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The Brachial Plexus
Directly from Dr. T's review notes
| Question | Answer |
|---|---|
| Where is the Brachial Plexus? (dorsal/ventral, levels) | Ventral Primary Rami (VPR) of spinal nerve roots C5-T1 |
| From proximal to distal, what are the different arrangements sections) of the brachial plexus? | roots, trunks divisions, cords, terminal branches |
| The "roots" are... | really the VPRs of C5-T1 |
| The trunks are... | upper: C5 & C6 middle: C7 Lower: C8 & T1 |
| The divisions are... | anterior and posterior from each VPR via the trunks (trunks bifurcate into an anterior and posterior division) |
| The cords are... | lateral: anterior divisions of the upper and middle trunks (C5-C7) medial: anterior divisions of the lower trunk (C8-T1) posterior: posterior divisions of all three trunks (C5-T1) |
| The terminal branches are... | Musculocutaneous (C5-C7): from lateral cord(C5-C7) Axillary (C5-C6): from posterior cord(C5-T1) Radial (C5-T1): from posterior cord(C5-T1) Median (C6-T1): from lateral cord(C5-C7) and medial cord(C8-T1) Ulnar (C8-T1): from medial cord(C8-T1) |
| Several important nerve branches arise from roots trunks, and cords prior to terminal branches (which also have branches). What are they? | dorsal scapular, suprascapular, subclavius, phrenic, 1st intercostal, long thoracic, lateral pectoral, lower subscapular, thoracodorsal, upper subscapular, medial antebrachial cutaneous, medial brachial cutaneous, medial pectoral |
| What are the supraclavicular branches of nerves arising from the roots (VPR of the spinal nerves before the plexus is formed) of the brachial plexus? | Dorsal Scapular Nerve: (C4), C5 Long Thoracic Nerve: C5, C6, C7, (C8) |
| What are the supraclavicular branches of nerves arising from the trunks of the brachial plexus? | Nerve to the subclavius: C5, C6 Suprascapular nerve: (C4), C5, (C6) (Supraspinatus m.) Suprascapular nerve: (C4), C5, C6 (Infraspinatus m.) |
| Describe the Dorsal Scapular Nerve (Supraclavicular branch arising from roots) | (C4) C5. Functionally, a posterior division nerve innervating rhomboid major & minor. Occasionally has branch to levator scapulae(levator scapulae is supplied by C3-C4 br. of cervical plexus).Nerve is accompanied by branches of transverse cervical artery. |
| Describe the Long Thoracic Nerve (Supraclavicular branch arising from roots) | C5-C7,(C8).Functionally, a posterior division nerve innervating the serratus anterior. Runs b/w anterior & middle scalenes; compression due to muscle spasm may result in weakness of serratus anterior. Scapular winging is a significant sign of weakness. |
| Describe the Nerve to the Subclavius (Supraclavicular branch arising from trunks) | C5-C6. Functionally, this is an anterior division nerve arising from the upper trunk innervating the subclavius muscle |
| Describe the Suprascapular Nerve pertaining to the supraspinatus muscle (Supraclavicular branch arising from trunks) | (C4), C5, (C6). Functionally, an anterior division nerve arising from the upper trunk innervating the supraspinatus (and infra) and provides sensory fibers to the acromioclavicular joint as well as the glenohumeral joint. |
| Describe the Suprascapular Nerve pertaining to the infraspinatus muscle (Supraclavicular branch arising from trunks) | (C4), C5, C6. Functionally, an anterior division nerve arising from the upper trunk innervating the infraspinatus muscle. |
| All remaining branches of the brachial plexus are derived from the cords of the plexus, but what are the infraclavicular branches? | Lateral pectoral nerve, medial pectoral nerve, upper subscapular nerve, lower subscapular nerve, thoracodorsal nerve |
| Describe the Lateral Pectoral Nerve | C5, C6, C7, innervates upper and lower fibers of pectoralis major, derived from LATERAL CORD(anterior divisions). |
| Describe the Medial Pectoral Nerve | (C6, C7), C8, T1, inntervates lower fibers of pectoralis major as well as the pectoralis minor, derived from MEDIAL CORD(anterior divisions). |
| Describe the Upper Subscapular Nerve | C5, C6, innervates subscapularis muscle, derived from POSTERIOR CORD(all posterior divisions). Muscle test: internal rotation of the shoulder |
| Describe the Lower Subscapular Nerve | C5, C6, (C7), innervates teres major (C6) and subscapularis muscles (C5), derived from POSTERIOR CORD(all posterior divisions). |
| Describe the Thoracodorsal Nerve | C6, C7, C8, innervates latissimus dorsi muscle, derived from POSTERIOR CORD(all posterior divisions). |
| Which cord and what levels is the Musculocutaneous Nerve derived from? | The Musculocutaneous nerve is a terminal branch of the LATERAL CORD, made up of VPR of C5, C6, C7 |
| Which muscles are innervated by the musculocutaneous nerve and by which levels? | Biceps (C5, 6), Brachialis (C5, 6), Coracobrachialis (C5, 6, 7) |
| What are the neurological level indicators of the Musculocutaneous nerve? | Biceps, C5 & C6; biceps reflex is C5 |
| What cutaneous contribution does the musculocutaneous nerve give rise to? | Lateral Antebrachial Cutaneous Nerve. Distribution to the lateral forearm, largely from C6. The C6 dermatome continues down to the thumb and includes the web. |
| Musculocutaneous nerve clinical notes: | It's rarely injured. The upper trunk is more often damaged. Tennis players may injure the lateral antebrachial cutaneous portion of the nerve at the elbow. However this may be accompanied by lateral epicondylitis, making the diagnosis more complicated. |
| Which cord and what levels is the Axillary Nerve derived from? | The Axillary Nerve is a terminal branch of the POSTERIOR CORD, made up of VPR from C5 & C6. |
| What muscles are innervated by the axillary nerve and by which levels? | Deltoid (C5, 6), and Teres minor (C6) |
| What is the neurological level indicator of the axillary nerve? | Deltoid, C5. |
| What cutaneous contribution does the axillary nerve give rise to? | Superior lateral cutaneous nerve: "regimental badge" area. |
| Axillary nerve clinical notes: | runs with posterior humeral circumflex a. Humeral fracture at the surgical neck could compromise both the nerve and the vessel. Anterior humeral dislocation may compromise the axillary nerve to the deltoid, but not the vessel. |
| Quadrangular Space Syndrome | Quadrangular Space Syndrome: Weakness of the deltoid and teres minor is noted. Paresthesia in the “regimental badge” area is noted. No loss of biceps reflex. |
| Which cord and what levels is the Median Nerve derived from? | The Median Nerve is a terminal branch arising from both the LATERAL & MEDIAL CORDS, made up of VPR of C6, C7, C8, T1. |
| What two nerve components are distributed to the cutaneous area via the two branches of the median nerve and what are the two branches? | The cutaneous GSA (somatic high and low threshold fibers) and GVA (vascular high and low threshold fibers) components. Palmar Cutaneous branch & Digital Cutaneous branch |
| Describe the cutaneous areas of the Median nerve | palm associated with the thenar eminence, the anterior surfaces of the thumb and lateral three and a half digits, and the distal tips of the posterior surfaces of the thumb and lateral two digits |
| What are the superficial muscles of the anterior forearm innervated by the median nerve? What levels of the nerve contribute to these muscles? | Pronator Teres C5 C6, Flexor carpi radialis C6 C7, Palmaris longus C7 C8, Flexor digitorum superficialis C7, C8, T1 |
| What are the deep muscles of the anterior forearm innervated by the Anterior Interosseus Branch of the Median Nerve? What levels of the nerve contribute to these muscles? | Flexor digitorum profundus (median nerve portion, digits 2/3) C7 C8 T1, Flexor pollicis longus C7 C8 T1, Pronator Quadratus C8 T1 |
| What are the muscles of the hand innervated by the Recurrent Branch of the Median Nerve? What levels of the nerve contribute to these muscles? | C8 & T1 for all three muscles. Abductor pollicis brevis, Flexor pollicis brevis (superficial head), Opponens pollicis *note: Within the thenar eminence, the Median Nerve DOES NOT innervate the Adductor pollicis: the Ulnar Nerve does. |
| What muscles and what levels make up the Palmar Digital Branch of the Median Nerve? | C8 & T1. Lumbricals I and II (of digits II and III: the thumb does not have lumbricals) |
| Significance of Median Nerve to Carpal Tunnel Syndrome and Pronator Teres Syndrome? | Video in her review is worth watching Basically, if the paresthesia is felt in palmar cutaneous branch area, then is PTS, if just digits, then CTS. If PTS, paresthesia will be worse when resistance applied to pronation when elbow flexed. |
| Which cord and what levels is the Ulnar Nerve derived from? | The Ulnar Nerve is the terminal branch of the MEDIAL CORD made up of VPR of C8 & T1 via the lower trunk. |
| Before the cutaneous innervations of the ulnar nerve in the hand it innervates what two muscles in the antebrachium? What are the levels associated with these muscles? | Flexor Carpi Ulnaris C8 T1 & Ulnar portion of Flexor Digitorum Profundus C8 T1 |
| Before innervating muscles of the hand, what does the Ulnar Nerve pass through? | Tunnel of Guyon (Guyon's canal or tunnel) |
| The Ulnar Nerve innervates what two muscles of the Thenar eminence (C8 T1)? | Adductor Pollicis & Flexor Pollicis brevis (deep head) |
| The Ulnar Nerve innervates what 7 muscles of the hypothenar eminence (C8 T1)? | Palmaris brevis, Abductor digiti minimi, flexor digiti minimi, opponens digiti minimi, lumbricals III & IV, Palmar interossei (PAD, adduction), Dorsal interossei (DAB, abduction) |
| What two cutaneous branches arise from the Ulnar Nerve? | The Palmar Cutaneous Branch: medial half of the palm. The Dorsal Cutaneous Branch: anterior and posterior aspects of the medial 1 ½ fingers. |
| Tunnel of Guyon Syndrome | Entrapment at the Tunnel of Guyon results in mainly hypothenar weakness and weakness in adduction of the thumb. |
| Cubital Tunnel Syndrome = Entrapment@cubital fossa which leads to what? Video in her review is worth watching | weakness of ulnar wrist flexion & hypothenar weakness, due to loss of all muscular innervation(adduction weakness of thumb, hypothenar weakness & in finger flexion due to loss of flexor carpi ulnaris & ulnar portion of profundus[digits 3 and 4] |
| Which cord and what levels is the Radial Nerve derived from? | The Radial Nerve is the terminal branch of the POSTERIOR CORD made up of posterior division axons from C5 C6 C7 C8 T1. |
| Other general info about Radial Nerve? | It innervates all muscles in posterior brachium & antebrachium. It consists of several motor branches & several cutaneous branches. It also innervates one flexor of forearm: brachioradialis; and often contributes a branch to the brachialis muscle. |
| What muscles are innervated by the Radial nerve in the brachium? Levels? | Triceps C7 C8, used as indicator of integrity of C7 by testing strength and reflex. m. test: resist patient's attempt to extend forearm. Anconeus C7 C8. |
| *A key indicator of whether or not the patient’s symptoms are due to a peripheral nerve loss or a spinal nerve root loss is to note the reflex associated with the neurological level. Explain. | If the reflex is diminished, the likely loss is of the spinal nerve root. If the reflex is normal, the loss is more likely to be in the course of the peripheral nerve. |
| What muscles are innervated by the Radial nerve in the antebrachium? Levels? | Brachioradialis C5 C6, Supinator C6, Extensor carpi radialis longus C6 C7 |
| What muscles are innervated by the Deep radial nerve (aka, the posterior interosseus nerve) in the antebrachium? Levels? | Extensor...: carpi radialis brevis C6 C7, carpi ulnaris C6 C7 C8, digitorum (C6) C7 (C8), digiti minimi (C6) C7 (C8), indicis C7 (C8), pollicis longus C7 C8, pollicis brevis C6 C7, Abductor pollicis longus C6 C7 |
| What are the cutaneous branches of the Radial nerve in the brachium? | The Lower Lateral Cutaneous Nerve, The Posterior Brachial Cutaneous Nerve |
| What are the cutaneous branches of the Radial nerve in the antebrachium? | The Posterior Antebrachial Cutaneous Nerve, The Superficial Radial Nerve |
| Median Nerve Proper innervates what muscle of the thumb? | Flexor Pollicis Longus |
| Recurrent Branch of the Median Nerve in the Thenar Eminence innervates what muscles of the thumb? | Abductor Pollicis Brevis, Opponens Pollicis, Flexor Pollicis Brevis (superficial portion) |
| Ulnar Nerve innervates what muscles of the thumb? | Flexor Pollicis Brevis (deep head), Adductor Pollicis |
| Radial Nerve innervates what muscles of the thumb? | Extensor Pollicis Longus, Extensor Pollicis Brevis, Abductor Pollicis Longus |
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Quickdraw03
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