Rosen & Barkin's 5-Minute Emergency Medicine Consult (566 page)

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  Emerg Med Clin North Am
  . 2009;27:459–476.
  
• Kremyanskaya M, Mascarenhas J, Hoffman R. Why does my patient have erythrocytosis?
  Hematol Oncol Clin North Am.
  2012;26(2):267–283.
  
• Landolfi R, Nicolazzi MA, Porfidia A, et al. Polycythemia vera.
  Intern Emerg Med.
  2010;5(5):375–384.
  
• McMullin MF. The classification and diagnosis of erythrocytosis.
  Int J Lab Hematol
  . 2008;30:447–459.
  
• Patnaik MM, Tefferi A. The complete evaluation of erythrocytosis: Congenital and acquired.
  Leukemia
  . 2009;23:834–844.
  
• Tefferi A. Polycythemia vera and essential thrombocythemia: 2012 update on diagnosis, risk stratification and management.
  Am J Hematol.
  2012;87(3):285–293.
  

CODES

• 238.4 Polycythemia vera
  
• 289.0 Polycythemia, secondary
  

BASICS

A peripheral nerve disorder in which many nerves throughout the body malfunction simultaneously:

• Acute polyneuropathy causes:
  
  • Infectious (toxin producing bacteria, viruses)
    
  • Autoimmune (Guillain–Barré)
    
  • Toxic (heavy metals):
    
    • Lead
      
    • Mercury
      
  • Drugs:
    
    • Anticonvulsants (phenytoin)
      
    • Antibiotics (chloramphenicol, nitrofurantoin, sulfonamides)
      
    • Chemotherapy (vinblastine, vincristine)
      
    • Sedatives (hexobarbital and barbital)
      
  • Cancer (multiple myeloma)
    
• Chronic polyneuropathy causes:
  
  • Diabetes (most common)
    
  • Alcohol abuse
    
  • Nutritional deficiencies (Thiamine, B
    ₁₂
    )
    
  • Hypothyroidism
    
  • Liver failure
    
  • Kidney failure
    
  • Lung cancer
    
  • Chronic inflammatory demyelinating polyneuropathy (CIDM)
    

• In US, the prevalence of polyneuropathy is ∼2% in the general population
  
• It is 8% in patients >55 yr of age
  
• The most common cause in US is diabetes and it occurs in ∼50% of diabetics on insulin
  

• Myelin dysfunction:
  
  • Parainfectious immune response triggered by antigens that cross-react with antigens in the peripheral nervous system:
    
    • Encapsulated bacteria (
      Campylobacter
      sp., diphtheria)
      
    • Viruses (enteric or influenza viruses, HIV)
      
    • Vaccines (influenza)
      
  • Guillain–Barré syndrome:
    
    • Acute onset due to myelin dysfunction
      
    • Rapidly progressive weakness and may lead to respiratory failure
      
  • CIDM:
    
    • Chronic illness of myelin dysfunction
      
    • Symptoms may recur or progress over months and years
      
• Vasa nervosum compromise:
  
  • Vascular supply to nerves compromised leading to nerve infarction
    
  • Causes:
    
    • Chronic atherosclerosis
      
    • Vasculitis
      
    • Infections
      
    • Hypercoagulable states
      
    • Axonopathy
      
  • Primary dysfunction of the axon
    
  • Most often the result of toxic–metabolic disorders:
    
    • Diabetes
      
    • Nutritional deficiencies
      
    • Drugs/chemicals
      

DIAGNOSIS

• May be acute or chronic
  
• May be predominately sensory, motor, combined sensory–motor, or autonomic dysfunction
  

• More commonly affects lower extremities than upper extremities and begins distally
  
• Typical complaints:
  
  • Dysaesthesias – numbness, burning, or tingling of the extremities
    
  • Weakness of extremities
    
  • Difficulty walking
    
  • Autonomic symptoms:
    
    • Constipation
      
    • Loss of bowel/bladder control
      
    • Sexual dysfunction
      
    • Orthostatic dizziness
      
    • Dry skin
      
    • Decreased sweating
      

• Typically, findings are bilateral symmetrical and stocking glove distribution
  
• Typical findings:
  
  • Decreased sensation
    
  • Decreased vibratory and position sense
    
  • Decreased motor function
    
  • Decreased reflexes
    
  • Muscle atrophy
    
  • Fasciculations
    
  • Paralysis
    
• Findings in specific types of polyneuropathy:
  
  • Myelin dysfunction (Guillain–Barré – acute and CIDP – chronic):
    
    • Muscle weakness greater than expected for degree of atrophy
      
    • Paresthesias
      
    • Greatly diminished reflexes
      
    • Proximal and distal symptoms
      
  • Ischemia to nerve (atherosclerosis, vasculitis, infectious, hypercoagulable):
    
    • Painful, burning sensory disturbances
      
    • Decreased pain and temperature sensation
      
    • Muscle weakness proportional to atrophy
      
    • Reflexes spared
      
    • Usually spares proximal nerves
      
    • Cranial nerve involvement rare
      
  • Primary axon dysfunction (toxic-metabolic disorders):
    
    • Have symptoms of either myelin dysfunction, ischemia, or combined
      
    • Painful
      
    • Distally symmetrical
      
    • Stocking glove
      
    • Lower extremities before upper
      

• Thorough past medical history and physical exam should be obtained to guide testing
  
• Initial lab testing:
  
  • CBC
    
  • Electrolytes
    
  • Glucose
    
  • Renal and liver function
    
  • TSH
    
  • ESR
    
  • ANA
    
  • Vitamin B
    ₁₂
    
  • Folate
    
  • RPR
    
  • HIV
    
  • Hepatitis B and C
    
  • Lyme
    
  • CPK
    
  • Serum protein electrophoresis
    
• Subsequent lab testing based on history:
  
  • Heavy metal levels (history of exposure)
    
  • Genetic testing for genetic neuropathies
    
  • Serum antibody testing for immune-mediated neuropathies
    

Should be guided by history and physical findings

• Electromyography (EMG)
  
• Nerve conduction studies
  
• Lumbar puncture:
  
  • Increased CSF protein level abnormal
    
  • Diagnostic of Guillain–Barré syndrome and CIDP
    
• Skin or nerve biopsy
  

• Primarily to differentiate between various causes of polyneuropathy:
  
  • Endocrine disease (diabetes)
    
  • Infections (Guillain–Barré, Lyme disease, HIV, syphilis)
    
  • Vitamin deficiency
    
  • Cancer/paraneoplastic
    
  • Toxins
    
  • Liver disease
    
  • Renal failure
    
  • Genetic disorders
    
  • Amyloidosis
    
• Other diseases with similar presentations:
  
  • Polio
    
  • Porphyria
    
  • Spinal muscular atrophy
    
  • Catecholamine disorders
    
  • Psychological disorders
    

TREATMENT

Primarily supportive care for ABCs

• ABCs
  
• Respiratory support for respiratory failure
  

• Pain control:
  
  • Parenteral or oral narcotics
    
  • Tricyclic antidepressants (amitriptyline)
    
  • Anticonvulsants (gabapentin)
    
• Plasma exchange or IV immune globulin for acute myelin dysfunction
  
• Corticosteroids or antimetabolite drugs for chronic myelin dysfunction
  
• Supportive care for autonomic dysfunction (IVF, pressors)
  
• Measure Negative Inspiratory Force (NIF) if concerned about respiratory compromise (Normal is Ã-60 cm H
  ₂
  O)
  

FOLLOW-UP