Differential Diagnosis in Neurology

7.5. Neoplasms Affecting the Brachial Plexus

Benign Tumors

• Neural sheath tumors:
  • 60–80% of brachial plexus tumors
  • Benign neurofibroma (solitary and fusiform)
  • Affects adults
  • Arise supraclavicularly (proximal upper and middle plexus)
  • Females 3:1 greater than males
• Neurofibromas associated with NF-1:
  • Comprises 40% of patients with brachial plexus neurofibromas
  • Males equal females in incidence
  • Occur both supra and infraclavicularly
  • Frequently multiple and plexiform
  • Present at an earlier age than other tumors
  • May extend intraspinally (dumbbell tumor); intradural extramedullary compartment
• Schwannomas:
  • Second most frequent benign neural sheath tumor; comprises approximately 20% of tumors of the plexus
  • Solitary
  • Affects adults
  • Upper plexus in origin
• Benign non-neural sheath plexus tumors:
  • Lipoma
  • Ganglioneuroma
  • Myoblastoma
  • Lymphangioma
  • Desmoid
• Clinical presentation of benign brachial plexus tumor:
  • Limb pain
  • Palpable mass
  • Combination of pain and mass
  • Frequently are tender to palpation; radiating paresthesias are common
  • Mild motor and sensory deficits; referable to the involved dermatomes and myotomes

Malignant Neural Sheath Tumor

• 15% of neural sheath tumors are malignant
• Primarily neurogenic sarcomas and fibrosarcomas
• Malignant transformation of benign neural sheath tumors:
  • Transformation most common in Von Recklinghausen's disease
  • Late transformation (20–40 years) to sarcoma in patients who have been irradiated for breast cancer or Hodgkin's disease

Metastatic Brachial Plexus Tumors

• 2/3 originate from the lung or breast
• Metastasis from:
  • Larynx
  • Pancreas
  • Colon
  • Bladder
  • Testes
  • Thyroid
  • Esophagus
  • Lymphoma
  • Melanoma
  • Ewing's sarcoma
• Metastatic tumors have often metastasized extensively prior to plexus involvement; upper lobe of the ipsilateral lung is a common site
• Blood borne metastasis greater than direct extension
• Metastatic spread:
  • Lymphatic spread from axillary lymph nodes
• Clinical features:
  • Known malignant disease
  • Long latent periods from treatment of primary tumor is not uncommon
  • Pain in the arm and shoulder
  • Weakness sensory loss and Horner's syndrome occur later
  • Associated extradural spread with cervical cord compression
  • Many breast cancer patients have received X-RT to the plexus prior to a metastatic disease presentation

Pancoast Tumors

• Direct spread from the apex of the lung (superior sulcus or thoracic inlet tumor)
• Apical lung neoplasm; squamous cell carcinoma or adenocarcinoma
• Males greater than 40 years of age; occasionally in a patient with an apical scar from Tbc
• Clinical presentation:
  • Pain in the shoulder, scapula or 4th and 5th finger; burning quality
  • Weakness, wasting and sensory loss in the lower trunk distribution
  • Horner's syndrome
  • Commonly CT evidence of rib and vertebral erosion
  • Other causes: Ewing's sarcoma, bacterial or fungal infection (actinomycosis), lymphoma or multiple myeloma

Radiation Induced Brachial Plexopathy

• Dosimetric considerations that induce lesions:
  • Field size
  • Amount of tissue irradiated
  • Time period of the irradiation
  • Number of fractions delivered
  • Dose of each fraction
  • Total dosage
• Extensive loss of myelin; proliferative endarteritis of the vasovasorum, progressive fibrosis
• Women irradiated for breast cancer is the most frequent cause; lung cancer and lymphoma make up the remainder of the tumor:
  • Latent period: 0–34 years after X-ray treatment
• Clinical presentation:
  • Paresthesias C5–C6 distribution; median nerve innervated fingers (damage to the lateral cord)
  • Pain develops late (moderate severity)
  • Weakness of intrinsic hand muscles
  • Supraclavicular greater than infraclavicular involvement; all parts of the plexus may be involved
  • Edema of the extremity
  • Most patients have a progressive course; some patients plateau

Rare Forms of Radiation Induced Brachial Plexus Lesions

• Severe edema (possible compartment syndrome)
• Acute onset ischemic process:
  • Injury to subclavian artery
  • Painless weakness and sensory loss
  • Segmental occlusion of the subclavian artery
• Reversible brachial plexopathy:
  • Syndrome develops 2–14 months after X-RT
  • Hand and forearm paresthesia; shoulder pain; mild hand weakness
  • Chemotherapy after X-RT may be causative or associative

Differential Diagnosis between Recurrent Neoplasm or Radiation Brachial Plexopathy Neoplastic Signs and Symptoms

• Pain in the shoulder
  • C8–T1 distribution
  • Burning in quality
• Less than six months post X-RT
• Rapidly progressive
• Horner's syndrome
• Widespread metastatic disease
• Focal mass
• Neoplasm on biopsy

Radiation Induced Brachial Plexopathy

• Paresthesias in C5, C6 root distribution; median nerve innervated fingers
• Slowly progressive; plateaus in symptoms may occur
• Symptom duration greater than four years
• Paresthesias predominant
• Associated hyperreflexia
• EMG:
  • Decreased median nerve sensory conduction early finding
  • Conduction block on supraclavicular stimulation
  • Fasciculations; myokymia (particularly with X-RT)
• Differential diagnosis of X-RT induced plexopathy:
  • CTS
  • Cervical radiculopathy (C6–C7)
  • Vasculitis
  • HNPP (chromosome 17)

Inherited Brachial Plexopathies

• Clinical presentations :
  • Onset in second and third decades; occasional will be initiated in childhood
  • Several acute episodes over years; usually with recovery
  • Weakness proceeded by pain in the affected extremity
  • Pain: severe, lancinating, burning in quality; exacerbated by movement; arm is splinted
  • Weakness ensues after pain; progresses over days to weeks; reaches a maximum by one month
  • Associated weakness of cranial nerves and lower extremities may occur (lumbosacral plexus)
  • Upper trunk of the brachial plexus most commonly affected; any muscle of plexus may be involved
  • Atrophy and fasciculations develop over months
  • Recovery begins weeks to months after onset and may continue for up to two years
  • Recurrent episodes are more common than those seen in neuralgic amyotrophy
  • Patients may suffer separate attacks of upper or lower limb plexopathy
  • Bilateral brachial plexopathy occurs
  • Cranial nerve involvement: VII, VIII and X may be involved; Horner's syndrome; may occur separately or with attacks of upper extremity weakness
  • Dysmorphic features that may be associated:
    • Hypotelorism
    • Epicanthic folds
    • Cleft palate
    • Syndactyly
    • Short stature
  • Precipitating factors that may be noted:
    • Infection
    • Strenuous exercise
    • Pregnancy and puerperium
  • In familial disease the first episode may occur in the first decade
    • Sporadic form of the disease onset is in the third and fourth decade
  • EMG:
    • Acute scattered axonal damage within the brachial plexus
  • Autosomal dominant inheritance