DISORDERS OF THE AUTONOMIC NERVOUS SYSTEM

DISORDERS OF THE AUTONOMIC NERVOUS SYSTEM is a topic covered in the Harrison's Manual of Medicine.

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Autonomic disorders may occur with many disorders of the central and/or peripheral nervous systems (Table 189-2). Diseases of the CNS may cause ANS dysfunction at many levels, including hypothalamus, brainstem, or spinal cord.

TABLE 189-2: Classification of Clinical Autonomic Disorders
I. Autonomic Disorders with Brain Involvement
  1. Associated with multisystem degeneration
    1. Multisystem degeneration: autonomic failure clinically prominent
      1. Multiple system atrophy (MSA)
      2. Parkinson’s disease with autonomic failure
      3. Diffuse Lewy body disease with autonomic failure
    2. Multisystem degeneration: autonomic failure clinically not usually prominent
      1. Parkinson’s disease without autonomic failure
      2. Other extrapyramidal disorders (inherited spinocerebellar atrophies, progressive supranuclear palsy, corticobasal degeneration, Machado-Joseph disease, fragile X syndrome [FXTAS])
  2. Unassociated with multisystem degeneration (focal CNS disorders)
    1. Disorders mainly due to cerebral cortex involvement
      1. Frontal cortex lesions causing urinary/bowel incontinence
      2. Focal seizures (temporal lobe or anterior cingulate)
      3. Cerebral infarction of the insula
    2. Disorders of the limbic and paralimbic circuits
      1. Shapiro’s syndrome (agenesis of corpus callosum, hyperhidrosis, hypothermia)
      2. Autonomic seizures
      3. Limbic encephalitis
    3. Disorders of the hypothalamus
      1. Thiamine deficiency (Wernicke-Korsakoff syndrome)
      2. Diencephalic syndrome
      3. Neuroleptic malignant syndrome
      4. Serotonin syndrome
      5. Fatal familial insomnia
      6. Antidiuretic hormone (ADH) syndromes (diabetes insipidus, inappropriate ADH secretion)
      7. Disturbances of temperature regulation (hyperthermia, hypothermia)
      8. Disturbances of sexual function
      9. Disturbances of appetite
      10. Disturbances of BP/HR and gastric function
      11. Horner’s syndrome
    4. Disorders of the brainstem and cerebellum
      1. Posterior fossa tumors
      2. Syringobulbia and Arnold-Chiari malformation
      3. Disorders of BP control (hypertension, hypotension)
      4. Cardiac arrhythmias
      5. Central sleep apnea
      6. Baroreflex failure
      7. Horner’s syndrome
      8. Vertebrobasilar and lateral medullary (Wallenberg’s) syndromes
      9. Brainstem encephalitis
II. Autonomic Disorders with Spinal Cord Involvement
  1. Traumatic quadriplegia
  2. Syringomyelia
  3. Subacute combined degeneration
  4. Multiple sclerosis and neuromyelitis optica
  5. Amyotrophic lateral sclerosis
  6. Tetanus
  7. Stiff-person syndrome
  8. Spinal cord tumors
III. Autonomic Neuropathies
  1. Acute/subacute autonomic neuropathies
    1. Subacute autoimmune autonomic ganglionopathy (AAG)
    2. Subacute paraneoplastic autonomic neuropathy
    3. Guillain-Barré syndrome
    4. Botulism
    5. Porphyria
    6. Drug induced autonomic neuropathies-stimulants, drug withdrawal, vasoconstrictor, vasodilators, beta-receptor antagonists, beta-agonists
    7. Toxin-induced autonomic neuropathies
    8. Subacute cholinergic neuropathy
  2. Chronic peripheral autonomic neuropathies
    1. Distal small fiber neuropathy
    2. Combined sympathetic and parasympathetic failure
      1. Amyloid
      2. Diabetic autonomic neuropathy
      3. AAG (paraneoplastic and idiopathic)
      4. Sensory neuronopathy with autonomic failure
      5. Familial dysautonomia (Riley-Day syndrome)
      6. Diabetic, uremic, or nutritional deficiency
      7. Geriatric dysautonomia (age >80 years)
    3. Disorders of orthostatic intolerance: reflex syncope; POTS; prolonged bed rest; space flight; chronic fatigue
Abbreviations: BP, blood pressure; CNS, central nervous system; HR, heart rate; POTS, postural orthostatic tachycardia syndrome.

Multiple system atrophy (MSA) is a progressive neurodegenerative disorder comprising autonomic failure (OH and/or a neurogenic bladder) combined with either parkinsonism (MSA-p) or cerebellar signs (MSA-c), often with progressive cognitive dysfunction. Dysautonomia is also common in advanced Parkinson’s disease and in dementia with Lewy bodies.

Spinal cord injury may produce autonomic hyperreflexia affecting bowel, bladder, sexual, temperature-regulation, or cardiovascular functions. With spinal cord lesions above T6, increased autonomic discharges (autonomic dysreflexia) can be elicited by irritation of bladder, skin, or muscles. Bladder distention from palpation, catheter insertion, catheter obstruction, or urinary infection is a common and correctable trigger of autonomic dysreflexia. Dangerous increases or decreases in body temperature can result from an inability to experience the sensory accompaniments of heat or cold exposure below the level of injury.

Peripheral neuropathies affecting small myelinated and unmyelinated fibers of the sympathetic and parasympathetic nerves are the most common cause of chronic autonomic insufficiency (Chap. 196: Peripheral Neuropathies, Including Guillain-Barré Syndrome). Autonomic involvement in diabetes mellitus typically begins ∼10 years after onset of diabetes and slowly progresses. Diabetic enteric neuropathy produces gastroparesis, nausea and vomiting, malnutrition, achlorhydria, and bowel incontinence. Impotence, urinary incontinence, pupillary abnormalities, and OH may occur as well. Prolongation of the QT interval increases risk of sudden death. Autonomic neuropathy occurs in sporadic and familial forms of amyloidosis. Pts typically present with distal, painful polyneuropathy. Alcoholic polyneuropathy produces symptoms of autonomic failure when the neuropathy is severe, and autonomic involvement contributes to the high mortality rates associated with alcoholism. Attacks of acute intermittent porphyria (AIP) are associated with tachycardia, sweating, urinary retention, and hypertension; other prominent symptoms include anxiety, abdominal pain, nausea, and vomiting. BP fluctuation and cardiac arrhythmias can be severe in Guillain-Barré syndrome. Autoimmune autonomic ganglionopathy presents as the subacute development of autonomic failure with OH, enteric neuropathy (gastroparesis, ileus, constipation/diarrhea), flaccid bladder, loss of sweating, sicca complex, and a tonic pupil. Onset may follow a viral infection; serum antibodies to the α3 subunit of the ganglionic ACh receptor (α3AChR) are diagnostic, and some pts appear to respond to immunotherapy. Rare pts develop dysautonomia as a paraneoplastic disorder (Chap. 79: Neurologic Paraneoplastic Syndromes). There are five known hereditary sensory and autonomic neuropathies (HSAN I–V).

Botulism is associated with blurred vision, dry mouth, nausea, unreactive or sluggishly reactive pupils, urinary retention, and constipation. Postural orthostatic tachycardia syndrome (POTS) presents with symptoms of orthostatic intolerance (not OH), including shortness of breath, light-headedness, and exercise intolerance accompanied by an increase in heart rate but no drop in bp. Primary hyperhidrosis affects 0.6–1.0% of the population; the usual symptoms are excessive sweating of the palms and soles. Onset is in adolescence, and symptoms tend to improve with age. Although not dangerous, this condition is socially embarrassing; treatment with sympathectomy or local injection of botulinum toxin is often effective.

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