Autonomic nervous system.

1. Autonomic Nervous System
Testing (SSR)
By: Syed Irshad Murtaza
Neurophysiology Dept
AKUH Karachi
18th
Dec 2014

4. Introduction
• The autonomic nervous system is a complex neural
network maintaining internal physiologic homeostasis,
especially, or
• The autonomic nervous system is a control system
that acts largely unconsciously and regulates heart
rate, digestion, respiratory rate, pupillary response,
sexual arousals and urination. This system is the
primary mechanism in control of the flight-or-fight
response and its role is mediated by two different
components

5. autonomic nervous system
The autonomic nervous system is the subdivision
of the peripheral nervous system that regulates
body activities that are generally not under
conscious control
Autonomic nervous system innervate
• smooth muscle (eg, blood vessels, gut wall,
urinary bladder)
• cardiac muscle
• glands (eg, sweat glands, salivary glands

6. The two main component of ANS
– the sympathetic and
– Parasympathetic
–1. Sympathetic nervous system
–The sympathetic nervous system originates
in the spinal cord and its main function is to
activate the physiological changes that
occur during the fight or flight response.
This component of the autonomic nervous
system utilizes and activates the release of
norepinephrine in the reaction.

7. 2. Parasympathetic nervous system
–The parasympathetic nervous system
originates in the spinal cord
and medulla and works in concert with the
sympathetic nervous system. Its main
function is to activate the "rest and digest"
response and return the body
to homeostasis after the fight or flight
response. This system utilizes and activates
the release of the
neurotransmitter acetylcholine

8. WHERE THEY COME FROM
•
Parasympathetic:
craniosacral
Sympathetic:
thoracolumbar

11. Symptoms of Autonomic Dysfunction
– orthostatic hypotension
– heat intolerance
– painful feet
– constipation
– diarrhea
– incontinence
– sexual dysfunction
– dry eyes
– dry mouth
– loss of visual accommodation
– pupillary irregularities
– extreme fatigue, tachycardia, Parkinson's-like symptoms, gastrointestinal
tract distress, anhidrosis, and hyperhidrosis

12. DIVISION OF ANS
•Parasysmpathetic: routine
maintenance
“rest &digest”
Sympathetic: mobilization &
increased metabolism
“fight, flight or fright”

13. Sympathetic nervous system
• The sympathetic division is the “fight-or-flight” system
• Involves E activities – exercise, excitement, emergency, and
embarrassment
• Non-essential activities are dampened (GI/urinary)
• Promotes adjustments during exercise – blood flow to
organs is reduced, flow to muscles is increased
• Its activity is illustrated by a person who is threatened
– Heart rate increases, and breathing is rapid and deep
– The skin is cold and sweaty, and the pupils dilate
– Bronchioles dilate…increasing ventilation, delivering more oxygen
to cells
– Constriction of visceral & cutaneous bv’s (blood is shunted to
skeletal mm)

14. Parasympathetic Nervous System
• Works to save energy, aids in digestion, and
supports restorative, resting body functions.
– Decrease in heart rate
– Increased gastro intestinal tract tone and
peristalsis
– Urinary sphincter relaxation
– Vasodilation – decrease in blood pressure

15. Diseases causing Autonomic Dysfunction
• Diseases of the central nervous system
• Diseases of the peripheral nervous system

16. Diseases of the CNS
• Neurodegenerative diseases
– Multiple system atrophy
– Parkinson’s disease
• Trauma
• Vascular diseases
• Neoplastic diseases
• Metabolic diseases
– Wernicke’s encephalopathy
– Cobalamin deficiency (Vitamin B12 and Cbi)
• Multiple sclerosis
• Medications

17. Diseases of the PNS
• Neuropathies
– Diabetes
– Guillain–Barre´ syndrome
– Lyme disease
– Human immunodeficiency virus infection
– Leprosy
– Acute idiopathic dysautonomia
– Amyloidosis
– Porphyria
– Uremia
– Alcoholism
– Familial neuropathies such as Riley–Day syndrome, Fabry’s disease, and
familial amyloidosis
• Diseases of the presynaptic neuromuscular junction
such as botulism

18. Levels of ANS Control
• The hypothalamus is the main integration center of
ANS activity
• Subconscious cerebral input via limbic lobe
connections influences hypothalamic function
• Other controls come from the cerebral cortex, the
reticular formation, and the spinal cord
• Centers of the hypothalamus control:
– Heart activity and blood pressure
– Body temperature, water balance, and endocrine
activity
– Emotional stages (rage, pleasure) and biological drives
(hunger, thirst, sex)
– Reactions to fear and the “fight-or-flight” system

19. Levels of ANS Control

20. Testing Autonomic Function in Clinical
Neurophysiology
• Tests of autonomic function
– clinically useful
– well validated
– sufficiently straightforward to perform routinely
– unambiguous interpretation

21. Testing Autonomic Function in Clinical
Neurophysiology
• The specific aims of clinical and electrodiagnostic
autonomic evaluation are
– to diagnose autonomic failure or dysfunction
– to define the severity and distribution of autonomic failure
– to define the site of the lesion

22. Testing Autonomic Function in Clinical
Neurophysiology
• Tests should be an extension of the clinical
autonomic history and examination
• These tests assess end organ function, so the
conclusions are largely extrapolative

23. Testing Autonomic Function in Clinical
Neurophysiology
• Optimal evaluation requires
– appropriate patient selection
– adequate patient preparation
– an adequate panel of autonomic tests

25. Preparation of the Patient
• No food, coffee, or nicotine are permitted for 3
hours before the study
• Medications are stopped for five half lives
– anticholinergic (including antidepressant, antihistamine,
and over-the-counter cough and cold medication)
– sympathomimetic and
– parasympathomimetic agents are forbidden for 48 hours

26. Evaluation of cardiovagal function using
heart rate recordings
• Heart rate response to deep breathing (HRDB)
• Valsalva ratio

27. Protocol of HRDB
• Supine position with the head elevated to 30°
• Patient breathes deeply at six respirations per minute,
allowing 5 s for inspiration and 5 s for expiration
• The maximal and minimal heart rates within each respiratory
cycle and the mean variation are determined.

28. Protocol of HRDB
• The E to I ratio can be calculated as
– the sum of the six longest R-R intervals of each of the six
respirations divided by the sum of the six shortest R-R
intervals.

31. Valsalva Ratio
• Normal Responses
– The Valsalva maneuver consists of respiratory strain which
increases intrathoracic and intraabdominal pressures and
alters hemodynamic and cardiac functions.

32. Protocol of Valsalva Ratio
• The patient is supine or with head slightly elevated
to about 30°.
• Most labs have the patient strain against 40 mmHg
applied for 15 s by blowing into a mouthpiece
attached to a sphygmomanometer.
• The system should have a slow leak to ensure the
patient strains continuously
• Following cessation of the Valsalva strain, the patient
relaxes and breathes at a normal comfortable rate.

33. Protocol of Valsalva Ratio
• The ECG is monitored during the strain and 30–45 s following
its release.
• The maximal heart rate of phase II actually occurs about 1 s
following cessation of the strain
• The minimal heart rate occurs about 15–20 s after releasing
the strain.

34. Protocol of Valsalva Ratio
• The ratio of the maximal-to-minimal heart rate is determined
as a simple ratio.
• After a brief rest, the maneuver is repeated until three ratios
are determined.

37. Sympathetic skin response (SSR)
• Thermoregulation is controlled by the sympathetic nervous
system, with the parasympathetic system playing a minor role
• Sympathetic sudomotor cholinergic fibers innervate sweat
glands to regulate evaporative heat loss

38. Indications of SSR
• Progressive autonomic failure syndromes
• Peripheral neuropathies where autonomic or other
small fiber involvement is suspected
• Distal small fiber neuropathies
• Diseases with sympathetically maintained pain

39. Protocol of SSR
• Low frequency (high pass) filter 0.1 or 0.5 Hz
• High-frequency (low pass) filter of 500 or 1000 Hz
• The gain 500 µV /Div
• The sweep 0.5-1 s/Div
• Temperatures are standardized to over 30°C, preferably over
32°C

40. Protocol of SSR
• The active electrodes are placed in the palm or sole and the
reference over the dorsum of the respective body part
• Electrodermal activity is brought out either directly or reflexly
(electric depolarization of a sensory nerve, startling auditory
sound or deep inspiratory gasps)
• Averaging should not be performed

41. Normal responses of SSR
• The morphology of the potentials are mono-, bi-, or triphasic
• Potentials are symmetric in homologous body regions.
• The potentials in the hands have larger amplitudes and
shorter latencies than those in the feet.
• Generally absent responses are considered to be abnormal

43. Normal Values of SSR
• The SSR is age dependent
– present in both hands and both feet in subjects under the
age of 60 years
– only 50% of feet and 73% of hands in subjects older than
60years
• Mean latency in hands is 1.5 s, mean amplitude in
hands is 0.450 mV, mean latency in feet is 1.9 s, and
mean amplitude in feet is 0.15 mV

44. Advantages of SSR
• Sensitive, reproducible, semiquantitative, simple,
fast, and readily obtained on most electrophysiologic
equipment
• SSR is comparable in its sensitivity to the quantitative
sudomotor axon reflex test (QSART) for the
detection of autonomic dysfunction

45. Disadvantages of SSR
• Only semiquantitative
• May be difficult to elicit or be habituated and
thereby be mistaken as abnormal