Ch 5 - EDX: Plexopathies Flashcards
What is a plexopathy?
Pathologic process occurring distal to the DRG and proximal to the peripheral nerves
How do plexopathies present?
ABN appear diffuse and will not follow any particular dermatomal or myotomal distribution
What are common etiologies of plexopathies?
– Trauma (traction, transection, obstetrical injuries, compression, and hemorrhage)
– Cancer (tumor and radiation therapy)
– Idiopathic (neuralgic amyotrophy)
How do SNAP’s help in EDX of plexopathies?
Localize lesion above or below DRG
If a lesion is proximal how will SNAP and CMAP appear?
SNAP preserved
CMAP ABN
What is the main prognostic factor for plexopathy in EDX?
Distal CMAP amplitude because it represents axonal loss and should be compared side to side
How do F-waves appear in plexopathy?
Delayed or absent
Nonspecific and cannot localize lesion
What is H-reflex helpful for in plexopathy?
Evaluate the S1 pathway but not pathognomonic
How do EMG findings appear in plexopathy?
ABN activity in peripheral muscles in distribution of plexus injury but with normal paraspinal activity
Where does the brachial plexus originate?
Ventral rami of the C5–T1 nerve roots
Where do the ventral rami of the brachial plexus emerge?
b/w anterior and middle scalenes
What happens in the posterior triangle of the neck?
C5 and C6 form the upper trunk
C7 forms the middle trunk
C8 and T1 form the lower trunk
What happens as the trunks pass under the clavicle?
Form anterior and posterior divisions to become cords
The cords are named in their relation to the __.
Axillary artery
Which muscles are innervated by the musculocutaneous nerve and C5/C6 roots?
Biceps
Brachialis
Which muscles are innervated by the musculocutaneous nerve and C5/C6/C7 roots?
Coracobrachialis
Which muscles are innervated by the axillary nerve and C5/C6 roots?
Deltoid
Teres minor
Which muscles are innervated by the radial nerve and C5/C6 roots?
Supinator
Which muscles are innervated by the radial nerve and C5/C6/C7 roots?
Brachioradialis
Which muscles are innervated by the radial nerve and C6/C7/C8 roots?
ECR longus
Triceps
Which muscles are innervated by the radial nerve and C7/C8 roots?
ECR brevis Ext digitorum EIP EDM ECU Abd pollicis longus Ext pollicis brevis Ext pollicis longus
Which muscles are innervated by the radial nerve and C7/C8/T1 roots?
Anconeus
Which muscles are innervated by the median nerve and C6/C7 roots?
Pronator teres
FCR
Which muscles are innervated by the median nerve and C7/C8 roots?
Palmaris longus
Which muscles are innervated by the median nerve and C7/C8/T1 roots?
FDS: 4 muscles
Which muscles are innervated by the median nerve and C8/T1 roots?
FDP: 2 muscles FPL Pronator quadratus Lumbricals: 2 muscles Opp pollicis APB 1/2 Flex pollicis brevis
Which muscles are innervated by the ulnar nerve and C7/C8 roots?
FCU
Which muscles are innervated by the ulnar nerve and C8/T1 roots?
Palmaris brevis FDP: 2 muscles Dorsal interossei: 4 muscles Plamar interossei: 3 muscles Lumbricals: 2 muscles 1/2 Flex pollicis brevis Hypothenar muscles -Opp dig minimi -Abd dig minimi -Flex dig minimi
What makes up the posterior cord?
Posterior divisions of upper, middle and lower trunks
What makes up the lateral cord?
Anterior divisions of the upper and middle trunks
What makes up the medial cord?
Anterior divisions of the lower trunk