Autonomic nervous system testing

all tests about autonomic nervous system

1. AUTONOMIC NERVOUS SYSTEM TESTING Presentation By: Dr. Vaibhavi Parmar Date: 6th Nov 2017

2. ANS made up of preganglionic & postganglionic neurons. Cell bodies of preganglionic neurons situated in lateral gray column of spinal cord & motor nuclei of 3 rd , 7 th , 9 th And 10 th cranial nerve.

3. FUNCTIONS: Responsible for homeostatic control like blood pressure & body temperature regulation Urinary function, Pupil size Sweating, sexual function & Digestion.

4. ANS dysfunction leads to orthostatic intolerance and syncope, abnormal sweating, Constipation, diarrhea & incontinence Sexual dysfunction Dry eyes and dry mouth Less obvious symptoms such as fatigue, problems with visual accommodation and heat intolerance.

5. Indication for testing ANS Chronic fatigue syndrome Fibromyalgia Anxiety & psychological disorders Sleep apnea Allergic conditions Hypertension Spinal cord injury

6. Examination 1) General observation Body built State of nutrition and any abnormal configurations The skin and mucous membrane, perspiration Hair and nails Salivation & lacrimation

7. ANS Reflexes Many reflexes are there some may be classify as mucous membrane and orifical reflexes others are as true visceral reflexes. ANS reflexes that are functions of various cranial nerves these are pupillary, salivary, sneeze, sucking, cough, vomiting, carotid sinus and oculocardinal reflex. There are many reflexes to check ANS some are Subcostogastric or cutaneogastric Bulbocavernous reflex Mass reflex Emotional reflex

8. AUTONOMIC FUNCTION TESTS A ] Tests for cardiac and vascular autonomic regulation Heart rate & blood pressure recording: Beat to beat analysis It can be documented on an ECG HR ( R – R/min) = sweep speed( mm/s) R-R interval in mm *60 Blood pressure is recorded from standard sphygmomanometer

9. 2) cardiovascular response to standing and 30:15 R-R ratio: BP changes during standing To assess integrity of sympathetic system & HR changes of PNS function. Tech: HR & BP measure in resting for 20 mins then serially for 1-3 min after standing. ECG allows determination of 30:15 R-R ratio. Helpful in diagnosis of orthostatic hypotension, orthostatic tachycardia. Normal values: 10 -29 yrs : 1.17 30-49 yrs : 1.09 50-65 yrs : 1.03

10. 3 ) Head up tilt table testing: Indication: to test integrity of autonomic cardiovascular and neurocardiogenic reflexs . Early response reflects – autonomic cardiovascular ( 30-60 sec ) Late response reflects – neurocardiogenic reflexs ( 30-60 min ) Method: starting position supine rest – at baseline BP & ECG recorded. – Then position into incline 80 degrees from supine with footrest & monitored for 3 -5 mins. ( ECG conti & BP every 1 min ) Orthostatic Hypotension Neurocardiogenic syncope ( bezold - jarisch reflex)

11. 4) Heart rate variation with respiration: (sinus arrhythmia , R-R interval analysis) Indication: to test the integrity of parasympathetic cholinergic function. The variation of HR with respiration known as sinus arrhythmia. Mediated by vagal innervation of heart. Method: No. of protocols for quantifying SA have been followed. Simple protocol is to have the patient supine with head elevated to 30 degrees and breath deeply at a rate of 6/min allows 5s each inspiration & expiration. Encourage to hyperventilate – hypocapnia – reduce variation. The E : I ratio or index = average of 6 ratios of the longest R-R interval in each 6 rep with shortest R-R interval in each 6 rep.

12. AGE ( years) NORMAL VALUES(E:I index) 16-20 >1.23 21-25 >1.20 26-30 >1.18 31-35 >1.16 36-40 >1.14 41-45 >1.12 46-50 >1.11 51-55 >1.09 56-60 >1.08 61-65 >1.07 66-70 >1.06 71-75 >1.06 76-80 >1.05

13. 5) Valsalva maneuver and Valsalva ration: Study of HR changes during VM allows assessment of parasympathetic cholinergic function. Valsalva maneuver has 4 phases: It consist of repiratory strain which increases intrathoracic and intraabdominal pressure and alters hemodynamic and cardiac functions. Method: patient supine with head elevated to 30 degrees – strain for 15s against 40mmHg by blowing into a mouthpiece attached to sphygmomanometer – following cessation patient relaxes & breathes at normal rate. ECG monitored during strain and 30-45 sec following release. The ration of max to min HR is calculated, procedure is repeated to 3 times with a brief rest.

14. Failure of HR to increase during strain suggest to sympathetic dysfunction and failure of rate to slow during BP overshoot suggests a parasympathetic disturbances. AGE ( years) Normal values 10-40 1.5 41-50 1.45 51-60 1.45 61-70 1.35

15. MISELLANEOUS TESTS: 1) BP response to mental stress: Mental stress such as arithmetic, sudden noise or emotional stress – increases BP & HR – excessive sympathetic outflow. Useful for measuring sympathetic efferent functions. Advantage of not requiring direct afferent stimulation but this lacks sensitivity

16. 2) Cold pressure test: The patient is submerge one limb into ice water for 60s. Rise of systolic BP by 15-20mmHg & diastolic by 10mmHg. Patient find difficulty to maintain limb into cold water for require time. The test lacks sensitivity – many normal subjects does not have a significant rise in BP on cold immersion.

17. TESTS FOR THERMOREGULATORY FUNTIONS Thermoregulatory sweat test: Indication: evaluation of sympathetic cholinergic functions in various disorders affecting the ANS. It evaluate overall autonomic regulation of body temperature esp cooling by providing a physiologic stimulus, heat and then recording the body’s ability to dissipate it. Method: the patient is placed in a controlled heat environment of about 45-60 degree and relative humidity od 45-50 %. The patient has a indicator powder, e.g. alizarin red mixed with corn-starch and sodium carbonate applied to body. The sweating reaches to max after 30-45 mins. Pattern and % of sweating area of body are recorded.

18. Normally it is generalised, symmetrical and there is variable involvement of proximal limbs. Abnormal patterns include distal anhydrosis, segmental, or regional anhydrosis and focal or global anhydrosis. Advantage: sensitive, physiological and assess overall thermoregulatory function and maps the topography of sweating pattern. Disadvantage : time consuming, messy, require special equipment and semi- quantitative.

19. 2) Sweat imprint test: It measures sweat output at a fixed time after the stimulus by visualizing and quantifying sweat droplets. Sweat gland stimulated by cholinergic agonist or by axon reflex. Method: stimulating agents such as Ach, pilocarpine can be injected intradermally or applied through iontophoresis. – after stimulation sweat output is visualized by starch iodine solution. Sweat droplets are recorded as hole or imprints which can be quantified by various methods. Advantage: sensitive, reproducible, accurate and quantitative. Disadvantage: expensive, require special equipment. In diabetic 24-36% patients had abnormality low sweat function in hand and 56-60% in feets .

20. Tests for exocrine and pupillary functions: Indication: to study pupillary function for evaluation of abnormalities such as horner’s syndrome, Adie’s syndrome, anisocoria , and syndrome of light near dissociation. Testing of lacrimation and salivation may be useful in dry eyes and dry mouth. Method: pilocarpine 0.125% or methacholine 2.5% agents Causes minimal constriction but in presence of parasympathetic denervation there is denervation hypersensitivity and pupils constricted.

21. Lacrimation measured by Schirmer’s test and tear osmolarity . Salivation tested by having the patient to chew a series of 5 gauze pads for 1 min each for 5 min. it should conducted after wiping sublingual gutter dry. Saliva production is calculated by subtracting pretest weight from post test weight of gauze pads. Normal value > 7.5ml/5min.

22. Tests for gastrointestinal autonomic regulation: Various activities such as peristalsis, absorption, secretion and sphincter coordination are controlled by these system. Videofluroscopy and pharyngoesophgeal studies help to identify causes of dysphagia. A barium swallow – in case of dysautonomic states.

23. Tests for genitourinary autonomic regulation: In patients with urinary and sexual dysfunction autonomic testing indicated. Cystometrogram measures intravesical pressure. Bladder atony determined by urinary catheterization immediately after voluntary voiding.

24. REFERENCES: The Neurologic Examination 5 th edition by Armin F. Haerer Clinical Neurophysiology 2 nd edition by UK M isra and J. Kalita Clinical autonomic disease and the role of autonomic testing By John C. Oakley, M.D., Ph.D Nov 2007 Autonomic dysfunction and autonomic neuropathy Emedicine - Wiki for Australian Emergency Medicine Doctors 2012