autonomic dysfunctions

8/20/2019 Autonomic Dysfunctions

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Disorders of the Autonomic Nervous System

Althea P. Tampos, M.D.


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Physiologic and Pharmacologic Considerations:

Has only sympathetic postganglionic fibers:1. Sweat glands

2. Cutaneous blood vessels

3. Hair follicles

Only preganglionic sympathetic innervation:

1. Adrenal medulla

Neurohumoral Transmission


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Neurohumoral Transmission Acetycholine (Ach)

Terminals of all preganglionic fibers

Skeletal muscle fibers

All postganglionic parasympathetic fibers:

Receptors:

1. Nicotinic – skeletal muscles; blocked by tubocurarine

2. Muscarinic – innervated organs; antagonized byatropine

Some postganglionic sympathetic (sweat glands)


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Neurohumoral Transmission

Noerpinephrine (NE) – postganglionic sympathetic fibers

Adrenergic receptors

1. Alpha – vasoconstriction, relaxation of gut, dilation of pupils

1. Alpha1 – postsynaptic

2. Alpha 2 – presynaptic, decrease release of transmitters

2. Beta – vasodilation, relaxation of bronchi, increased heartrate and contractility

1. Beta 1 – increases heart rate and contractility

2. Beta 2 – relaxes smooth muscles of bronchi, bloodvessels of skeletal muscles


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Central Regulation

1. Brainstem –1. Nucleus tractus solitarius – main visceral afferent

1. CN X (nodose ganglion) carry cardiovascular, respi-

2. CN IX (petrosal ganglion) ratory and GI afferents,baroreceptor and chemo-receptor info.

3. Caudal subnuclei – main receiving site for viscerosensoryfibers, receives baroreceptor and chemoreceptor info.

Projects to hypothalamus, amygdala, insular cortex,pontine and medullary nuclei


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Central Regulation

2. Cerebrum

1. Hypothalamus – integrates ANS and limbic system via:

1. Direct pathway

1. Ventromedial – prefrontal (temperature, sweating)2. Cingulate cortices - voluntary control of bladder and

bowel

3. Insular cortex – cardiac arrythmias, alteration ofvisceral functions

4. Limbic lobe – visceral brain2. Pituitary – endocrine glands


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Regulation of Blood Pressure

Baroreceptors (afferent components)

Sensitive to decrease in pulse pressure

1. Carotid sinus – rapidly responsive, responds to beat-to-beatchanges

2. Aortic arch – longer response time, discriminate only larger andmore prolonged alterations in pressure

Alterations in blood volume1. Right heart chamber

2. Pulmonary vessels

Afferent fibers – CN IX and X; motor nucleus of vagus nerve

Terminal ganglion – nucleus of tractus solitarius

Main sympathetic flow – via greater splanchnic nerve to celiacganglion

Renal Juxtaglomerular cells – release renin which stimulatesangiotensin production and influence aldosterone producion


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Regulation of bladder function

Parasympathetic innervation

S2-S4

Muscarinic acetycholine receptors of detrusor muscles

Sympathetic innervation

Detrusor muscle

T10-T12

From inferior mesenteric ganglia through hypogastricnerve to pelvic plexus

Supplies beta adrenergic receptors at bladder dome

Internal sphincter

Alpha receptors

Internal sphincter and base of basal trigone

External urethral and anal sphincter – innervated by pudendalnerve from S2-S4; Ventrolateral part of Onuf’s nucleus


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Central regulation of bladder functions:

Micturition centers:

1. Pontomesencephalic tegmentum

2. Frontal lobe ( paracentral region)


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Examination of ANS

Postural Hypotension

Fall in BP of >30mmHg systolic and 15mmHg diastolic

Increase heart rate

Failure of above responses – vagal dysfunction

Bladder Function Test

cystometogram


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Tests for vasomotor function:

Normal skin temperature : 31-33 ˚C Cold pressor test

immerse hand in cold water for 1 – 5 min

Increase systolic BP to 15-20 and diastolic BP to 10 -15mmHg

Sustained isometric contraction test

Hand grip for 5 min

Increase HR and BP

Test for GI function

Barrium swallow


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Test for sudomotor functions

Galvanic skin resistance test

Lacrimal function

Schirmer test – Normal: wet area in filter paper is15 mm

If < 15 mm suggest keratoconjunctivitis


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Acute Autonomic Paralysis

Dysautonomic Polyneuropathy

Pure Pandysautonomia

Both sympathetic and parasympathetic systems areaffected mainly at postganglionic level

Somatosensory and motors fibers are spared

Idiopathic

(+) antibodies against ganglionic acetylcholinereceptors


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Signs and symptoms:

1. Anhidrosis

2. Orthostatic hypotension

3. Paralysis of pupillary reflexes

4. Loss of lacrimation and salivation

5. Impotence

6. Impaired bladder and bowel dysfunction (urinary

retention, postprandial bloating, ileus orconstipation)

7. Loss of pilomotor or vasomotor responses in skin(flushing and heat intolerance)


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Treatment:

IVIg

Plasma exchange

Variants:

Sympathetic orthostatic hypotension

Postural orthostatic tachycardia syndrome


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Idiopathic Orthostatic Hypotension

Degenerative disease of middle and late adult life

Lesions involve

mainly postganglionic sympathetic neurons

Preganglionic lateral horn neurons of thoracic and spinalhorn neurons degenerate

Signs and symptoms:

1. Orthostatic hypotension

2. Impotence

3. Anhidrosis

4. Atonicity of bladder


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2 types (multiple system atrophy):

1. Postganglionic type

NE is decreased in supine and standing position becauseof failure of damaged nerve terminals to synthesize or

release catecholamines2. Central type

1. Striatonigral degeneration or Shy-Drager syndrome –autonomic failure was associated with Parkinsoniansyndrome and cytoplasmic inclusions in sympathetic

neurons

2. Olivopontocerebellar degeneration – involves stiatum,cerebellum,pons and medulla


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Treatment:

Sleep with elevation of head

Mineralocorticoids:

Fludrocortisone acetate

Midrodine

Elastic/compression stockings


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Peripheral Neuropathy With

Secondary Orthostaic Hypotension Acute and chronic peripheral neuropathies affect

autonomic fibers

Diabetes, alcoholic-nutritional, amyloid, GBS, heavymetal and toxic neuropathies

Hyponatremia maybe secondary to release of anti-diuretic hormone


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Diabetic Neuropathy

Impotence

Constipation

Diarrhea (especially at night)

Hypotonia of bladder Gastroparesis

Orthostatic hypotension

Sensory polyneuropathy

Argyll-Robertson pupils


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Pathophysiology

Vacuolization of sympathetic ganglionic neurons

Cell necrosis and inflammation Loss of myelinated fibers in vagi and white rami

communicantes

Loss of lateral horn cells in spinal cord


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Pathophysiology:

Deficiency of neurons in superior cervical ganglion andlateral horn of spinal cord

Mutation in gene IKAP Failure of embryonic migration or formation of first and

second order sympathetic neurons


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Autonomic Failure in Elderly

65 years and above

Orthostatic hypotension

Lability of temperature Loss of sewating of lower parts of body and

increased sweating of head and arms

Impotence and incontinence


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Horner or Oculosympathetic

Syndrome Triad:

1. Ptosis

2. Miosis

3. Anhydrosis Pathophysiology includes interruption of:

postganglionic sympathetic fibers along internal carotidartery

superior cervical ganglion

preganglionic fibers between their origin inintermediolateral horn cells (C8-T2) spinal segments andsuperior cervical ganglion

Descending , uncrossed hypothalamospinal fibers integmentum of brainstem


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Common causes:

1. Neoplastic or inflammatory involvement of cervicallymph nodes or proximal part of brachial plexus

2. Surgical or trauma to cervical structures

3. Carotid artery dissections

4. Syringomyelia or trauma of second thoracic spinalsegments

5. Infarcts or other lesions of lateral part of medulla


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Other manifestations:

Heterochromia iridis

Harlequin effect

Ross syndrome

Combination of segmental anhidrosis and Adie pupil


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Sympathetic and ParasympatheticParalysis in Tetraplegia and Paraplegia

Complete lesion in C4/C5 and upper thoracic (aboveT6)

Usual causes:

Traumatic necrosis of spinal cord

Infarction

Necrotic myelitis

Tumors

Acute cervical cord transection – abolishedsensorimotor, reflex, and autonomic functions ofspinal cord


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Spinal shock:

Acute cervical cord transection – abolishedsensorimotor, reflex, and autonomic functionsof spinal cord

Hypotension

Loss of sweating

Piloerection

Paralytic ileus and gastric atony

Paralysis of bladder

Decrease plasma epinephrine andnorepinephrine


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Mass reflex

Flexor spasms of legs and involuntaryemptying of bladder are associated with:

marked rise in BP

Bradycardia

Sweating

pilomotor reactions in parts below cervicalsegment (autonomic dysreflexia)


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Autonomic crises

Sympathetic storm

Abrupt over activity of sympathetic andparasympathetic nervous systems – hypertensionand midriasis coupled with signs of CNSexcitation

Maybe caused by drugs as:

Phenylpropanolamine Cocaine

Tricyclic antidepressants Cholinergic blockers


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Severe head injury with hypertensive cerebral

hemorrhage

Syndromes of unopposed sympathetic-adrenal medullaryhyperactivity

Mechanisms:

1. Outpouring of adrenal catecholamines with acutehypertension and tachycardia

2. Cushing response – brainstem mediated vasopressor reaction(hypertension, bradycardia, slow, irregular breathing)

3. Extreme hypertension, profuse diaphoresis, pupillary

dilatation usually arising during diencephalic autonomicseizures

Myocardial abnormalities maybe due to norepinephrineand cortisol surge


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Disorders of Sweating

Hyperhydrosis:

Results from overactivity of sudomotor nerve

Botulinum toxin

Interruption of postganglionic sympatheticfibers


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Raynaud Syndrome

Episodic, painful blanching of fingers probably dueto digital artery spasm

Age of onset: 14 years

Pallor, cyanosis, and rubor discoloration of fingersor toes

Brought about by cold or emotional stress

Numbness, paresthesias, burning sensation

Maybe associated with connective tissue diseases:scleroderma, rhematoid disease

Maybe due to obstructive arterial disease, minortrauma


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Treatment:

Avoidance of cold exposure

Drugs that an cause vasoconstriction ( clonidine)

Calcium channel blockers (nifedipine)


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Disturbances of bladder function

complete destruction of cord below T12

No awareness of state of fullness, voluntary initiation ofmicturition is impossible; bladder distends as urine

accumulates until there is overflow incontinence, voidingis possible only by Crede maneuver, saddle aneshesia,loss of bulbocavernosus and anal reflexes as well astendon reflexes

Disease of sacral motor neurons in spinal gray

matter, anterior sacral roots or peripheral nervesinnervating the bladder

Same as in I but sacral and bladder sensations are intact


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Frontal lobe incontinence

Supranuclear hyperactivity of detrusor and precipitantevacuation

Nocturnal enuresis

Urinary incontinence during sleep

Delay in acquiring inhibition of micturition

Interruption sensory afferent fibers from bladder


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Therapy of disordered micturition:

Bethanicol – for flaccid bladder paralysis; contractsdetrusor by stimulating its muscarinic cholinergicreceptors

Propatheline, atropine – for spastic bladder paralysis; act

as muscarinic antagonist

Alpha1synpathomimetic blocking drugs (terazosin,doxazosin) – relax urinary sphincter and facilitate voiding

Intermittent catheterization

Implantation of sacral anterior root stimulator


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Disturbances of Bowel Function

Congenital Megacolon ( Hirschsprung Disease)

Affects mainly male infants and children

Congenital absence of ganglionic cells in the myentericplexus

Often involves internal anal sphincter and rectosigmoid

Most serious complication: enterocolitis and has highmortality

autonomic dysfunctions

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