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The autonomic nervous system dysfunction
Tamer Belal,MD.PHD
Neurology Department
Mansoura University Hospitals
Autonomic system Divisions
Sympathetic nervous system (fight or flight)
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Diverts blood flow away from the gastro-intestinal (GI) tract and
skin via vasoconstriction
Blood flow to skeletal muscles and the lungs is enhanced (by as
much as 1200% in the case of skeletal muscles)
Dilates bronchioles of the lung, which allows for greater alveolar
oxygen exchange
Increases heart rate and the contractility of cardiac cells
(myocytes), thereby providing a mechanism for enhanced blood flow
to skeletal muscles
Dilates pupils and relaxes the ciliary muscle to the lens, allowing
more light to enter the eye and far vision
Provides vasodilation for the coronary vessels of the heart
Constricts all the intestinal sphincters and the urinary sphincter
Inhibits peristalsis
Stimulates orgasm
Autonomic system Divisions
Parasympathetic nervous (Rest and digest)
Dilate blood vessels leading to the GI tract, increasing blood flow
Constrict the bronchiolar diameter when the need for oxygen has
diminished
Dedicated cardiac branches of the vagus and thoracic spinal
accessory nerves impart parasympathetic control of the heart
During accommodation, causes constriction of the pupil and
contraction of the ciliary muscle to the lens, allowing for closer vision
Stimulates salivary gland secretion, and accelerates peristalsis,
mediating digestion of food and, indirectly, the absorption of nutrients
The PNS is also involved in the erection of genital tissues via the
pelvic splanchnic nerves 2–4.
The PNS is responsible for stimulating sexual arousal
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Central control of the
Autonomic NS
Amygdala: main limbic
region for emotions
-Stimulates sympathetic activity,
especially previously learned
fear-related behavior
-Can be voluntary when decide
to recall frightful experience cerebral cortex acts through
amygdala
-Some people can regulate some
autonomic activities by gaining
extraordinary control over their
emotions
Hypothalamus: main
integration center
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Reticular formation: most
direct influence over
8 function
autonomic
Classification
Localized disorders: Affect an organ or region of the body but they
may be part of generalized disease, such as gustatory sweating in
diabetes mellitus
Generalized disorders: often affect systems, such as those involved
in blood pressure control and thermoregulation. They can be primary
when the cause is often unclear, or secondary when associated with
a specific disease or its complications
Drugs are a common cause of autonomic dysfunction, either because
of their pharmacological effects or because of autonomic nerve
damage.
Damage to the autonomic nervous system often causes irreversible
abnormalities
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Clinical features
Clinical features of autonomic disease cover a wide spectrum and
result from Underactivity or Overactivity.
•Sympathetic adrenergic failure causes orthostatic (postural)
hypotension and ejaculatory failure in the male;
• Sympathetic cholinergic failure causes anhidrosis;
• Parasympathetic failure causes dilated pupils, fixed heart rate,
sluggish urinary bladder, atonic large bowel and, in the male,
erectile failure
In some disorders, particularly in neurally mediated syncope, there
may be a combination of over-activity and under-activity, with
bradycardia caused by increased parasympathetic activity and
hypotension brought about by withdrawal of sympathetic activity
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System
Cardiovascular
Postural hypotension
Lability of blood pressure
Tachycardia
Supine hypertension
Paroxysmal hypertension
Bradycardia
Hypohidrosis or anhidrosis
Gustatory sweating
Hyperpyrexia
Hyperhidrosis
Xerostomia
Gastric stasis
Constipation
Dysphagia
Dumping syndromes
Diarrhoea
Nocturia
Urgency
Retention
Frequency
incontinence
Erectile failure
Retrograde ejaculation
Ejaculatory failure
Pupillary abnormalities
Alachryma
Ptosis
Abnormal
ingestion
Sudomotor
Heat intolerance
Alimentary
Urinary
Sexual
Eye
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lachrymation
Clinical manifestations of autonomic dysfunction
with
food
Cardiovascular system
Orthostatic hypotension
Orthostatic or postural hypotension is defined as a fall in blood
pressure of 20 mmHg systolic or 10 mmHg diastolic on sitting,
standing or during 60° head-up tilt.
In neurogenic orthostatic hypotension, levels of plasma
noradrenaline do not rise when upright, as occurs in normal
subjects .
Hypoperfusion of organs, especially above heart level such as the
brain, cause the malaise, nausea, dizziness and visual
disturbances that often precede loss of consciousness.
A variety of symptoms result from hypoperfusion elsewhere. Neck
pain in a coat-hanger distribution (suboccipital and shoulder
regions) differs from other types of neck pain by developing when
upright. It is relieved by sitting or lying flat
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Cerebral hypoperfusion
Symptoms
of orthostatic
hypotension
and impaired
perfusion
Dizziness
Visual disturbances
Blurred – tunnel
Scotoma
Greying out – blacking out
Colour defects
Syncope
Cognitive deficits
Muscle hypoperfusion
Paracervical and suboccipital (‘coat-hanger’) ache
Lower back/buttock ache
Subclavian steal-like syndrome
Renal hypoperfusion
Oliguria
Spinal cord hypoperfusion
Non-specific
Weakness, lethargy, fatigue
Fall
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Cardiovascular system
Syncope without orthostatic hypotension
Syncope has many causes (autonomic, cardiac, neurogenic
and metabolic). Autonomic causes of syncope without
orthostatic hypotension include neurally mediated syncope,
where there is transient hypotension and bradycardia. There
are three major forms: vasovagal syncope, carotid sinus
hypersensitivity and situational syncope. Blood pressure
falls because of sympathetic withdrawal while heart rate falls
because of increased vagal activity.
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Cardiovascular system
Orthostatic intolerance with posturally induced tachycardia
When orthostatic intolerance occurs without orthostatic
hypotension, but with a substantial rise in heart rate (of over
30 beats/ minute), the term ‘postural tachycardia syndrome’
(PoTS) is used. It predominantly affects women below the
age of 50 years. Symptoms include marked dizziness on
postural change or modest exertion; syncope may occur.
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Cardiovascular system
Hypertension
Unlike hypotension, hypertension typically causes few
symptoms other than headaches – and these only
occasionally.
• In high spinal cord lesions, severe paroxysmal
hypertension can develop as part of autonomic dysreflexia,
when an uninhibited increase in spinal sympathetic activity
is caused by contraction of the urinary bladder, irritation of
the large bowel, noxious cutaneous stimulation or skeletal
muscle spasms.
• In tetanus, hypertension in ventilated patients may be
precipitated by muscle spasms or tracheal suction.
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Cardiovascular system
Hypertension
• Intermittent hypertension may occur in the Guillain–Barré
syndrome, porphyria, posterior fossa tumours and
phaeochromocytoma , often without any evident precipitating
cause.
•Hypertension in the supine position may complicate
orthostatic hypotension in pure autonomic failure (PAF). The
mechanisms include impaired baroreflex activity,
adrenoceptor supersensitivity, an increase in central blood
volume because of a shift from the periphery and the effects
of drugs used to prevent orthostatic hypotension
.
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Cardiovascular system
Heart rate disturbances
Bradycardia, along with hypertension, may occur in cerebral
tumours with or without raised intracranial pressure and
during autonomic dysreflexia in high spinal cord injuries
In PoTS, tachycardia usually is associated with head-up
postural change and exertion
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Sudomotor system
Anhidrosis or hypohidrosis is common in PAF and
differences in sweating may first be noticed during exposure
to warm temperatures
Alimentary system
Reduced salivation and a dry mouth (xerostomia) occur in
autonomic disease. Constipation is common in PAF.
Diarrhoea also may occur as result of overflow. Diarrhoea,
especially at night, can be a distressing problem in diabetes
mellitus
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Kidneys and urinary tract
Nocturnal polyuria is a frequent symptom in PAF. The causes
include restitution of blood pressure sometimes to elevated
levels while supine, redistribution of blood from the
peripheral into the central compartment. Autonomic disease
can cause urinary frequency, urgency, incontinence or
retention. Ureteric reflux predisposes to renal damage,
especially in the presence of infection
Sexual function
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Failure of erection ( parasympathetic damage) may cause
impotence. Retrograde ejaculation may occur, especially if
there are urinary sphincter abnormalities. Priapism resulting
from abnormal spinal reflexes may occur in patients with
spinal cord lesions.
Eyes and lacrimal glands
Mild ptosis is part of Horner’s syndrome. pupillary abnormalities
may occur with autonomic involvement, miosis in Horner’s
syndrome and dilated myotonic pupils in Holmes–Adie syndrome
Impaired tear production may occur in PAF, sometimes as part of a
presumed sicca or Sjögren’s syndrome, along with diminished
salivary secretion. Excessive and inappropriate lacrimation occurs
in crocodile tears syndrome (gusto-lacrimal reflex)
Respiratory system
Involuntary inspiratory sighs, stridor and snoring of recent onset
are more frequent . Nocturnal apnoea is caused by involvement of
brainstem respiratory centres
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Facial and peripheral vascular changes
Facial pallor with an ashen appearance with fall of pressure
in postural hypotension, Restoration of colour follows
promptly on assuming the supine position
In longstanding tetraplegia, hypertension during autonomic
dysreflexia is often accompanied by fl ushing and sweating
over the face and neck
Harlequin syndrome there is vasodilatation and anhidrosis
on one side of the face caused by sympathetic impairment,
with sparing of the pupil.
Raynaud’s phenomenon may be seen in both PAF and MSA,
for uncertain reasons.
In erythromelalgia there is limb discomfort with vascular
changes
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Clinical examination
The combination of a detailed history and physical
examination is crucial in determining if autonomic disease is
present, in ascertaining the probable underlying diagnosis,
and also for interpreting the results of autonomic tests in the
context of the associated disorder
Measurement of blood pressure, both lying and standing (or
sitting), is needed to determine if orthostatic hypotension is
present, as is recording the pulse rate changes
in patients with PoTS
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The extent and distribution of the neurological abnormalities
provide important clues to underlying central or peripheral
autonomic disorders. Examination of other systems, as in
hepatic disease or diabetes, is necessary along with
urine testing for glucose and protein
Investigations
The aims of investigations in autonomic dysfunction are
twofold.
The first relates to diagnosis
The second is to understand
the pathophysiological basis
of disturbed autonomic
function, as this often forms
the basis of treatment
strategies and their
evaluation.
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Investigations
Cardiovascular
Pressor stimuli* (isometric exercise, cold pressor,
mental arithmetic)
Head-up tilt (60º);* standing;* Valsalva maneouvre
Heart rate responses – deep breathing,*
hyperventilation,* standing,*
Liquid meal challenge
Exercise testing
Carotid sinus massage
Plasma noradrenaline: supine and head-up tilt or
standing
Noradrenaline: alpha-adrenoceptors,
Cardiac sympathetic innervation
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Outline of investigations in autonomic disease
Endocrine
Clonidine alpha-2 adrenoceptor agonist: noradrenaline
suppression; growth hormone stimulation
Sudomotor
Central regulation thermoregulatory sweat test
Sweat gland response to intradermal acetylcholine,
quantitative sudomotor reflex test, localized sweat test
Sympathetic skin response
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Outline of investigations in autonomic disease
Gastrointestinal
Video-cine-fluoroscopy, barium studies, endoscopy,
gastric emptying studies,
lower gut studies
Renal function and urinary tract
Day and night urine volumes and sodium/potassium
excretion
Urodynamic studies, intravenous urography,
ultrasound examination,
sphincterelectromyograph
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Outline of investigations in autonomic disease
Sexual function
Penile plethysmography
Intracavernosal papaverine
Respiratory
Laryngoscopy
Sleep studies to assess apnoea and oxygen
desaturation
Eye and lacrimal function
Pupil function, pharmacological and physiological
Schirmer’s test
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Outline of investigations in autonomic disease
Management
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Management strategy in autonomic failure
Management
Approaches to
management of orthostatic
hypotension
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Thank You
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