Brachial Plexopathy (Brachial Plexus Syndromes)
Brachial plexopathy คือความผิดปกติของ brachial
plexus ซึ่งอาจเกิดจาก trauma, inflammation, neoplasm,
radiation, compression, metabolic disease หรือ iatrogenic
injury โดยอาการมักเป็น combination ของ pain
+ weakness + sensory deficit ใน distribution ที่ไม่ตรงกับ single root หรือ single
peripheral nerve ชัดเจน
Anatomy ที่สำคัญทางคลินิก
Brachial plexus roots
เกิดจาก ventral rami ของ C5-T1
Trunks
- Upper
trunk = C5-C6
- Middle
trunk = C7
- Lower
trunk = C8-T1
Cords
- Lateral
cord
- Posterior
cord
- Medial
cord
Major terminal nerves
- Musculocutaneous
- Axillary
- Radial
- Median
- Ulnar
Important branch nerves
- Long
thoracic nerve →
serratus anterior
- Suprascapular
nerve
- Dorsal
scapular nerve
Pathophysiology
Mechanisms
- Compression
- Traction
injury
- Root
avulsion
- Ischemia
(vasa nervorum)
- Inflammation
- Radiation
injury
- Tumor
infiltration
- Metabolic
injury (เช่น diabetes)
Clinical Features
Typical symptoms
Acute onset
มักเป็น:
- severe
shoulder/upper arm pain
- followed
by weakness
มักสัมพันธ์กับ:
- inflammatory
- ischemic
- neuralgic
amyotrophy
- trauma
Chronic progressive
คิดถึง:
- neoplasm
- radiation-induced
plexopathy
- thoracic
outlet syndrome
Physical Examination
Motor
- weakness
- muscle
atrophy
- scapular
winging
- reduced
reflexes
Sensory
- patchy
sensory loss
- non-dermatomal
distribution
Important clues
Horner syndrome
คิดถึง:
- lower
trunk lesion
- Pancoast
tumor
Scapular winging
long thoracic nerve involvement
Localization Clues
|
Pattern |
Suggest lesion |
|
Shoulder abduction/external
rotation weakness |
Upper trunk |
|
Hand intrinsic weakness |
Lower trunk |
|
Median + ulnar involvement
together |
Plexus lesion |
|
Normal paraspinal EMG |
Plexopathy มากกว่า radiculopathy |
|
Sensory NCS abnormal |
Postganglionic lesion (plexus) |
Diagnostic Workup
Electrodiagnostic studies
Nerve conduction studies (NCS)
ช่วย:
- distinguish
plexopathy vs radiculopathy
- detect
sensory involvement
- localize
lesion
Key point
Sensory NCS abnormal →
supports plexopathy
(radiculopathy มัก sensory SNAP (nerve action potential)
preserved)
Needle EMG
เป็น test ที่ sensitive
ที่สุดต่อ axonal loss
Useful findings
- denervation
- localization
- severity
Timing
fibrillation/positive sharp wave อาจยังไม่เห็นจน
>3 weeks หลัง acute injury
Imaging
MRI brachial plexus
best overall imaging modality
Useful for:
- tumor
- inflammation
- radiation
injury
- edema
- thickening
- nerve
enhancement
MR neurography
เห็น:
- focal
constriction
- nerve
edema
- hourglass
lesion
CT myelography
useful for:
- root
avulsion
Ultrasound
ช่วยดู:
- structural
lesion
- traumatic
lesion
- hypertrophic
neuropathy
Important Brachial Plexopathy Syndromes
1. Traumatic Plexopathy
พบบ่อยที่สุด
Causes
- motorcycle
accident
- traction
injury
- sports
injury
- falls
- penetrating
trauma
Root avulsion
Mechanism
high-energy traction injury
Clinical clues
- severe
weakness
- sensory
loss
- severe
neuropathic pain
- poor
recovery
Common roots
- C8-T1
avulsion มากที่สุด
Diagnosis
- CT
myelography
- MRI
Prognosis
poor
เพราะ nerve root torn from spinal cord → regenerate ไม่ได้
Burner/Stinger syndrome
พบบ่อยใน contact sports
Mechanism
traction/compression of upper trunk
Symptoms
- burning
pain
- transient
paresthesia
- unilateral
arm symptoms
ส่วนใหญ่หายเองภายใน minutes-hours
Red flags
persistent weakness →
evaluate further
Backpack palsy
เกิดจาก prolonged backpack compression
Features
- painless
upper plexus weakness
- usually
demyelinating lesion
- recovery
generally good
2. Neuralgic Amyotrophy (Parsonage-Turner Syndrome)
important inflammatory plexopathy
Pathophysiology
likely immune-mediated inflammatory neuropathy
Triggers:
- infection
- surgery
- exercise
- vaccination
- pregnancy
Classic Presentation
Phase 1
sudden severe shoulder pain
Phase 2
days-weeks later:
- weakness
- atrophy
Common nerves involved
- suprascapular
- long
thoracic
- anterior
interosseous
- axillary
- musculocutaneous
Common sign
scapular winging
Important Clinical Pearls
Pain characteristics
- severe
- nocturnal
- awakens
patient from sleep
Weakness timing
may occur:
- within
24 hr
OR - 2
weeks later
Bilateral involvement
พบได้ ~30%
Extra-brachial involvement
อาจ involve:
- phrenic
nerve
- recurrent
laryngeal nerve
- lumbosacral
plexus
Phrenic neuropathy clues
- orthopnea
- exertional
dyspnea
- supine
FVC drop
Diagnosis of Neuralgic Amyotrophy
Clinical diagnosis เป็นหลัก
Supported by:
- EMG
- MRI/MR
neurography
Labs เพื่อ exclude mimics
- CBC
- ESR
- glucose/HbA1C
- HIV
- syphilis
- Lyme
disease
Imaging Findings
MRI/MR neurography:
- T2
hyperintensity
- focal
thickening
- gadolinium
enhancement
- hourglass
constriction
Treatment
Conservative management
- analgesia
- PT/OT
Steroid
มีการใช้ แต่ evidence จำกัด
Prognosis
recovery ช้า:
- months
to years
Residual weakness/pain พบได้บ่อย
Recurrence ~25%
3. Neoplastic Plexopathy
Common cancers
- breast
cancer
- lung
cancer
- lymphoma
Classic features
- severe
pain
- progressive
weakness
- lower
trunk involvement
- Horner
syndrome
Pancoast tumor clues
- shoulder
pain
- Horner
syndrome
- hand
weakness
Distinguish Neoplastic vs Radiation Plexopathy
|
Feature |
Neoplastic |
Radiation |
|
Pain |
Early/severe |
Mild/late |
|
Lower trunk |
Common |
Less |
|
Horner syndrome |
More common |
Rare |
|
Myokymia on EMG |
Rare |
Common |
4. Radiation-induced Plexopathy
Risk factors
- breast
cancer radiation
- supraclavicular
radiation
- high
dose radiation
- concurrent
chemotherapy
Symptoms
- numbness
- paresthesia
- weakness
- less
pain than neoplastic plexopathy
EMG clue
myokymic discharges strongly support diagnosis
5. Thoracic Outlet Syndrome (TOS)
True Neurogenic TOS
rare but important
Pathophysiology
compression/stretch of lower trunk:
- cervical
rib
- fibrous
band
Symptoms
- hand
intrinsic weakness
- ulnar
sensory symptoms
- thenar
atrophy
motor > sensory
Electrodiagnostic Pattern
Classic:
- T1
> C8 involvement
- reduced
medial antebrachial cutaneous SNAP
- lower
trunk denervation
Treatment
- PT
- posture
correction
- surgery
in selected cases
6. Diabetic-related Plexopathy
มักร่วมกับ:
- diabetic
amyotrophy
- lumbosacral
radiculoplexus neuropathy
Upper limb involvement พบได้
7. Iatrogenic Plexopathy
Causes
- surgical
traction injury
- median
sternotomy
- anesthetic
block
- hematoma
- compartment
syndrome
Red Flags
Suspect serious pathology if:
- progressive
weakness
- severe
persistent pain
- Horner
syndrome
- cancer
history
- bilateral
severe involvement
- respiratory
symptoms
- scapular
winging
- upper
+ lower trunk involvement together
Practical Clinical Approach
Step 1 — Localize
- plexus
vs root vs mononeuropathy
Step 2 — Pattern
- upper
trunk?
- lower
trunk?
- diffuse?
Step 3 — Time course
- acute
painful →
inflammatory/traumatic
- progressive
→ tumor/radiation
Step 4 — Investigate
- EMG/NCS
- MRI
brachial plexus
- cervical
spine imaging if needed
Step 5 — Search etiology
- trauma
- cancer
- diabetes
- radiation
- surgery
- infection
- autoimmune
Key Pearls
- Sensory
NCS abnormal → favors
plexopathy over radiculopathy
- Severe
nocturnal shoulder pain followed by weakness → think neuralgic amyotrophy
- Horner
syndrome + shoulder pain →
think Pancoast tumor
- Myokymia
on EMG → suggests
radiation plexopathy
- Scapular
winging → long
thoracic nerve involvement
- Root
avulsion has very poor prognosis
- MRI
brachial plexus is imaging of choice
- EMG
may be falsely normal in first 2-3 weeks after acute injury
ไม่มีความคิดเห็น:
แสดงความคิดเห็น