413-414 - Brachial plexus Flashcards
Put the following in order from proximal to distal: cords, divisions, roots, branches, trunks
Roots, trunks, divisions, cords, branches
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What nerve injury causes Erb palsy?
Traction or tear of upper trunk: C5-C6 roots
“Erb-er” trunk
What can cause Erb’s palsy in infants? In adults?
lateral traction on neck during delivery; trauma
What muscles and related deficits are involved in Erb’s palsy?
- Deltoid, supraspinatus → can’t abduct (arm hangs by side)
- Infraspinatus → can’t laterally rotate (arm hangs medially rotated)
- Biceps brachii → can’t flex or supinate (arm extended and pronated)
What nerve injury causes Klumpke palsy?
traction or tear of lower trunk: C8-T1 root
How can infants get Klumpke palsy? Adults?
upward force on arm during delivery; trauma (eg. grabbing a tree branch to break a fall)
What muscles are affected in Klumpke palsy?
Intrinsic hand muscles:
- lumbricals
- interossei
- thenar
- hypothenar
How does Klumpke palsy present? Why?
Total claw hand; lumbricals normally flex MCP joints and extend DIP and PIP → MCP is extended and DIP/PIP are flexed
What nerve injury leads to thoracic outlet syndrome?
Compression of lower trunk [of the brachial plexus] and subclavian vessels
What spinal roots make up the upper, middle and lower trunks of the brachial plexus?
C5 & C6 => upper
C7 => middle
C8 & T1 => lower
What trunks make up the lateral cord of the brachial plexus?
upper & middle
What trunks make up the posterior cord of the brachial plexus?
upper, middle, and lower
What trunks make up the medial cord of the brachial plexus?
the lower trunk only
What nerves arise from the posterior cord of the brachial plexus? Do they lead to flexors or extensors?
axillary and radial
both → extensors
Which cords give rise to the musculocutaneous nerve?
lateral cord
Where does the long thoracic n. arise from?
C5, C6, C7 roots
What are two causes of thoracic outlet syndrome?
Cervical rib injury
Pancoast tumor
What muscles are affected in thoracic outlet syndrome?
Intrinsic hand muscles:
- lumbricals
- interossei
- thenar
- hypothenar
What deficits are present in thoracic outlet syndrome?
atrophy of intrinsic hand muscles, ischemia, pain, and edema due to vascular compression
What nerve is compromised in a patient presenting with a winged scapula?
long thoracic nerve
What are two causes of injuries that lead to winged scapula?
- axillary node dissection after mastectomy
2. stab wounds
What muscle is affected in a patient with a winged scapula? What functional deficit results?
Serratus anterior → inability to anchor scapula to thoracic cage → can’t abduct arm above horizontal position
Which cords give rise to the median nerve?
lateral and medial
Which cords give rise to the ulnar nerve?
medial
A patient presents with an atrophied shoulder. On physical exam they can’t abduct their shoulder more than 15 degrees. There is also a loss of sensation over the shoulder and lateral arm. Which nerve is lesioned? What muscle is atrophied? What are some causes of this nerve injury?
Axillary nerve lesion (from C5-C6 roots); deltoid muscle; causes include fractured surgical neck of humerus and anterior dislocation of humerus
A patient presents with wrist drop. What cord of the brachial plexus might be lesioned?
posterior cord
What are the symptoms of a lesion to the musculocutaneous nerve?
loss of forearm flexion and supination
loss of sensation over lateral forearm
Which spinal roots contribute to the musculocutaneous nerve?
C5-C7
What is a common cause of injury to the musculocutaneous nerve?
compression of the upper trunk of the brachial plexus
What are the spinal roots of the radial nerve?
C5-T1
What symptoms are present in a radial nerve injury patient?
Wrist drop: loss of elbow, wrist, and finger extension
↓ grip strength (wrist extension necessary for maximal action of flexors)
Loss of sensation over posterior arm/forearm and dorsal hand
What are 2 causes of radial nerve injury?
- Midshaft fracture of humerus
- Compression of axilla e.g. due to crutches, sleeping with arm over chair (“Saturday night palsy”), or with someone laying on inner arm (“Honeymoon palsy”).
What are the symptoms of median nerve injury?
“Ape hand” and “Pope’s blessing”
Motor: Loss of wrist and lateral finger flexion, thumb opposition, lumbricals of 2nd and 3rd digits
Sensory: loss of sensation over thenar eminence and dorsal and palmar aspects of lateral 3 1/2 fingers with proximal lesion
Tinel sign (tingling on percussion) in carpal tunnel syndrome
What are 3 causes of median nerve injury?
- Supracondylar fracture of humerus (proximal lesion)
- Carpal tunnel syndrome
- Wrist laceration (distal lesion)
What are 2 causes of axillary nerve injury?
- fractured surgical neck of humerus
2. anterior dislocation of humerus
What are the spinal roots of the axillary nerve?
C5-C6
What are the symptoms of axillary nerve injury?
- flattened deltoid
- loss of arm abduction at the shoulder (>15 degrees)
- Loss of sensation over deltoid muscle and lateral arm
What are the symptoms of an ulnar nerve lesion?
- “ulnar claw” on digit extension
- Radial deviation of wrist upon flexion (proximal lesion)
- Loss of flexion of wrist and medial fingers, abduction and adduction of fingers (interossei), actions of medial 2 lumbrical muscles
- Loss of sensation over medial 1 1/2 fingers including hypothenar eminence
What are the spinal roots of the ulnar nerve?
C8 - T1
What are two causes of injury to the ulnar nerve?
- Fracture of medial epicondyle of humerus “funny bone” (proximal lesion)
- Fractured hook of hamate (distal lesion)
What are the symptoms of a lesion to the recurrent branch of the median nerve?
- “Ape hand”
- loss of thenar muscle group: opposition, abduction, and flexion of thumb
- no loss of sensation
