Upper Limb Nerve Supply & Brachial Plexus – Review Flashcards

These question-and-answer flashcards review the key anatomy, innervation patterns, and clinical correlations of the brachial plexus, its branches, and associated injuries in the upper limb.

What are the two major types of innervation discussed for the upper limb?

Cutaneous (sensory) innervation and Motor innervation.

Which spinal roots form the brachial plexus?

Anterior rami of C5, C6, C7, C8 and T1.

Name the five parts of the brachial plexus in order from proximal to distal.

Roots, Trunks, Divisions, Cords, Terminal branches.

Which dermatome maps are commonly referenced in clinical practice for the upper limb?

Foerster (1933) and Keegan & Garrett (1948).

What is the only reliable clinical method to localise a brachial plexus injury?

Examination of cutaneous (sensory) innervation patterns.

Which nerve supplies the 5th digit and medial half of the 4th digit on the palmar surface?

Ulnar nerve (anterior).

Which nerve supplies the thenar muscles and lateral two lumbricals?

Median nerve.

Which spinal roots give rise to the long thoracic nerve?

C5, C6, and C7.

Which muscle is innervated by the long thoracic nerve and what happens when it is paralyzed?

Serratus anterior; paralysis produces a winged scapula.

Name the three trunks of the brachial plexus and their root contributions.

Superior (C5-C6), Middle (C7), Inferior (C8-T1).

Into what do each of the three trunks divide?

An anterior division and a posterior division.

How are the cords of the brachial plexus named?

By their position relative to the second part of the axillary artery (lateral, posterior, medial cords).

Which terminal branches arise from the lateral cord?

Musculocutaneous nerve and the lateral contribution to the median nerve.

Which terminal branches arise from the posterior cord?

Axillary nerve and Radial nerve.

Which terminal branches arise from the medial cord?

Ulnar nerve and the medial contribution to the median nerve.

What mnemonic helps recall anterior-compartment nerves of the upper limb?

MMR – Musculocutaneous (arm), Median (forearm), Radial (posterior compartments).

Which nerve exits the axilla via the quadrangular space with the posterior circumflex humeral artery?

Axillary nerve.

Primary motor function lost with axillary nerve injury?

Shoulder abduction from 15° to 90° (deltoid paralysis).

Clinical sign of axillary nerve injury visible on inspection?

Deltoid atrophy causing a flattened shoulder contour.

Which nerve runs in the radial groove of the humerus with the deep brachial artery?

Radial nerve.

Classic motor deficit of radial nerve palsy?

Wrist drop – inability to extend wrist and fingers.

Which digits are supplied by the radial nerve on the dorsal hand?

Radial half of digits 1, 2, 3 and lateral half of 4 proximally.

Which nerve passes posterior to the medial epicondyle ("funny bone")?

Ulnar nerve.

Four common entrapment sites of the ulnar nerve?

Posterior to medial epicondyle, Cubital tunnel, Guyon’s canal (wrist), Hand.

Classic hand deformity of chronic ulnar nerve injury?

Claw hand of digits 4 and 5 due to unopposed FDP and extensors.

Which two forearm muscles are ulnar-innervated despite being in the anterior compartment?

Flexor carpi ulnaris and medial half of flexor digitorum profundus.

Through which structure does the median nerve enter the hand?

Carpal tunnel beneath the flexor retinaculum.

Motor deficit seen in distal median nerve lesion within the carpal tunnel?

Thenar eminence atrophy and loss of thumb opposition (ape/simian hand).

What sensory area is spared in carpal tunnel syndrome and why?

Central palm—supplied by the palmar cutaneous branch of median nerve, which passes superficial to the tunnel.

Which nerve supplies all three muscles of the anterior arm (BBC)?

Musculocutaneous nerve (Biceps brachii, Brachialis, Coracobrachialis).

Primary motor actions mediated by the musculocutaneous nerve?

Elbow flexion and forearm supination.

Sensory territory of the musculocutaneous nerve in the forearm?

Lateral antebrachial cutaneous nerve to lateral forearm.

Root lesion causing winged scapula when pushing against a wall?

Injury to C5-C7 roots affecting long thoracic nerve.

What is Erb-Duchenne palsy and which trunk is injured?

Paralysis producing “waiter’s tip” posture; injury of the upper trunk (C5-C6).

Which nerves are mainly affected in Erb’s palsy?

Musculocutaneous, Axillary, Suprascapular, and partly Median nerve.

Mechanism commonly producing Klumpke’s palsy?

Sudden superior pull on an abducted arm stretching/tearing C8-T1 (lower trunk).

Characteristic hand posture of Klumpke’s palsy?

Claw hand with lumbrical paralysis and weak grasp.

Define "Saturday night" or "honeymoon" palsy.

Compression of the posterior cord/radial nerve during prolonged pressure, causing wrist drop.

Which nerve has no motor supply in the hand but provides purely sensory innervation to dorsolateral hand?

Superficial branch of radial nerve.

What boundaries form the cervico-axillary canal?

Clavicle (anterior), first rib (medial), scapular edge (posterior).

Which nerve is most commonly injured during mastectomy?

Long thoracic nerve.

Which nerve innervates the hypothenar muscles?

Deep branch of the ulnar nerve.

Which myotome is responsible for intrinsic hand muscle movement?

T1.

Name the principal nerve of the posterior compartment of the forearm.

Radial nerve (deep branch/posterior interosseous).

Which nerve forms the lateral cord’s major terminal branch?

Musculocutaneous nerve.

What clinical sign results from median nerve injury at the elbow when attempting to make a fist?

Hand of Benediction (cannot flex index and middle fingers).

Which cutaneous nerve supplies skin over the inferolateral arm?

Inferior lateral cutaneous nerve of arm (branch of radial nerve).

Which two cutaneous nerves of the forearm derive from outside the brachial plexus roots?

Supraclavicular nerves (C3-C4) and Intercostobrachial nerve (T2).

Which nerve pierces coracobrachialis?

Musculocutaneous nerve.

What artery is used as a landmark for naming the cords of the brachial plexus?

Second part of the axillary artery.

Which nerve supply deficit causes inability to abduct/adduct fingers (paper test failure)?

Ulnar nerve (interossei paralysis).

What sensory loss accompanies axillary nerve injury?

Loss over the lateral shoulder (superior lateral brachial cutaneous nerve).

Which lesion presents with numbness/tingling in thumb, index and middle fingers at night?

Median nerve compression – carpal tunnel syndrome.

Why does radial nerve injury at the humeral shaft spare triceps function?

Triceps branches leave the radial nerve proximal to the spiral (radial) groove.

Name the terminal sensory branch of the axillary nerve.

Superior lateral cutaneous nerve of arm.

What does the mnemonic "BBC" stand for in arm musculature?

Biceps brachii, Brachialis, Coracobrachialis – all musculocutaneous.

Which ligament forms the roof of the carpal tunnel?

Transverse carpal ligament (flexor retinaculum).

What is the root value of the suprascapular nerve and what muscles does it supply?

C5-C6; supplies supraspinatus and infraspinatus.

Explain the term "MMR" in brachial plexus clinical localization.

Musculocutaneous = anterior arm, Median = anterior forearm, Radial = posterior arm & forearm (motor and sensory territories).

Which nerve lesion is indicated by loss of thumb opposition but preserved wrist flexion?

Median nerve lesion distal to elbow (thenar weakness).

Identify the nerve compressed in Guyon’s canal syndrome.

Ulnar nerve at the wrist.

What hand posture indicates an isolated distal ulnar nerve lesion?

Clawing of digits 4 and 5 with MCP hyperextension and IP flexion.

Name the cutaneous branch of the median nerve that does NOT pass through the carpal tunnel.

Palmar cutaneous branch.

Which nerve injury is associated with "crutch palsy"?

Radial nerve compression in the axilla.

What is the primary sensory territory of the medial cutaneous nerve of forearm?

Skin of the anteromedial forearm to the wrist (C8–T1).

Which nerve root primarily controls elbow extension (triceps reflex)?

C7 (via radial nerve).

List three common mechanisms causing brachial plexus injuries based on Leffert classification.

Open trauma (stab, gunshot), Closed traction/compression, Obstetric (Erb’s/Klumpke).

How is diagnosis of brachial plexus injury chiefly made?

Physical examination (≈90%); imaging and electrodiagnostics are supplementary.

Which nerve carries fibers from both lateral and medial cords?

Median nerve (formed by union of lateral and medial roots).

What are the two major types of innervation for the upper limb: Cutaneous and Motor?

Cutaneous: sensation (touch, pain, temp, proprioception); Motor: muscle contraction, movement, posture.

What specific type of innervation is responsible for controlling muscle contraction?

Motor innervation.

What specific type of innervation is responsible for providing sensation from the skin?

Cutaneous (sensory) innervation.

Which specific spinal nerve rami contribute to the formation of the brachial plexus?

Anterior rami of C5-T1. Sometimes C4 (prefixed) or T2 (postfixed).

What defines a prefixed brachial plexus?

Significant C4 contribution to the brachial plexus.

What defines a postfixed brachial plexus?

Significant T2 contribution to the brachial plexus.

List the five hierarchical parts of the brachial plexus, arranged in order from proximal to distal.

Roots, Trunks, Divisions, Cords, Terminal branches.

Identify the two commonly referenced dermatome maps for the upper limb in clinical practice and briefly note their key difference.

Foerster (nerve transection, more overlap) and Keegan & Garrett (radicular pain, more discrete).

Explain why and how examination of cutaneous (sensory) innervation patterns is considered the most reliable clinical method to localize a brachial plexus injury.

Dermatomes pinpoint root damage via distinct sensory deficits (e.g., C5-T1), unlike motor innervation which can be shared.

Which nerve is responsible for sensory innervation to the 5th digit and the medial half of the 4th digit, on both the palmar and dorsal surfaces of the hand?

Ulnar nerve.

Which specific branch of the ulnar nerve provides sensory innervation to the dorsal aspect of the 5th digit and medial half of the 4th digit?

Dorsal cutaneous branch of the ulnar nerve.

Identify the nerve that innervates the thenar eminence muscles and the lateral two lumbrals, and specify the relevant nerve branches.

Median nerve (recurrent/thenar branch for thenar muscles; direct branches for lateral lumbricals).

Name the specific thenar muscles innervated by the recurrent branch of the median nerve.

Abductor pollicis brevis, Opponens pollicis, superficial head of Flexor pollicis brevis.

From which specific spinal roots does the long thoracic nerve originate, and what is its anatomical course relative to the brachial plexus?

C5, C6, and C7 anterior rami; descends posterior to plexus, runs on serratus anterior.

Name the muscle innervated by the long thoracic nerve and explain the specific clinical sign observed upon its paralysis.

Serratus anterior; paralysis causes winged scapula (medial scapular border protrudes, especially when pushing against wall).

When is a 'winged scapula' most apparent, and what muscle paralysis causes it?

Most apparent when pushing against a wall or abducting arm above 90^\circ; caused by serratus anterior paralysis.

List the three trunks of the brachial plexus and their precise spinal nerve root contributions.

Superior (C5-C6), Middle (C7), Inferior (C8-T1).

Describe the division pattern of each of the three brachial plexus trunks and indicate the general target compartments for these divisions.

Each trunk divides into anterior (flexor compartments) and posterior (extensor compartments) divisions.

Which compartment of the upper limb do the anterior divisions of the brachial plexus typically supply?

Flexor (anterior) compartments of arm and forearm.

Which compartment of the upper limb do the posterior divisions of the brachial plexus typically supply?

Extensor (posterior) compartments of arm and forearm.

What anatomical landmark is used to name the cords of the brachial plexus, and how are they specifically named in relation to it?

Relation to the second part of the axillary artery: Lateral, Posterior, Medial cords.

Which cord of the brachial plexus is positioned lateral to the second part of the axillary artery?

Lateral cord.

Which cord of the brachial plexus is positioned posterior to the second part of the axillary artery?

Posterior cord.

Which cord of the brachial plexus is positioned medial to the second part of the axillary artery?

Medial cord.

Identify the two main terminal branches that emerge directly from the lateral cord of the brachial plexus.

Musculocutaneous nerve and lateral root of Median nerve.

Which two major terminal nerves are direct continuations or branches of the posterior cord of the brachial plexus?

Axillary nerve and Radial nerve.

Name the two primary terminal branches that originate from the medial cord of the brachial plexus.

Ulnar nerve and medial root of Median nerve.

What mnemonic is commonly used to remember the major nerves of the upper limb and what do its letters represent?

MMR: Musculocutaneous (anterior arm), Median (anterior forearm), Radial (posterior arm & forearm).

Identify the nerve that exits the axilla through the quadrangular space, mentioning its common arterial companion and the anatomical boundaries of this space.

Axillary nerve; with posterior circumflex humeral artery. Boundaries: teres minor (superior), teres major (inferior), long head of triceps (medial), humeral surgical neck (lateral).

What are the primary motor functions lost following an axillary nerve injury, specifying the muscles involved?

Shoulder abduction from 15^\circ to 90^\circ (deltoid paralysis); weakened external rotation (teres minor paralysis).

Besides deltoid paralysis, what other motor deficit is seen with axillary nerve injury, and which muscle is responsible?

Weakened external rotation; teres minor paralysis.