short lecture on brachial plexopathies

1. By dr rzgar hamed
Brachial Plexopathies

2. INTRODUCTION:
 The brachial plexus extends inferolaterally from the
spinal cord to the axilla and supplies the sensory and
motor innervation to the entire upper extremity and most
of the shoulder.
 The incidence of brachial plexopathies far exceeds the
combined incidences of cervical, lumbar, and sacral
plexopathies because of its:
(1) Susceptibility to trauma (eg, large size, superficial
location, and position between two mobile structures)
(2) vulnerability to diseases involving adjacent structures
(eg, lung apex, blood vessels, and lymph nodes) (Figure
9-1).
 Thus, brachial plexus disorders are common, and
neurologists must be familiar with brachial plexus
assessment and the management of its disorders.

3. Figure 9-1. The brachial plexus. The brachial plexus’ susceptibility to trauma
reflects its large size, superficial location, and position between two mobile
structures. It also is vulnerable to diseases involving adjacent structures such as
the lung apex, blood vessels, lymph nodes, and clavicle. 3

4. ANATOMY:
 Each sensory and motor neuron contributing to the brachial
plexus is composed of a cell body and one or more axons.
 Motor neuron cell bodies (anterior horn cells) are located in
the anterior horn of the spinal cord, and each innervates
multiple muscle fibers.
 A motor unit, defined as: one anterior horn cell and all of
the muscle fibers it innervates, constitutes the smallest unit
of muscle force.
 The innervation ratio (muscle fibers to anterior horn cells) is
inversely proportional to the dexterity required of the muscle.
 Collections of sensory neuron cell bodies termed dorsal root
ganglia, are situated in the intervertebral foramina of the
spinal column. Each gives off two axons, one projecting
centrally (conveying sensation to the CNS) and one
peripherally (innervating a single sensory receptor).
 The brachial plexus contains over 100,000 axons.As groups
of these axons advance peripherally, they come together,
exchange axons, and separate, thereby creating the brachial
plexus elements: five roots, three trunks, six divisions,
three cords, and five terminal nerves 5363-5.

7. Figure 9-2. The elemental composition of the brachial plexus. The
brachial plexus is composed of five roots, three trunks, six divisions,
three cords, and five terminal nerves.APR = anterior primary ramus;
n. = nerve.
7

8. 1- Roots (5):
 The sensory and motor axons exiting the spinal cord are
grouped into dorsal and ventral roots, respectively. They
fuse within the intervertebral foramina just beyond the
dorsal root ganglia, forming mixed spinal nerves,
termed mixed because they contain sensory and motor
axons.
 Upon exiting these foramina, each mixed spinal nerve
traverses a gutter in the adjacent transverse process.
 The C5 and C6 mixed spinal nerves are anchored by
connective tissue at this site, whereas the C8 and T1 mixed
spinal nerves are not (anchoring at C7 varies). Hence,
traction injuries, which tend to disrupt axons at their
anchorage points, are more frequently associated with C5
and C6 mixed spinal nerve ruptures and C8 and T1 root
avulsions.
 Next, each mixed spinal nerve divides into a posteriorly

9.  The C5 to T1 anterior primary rami exit between the
anterior and middle scalenes and give off several motor
nerve branches, some of which directly innervate
muscles (scalene and longus colli muscles [C5 to C8]),
whereas others join to form nerves (long thoracic [C5 to
C7], phrenic [C3 to C5], and dorsal scapular [C4 to C5]).
 Myelinated, preganglionic sympathetic fibers exit the
C8 to T1 roots (white rami communicantes) and enter the
sympathetic ganglia.
 whereas Unmyelinated postganglionic fibers (gray
rami communicantes) exit the ganglia and enter the C5
to T1 mixed spinal nerves.
 Because the preganglionic sympathetic fibers
supplying the head and neck traverse the C8 and T1
roots, lesions here are associated with Horner
syndrome.

10. Figure 9-3. The relationship between the spinal column and the proximal
elements of the brachial plexus. At each spinal cord segment that contributes
axons to the brachial plexus, the dorsal and ventral roots fuse to a mixed
spinal nerve, which then divides into posteriorly and anteriorly directed
branches (the posterior and anterior primary rami, respectively).
10

11.  Traditionally, the C5 to T1 roots compose the brachial
plexus.
 The number of axons per root varies; the C6, C7, and
C8 roots contain approximately 25% of the brachial
plexus axons, whereas the C5 and T1 roots share the
remaining 25%.
 The axon type also varies; the C5 and C6 roots have
the highest percentage of motor axons, while the C7
and T1 roots have the least, and the C7 root has the
highest percentage of sensory axons, followed in
descending order by C6, C8, T1, and C5.
 Vertical variations include expansions (contributions
from C4 or T2) and single-level shifts, termed prefixed,
whenever the C4 contribution is large and the T1
contribution is small, and postfixed, whenever the C5
contribution is small and the T2 contribution is large.
 Because these changes do not affect brachial plexus
organization, the clinical and electrodiagnostic

12. 2- Trunks (3):
 The upper, middle, and lower trunks, named for their
relationship to each other, are formed from the anterior
primary rami at the lateral borders of the scalene
muscles.
 The C5 and C6 anterior primary rami form the upper
trunk, the C7 anterior primary ramus continues as the
middle trunk, and the C8 and T1 anterior primary rami
form the lower trunk.
 Trunk anomalies are infrequent. In one report, the
middle trunk was a direct extension of the C7 anterior
primary ramus in 100% of studied individuals, and the
upper and lower trunks were of customary formation in
over 90% and 95%, respectively.
 The superficial location of the trunks as they traverse the
posterior cervical triangle renders them susceptible to
trauma.

13. 3- Divisions (6):
 Each trunk divides into two divisions, anterior and
posterior, at which point the segmental nature
demonstrated at the root and trunk level of the brachial
plexus is lost.
 The anterior divisions primarily innervate flexors,
whereas the posterior divisions primarily supply
extensors.
 The divisions are retroclavicular, situated between the
middle third of the clavicle and the first thoracic rib.
 The anterior and posterior divisions of the upper trunk
are similar in caliber, whereas the posterior division of
the middle trunk dominates the anterior division because
the C7 root is primarily responsible for extensor
innervation, while the anterior division of the lower trunk
dominates the posterior division because the C8 and T1

14. 4- Cords(3):
 The lateral, posterior, and medial cords are named for their
orientation to the axillary artery, to which they usually are
bound (Figure 9-1).
 They are the longest elements and are proximally situated in
the axilla, near the axillary lymph node chain.
 The three posterior divisions form the posterior cord, the
anterior divisions of the upper and middle trunk form the
lateral cord, and the anterior division of the lower trunk
continues as the medial cord.
 The lateral cord gives off the lateral pectoral and
musculocutaneous nerves before terminating as the lateral
head of the median nerve.
 The posterior cord gives off the upper subscapular,
thoracodorsal, and lower subscapular nerves before
terminating as the axillary and radial nerves.
 The posterior cord contributes sensory axons to the C5
dermatome via the upper and lower lateral brachial cutaneous
nerves of the axillary and radial nerves, respectively.
 The medial cord gives off the medial pectoral, medial
brachial cutaneous, medial antebrachial cutaneous, and ulnar

15. 5- Terminal Nerves(5):
 The five terminal nerves
(musculocutaneous, axillary, median,
ulnar, and radial) are distally situated in
the axilla.
 Upon exiting the axilla, they become the
peripheral nerves of the upper extremity.
 The other cord-derived nerves (lateral
pectoral, thoracodorsal, subscapular,
medial pectoral, medial brachial
cutaneous, and medial antebrachial

16. CLASSIFICATION:
 The brachial plexus is divided into smaller plexuses:
-supraclavicular (roots and trunks)
-retroclavicular (divisions)
-infraclavicular (cords and terminal nerves).
 Compared with infraclavicular plexopathies, supraclavicular
plexopathies have a higher incidence, are associated with
different lesion types (closed traction injuries are more
frequent), and typically are more severe because greater
force is required to produce them.
 The supraclavicular plexus contains three smaller plexuses:
-upper (upper trunk, C5 and C6 roots),
-middle (middle trunk, C7 root)
-lower (lower trunk, C8 and T1 roots) (Figure 9-4).
 Upper plexopathies have the highest incidence (lower
plexopathies the lowest), tend to occur in isolation, (middle
plexopathies rarely occur in isolation), and, like middle
plexopathies, most commonly follow trauma, especially

17.  Overall, upper plexopathies are less severe because
they are closer to the skin and muscle they supply, more
frequently extraforaminal (potential for surgical
intervention), and have a higher incidence of
demyelination than the other plexopathies.
 This classification also facilitates communication among
physicians, especially with examination limitations, such
as pain, cognitive changes, and higher priority injuries
(eg, arterial lacerations, bone fractures, and head
injuries) or prior to diagnostic testing (ie, it is easier to
discuss an upper plexus lesion than to commit to one of
its elements).

18. Figure 9-4. The divisions of the supraclavicular plexus. The
supraclavicular plexus is composed of three plexuses: upper
(upper trunk and C5 and C6 roots), middle (middle trunk and
C7 root), and lower (lower trunk and C8 and T1 roots). 18

19. ASSESSMENT OF THE BRACHIAL PLEXUS
Clinical:
 With traumatic brachial plexus lesions, the neck, shoulder, and
upper extremity position at impact identifies the axons at greatest
risk, as do concomitant injuries such as scapular, clavicular, or
humeral fractures, as well as glenohumeral dislocation and
scapulothoracic dissociation.
 The general examination includes visual inspection of the skin
and bones for traumatic stigmata and of the muscles for atrophy, as
well as palpation of the neck, axilla, supraclavicular, infraclavicular,
and scapular regions for masses, bony abnormalities, tenderness,
and a Tinel sign.
 The neurologic examination determines the status of the cervical
spinal cord, cervical plexus, and spinal accessory nerves.
 The head, neck, shoulder, and upper extremity are examined for
dysautonomic features (eg, sudomotor or vasomotor
abnormalities and Horner syndrome).
 Features indicating proximal brachial plexus involvement, such
as dorsal scapular, phrenic, or long thoracic neuropathy, as well as
Horner syndrome, portend a worse prognosis.

20.  Because brachial plexus lesions typically involve axon disruption,
negative deficits such as weakness and numbness are expected.
 Supraclavicular plexopathies, the deficits resemble those seen with
lesions involving one or more roots
 Infraclavicular plexopathies resemble lesions involving one or more
terminal nerves.
 The sensory loss with upper plexopathies involves the lateral aspects
of the arm and forearm and the dorsolateral aspect of the hand,
especially the thumb (the cutaneous distributions of the superior and
inferior lateral brachial cutaneous nerves, the lateral antebrachial
cutaneous nerve, and the median nerve thumb branches). The cutaneous
territories of the superficial radial, median nerve to index finger and
median nerve to middle finger branches may also be involved (60%, 20%,
and 10%, respectively).
 Weakness affects C5 and C6 functions: external humeral rotation,
shoulder abduction, forearm flexion and supination, and, to a lesser
degree, forearm pronation and extension as well as dorsal scapular and
long thoracic nerve function.
 Additionally, the biceps and brachioradialis muscle stretch reflexes may
be affected.
 With middle plexopathies, sensory loss and weakness have a C7
distribution, affecting forearm extension and pronation, radial wrist
extension and flexion, and, to a lesser degree, finger extension; the triceps
muscle stretch reflex may be affected.

21. Radiologic Assessment:
 Plain films of the cervical spine, clavicle, scapula, chest, and
humerus identify foreign bodies and concomitant injuries such
as elevated hemidiaphragm with phrenic neuropathy, mediastinal
widening with vascular trauma, and pneumothorax/hemothorax
with lung breach.
o Features associated with root avulsion include lateral tilt of the
cervical spinal column and transverse process or proximal first rib
fracture.
o Inadequately treated clavicular fractures with resultant
nonunion or excessive callus formation may disrupt the divisions.
o Infraclavicular plexopathies are associated with humeral fracture
or glenohumeral dislocation, and neoplastic and radiation damage
are associated with bone and lung abnormalities.
o True neurogenic thoracic outlet syndrome is associated with C7
rudimentary ribs and elongated transverse processes.
 CT identifies bony abnormalities and blood, while CT myelography
identifies intraspinal canal masses and indirectly reflects spinal cord
edema and atrophy, where the width of the dye column in the
cervical gutter is narrowed or widened, respectively.
o When root avulsion is suspected, very thin slice (2 mm) CT
myelography assesses the horizontally oriented preganglionic root
elements.

22. o A contrast-filled meningeal diverticulum may be
observed when the meninges are pulled through the
intervertebral foramen. Other avulsion features include
deformed dural pouches, poor root sleeve filling, and
cord edema or atrophy.
o However, extraforaminal injuries and meningeal
tearing may occur without root damage (false-positive),
and healing and scarring of the dural pouch may conceal
root damage (false-negative).
o The overall reliability of CT myelography is greatest for
C8 and T1 root avulsions.
o Although MRI is less sensitive than CT myelography for
root avulsion, its multiplanar imaging and tissue
differentiating ability, lack of radiation and bone-related
image degradation, and noninvasive qualities render it
the radiologic procedure of choice for extraforaminal

23.  Magnetic resonance myelography is a relatively quick
technique in which T2-weighted images of the CSF are
reconstructed to generate three-dimensional–myelogram-like
images of the intraspinal canal and intervertebral foramina.
 Magnetic resonance neurography images peripheral
nerves using either diffusion neurography, where tissue
differentiation reflects diffusion differences, or T2-based
neurography, which images intraneural fascicles following fat
and blood suppression and voxel shortening.
o Because intraneural water molecules diffuse longitudinally, a
perpendicular magnetic field gradient is applied to make them
spin in phase and at the same rate so that neural tissue
appears brighter.
o Patient motion and the nonperpendicular orientation of the
extraforaminal brachial plexus to the sagittal plane
significantly degrade image quality.
o Magnetic resonance neurography, best applied following
lesion localization, may identify nerve discontinuities, ball
neuromas, nerve deflections, and neural tumors

24.  Vascular Assessment:
o Angiographic studies are helpful, especially when the
plexopathy follows a penetrating injury or when examination
demonstrates an absent carotid or radial pulse, bruit, thrill, or
expanding mass.
o The prognosis typically is worse for brachial plexopathies
associated with vascular injuries because the force required
to produce neural and vascular disruption is greater than that
for neural disruption alone.
 Electrodiagnostic Assessment:
o localizes and helps characterize the pathophysiology,
severity, and rate of progression of the lesion, thereby
contributing to patient management, treatment, and
prognostication.
o Electrodiagnostic assessment of the entire brachial plexus is
impractical given its large size. Because most lesions are
partial, a regional approach usually suffices; moreover,

25. o The motor axons contained within each element are
calculable from myotomal charts and dictate its
compound muscle action potential (CMAP) and muscle
domains.
o For example, the biceps is C5,6-musculocutaneous
nerve-innervated, thus, the motor axons innervating it
traverse the upper plexus and lateral cord. Therefore, the
musculocutaneous CMAP and biceps needle EMG
assess the upper plexus and lateral cord, in addition to
the musculocutaneous nerve.
o Similarly, the sensory axons composing each element,
which are determined from their dorsal root ganglion of
origin, dictate their sensory nerve action potential
(SNAP) domains.10(Figure 9-5) The unique SNAP,
CMAP, and needle EMG domains of each brachial
plexus element are provided in Table 9-1.

26. 26

27. Regional Approach:
o All three portions of the electrodiagnostic examination, sensory
nerve conduction study, motor nerve conduction study, and
needle EMG, are performed because each yields information not
provided by the others.
o Because of their greater sensitivity to axon loss lesions and their
localizing value, sensory nerve conduction studies are
performed first.
o In addition to differentiating preganglionic and postganglionic
lesions, the pattern of SNAP abnormalities identifies the brachial
plexus region involved.
o In our EMG laboratory, all patients referred for upper extremity
symptoms initially undergo screening sensory nerve conduction
studies: superficial radial, median (second digit), and ulnar (fifth
digit).
o When the median (second digit) response is abnormal (assesses
C6/C7 dorsal root ganglion–derived sensory axons), potential
localizations include median nerve, lateral cord, upper plexus, or
middle plexus.
o When the superficial radial response is abnormal (assesses
C6/C7 dorsal root ganglion–derived sensory axons), potential
localizations include superficial radial or radial nerve, posterior
cord, or upper or middle plexus.

28. o The screening sensory nerve conduction study findings
dictate the subsequent sensory nerve conduction studies
performed.
o Whenever the superficial radial or median (second digit)
response is abnormal (both assess C6/C7 dorsal root
ganglion–derived axons), the lateral antebrachial cutaneous
and median (first digit) studies (these studies assess C6
dorsal root ganglion–derived sensory axons) are added.
o With median (second digit) response abnormalities, whenever
the lateral antebrachial cutaneous or median (first digit)
response is abnormal, the lesion localizes to the lateral cord
or upper plexus.
o With superficial radial response abnormalities, whenever the
lateral antebrachial cutaneous or median (first digit) response
is abnormal, the lesion localizes to the upper plexus.
o If the ulnar (fifth digit) response is abnormal, then the medial
antebrachial cutaneous study is added and, if also abnormal,
permits localization to the medial cord or lower plexus.
o Next, the screening motor nerve conduction studies (median
abductor pollicis brevis and ulnar abductor digiti minimi) and
the motor nerve conduction studies assessing the lesion

29. o The motor nerve conduction studies provide information
regarding pathology and lesion severity through comparison
of distal response amplitude or negative area under the curve
value, with that of the contralateral, asymptomatic side.
o The needle EMG, which is performed last, further refines
localization (especially its proximal extent), quantifies chronic
changes, determines the rate of progression (based on the
relationship between the degree of acute abnormalities
present, such as fibrillation potentials, and the degree of
chronic abnormalities, such as motor unit action potential
enlargement), and can identify continuity when, clinically,
there may be no apparent muscle movement.
o The temptation to grade severity by fibrillation density must be
resisted because it is more reflective of study timing and the
innervation ratio.
o When required, contralateral studies permit relative
abnormalities (side-to-side differences exceeding 50% on
nerve conduction studies, motor unit action potential duration
on needle EMG) to be identified. The significance of these

30. conduction studies. Solid lines represent the
more common courses through the plexus;
dashed lines represent the less common
courses through the plexus. A, The lateral
antebrachial cutaneous nerve pathway. The
brachial plexus regions assessed by the
sensory nerve fibers subserving the lateral
antebrachial cutaneous sensory nerve
conduction study. B, The median thumb
pathway. The brachial plexus regions
assessed by the sensory nerve fibers
subserving the median thumb sensory nerve
conduction study. C, The median index
finger pathway. The brachial plexus regions
assessed by the sensory nerve fibers
subserving the median index finger sensory
nerve conduction study. D, The median
middle finger pathway. The brachial plexus
regions assessed by the sensory nerve
fibers subserving the median middle finger
sensory nerve conduction study. E, The
superficial radial pathway. The brachial
plexus regions assessed by the sensory
nerve fibers subserving the superficial radial
sensory nerve conduction study. F, The ulnar
little finger pathway. The brachial plexus
regions assessed by the sensory nerve
fibers subserving the ulnar little finger
sensory nerve conduction study. G, The
medial antebrachial cutaneous nerve
pathway. The brachial plexus regions
assessed by the sensory nerve fibers
subserving the medial antebrachial
cutaneous sensory nerve conduction study.
30

31. Table 9-2 The Regional Predilection of Particular Brachial Plexus Disorders 31

32. SITE-SPECIFIC BRACHIAL PLEXUS DISORDERS
 Many brachial plexus disorders are regionally specific (Table
9-2).
 Common upper plexopathies include burner (stinger)
syndrome, rucksack paralysis, and classic postoperative
paralysis.
 Isolated middle plexopathies are rare. In our series, only one
of 417 brachial plexus lesions was restricted to the middle
plexus (surgically verified idiopathic fibrosis).
 Common lower plexopathies include true neurogenic thoracic
outlet syndrome, post–median sternotomy brachial
plexopathy, and Pancoast syndrome.
 Disorders affecting the infraclavicular plexus are less site-
specific. Cord involvement follows axillary lymph node
irradiation (especially the lateral cord) and midshaft clavicular
fractures (especially the medial cord).
 Crutch palsies more frequently involve the radial terminal
nerve, procedures in the vicinity of the coracoid process more
frequently injure the musculocutaneous terminal nerve, and
proximal humerus fractures and glenohumeral dislocations
more frequently damage the axillary terminal nerve. These

33. True Neurogenic Thoracic Outlet Syndrome
o The thoracic outlet, which is actually the thoracic inlet since
the outlet is where the diaphragm muscle attaches, extends
from the supraclavicular fossa to the axilla and includes the
area between the clavicle and the first rib.
o more commonly affects young to middle-aged females, is a
rare disorder caused by angulation and stretching of the
lower plexus axons by a taut fibrous band extending from
the first thoracic rib to a C7 bony anomaly such as a
rudimentary rib or elongated transverse process and,
rarely, by scalene hypertrophy (scalenus anticus
syndrome).23
 Because the lower plexus is angulated from below, the T1
axons are affected more than the C8 axons.
 Although most patients have a long history of sensory
symptoms (mild aching and paresthesia along the medial
aspects of the arm and forearm more than the hand), they
typically present with motor symptoms such as progressive
forearm and hand weakness and atrophy as well as loss of
hand dexterity.
 The thenar muscles are heavily T1-innervated and,

34. o On nerve conduction studies of individuals with this
disorder, the medial antebrachial cutaneous (typically
unelicitable) and median abductor pollicis brevis (usually very
low in amplitude) responses are more abnormal than the
ulnar sensory and motor responses.
o On needle EMG, features of a slowly progressive, axonal
process are observed (eg, chronic motor unit action potential
changes and sparse fibrillations), most pronounced in
muscles with heavy T1 input (thenar muscles), less
pronounced in muscles receiving more equivalent C8 and T1
input (hypothenar muscles), and least pronounced in heavy
C8 muscles (extensor indicis, flexor pollicis longus).
o The fibrous band is radiolucent and, therefore, not reliably
visualized by plain films or CT imaging. MRI may identify
brachial plexus distortion (as may magnetic resonance
neurography), but does not reliably identify the band.
o Although the C7 bony anomalies are easily identified by plain
films, special views may be required.26When bilateral cervical
ribs are identified, the smaller rib is usually on the

35.  The presence of a cervical rib is not diagnostic because
for every 20,000 to 80,000 individuals with a cervical rib,
only one has true neurogenic thoracic outlet syndrome.
 Because slow progression permits reinnervation to keep
pace with denervation, conservative treatment does not
lead to improvement. Thus, patients are treated
surgically.
 Using a supraclavicular approach, which is more
proximate to the band and provides better visualization,
the band is sectioned; the distal portion of the bony
anomaly may be removed, but not the normal first
thoracic rib or scalene muscles.
 Postoperatively, the sensory features resolve, and the
motor features stop progressing. The other forms of
thoracic outlet syndrome have been recently reviewed

36. Post–Median Sternotomy Plexopathy
 Post–median sternotomy plexopathy is a traction-
induced lower plexopathy that follows operations
requiring median sternotomy, especially coronary artery
bypass.
 Either chest wall retraction drives the clavicle posteriorly,
thereby rotating the first rib into the C8 anterior primary
ramus or, more likely, the C8 anterior primary ramus is
damaged by a retraction-induced first rib fracture.
 Because the C8 anterior primary ramus contains
sensory axons primarily destined for the ulnar nerve,
disruption mimics an ulnar neuropathy. When
unrecognized and misattributed to malpositioning, the
anesthesiologist may inappropriately be blamed, and the
patient may undergo an unnecessary operation.
 Because the C8 anterior primary ramus also contains
axons innervating C8 radial (extensor indicis) and C8
median (flexor pollicis longus) muscles, the latter should

37.  On sensory nerve conduction studies, the ulnar (fifth digit)
response is abnormal and the medial antebrachial cutaneous
response is spared. The abnormal ulnar (fifth digit) response
indicates a lesion involving the ulnar nerve, medial cord, lower
trunk, or C8 anterior primary ramus.
 The normal medial antebrachial cutaneous response argues
against medial cord and lower trunk involvement. Thus, this
sensory nerve conduction study pattern of abnormal ulnar
(fifth digit) response with normal medial antebrachial
cutaneous response is most consistent with an ulnar
neuropathy or a C8 anterior primary ramus lesion, although a
partial lesion of the medial cord or lower trunk cannot be
excluded.
 On motor nerve conduction studies, whenever the radial
extensor indicis and median abductor pollicis brevis
responses are spared, an ulnar neuropathy is again
suggested.1
 On needle EMG, however, C8 median or C8 radial
involvement usually is present and, at this point, an ulnar
neuropathy is excludable.
 Because the typical pathology is predominantly

38. ITE-NONSPECIFIC BRACHIAL PLEXUS DISORDERS
Neuralgic Amyotrophy (Parsonage-Turner Syndrome)
 The term neuralgic amyotrophy best conveys the two
major clinical features of this disorder: pain and muscle
atrophy.
 is a multifocal, immune-mediated, inflammatory
peripheral nervous system disorder that involves the
forequarter body region.
 affecting individuals of all ages is more common among
middle-aged males.
 Most of our patients had a unilateral onset (80%)
involving the dominant limb (60%), and when bilateral
(18%), involvement was more often sequential than
simultaneous. Infrequently (12%), patients had multiple
bouts. When recurring in a previously affected limb,
neuralgic amyotrophy may affect the same or different
nerves and frequently is precipitated by the same trigger.

39.  Because of its predilection for nerves composed solely or
predominantly of motor axons, proximal involvement more
frequently affects the long thoracic, suprascapular, axillary, and
musculocutaneous nerves, whereas the anterior and posterior
interosseous nerves and the motor branches to individual muscles
are more frequently involved distally.31 Extraplexal motor nerves
(eg, spinal accessory and superior laryngeal) are less frequently
involved. Proximal lesions of the radial, median, and ulnar nerves
are less frequently observed, likely because of their mixed sensory
and motor composition. Pure sensory nerves are involved least
frequently, but of these, the lateral antebrachial cutaneous is most
commonly affected.31,32 In our series of 703 lesions, only 18
involved a pure sensory nerve: 15 lateral antebrachial cutaneous,
one medial antebrachial cutaneous, one superficial radial, and one
median digital branch.31 When neuralgic amyotrophy involves a
single nerve, the diagnosis may be missed. For example, when
neuralgic amyotrophy patients present with severe posterior
shoulder pain related to suprascapular nerve involvement, a
consulting physician unfamiliar with neuralgic amyotrophy might
consider suprascapular nerve entrapment to be the underlying
entity, precipitating an orthopedic consult and an unnecessary
release. Because the natural history includes recovery, the
procedure would erroneously be deemed successful. When
neuralgic amyotrophy involves multiple proximal nerves, it may be
mislocalized to the upper plexus. In our series, in which 50% of

40.  The pain of neuralgic amyotrophy is characteristically severe
in degree, sudden in onset, and typically involves the lateral
aspect of the shoulder. The pain often awakens the patient, or
is apparent immediately upon awakening, and maximizes
quickly. There may also be pain over the inflamed nerve:
lateral shoulder (axillary nerve), scapula (suprascapular
nerve), superolateral thoracic wall (long thoracic nerve),
antecubital fossa (anterior interosseous nerve), and lateral
arm or forearm (musculocutaneous nerve). The pain usually
resolves within a few weeks or is replaced by dull aching.
Paresthesia may be noted, but numbness is less common. As
the pain lessens and the patient begins to move the limb,
weakness becomes evident, followed by atrophy. In our
series, nearly 75% (196 of 268) reported a trigger: operative
or medical procedure (57%), recent illness (48%), excessive
or unaccustomed activity (34%), closed trauma (19%),
childbirth (13%), dental procedure (11%), vaccination (10%),
and open trauma (4%).33 In our study, the delay between the
trigger and the onset of pain ranged from 1 to 28 days, but
was less than 7 days in over two-thirds of patients.33 The

41.  It is important for examining clinicians to recognize neuralgic
amyotrophy because accurate diagnosis protects patients from
unnecessary surgical procedures such as cervical spinal column
surgery, rotator cuff repair, and nerve release and also prevents
unjustified medical malpractice claims against physicians when
medical procedures serve as triggers. Imaging studies help exclude
musculoskeletal disorders, such as rotator cuff tear and
acromioclavicular joint separation, and are especially useful when
pain limits the examination, atrophy has not yet occurred, or only a
single nerve is involved. Electrodiagnostic studies reliably identify
and characterize the lesion and establish its distribution.
 Regarding management, the initially severe pain is treated with
analgesics, including narcotics, pending the effect of neuropathic
pain medications such as tricyclic and antiepileptic agents. A short
course of corticosteroids is also acutely helpful in lessening the
severe pain. Strengthening and stretching exercises are
recommended once the pain is controlled. Although recovery rates
of 36% at 1 year, 75% at 2 years, and 89% at 3 years have been
reported,34 it is helpful to prognosticate each lesion individually
based on its completeness and distance from the denervated
muscle fibers. With complete lesions, reinnervation via collateral
sprouting cannot occur, and with lesions more than 24 inches from
the denervated muscle, reinnervation via proximodistal axon
advancement cannot occur. Consequently, recovery is unexpected
for complete lesions located more than 24 inches from the

42.  LESS FREQUENTLY ENCOUNTERED DISORDERS
 Pancoast Syndrome
 Pancoast reported the direct extension of apical lung cancer
to the lower plexus and the associated clinical features
(Pancoast syndrome).35 Although any disorder of the thoracic
inlet may produce these features, bronchogenic carcinoma is
most common. Because only the pleural lining separates the
lung apex and the lower plexus, lower plexus invasion is
frequent. Patients typically present with severe, unrelenting
shoulder pain, often with extension into the axilla and along
the medial aspect of the arm (T2 dermatome) and, less
frequently, the forearm (T1 dermatome) and hand (C8
dermatome). Horner syndrome follows involvement of the T1
root or inferior cervical sympathetic ganglion. Because apical
lung cancers are slow-growing, radiosensitive, locally
aggressive, and infrequently metastatic, earlier recognition
and treatment yield greater survival and cure rates.36Typically,
diagnosis is by tissue procurement following imaging studies,
and therapy is directed toward the underlying cause.
Favorable features include absence of metastatic disease,

43.  Case 9-1
 A 47-year-old man was referred for electrodiagnostic
assessment of the left upper extremity. Six months previously,
he had developed left shoulder pain followed by paresthesia
along the medial aspect of the arm which, approximately 4
months later, spread to the forearm and then the hand. He
also noted grip-strength loss. Two weeks prior to presentation
to the EMG laboratory, the shoulder pain became severe and
unrelenting, extended into his axilla, and interfered with sleep.
The paresthesia became dysesthetic. Examination
demonstrated left-sided Horner syndrome, C8 and T1 left
forearm and hand muscle weakness and atrophy, and
sensory loss along the medial aspects of the left arm,
forearm, and hand. Electrodiagnostic assessment indicated a
lower plexopathy including absent medial antebrachial
cutaneous and ulnar (fifth digit) sensory responses; low-
amplitude median abductor pollicis brevis and ulnar abductor
digiti minimi responses; as well as fibrillations,neurogenic
recruitment, and some chronic changes involving C8/T1 ulnar,
C8/T1 median, and C8 radial muscles. Chest MRI showed an
apical lung mass, and biopsy showed squamous cell
carcinoma.

44.  Burner (Stinger) Syndrome
 An upper plexus traction injury may be caused by the
sudden application of force to the head or shoulder,
causing their deviation away from each other. These
injuries, which are more common among males
participating in contact sports, are associated with
transient (minutes to hours) pain or paresthesia and
often referred to as burnersor stingers. Among sports-
related injuries, burners are the most commonly
encountered, accounting for 38% of 190 injuries in one
report.38 Most sports medicine providers only refer
patients when the symptoms persist or when a more
severe process is suspected. When electrodiagnostic
abnormalities are noted, they typically indicate an axon
loss upper plexopathy of mild severity. The term upper
plexusavoids the debate as to whether the lesion is

45.  Case 9-2
 A 17-year-old high school football player was referred for
electrodiagnostic assessment of episodic right upper
extremity burning. Three weeks prior, while tackling an
opponent, he developed a several-minute episode of
sharp, burning pain that radiated to his right thumb.
Similar episodes had occurred throughout the season,
but that time he developed residual weakness. His
neurologic examination was limited by shoulder pain.
Electrodiagnostic assessment showed normal nerve
conduction studies (including median [first digit] and
lateral antebrachial cutaneous sensory responses) and
sparse fibrillations in the right biceps and infraspinatus
muscles, consistent with an upper plexopathy.
 Comment. This patient’s clinical history and
electrodiagnostic findings are typical of burner syndrome
(also called stinger syndrome). When electrodiagnostic
abnormalities are noted, they typically indicate an axon

46.  Rucksack Paralysis
 Rucksack paralysis (pack palsy or cadet palsy) is a rare
upper plexopathy related to wearing a rucksack or similar
device. It likely reflects upper plexus compression related
to direct pressure from the straps where they traverse
the shoulders. Most patients note painless, unilateral
weakness in an upper plexus distribution, beginning
during or after rucksack usage. Associated sensory
symptoms are common. Risk factors include heavy load,
long-duration wear, narrow or unpadded straps, and lack
of a waist belt, which acts to shift weight from shoulder
straps to hips. When demyelination predominates (65%
of patients with this condition), sensory nerve conduction
studies are normal, motor nerve conduction studies and
needle EMG findings are abnormal, and recovery is
rapid. When axon loss predominates (35% of patients

47.  Case 9-3
 A 24-year-old man was referred for electrodiagnostic
assessment of weakness. While jogging with a weighted
backpack 4 weeks prior, he developed persistent right upper
extremity weakness and associated arm, forearm, and hand
numbness. Neurologic examination showed right C5/6–
distribution weakness and sensory loss. Biceps and
brachioradialis muscle stretch reflexes were diminished on
the right. Electrodiagnostic studies showed an upper
plexopathy that was predominantly demyelinating conduction
block in nature. The patient was reassured and made a full
recovery 3 months later.
 Comment. The patient’s history and examination are typical
of rucksack paralysis.Dueto the underlying demyelination, he
wasmanaged conservatively with passive and active range-of-
motion exercises and made a full recovery. Strengthening
exercises were not employed because, in the setting of
demyelinating conduction block, the motor axons are not
disrupted, the affected muscle fibers cannot be exercised (the
action potentials propagating along the nerve cannot traverse

48.  Classic Postoperative Paralysis
 Initially described in 1894,39 classic postoperative paralysis
presents in the immediate postoperative setting and is felt to be a
traction or pressure injury related to multiple variables such as
patient positioning, anesthesia-related loss of muscle tone, and
inability to weight-shift during anesthesia. Reported predisposing
factors include Trendelenburg position, upper extremity abduction
exceeding 90 degrees, contralateral head deviation and rotation,
and arm restraint in an abducted, extended, and externally rotated
position.40 Patients present with unilateral, painless weakness with
or without associated paresthesia. The upper plexus is affected in
isolation or, with supraclavicular plexus involvement, is affected out
of proportion to the middle and lower plexus portions of the
supraclavicular plexus. When the entire supraclavicular plexus is
involved, the middle and lower plexuses recover much more
quickly, ultimately leaving an isolated upper plexopathy.1,2 The
underlying pathophysiology usually is demyelinating conduction
block (axon loss infrequently predominates), in which case the
sensory nerve conduction studies are normal, the motor nerve
conduction studies show demyelinating conduction block, and the
needle EMG shows neurogenic motor unit action potential
recruitment of involved muscles. The axillary and suprascapular
responses may be reduced or absent, but, because these motor
nerve conduction studies can only be recorded with supraclavicular
stimulation, the underlying pathophysiology cannot be determined

49.  Case 9-4
 A 59-year-old man noted right upper extremity weakness
in the recovery room following bladder surgery.
Examination showed severe weakness of external
humeral rotation, shoulder abduction, and forearm
flexion. Patchy upper plexus-distribution sensory loss
also was noted. Electrodiagnostic testing showed right
upper plexus-distribution demyelinating conduction block
with normal sensory responses, very low amplitude
axillary and suprascapular motor responses, 90%
musculocutaneous demyelinating conduction block
between supraclavicular and axillary stimulation sites,
and moderate to severe neurogenic recruitment. He was
diagnosed with classic postoperative paralysis.
 Comment. This patient had classic postoperative
paralysis. He was treated conservatively and made a full