[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [Anatomy](https://durgical.com/en/anatomy/) › [Spine](https://durgical.com/en/anatomy/region/spine/) › Brachial plexus roots [Nervous system](https://durgical.com/en/anatomy/system/nervous-system/) · [Spine](https://durgical.com/en/anatomy/region/spine/) # Brachial plexus roots The brachial plexus roots are the C5 to T1 nerve roots joining between the scalene muscles to form the nerve network of the arm. Official name: Brachial plexus [See in 3D →](https://durgical.app/?from=durgipedia&lang=en#region=spine&select=brachial_plexus_roots&side=r) Opens in the Durgical app, no sign-up needed. ## What it is The C5 to T1 nerve roots joining into trunks between the scalene muscles, on their way to the arm. ## What it does Form the nerve network for the shoulder, arm and hand. See the upper-limb model for the rest. ## Key points - Upper root injury (C5–C6, Erb palsy): arm adducted, internally rotated, elbow straight ('waiter's tip'); lower root injury (C8–T1, Klumpke palsy): claw hand, sometimes with Horner syndrome - Signs of root avulsion (preganglionic, not repairable directly): Horner syndrome, winged [scapula](https://durgical.com/en/anatomy/scapula/), rhomboid weakness, a raised hemidiaphragm and normal sensory potentials in a numb arm - The interscalene block targets the roots and trunks between the anterior and middle scalenes and almost always blocks the phrenic nerve on that side ## Key facts **Roots** Ventral rami of C5–T1 (varies: prefixed with C4, postfixed with T2); emerge between anterior and middle scalenes **Moves** Root branches: [dorsal scapular nerve](https://durgical.com/en/anatomy/dorsal-scapular-nerve/) (C5: [rhomboids](https://durgical.com/en/anatomy/rhomboid-major-muscle/), [levator scapulae](https://durgical.com/en/anatomy/levator-scapulae/)), [long thoracic nerve](https://durgical.com/en/anatomy/long-thoracic-nerve/) (C5–C7: [serratus anterior](https://durgical.com/en/anatomy/serratus-anterior/)); plexus: all [upper limb](https://durgical.com/en/anatomy/region/upper-limb/) muscles **Feeling from** Upper limb dermatomes C5–T1 via the terminal branches ## Relations **Course** The ventral rami leave the foramina behind the [vertebral artery](https://durgical.com/en/anatomy/vertebral-artery/), emerge between the anterior and middle [scalenes](https://durgical.com/en/anatomy/scalenus-anterior-muscle/), join into upper (C5–C6), middle (C7) and lower (C8–T1) trunks in the posterior triangle and pass over the [first rib](https://durgical.com/en/anatomy/first-rib/) behind the [clavicle](https://durgical.com/en/anatomy/clavicle/) with the [subclavian artery](https://durgical.com/en/anatomy/right-subclavian-artery/) **In front** The anterior scalene with the [phrenic nerve](https://durgical.com/en/anatomy/phrenic-nerve/) on its front; the subclavian artery lies in front of the lower trunk on the first rib **Behind** The middle scalene **Below** The first rib and the dome of the [pleura](https://durgical.com/en/anatomy/pleura/); T1 rises over the neck of the first rib to reach the plexus **Superficial** [Platysma](https://durgical.com/en/anatomy/platysma/), supraclavicular nerves, [external jugular vein](https://durgical.com/en/anatomy/external-jugular-vein/) and the inferior belly of [omohyoid](https://durgical.com/en/anatomy/omohyoid-muscle/); the transverse cervical artery crosses the trunks ## How to find it The interscalene groove is found by sliding a finger off the back edge of the [sternocleidomastoid](https://durgical.com/en/anatomy/sternocleidomastoid-muscle/) at the level of the [cricoid cartilage](https://durgical.com/en/anatomy/cricoid-cartilage/) (C6) onto the scalenes. On ultrasound the roots and trunks look like a vertical row of round dark dots ('traffic light') between the two muscles. ## Examination - Tinel sign over the supraclavicular plexus: tingling down the arm, used to follow regeneration or locate a neuroma - Roos (elevated arm stress) test: opening and closing the hands with the arms raised reproduces the symptoms in thoracic outlet syndrome ## On imaging MRI or CT myelography shows pseudomeningoceles (CSF pouches) at the foramina after root avulsion; MRI neurography shows the plexus beyond. A [chest](https://durgical.com/en/anatomy/region/chest/) radiograph checks for a raised hemidiaphragm and for a cervical rib. ## Clinical notes - Neurogenic thoracic outlet syndrome: the lower trunk (C8–T1) is stretched over a cervical rib or fibrous band, causing ulnar-side numbness and thenar wasting (Gilliatt-Sumner hand) - Pancoast tumour at the lung apex invades the lower trunk and the stellate ganglion: shoulder and inner-arm pain, hand weakness and Horner syndrome - Motorcycle accidents that force the head and shoulder apart are the classic cause of adult supraclavicular injury; nerve transfers (e.g. spinal accessory to suprascapular) help when roots are avulsed - Neuralgic amyotrophy (Parsonage-Turner syndrome): sudden severe shoulder pain followed by patchy weakness, often in upper trunk muscles ## Anatomical variants - Cervical rib or a fibrous band from C7, in under 1 in 100 people, can lift and kink the lower trunk - A root or trunk (most often C5 or C6) may pass through the anterior scalene instead of behind it ## Memory aid Roots, trunks, divisions, cords, branches: "Randy Travis Drinks Cold Beer". ## Related conditions - [Brachial plexus injury](https://durgical.com/en/conditions/brachial-plexus-injury/) ## Test yourself Think of the answer, then tap the question to see it. ## Which ventral rami form the brachial plexus, and between which muscles do they emerge? C5–T1, emerging between the anterior and middle scalenes. ## Which trunks do the brachial plexus roots form? Upper trunk C5–C6, middle trunk C7 and lower trunk C8–T1. ## What is the posture in Erb palsy, and which roots are injured? C5–C6: arm adducted, internally rotated, elbow straight (waiter's tip). ## Which signs suggest a preganglionic root avulsion of the brachial plexus? Horner syndrome, winged scapula, rhomboid weakness, a raised hemidiaphragm and normal sensory potentials in a numb arm. ## What does a Pancoast tumour at the lung apex cause by invading the lower trunk and stellate ganglion? Shoulder and inner-arm pain, hand weakness and Horner syndrome. [Add to my cards (5)](https://durgical.app/estudiar/?add=/en/anatomy/roots-of-brachial-plexus/) Educational information, not medical advice. For any symptom, see a health professional. ## Its names **Official Latin (TA2)** plexus brachialis TA2 6395 **Official Spanish (DeCS)** Plexo braquial DeCS D001917 **English (TA2)** Brachial plexus ## Related - [Neck nerve roots](https://durgical.com/en/anatomy/anterior-root-of-spinal-nerve/) - [Scalenes](https://durgical.com/en/anatomy/scalenus-anterior-muscle/) - [Rhomboids](https://durgical.com/en/anatomy/rhomboid-major-muscle/) - [Levator scapulae](https://durgical.com/en/anatomy/levator-scapulae/) Sources: Terminologia Anatomica (TA2); [DeCS](https://decs.bvsalud.org/es/ths/resource/?id=1942); [Anatomy, Head and Neck: Cervical Nerves](https://www.ncbi.nlm.nih.gov/books/NBK538136/); [Anatomy, Shoulder and Upper Limb, Brachial Plexus](https://www.ncbi.nlm.nih.gov/books/NBK500016/). ## **Spotted a mistake?** We are always improving for the community. Tell us what is wrong and our team will review it. Report a mistake Representative model, for educational purposes only. --- Source: https://durgical.com/en/anatomy/roots-of-brachial-plexus/ License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/anatomy/roots-of-brachial-plexus/