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Myotomes: Difference between revisions
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A myotome is the group of muscles that a single spinal nerve innervates. Most muscles are innervated by more than one spinal nerve root, and therefore consist of multiple myotomes. ย | A myotome is the group of muscles that a single spinal nerve innervates. Most muscles are innervated by more than one spinal nerve root, and therefore consist of multiple myotomes. Understanding the myotomes is integral for performing an accurate [[Motor System Examination|motor system examination]]. ย | ||
==Simplified Examination== | ==Simplified Examination== | ||
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| Ankle plantarflexion ||ย || S1/S2 || + || Tibial || Gastrocnemius, soleus | | Ankle plantarflexion ||ย || S1/S2 || + || Tibial || Gastrocnemius, soleus | ||
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| Big toe extension ||ย || L5 || | | Big toe extension ||ย || L5 || ย | ||
| Deep peroneal || Extensor hallucis longus | |||
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! Muscle !! Nerve !! colspan="7" |Spinal Roots | ! Muscle !! Nerve !! colspan="7" |Spinal Roots | ||
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! colspan="9" style="text-align: center;" class="tableSubHeading" |Upper Limb <ref>{{#pmid:26409623}}</ref><ref name="brain"></ref> | ! colspan="9" style="text-align: center;" class="tableSubHeading" |Upper Limb <ref>{{#pmid:26409623}}</ref><ref name="brain"></ref><ref name=":0">McGee, Steven R. ''Evidence-based physical diagnosis''. Philadelphia, PA: Elsevier, 2018.</ref> | ||
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|Triceps || rowspan=" | |Triceps || rowspan="5" |Radial nerve || ย | ||
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| | |ECRL || | ||
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|Finger extensors | |||
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|FCR, pronator teres || rowspan=" | |FCR, pronator teres || rowspan="3" |Median nerve|| ย | ||
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|FDS | |FDS || ย | ||
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|APB | |||
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|FPL, FDP, PQ || Anterior interosseous nerve|| ย | |FPL, FDP, PQ || Anterior interosseous nerve|| ย | ||
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|๐ณ | |๐ณ | ||
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! colspan="9" style="text-align: center;" class="tableSubHeading" |Lower Limb <ref name="brain"></ref> | ! colspan="9" style="text-align: center;" class="tableSubHeading" |Lower Limb <ref name="brain"></ref><ref name=":0" /> | ||
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|Semitendinosus, biceps femoris, semimembranosus| | |Semitendinosus, biceps femoris, semimembranosus||Sciatic nerve trunkโ || | ||
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| | |Tibialis posterior | ||
| rowspan="3" |Tibial nerveโ || | |||
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| | |Gastrocnemius and soleus | ||
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|๐ฒ | |๐ฒ | ||
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|Flexor digitorum longus|| | |Flexor digitorum longus|| | ||
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|๐ณ | |๐ณ | ||
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| | |Tibialis anterior | ||
| rowspan="4" |Peroneal nerveโ | |||
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| | |Extensor digitorum longus, extensor hallucis longus || ย | ||
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|Abductor hallucis, abductor digiti minimi, interossei|| | |||
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|๐ฒ | |๐ฒ | ||
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|Extensor digitorum brevis, peroneus longus, peroneus brevis|| | |Extensor digitorum brevis, peroneus longus, peroneus brevis|| | ||
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| colspan="9" |๐ฒ segmental contribution, ๐ณ ''significant'' segmental contribution. | | colspan="9" |๐ฒ segmental contribution, ๐ณ ''significant'' segmental contribution. | ||
โ The sciatic nerve trunk divides above the knee into the peroneal and tibial nerves, therefore lesions of the sciatic nerve trunk affect the muscles of all three branches. | |||
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Latest revision as of 11:16, 4 March 2022
This article is still missing information.
A myotome is the group of muscles that a single spinal nerve innervates. Most muscles are innervated by more than one spinal nerve root, and therefore consist of multiple myotomes. Understanding the myotomes is integral for performing an accurate motor system examination.
Simplified Examination
Spinal Level | Movement |
---|---|
Upper Limb | |
C5 | Shoulder abduction |
C6 | Elbow flexion |
C7 | Elbow extension |
C8 | Finger flexion |
T1 | Finger abduction |
Lower Limb | |
L2 | Hip flexion |
L3 | Hip adduction |
L4 | Knee extension |
L5 | Ankle dorsiflexion |
S1 | Ankle plantarflexion |
Commonly Tested Movements
Movement | UMN | Root | Reflex | Nerve | Muscle |
---|---|---|---|---|---|
Upper Limb | |||||
Shoulder abduction | ++ | C5 | Axillary | Deltoid | |
Elbow flexion | C5/6 C6 |
+ + |
Musculocutaneous Radial |
Biceps Brachioradialis | |
Elbow extension | + | C7 | + | Radial | Triceps |
Radial wrist extension | + | C6 | Radial | Extensor carpi radialis longus | |
Finger extension | + | C7 | Posterior interosseous nerve | Extensor digitorum communis | |
Finger flexion | C8 |
+ |
Anterior interosseous nerve Ulnar |
Flexor pollicis longus and flexor digitorum profundus (index) Flexor digitorum profundus (ring and little) | |
Finger abduction | ++ |
T1 T1 |
Ulnar Median |
First dorsal interosseous Abductor pollicis brevis | |
Lower Limb | |||||
Hip flexion | ++ | L1/2 | Iliopsoas | ||
Hip adduction | L2/3 | + | Obturator | Adductors | |
Hip extension | L5/S1 | Sciatic | Gluteus Maximus | ||
Knee flexion | + | S1 | Sciatic | Hamstrings | |
Knee extension | L3/4 | + | Femoral | Quadriceps | |
Ankle dorsiflexion | ++ | L4 | Deep peroneal | Tibialis anterior | |
Ankle eversion | L5/S1 | Superficial peroneal | Peronei | ||
Ankle plantarflexion | S1/S2 | + | Tibial | Gastrocnemius, soleus | |
Big toe extension | L5 | Deep peroneal | Extensor hallucis longus |
Complete Myotome Chart
Muscle | Nerve | Spinal Roots | ||||||
---|---|---|---|---|---|---|---|---|
Upper Limb [3][2][4] | ||||||||
C3 | C4 | C5 | C6 | C7 | C8 | T1 | ||
Trapezius | Spinal accessory nerve | ๐ฒ | ๐ฒ | |||||
Supraspinatus, infraspinatus | Suprascapular nerve | ๐ณ | ๐ฒ | |||||
Pectoralis major | Lateral and medial pectoral nerves | ๐ฒ | ๐ฒ | ๐ฒ | ๐ฒ | |||
Latissimus dorsi | Thoracodorsal nerve | ๐ฒ | ๐ณ | ๐ฒ | ||||
Teres major | Lower subscapular nerve | ๐ฒ | ๐ฒ | ๐ฒ | ||||
Serratus anterior | Long thoracic nerve | ๐ฒ | ๐ฒ | ๐ฒ | ||||
Rhomboids | Dorsal scapular nerve | ๐ฒ | ๐ฒ | |||||
Deltoid | Axillary nerve | ๐ฒ | ๐ฒ | |||||
Biceps and brachialis | Musculocutaneous nerve | ๐ฒ | ๐ฒ | |||||
Triceps | Radial nerve | ๐ฒ | ๐ณ | ๐ฒ | ||||
Brachioradialis | ๐ฒ | ๐ณ | ||||||
ECRL | ๐ฒ | ๐ณ | ๐ฒ | |||||
ECU | ๐ณ | ๐ฒ | ||||||
Finger extensors | ๐ฒ | ๐ฒ | ||||||
FCR, pronator teres | Median nerve | ๐ฒ | ๐ฒ | |||||
FDS | ๐ฒ | ๐ณ | ||||||
APB | ๐ฒ | ๐ฒ | ||||||
FPL, FDP, PQ | Anterior interosseous nerve | ๐ฒ | ๐ณ | ๐ฒ | ||||
EDC, EPL | Posterior interosseous nerve | ๐ณ | ๐ฒ | ๐ฒ | ||||
FCU | Ulnar nerve | ๐ฒ | ๐ณ | ๐ฒ | ||||
FDP radial digits | ๐ณ | ๐ฒ | ||||||
FDP ulnar digits | ๐ฒ | ๐ณ | ๐ฒ | |||||
Interossei | ๐ฒ | ๐ฒ | ๐ณ | |||||
Lower Limb [2][4] | ||||||||
L1 | L2 | L3 | L4 | L5 | S1 | S2 | ||
Iliopsoas | Femoral nerve | ๐ณ | ๐ณ | ๐ฒ | ||||
Quadriceps femoris | ๐ฒ | ๐ณ | ๐ณ | |||||
Adductor longus and magnus | Obturator nerve | ๐ณ | ๐ณ | ๐ฒ | ||||
Gluteus medius, minimis, tensor fascia lata | Superior gluteal nerve | ๐ณ | ๐ณ | ๐ฒ | ||||
Gluteus maximus | Inferior gluteal nerve | ๐ณ | ๐ณ | ๐ฒ | ||||
Semitendinosus, biceps femoris, semimembranosus | Sciatic nerve trunkโ | ๐ฒ | ๐ณ | ๐ฒ | ||||
Tibialis posterior | Tibial nerveโ | ๐ฒ | ๐ฒ | |||||
Gastrocnemius and soleus | ๐ฒ | ๐ฒ | ||||||
Flexor digitorum longus | ๐ฒ | ๐ณ | ๐ณ | |||||
Tibialis anterior | Peroneal nerveโ | ๐ณ | ๐ฒ | |||||
Extensor digitorum longus, extensor hallucis longus | ๐ณ | ๐ฒ | ||||||
Abductor hallucis, abductor digiti minimi, interossei | ๐ฒ | ๐ฒ | ||||||
Extensor digitorum brevis, peroneus longus, peroneus brevis | ๐ฒ | ๐ฒ | ||||||
๐ฒ segmental contribution, ๐ณ significant segmental contribution.
โ The sciatic nerve trunk divides above the knee into the peroneal and tibial nerves, therefore lesions of the sciatic nerve trunk affect the muscles of all three branches. |
Myotome Dance
Spinal Levels | Memory Aid | Action |
---|---|---|
Upper Limb | ||
C1, 2 | I nod to you | Neck flexion/extension |
C3 | Donโt tickle me | Neck lateral flexion |
C4 | Iโm not sure | Shoulder elevation |
C5 | Feel alive | Shoulder flexion, abduction, & lateral rotation |
C6, 7, 8 | Close the gate | Shoulder extension, adduction & medial rotation |
C5, 6 | Pick up sticks | Elbow flexion |
C7, 8 | Lay them straight | Elbow extension |
C5, 6 | Flick my wrists | Forearm supination |
C7, 8 | The time is late | Forearm pronation |
C6, 7 | Fly up to heaven | Wrist flexion & extension |
C7 | Paper | Finger extension |
C8 | Rock | Finger flexion (though some sources say C7, 8 does both finger extension and flexion) |
T1 | Scissors | Finger abduction & adduction |
Lower Limb | ||
L2, 3 | Lift my knee | Hip flexion |
L3, 4 | Kick the door | Knee extension (& knee-jerk reaction) |
L4, 5 | Foot points to the sky | Ankle dorsiflexion |
L4, 5 | Extend my thigh | Hip extension |
L5, S1, (S2) | Kick my bum (Run to poo) | Knee flexion |
S1, 2 | Stand on my shoes | Ankle plantarflexion (& ankle jerk) |
L2, 3, 4 | Modestly close the door | Hip adduction & internal/medial rotation |
L4 - S2 | The opposite is true | Hip abduction & external/lateral rotation |
C3, 4, 5 | Keeps the diaphragm alive | Innervates the diaphragm |
S2, 3, 4 | Keeps poo off the floor | Innervates bowel, bladder, sex organs, anal sphincter, pelvic muscles. (& anal wink reflex) |
Note
- T1-12 Supplies chest wall and abdominal muscles
- L1 Contributes to hip flexion & adduction
- L5, S1, S2 Babinski plantar reflex/extensor response in UMN lesion
Other Videos
References
- โ The Noted Anatomist. Myotomes. Feb 29, 2020. Available on youtube
- โ 2.0 2.1 2.2 Brain. Aids to the Examination of the Peripheral Nervous System, 4th edition. 2000
- โ Bell et al.. Refinement of myotome values in the upper limb: Evidence from brachial plexus injuries. The surgeon : journal of the Royal Colleges of Surgeons of Edinburgh and Ireland 2017. 15:1-6. PMID: 26409623. DOI.
- โ 4.0 4.1 McGee, Steven R. Evidence-based physical diagnosis. Philadelphia, PA: Elsevier, 2018.