intercostal space. Feel the front of the chest for the third rib; the space is just below it. | Chest and abdomen |
| T4 | On the midclavicular line in the fourth intercostal space, at the level of the nipples. | Chest and abdomen |
| T5 | On the midclavicular line in the fifth intercostal space, halfway between the level of the nipples and the level of the lower end of the breastbone (xiphisternum). | Chest and abdomen |
| T6 | On the midclavicular line, at the level of the xiphisternum. | Chest and abdomen |
| T7 | On the midclavicular line, one quarter of the way from the level of the xiphisternum down to the level of the belly button (umbilicus). | Chest and abdomen |
| T8 | On the midclavicular line, halfway between the level of the xiphisternum and the level of the umbilicus. | Chest and abdomen |
| T9 | On the midclavicular line, three quarters of the way from the level of the xiphisternum down to the level of the umbilicus. | Chest and abdomen |
| T10 | On the midclavicular line, at the level of the umbilicus. | Chest and abdomen |
| T11 | On the midclavicular line, halfway between the level of the umbilicus and the inguinal ligament. | Chest and abdomen |
| T12 | On the midclavicular line, over the midpoint of the inguinal ligament in the groin. | Chest and abdomen |
| L1 | Halfway between the key sensory points for T12 and L2. | Leg and foot |
| L2 | On the front and inner (anterior-medial) thigh, halfway along an imaginary line from the midpoint of the inguinal ligament to the medial femoral condyle. | Leg and foot |
| L3 | At the medial femoral condyle, on the inner side just above the knee. | Leg and foot |
| L4 | Over the inner ankle bone (medial malleolus). | Leg and foot |
| L5 | On the top (dorsum) of the foot at the third metatarsophalangeal joint. | Leg and foot |
| S1 | On the outer (lateral) side of the heel bone (calcaneus). | Leg and foot |
| S2 | At the midpoint of the back of the knee (popliteal fossa). | Leg and foot |
| S3 | Over the ischial tuberosity (sitting bone) or the fold under the buttock (infragluteal fold). ASIA notes that the skin can move up, down or sideways over the sitting bone, depending on the patient. | Buttock and perianal area |
| S4-5 | In the perianal area, less than 1 cm to the side of the mucocutaneous junction. S4 and S5 are tested as one level. | Buttock and perianal area |
No key sensory point matches this search.
Each point is scored 0 (absent), 1 (altered, meaning reduced, impaired or heightened feeling) or 2 (normal), or NT if it cannot be tested. With 28 points a side, the worksheet gives a maximum of 56 per side for light touch and 56 per side for pin prick. The sensory level on each side is the lowest dermatome where both light touch and pin prick are intact.
Myotome chart: the 10 ISNCSCI key muscles
A myotome is the group of muscles supplied by one spinal nerve root. The ISNCSCI exam picks one key muscle function for each of 10 levels, 5 in each arm and 5 in each leg. For each one, the table gives the muscles named in ASIA's motor exam guide and a short version of the test: the grade 3 position, then what changes for grades 4 and 5. Grades 0 to 2 need a different position with gravity taken out, and the guide describes it muscle by muscle. All 10 are tested with the patient lying on their back (supine).
| Level | Key muscle function | Main muscles | How it is tested |
|---|---|---|---|
| C5 | Elbow flexors | Biceps brachii, brachialis | Grade 3: elbow straight, forearm fully turned palm up. The patient bends the elbow through its full range, bringing the hand up toward the face. For grades 4 and 5, the elbow is held at 90 degrees and you pull at the wrist toward straightening, with your other hand steadying the front of the shoulder. |
| C6 | Wrist extensors | Extensor carpi radialis longus and brevis | Grade 3: elbow straight, forearm palm down, wrist bent. The patient lifts the back of the hand through full wrist extension. For grades 4 and 5, press down across the back of the hand toward flexion and the little finger side. |
| C7 | Elbow extensors | Triceps | Grade 3: shoulder at 90 degrees of flexion, elbow fully bent with the palm by the ear. The patient straightens the elbow through its full range. For grades 4 and 5, the elbow is held at 45 degrees and you push on the lower forearm toward bending. |
| C8 | Finger flexors | Flexor digitorum profundus (middle finger) | Grade 3: hold the wrist straight and the knuckle and middle joints of the middle finger straight. The patient bends only the end joint of the middle finger through its full range. For grades 4 and 5, push the fingertip toward straightening while the patient holds it bent. |
| T1 | Finger abductors (little finger) | Abductor digiti minimi | Grade 3: elbow at 90 degrees, forearm palm down, knuckles steadied. The patient moves the little finger away from the ring finger through its full range. For grades 4 and 5, push on the side of the end of the little finger while the patient holds it out. |
| L2 | Hip flexors | Iliopsoas | Grade 3: hip and knee in 15 degrees of flexion. The patient bends the hip up to 90 degrees without dragging the foot on the table. For grades 4 and 5, the hip is at 90 degrees and you push just above the knee toward hip extension. With an acute traumatic lesion below T8, do not let the hip bend past 90 degrees. |
| L3 | Knee extensors | Quadriceps | Grade 3: your arm under the knee holds it at about 30 degrees of flexion. The patient straightens the knee through its full range. For grades 4 and 5, the knee is at 15 degrees and you push just above the ankle toward bending. |
| L4 | Ankle dorsiflexors | Tibialis anterior | Grade 3: hip and knee slightly bent, ankle pointed down. The patient pulls the foot up through the full range of ankle dorsiflexion. For grades 4 and 5, press down on the top of the foot. Watch the ankle move: lifting the toes alone can look like dorsiflexion. |
| L5 | Long toe extensors | Extensor hallucis longus | Grade 3: leg straight, foot supported. The patient lifts the big toe up through its full range. For grades 4 and 5, press down on the end of the big toe while the patient holds it up. |
| S1 | Ankle plantar flexors | Gastrocnemius, soleus | Grade 3: hip at 45 degrees, knee fully bent, foot pushed up by your hand. The patient pushes the front of the foot down into your hand, lifting the heel off the table through the full range. For grades 4 and 5, the leg is straight and you push up on the ball of the foot while the patient holds it pointed. |
No key muscle matches this search. Levels C2 to C4 and T2 to L1 have no key muscle.
The ISNCSCI grades each key muscle from 0 to 5, or NT. Here grades 2 to 5 all ask for movement through the full range, which the MRC wording on our manual muscle testing grades page does not say. The motor level is the lowest key muscle graded at least 3 when tested lying down, as long as the key muscles above it are graded 5. From C2 to C4 and from T2 to L1 there is no key muscle, so the motor level there is taken to be the same as the sensory level, if the testable muscles above it are normal.
ASIA's guide lists common trick movements. Toe extension can look like ankle dorsiflexion at L4, and a quick bend and relax of the elbow can look like triceps action at C7. Stabilize well and feel the muscle you are testing.
Upper and lower limb reflexes and their root levels
The ISNCSCI worksheet does not score reflexes, but you will often test them alongside it. Root levels differ between sources, so the table shows two StatPearls chapters side by side.
| Reflex | Root level (Zimmerman and Hubbard) | Root level (Rodriguez-Beato and De Jesus) | Nerve | Where to tap |
|---|---|---|---|---|
| Biceps | C5-C6 | C5-C6 | Musculocutaneous | Just in front of the elbow |
| Brachioradialis | C5-C6 | C5-C6 | Radial | About 10 cm above the wrist, on the thumb side of the forearm |
| Triceps | C7-C8 (mainly C7) | C7-C8 | Radial | Just behind the elbow |
| Knee (patellar, quadriceps) | L2-L4 (mainly L4) | L2-L4 | Femoral | Just below the kneecap |
| Ankle (Achilles) | S1 | S1-S2 | Tibial | On the Achilles tendon, behind the ankle joint |
No reflex matches this search.
The two chapters agree on the arm reflexes and on L2 to L4 for the knee. They part ways at the ankle: S1 in Zimmerman and Hubbard, S1 to S2 in Rodriguez-Beato and De Jesus. Even one chapter is not fully consistent. The memory rhyme in Zimmerman and Hubbard gives S1 to S2 for the ankle and L3 to L4 for the knee.
Nerve and tap site come from Zimmerman and Hubbard. They note that a reflex absent on both sides can be normal when there is no other sign of disease or reason for concern. Reinforcement can bring out a reflex that seemed absent. For the leg reflexes, the patient hooks their fingers together and pulls (the Jendrassik maneuver). Write down whether you used it.
Limits: dermatome maps vary
- Maps do not agree. Lee, McPhee and Stringer (2008) point out significant variation between the dermatome maps in standard anatomy texts. After a systematic review of the evidence, they concluded that current maps are inaccurate and based on flawed studies.
- Their own evidence-based map shows the most consistent area for each nerve root in most people, not a fixed border that fits everyone. They wrote that overlap and variation between dermatomes deserve greater emphasis.
- Neighboring dermatomes overlap a lot. Whitman and colleagues (StatPearls) give this overlap as the reason maps vary. So a small change at one key point may not follow a textbook border.
- A key sensory point is a test site, not the whole dermatome. Test the same points in the same way each time, so that one exam can be compared with the next.
- Myotomes overlap too. The ISNCSCI paper by Rupp and colleagues (2021) notes that most muscles are supplied by more than one nerve root, usually two. Each key muscle is listed under one level by convention, so weakness in one key muscle does not on its own point to a single root.
- The ISNCSCI was built to classify spinal cord injury. It was not designed to show which nerve root is affected in conditions such as sciatica or a trapped nerve in the neck.
- Sources give different root levels for some reflexes. The ankle reflex in the table above is the clearest case: S1 in one chapter, S1 to S2 in the other.
- ASIA's key sensory points sheet is dated June 2008. The current worksheet (revision 04/26) still tests the same 28 levels from C2 to S4-5. It cites a 2026 revision of the standards that was not yet available for us to read, so check the points against the worksheet diagram.
Use the charts to record and compare findings, alongside the rest of your examination. They do not tell you the cause of a sensory change or weakness.
When weakness or numbness is urgent
Sudden or worsening weakness or numbness, or a new change in bladder or bowel control, needs urgent assessment. If you are a patient reading this page:
- Emergency: numbness, tingling or altered feeling around or under your genitals, between your inner thighs, or around your bottom (anus), for example it feels different when you wipe after using the toilet. Call emergency services or go to an emergency department straight away. This can be a sign of pressure on the bundle of nerves at the base of the spine (cauda equina syndrome), which needs emergency treatment.
- Emergency: you find it hard to start peeing, cannot pee, cannot feel yourself peeing or cannot control when you pee, or you do not notice when you need to poo or cannot control when you poo, and this is not normal for you. The same applies to a new change in how your genitals feel during sex, or new trouble getting an erection or ejaculating. Call emergency services or go to an emergency department straight away. These can also be signs of cauda equina syndrome.
- Emergency: sciatica in both legs, or pain, tingling, numbness or weakness in both legs. The same applies if you lose feeling in one leg. Call emergency services or go to an emergency department straight away.
- Emergency: new problems walking, for example your legs feel stiff, heavy or weak or you have become unsteady on your feet, new trouble controlling your bladder or bowels, or hands that suddenly become clumsy, for example you can no longer do up buttons. Call emergency services straight away. These can be signs of pressure on the spinal cord in the neck.
- Emergency: any sign of a stroke, even if it goes away. That means a face that droops on one side, an arm you cannot lift or keep up, slurred or muddled speech, weakness or numbness on one side of your body or face, sudden blurred vision, double vision or loss of sight, trouble swallowing, sudden dizziness with unsteadiness or falling over, a sudden severe headache, or a sudden fall where your legs give way but you do not black out (a drop attack). Call emergency services straight away. With neck pain, these can rarely come from a tear in an artery in the neck.
- A leg or foot that is getting weaker, for example your foot drags, catches on the ground or slaps down when you walk (foot drop). Get medical advice the same day. If the weakness is getting worse by the hour, go to an emergency department.
- An arm or hand that is getting weaker. Get medical advice the same day.
- Hands that have slowly become clumsy, for example trouble doing up buttons or dropping things, or numbness in both hands. Get medical advice the same day. These can be signs of pressure on the spinal cord in the neck (cervical myelopathy). If the clumsiness or numbness gets worse quickly, call emergency services straight away.
- Pain or tingling in both arms at the same time, rather than in one. Get medical advice the same day. This can also be a sign of pressure on the spinal cord in the neck.
The ASIA worksheet
ASIA publishes the ISNCSCI worksheet under a Creative Commons license (CC BY-NC-ND 4.0). It may be copied freely for non-commercial use but may not be altered without ASIA's approval. We do not copy the worksheet or its body diagram here. You can download the current ISNCSCI worksheet from ASIA, with its body diagram of the key sensory points, the scoring rules and the steps to classify an injury.
References
- American Spinal Injury Association. International Standards for the Classification of Spinal Cord Injury: Key Sensory Points. June 2008. asia-spinalinjury.org (PDF)
- American Spinal Injury Association. International Standards for the Classification of Spinal Cord Injury: Motor Exam Guide. February 2020. asia-spinalinjury.org (PDF)
- American Spinal Injury Association. International Standards for Neurological Classification of Spinal Cord Injury (ISNCSCI) worksheet, revision 04/26, and permissions. asia-spinalinjury.org
- Rupp R, Biering-Sørensen F, Burns SP, et al. International Standards for Neurological Classification of Spinal Cord Injury: Revised 2019. Topics in Spinal Cord Injury Rehabilitation. 2021;27(2):1-22. doi:10.46292/sci2702-1
- Lee MW, McPhee RW, Stringer MD. An evidence-based approach to human dermatomes. Clinical Anatomy. 2008;21(5):363-373. doi:10.1002/ca.20636
- Whitman PA, Launico MV, Adigun OO. Anatomy, skin, dermatomes. In: StatPearls. Treasure Island (FL): StatPearls Publishing; updated 2023. ncbi.nlm.nih.gov
- Zimmerman B, Hubbard JB. Deep tendon reflexes. In: StatPearls. Treasure Island (FL): StatPearls Publishing; updated 2023. ncbi.nlm.nih.gov
- Rodriguez-Beato FY, De Jesus O. Physiology, deep tendon reflexes. In: StatPearls. Treasure Island (FL): StatPearls Publishing; updated 2023. ncbi.nlm.nih.gov
These charts are a reference for clinicians and students. They are not a medical assessment.