Autonomic dysfunction

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Autonomic Dysfunction
  • Clinical Manifestations:
    • ANS disorders: due to--
      • central nervous system (CNS) causes
      • Peripheral nervous system (PNS) causes
    • Signs/Symptoms: due to interruption of reflex arc
      • Site of interruption:
        • afferent limb
        • CNS processing center
        • efferent limb
      • Examples:
        •  posterior fossa tumors: medullary lesions may cause --
          • impaired blood-pressure responses to postural change (orthostatic hypotension)
        • Lesions of vasomotor nerve fibers to blood vessels (e.g. diabetes or spinal cord disease)
        • Lesions to afferent connections (e.g. Guillain-Barre syndrome)
        •  Segmental disorders (focal deficits):
          • in spinal cord disease
          • reflex sympathetic dystrophy
          • Horner's syndrome
  • Autonomic Dysfunction: symptoms-- Organ dependent
    • Impotence-- first sign of autonomic failure-- sequence
      1. lost of spontaneous early morning erection
      2. loss of nocturnal penile tumescence
      3. total impotence
    • Bladder dysfunction:
      • occurs early both in men and women (especially with CNS involvement)
      • Brain/spinal cord disease: above the level of the lumbar spine(upper motor neuron) disease:
        1. urinary frequency/small bladder volumes
        2. incontinence
      •  Autonomic fiber disease to the bladder (lower motor neuron disease) or sensory denervation:
        • large bladder volumes
        • urinary frequency
        • overflow incontinence
    • Gastrointestinal Dysfunction:
      • severe constipation typically
        • Exception -- diabetes diarrhea-- cause
          1. rapid transit of contents
          2. uncoordinated small bowel activity
        • osmotic diarrhea (bacterial overgrowth -- small bowel stasis
      • Decreased salvation (glandular effects)
    • Eye irritation: -- reduced lacrimation
    •  Orthostatic Hypotension: most disabling feature of autonomic dysfunction
      • Definition: postural decrease of at least 20 mm Hg in systolic or 10 mm Hg in diastolic blood pressure sustained for least 3 minutes (to differentiate between autonomic dysfunction and sluggish baroreceptor reflex response {common in the elderly})
      •  Symptoms of postural hypotension:
        • dimming or loss of vision
        • light headedness
        • diaphoresis
        • impaired hearing
        • pallor/weakness
        • syncope
Engstrom, J, and Martin, J.B. Disorders of the Autonomic Nervous System, In Harrison's Principles of Internal Medicine 14th edition, (Isselbacher, K.J., Braunwald, E., Wilson, J.D., Martin, J.B., Fauci, A.S. and Kasper, D.L., eds) McGraw-Hill, Inc (Health Professions Division), 1998, pp 2372-2377.