Neurology Book

Headache Disorders

Neuropathy

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Peripheral NeuropathyAka: Neuropathy

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  1. Pathophysiology: Injury affects one of four components
    1. Neuronal or Axonal Neuropathy
      1. Affects cell body or axon of nerve
      2. See Symmetric Peripheral Neuropathy (Polyneuropathy)
      3. See Asymmetric Peripheral Neuropathy (Mononeuropathy)
    2. Demyelinating Neuropathy (Myelinopathy)
      1. Affects myelin swan cell sheath around axon
      2. See Symmetric Peripheral Neuropathy (Polyneuropathy)
      3. See Asymmetric Peripheral Neuropathy (Mononeuropathy)
    3. Infiltrative neuropathy: Affects supporting tissue
      1. Appears similar to demyelinating neuropathy
      2. Sarcoidosis
      3. Myelomatosis
      4. Amyloidosis
    4. Ischemic neuropathy: Affects nerve vascular supply
      1. Diabetes Mellitus
      2. Collagen vascular disease
  2. History
    1. What is the distribution of nerve involvement?
      1. Symmetric: Polyneuropathy
        1. Usually due to systemic or hereditary condition
        2. Idiopathic in 20% of cases
      2. Asymmetric: Mononeuropathy
        1. Usually due to nerve compression or inflammation
        2. Mononeuropathy: Isolated to a single nerve
        3. Mononeuropathy Multiplex: >1 discrete nerve
    2. Is the deficit sensory, motor or sensorimotor?
      1. Most neuropathies affect both sensory and motor
      2. Pure motor or sensory seen in distal Mononeuropathy
      3. Is motor more than sensory involvement?
        1. Amyotrophic Lateral Sclerosis
        2. Poliomyelitis or other chronic infectious cause
        3. Hereditary sensorimotor neuropathy
        4. Toxin exposure
      4. Is sensory more than motor involvement?
        1. Toxin exposure
        2. Vitamin B12 Deficiency
        3. Hereditary sensory neuropathy
        4. Systemic condition
          1. Diabetes Mellitus
          2. Uremia
          3. Myelomatosis
          4. Dysproteinemia
    3. When was the onset of symptoms?
      1. Acute over hours or days
        1. Motor neuropathy most common
          1. See Acute Motor Weakness Causes
          2. Acute motor loss is risk for respiratory failure
          3. Requires urgent evaluation
        2. Sensory neuropathy: Herpes Zoster
      2. Subacute over days to weeks
      3. Chronic over months
        1. Accounts for most cases of neuropathy
  3. Signs: Sensory
    1. Demyelinating or infiltrative neuropathy
      1. Loss of vibration sense
      2. Loss of joint position sense
      3. Loss of tactile discrimination
    2. Axonal neuropathy
      1. Sensory modes affected equivalently
      2. Neuropathy begins distally and moves proximally
      3. Injured nerve cell body cannot pump to axon end
      4. Results in stocking-and-glove distribution
      5. Long axons (e.g. legs) lose distal function first
        1. First: Sensory loss begins in feet
        2. Next: Deficit progresses proximally to knees
        3. Next: Hands begin to lose sensation
        4. Face is rarely affected (generally short axons)
  4. Signs: Motor
    1. Demyelinating or infiltrative neuropathy
      1. Early loss of Deep Tendon Reflexes
      2. Sensory often affected more than motor function
    2. Axonal neuropathy
      1. Initial: Damage to anterior horn cell at spinal cord
        1. Weakness
        2. Muscle wasting
        3. Muscle fasciculations
      2. Later
        1. Deep Tendon Reflex loss in chronic neuropathy
        2. Demyelination may occur secondary to axonal loss
          1. Differentiate from primary demyelination as above
      3. Motor loss follows same pattern as for sensory loss
        1. Distal affected before proximal involvement
  5. Causes
    1. See Symmetric Peripheral Neuropathy (Polyneuropathy)
    2. See Asymmetric Peripheral Neuropathy (Mononeuropathy)
  6. Diagnostics
    1. General
      1. EMG and NCS used in combination
      2. Differentiate axonal from myelin-infiltrative cause
      3. See Nerve Conduction Velocity for Interpretation
    2. Studies
      1. Needle Electromyography (EMG)
      2. Nerve Conduction Studies (Nerve Conduction Velocity)
      3. Nerve biopsy
    3. Additional studies
      1. MRI Brain
      2. Lumbar Puncture
  7. Red flags
    1. Focal weakness (risk of respiratory failure)
  8. References
    1. Gallagher in Marx (2002) Rosen's Emergency Med, p. 1506
    2. Pryse-Phillips in Noble (2001) Primary Care, p. 1579

Neuropathy (C0442874)

Definition (NCI)A disorder affecting the cranial nerves or the peripheral nervous system. It is manifested with pain, tingling, numbness, and muscle weakness. It may be the result of physical injury, toxic substances, viral diseases, diabetes, renal failure, cancer, and drugs. -- 2004
ConceptsDisease or Syndrome (T047)
EnglishNeuropathy
Spanishneuropatía, neuropatia
CreditsDerived from the NIH UMLS (Unified Medical Language System)



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