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
What does the lateral cord split into?
Musculocutaneous branch and also fuses with the medial
cord to form the median branch
What does the posterior cord split into?
Radial and axillary branches
What does the medial cord split into?
Contribute to the median branch and the ulnar branch
What is injured in Erb’s palsy?
C5-C6 nerve roots of upper trunk
What is the etiology of Erb’s palsy?
Traction, compression, obstetrical injury or stinger from sports injury
What is the classic arm position in Erb’s pasly?
Waiter's tip Adducted (deltoid and SS) IR (teres minor and IS) Extended (biceps and BR) Pronated (supinator and BR) Wrist flexed (ECRL and ECRB)
Where is Erb’s point for EDX?
Stimulate at the tip of the C6 transverse process over the trunks of the brachial plexus
What is the treatment for Erb’s palsy?
Rehabilitation, intermittent splinting and activity restriction
What is injured in Klumpke’s Palsy?
C8–T1 nerve roots or lower trunk
What is the etiology of Klumpke’s Palsy?
Obstetrical traction injury
Forced adduction seen in an MVA, falls, shoulder dislocations
What is the clinical presentation of Klumpke’s Palsy?
Wasting of the small hand muscles and
a claw hand deformity (lumbrical weakness).
Shoulder girdle muscle function is preserved
What will be seen on NCS in Klumpke’s palsy?
SNAP perserved if nerve root avulsed
Medial antebrachial cutaneous sensory response will be
absent or reduced
Why is nerve root avulsion associated with C8 and T1 injury?
Lack of protective support at C8/T1
What is injured in Thoracic outlet syndrome?
Injury involves the subclavian artery, subclavian vein, or axillary vein
What is the clinical presentation of arterial involvement in Thoracic outlet syndrome?
Limb ischemia Necrosis Vague pain Fatigue Decreased color and temperature
What is the clinical presentation of venous involvement in Thoracic outlet syndrome?
Bluish, swollen, achy limb
What is the etiology of neurologic thoracic outlet syndrome?
Compression of the lower trunk of the brachial plexus b/w a fibrous band, b/w the first cervical rib and clavicle (costoclavicular syndrome)
Muscular entrapment by the scalenes or Pectoralis minor muscle
What is the clinical presentation of TOS?
Pain and numbness along the medial aspect of the forearm and hand, which increases with overhead activity. Discomfort can present in the neck, clavicle, and axilla
What is seen on NCS in TOS?
Dec amp for the median CMAP, ulnar SNAP/CMAP, and medial antebrachial cutaneous studies Median SNAP is
spared
What is seen on EMG in TOS?
ABN spontaneous activity median and ulnar hand muscles
What are different names for Neuralgic Amyotrophy?
Parsonage–Turner syndrome Brachial neuritis Brachial neuropathy Idiopathic brachial plexopathy Shoulder-girdle neuritis Paralytic brachial neuritis
What is the clinical presentation of Neuralgic Amyotrophy?
Abrupt onset severe pain in periscapular region
Exacerbated by rotation and abduction
Pain resolves in hours to 2-3 weeks
Develops weakness in patchy fashion
How many presentations of Neuralgic Amyotrophy are bilateral?
1/3 of cases
What are primary plexus tumors?
Schwannomas
Neuromas
Neurofibromas
Which tumors can cause secondary plexus involvement?
Breast and lung
What can radiation therapy cause?
Neural fibrosis and constriction of the vasa nervorum, leading to destruction of the axon and Schwann cell
Describe location and characteristics of radiation plexopathy.
Located Upper trunk
Painless sensation
Myokymia on EDX
Describe location and characteristics of tumor plexopathy.
Located Lower trunk
Painful sensation
Horner’s syndrome
What is the MC site of nerve root avulsion?
C8 and T1 roots
What can determine the difference between a nerve root stretch and avulsion?
MRI
What is seen on NCS in nerve root avulsion?
Absent CMAPs with normal SNAPs
What is seen on EMG in nerve root avulsion?
Absent recruitment and ABN spontaneous activity in a myotomal distribution, including the paraspinals
What is the origin of the lumbar plexus?
Ventral rami of L1, L2, L3, and L4 roots
What is the origin of the sacral plexus?
Ventral rami of L4, L5, S1, S2, S3, and S4 roots
What do the ventral rami of lumbar/sacral levels divide to form?
Anterior and posterior divisions in each plexus
What does the anterior division of the lumbar plexus form?
Obturator nerve
What does the posterior division of the lumbar plexus form?
Femoral nerve and the lateral femoral cutaneous nerve
What are terminal branches directly off the lumbar plexus?
Iliohypogastric nerve
Ilioinguinal nerve
Genitofemoral nerve
What does the anterior division of the sacral plexus form?
Tibial portion
What does the posterior division of the sacral plexus form?
Common peroneal nerve
Where does the lumbosacral trunk connect?
L4 and L5 nerve fibers connect lumbar to sacral plexus and travel over the pelvic brim
What are terminal branches directly off the sacral plexus?
Superior gluteal nerve
Inferior gluteal nerve
What are common etiologies of lumbar plexopathies?
Neuralgic amyotrophy Neoplastic versus radiation plexopathy Retroperitoneal bleed Hip dislocation Obstetric injuries/cephalopelvic disproportion: Presents as a postpartum foot drop
What should be evaluated on NCS for lumbar plexopathy evaluation?
SNAP: Lateral femoral cutaneous nerve (L2–L3), saphenous nerve (L4)
CMAP: Femoral nerve (L2–L4)
What should be evaluated on EMG for lumbar plexopathy evaluation?
Muscles innervated by the femoral nerve, obturator nerve, and the iliopsoas muscle.
Normal paraspinals
What should be evaluated on NCS for sacral plexopathy evaluation?
SNAP: Superficial peroneal (fibular) nerve (L5), sural nerve (S1)
CMAP: Deep peroneal (fibular) nerve (L4–S1), tibial nerve (L5–S2)
What should be evaluated on EMG for sacral plexopathy evaluation?
Muscles innervated by the tibial nerve, peroneal (fibular) nerve, and superior and inferior gluteal nerves.
Normal paraspinals
