EVALUATING PERIPHERAL AND AUTONOMIC NERV

EVALUATING PERIPHERAL AND AUTONOMIC NERVOUS SYSTEM : 

EVALUATING PERIPHERAL AND AUTONOMIC NERVOUS SYSTEM SPEAKER– ARINDAM PANDE CHAIRPERSON– DR. GAUTAM GUHA

ORGANIZATION OF THE NERVOUS SYSTEM : 

ORGANIZATION OF THE NERVOUS SYSTEM BRAIN SPINAL CORD CENTRAL NERVOUS SYSTEM (CNS) PERIPHERAL NERVOUS SYSTEM AFFERENT NERVES EFFERENT NERVES EXTERO- RECEPTORS INTERO- RECEPTORS SOMATIC AUTONOMIC EFFECTOR ORGANS SKELETAL MUSCLES SMOOTH AND CARDIAC MUSCLES AND GLANDS

PNS__ORGANIZATION : 

PNS__ORGANIZATION PNS includes all neural structures lying outside the pial membrane Dorsal and ventral nerve roots; dorsal root ganglia; brachial and lumbosacral plexus; cranial nerves; and other sensory, motor, autonomic, or mixed nerves Exception- optic nerves & olfactory bulbs

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Structures outside the brain and spinal Cord (CNS) Peripheral Nervous System

SYMPTOMATOLOGY OF PERIPHERAL NERVE DISEASES : 

SYMPTOMATOLOGY OF PERIPHERAL NERVE DISEASES Number of motor, sensory, reflex, autonomic, and trophic symptoms and signs Grouping them into syndromes helps in clinical diagnosis Both sensory and motor function impairment in most polyneuropathies, but one may be affected more than the other

IMPAIRMENT OF MOTOR FUNCTIONS : 

IMPAIRMENT OF MOTOR FUNCTIONS Temporary weakness- anaesthetic agents, nerve toxins, cooling, ischemia Persistent impairment- segmental demyelination, axonal interruption, destruction of motor neurons Degree of weakness proportional to the number of alpha motor neurons affected Characteristic distribution of weakness in polyneuropathies Denervation atrophy- max degree in 90-120 days (75-80% ? in muscle volume)

TENDON REFLEXES : 

TENDON REFLEXES ? or loss- invariable sign in peripheral nerve diseases Exception- small fiber neuropathy Reflexes can ? out of proportion to weakness (involvement of afferent fiber of muscle spindles)

FASCICULATIONS, CRAMPS AND SPASMS : 

FASCICULATIONS, CRAMPS AND SPASMS Less important findings Myokymia, continuous muscle activity, neuromyotonia – upon recovery from mild motor polyneuropathy

SENSORY LOSS : 

SENSORY LOSS In polyneuropathy, sensory loss > motor dysfunction Simultaneous all modality Vs one modality out of proportionate Dissociative sensory loss Proprioception- loss of vibratory sense > position & tactile sense

PARESTHESIA AND DYSESTHESIAS : 

PARESTHESIA AND DYSESTHESIAS Terms used interchangeably to describe unpleasant, unusual, or abnormal sensations such as burning or cutting pain, electrical shock-like sensations, tingling, pins and needles, formication, prickly feelings such as limb falling asleep or cramp like sensations

SENSORY ATAXIA AND TREMOR : 

SENSORY ATAXIA AND TREMOR Basis of ataxia of gait and limb movement- proprioceptive deafferentation with retention of reasonable motor function Fast frequency type action tremor in certain phases of polyneuropathy

DEFORMITY AND TROPHIC CHANGES : 

DEFORMITY AND TROPHIC CHANGES Feet, hands and spine deformity- if disease begins in childhood, due to disproportionate weakness of two groups of muscles Analgesia of distal parts ? susceptibility to burns, pressure sores and other injuries which are easily infected and heal poorly Painless loss of digits and formation of planter ulcers (mal perforant du pied)- due to chronic subcutaneous and osteomyelitic infection ? hair growth in denervated areas

AUTONOMIC DISORDERS : 

AUTONOMIC DISORDERS Usually, loss of autonomic function in the same zone as sensory loss in any neuropathy involving sensory nerves (not true in radicular diseases) Anhidrosis & orthostatic hypotension- two most frequent manifestations

APPROACH TO THE PATIENT : 

APPROACH TO THE PATIENT Establishing the existence of disease of PNS Ascertaining its nature and the possibilities of treatment

ESTABLISHMENT OF EXISTENCE OF DISEASE OF PNS : 

ESTABLISHMENT OF EXISTENCE OF DISEASE OF PNS Initial symptoms often intermittent, examination can be normal Sensory symptoms usually precedes motor

DISTRIBUTION : 

DISTRIBUTION Mononeuropathy, multiple mononeuropathy (mononeuritis multiplex), polyneuropathy, polyradiculopathy, or plexopathy (involvement of multiple nerves in a plexus) Mononeuropathies are usually due to compression, trauma or vascular causes

TYPES OF FIBER AFFECTED : 

TYPES OF FIBER AFFECTED

ANATOMICAL PATTERN : 

ANATOMICAL PATTERN

TIME COURSE : 

TIME COURSE Acute- evolution in terms of days Sub acute- in weeks Early chronic- months to few years Late chronic- more than several years

ETIOLOGY : 

ETIOLOGY Metabolic- DM, renal failure, amyloid, porphyria Infectious- HIV, Lyme disease, CMV, syphilis, leprosy, diphtheria Immune mediated- GBS, CIDP, MMN, anti-myelin-associated glycoprotein (MAG) neuropathy Hereditary- CMT Toxic- HIV drugs, anticancer drugs, alcohol, heavy metal, tick bite Vasculitic- PAN, Churg-Strauss, cryoglobulinemia, isolated vasculitis Paraneoplastic Nutritional- Vit B1, B6, B12 deficiency Misc- celiac disease, Fabry disease, hypothyroidism

TESTS INDICATED : 

TESTS INDICATED FBG, HbA1c Serum B12 Tests for systemic vasculitis or collagen vascular diseases Neuropathy associated antibodies Urine screen for heavy metals Spinal fluid analysis Autonomic function testing Nerve and muscle biopsy Genetic tests for hereditary neuropathies

ELECTROPHYSIOLOGICAL STUDIES : 

ELECTROPHYSIOLOGICAL STUDIES Axonal or demyelinating Focal or generalized & symmetric or asymmetric Length-dependent Severity Approximate age of the lesion Hereditary or acquired Sub clinical neuropathy Prognosis

QUANTITATIVE SENSORY TESTING(QST) : 

QUANTITATIVE SENSORY TESTING(QST) Delivering a series of hot, cold and vibrating impulses to affected and unaffected regions of the body. --Impulses administered at specific intensity levels to test a patient’s sensory threshold (the minimum and maximum point at which an individual can feel the stimulus). In addition to diagnosing different types of neuropathy, QST used to monitor the state of patient’s previously diagnosed neuropathy to determine response to treatment. More sensitive than EMG and NCV tests in detecting damage to small nerve fibers that carry information about pain and temperature sensations.

QST VS EMG/NCV : 

QST VS EMG/NCV EMG and NCV may be more effective in detecting nerve weakness. QST requires active patient cooperation, EMG and NCV do not. EMG and NCV more invasive and require use of needles and electrical shocks, which QST does not.

ANS__ORGANISATION : 

ANS__ORGANISATION Preganglionic neurons of parasympathetic system leave CNS in CN 3,7,9,10 and 2nd & 3rd sacral nerves Preganglionic neurons of sympathetic system leave spinal cord b/w 1st thoracic and 2nd lumber segment

Autonomic Nervous System : 

Autonomic Nervous System 2 divisions: Sympathetic “Fight or flight” “E” division Exercise, excitement, emergency, and embarrassment Parasympathetic “Rest and digest” “D” division Digestion, defecation, and diuresis

NORMAL ANS FUNCTIONS : 

NORMAL ANS FUNCTIONS

SYMPTOMATOLOGY : 

SYMPTOMATOLOGY Orthostatic hypotension- light headedness in young and cognitive impairment in elderly Altered sweating- hyper/hypohidrosis Gastroparesis- bloating, nausea, vomiting of old food Constipation Impotence Bladder dysfunction- urinary frequency, hesitancy, or incontinence

REVIEW OF MEDICATIONS : 

REVIEW OF MEDICATIONS

PHYSICAL EXAMINATION : 

PHYSICAL EXAMINATION Supine and standing pulse & BP- OH defined as sustained drop in systolic ( = 20mmHg) or diastolic ( = 10mmHg) BP within 3 minutes of standing Failure of HR to ? after drop in BP- most reliable bedside indicator of vagal nerve dysfunction Mental status Cranial nerves Motor tone Reflexes and sensation

AUTONOMIC TESTINGS : 

AUTONOMIC TESTINGS Helpful when history and examination findings inconclusive To detect sub clinical involvement To follow the course of an autonomic disorder Combination of tests necessary

HRDB (Heart Rate variation with Deep breathing) : 

HRDB (Heart Rate variation with Deep breathing) Test of parasympathetic function on cardiovascular reflexes, via the vagus nerve 6 breaths/minute and FVC > 1.5 L optimal Test data compared with result from normal individual, collected under same test conditions HR variation >15-20 beats/min in persons < 20 years but 5-8 beats/min for persons over 60 yrs Best validated- RR interval in expiration and inspiration (E:I ratio), up to 40years <1.2 abnormal Influenced by posture, medication, degree of hypocapnia Abolished by atropine, unaffected by propranolol

VALSALVA RESPONSE : 

VALSALVA RESPONSE Assesses integrity of baroreflex control of heart rate (parasympathetic) and BP (adrenergic) Constant expiratory pressure of 40 mmHg maintained for 15 sec in supine posture Heart rate and beat to beat BP changes measured Valsalva ratio- maximum phase 2 tachycardia / minimum phase 4 bradycardia (normal = 1.4) Ratio reflects cardiovagal function

VALSALVA RESPONSE : 

VALSALVA RESPONSE

ORTHOSTATIC BP RECORDING : 

ORTHOSTATIC BP RECORDING Beat to beat BP in supine, 70º tilt, and tilt back position 20 min supine rest before assessing BP changes during tilting Evaluate suspected OH, unexplained syncope, or to detect vagally mediated syncope Ratio of RR interval corresponding to 30th and 15th (the 30:15 ratio)- sensitive indicator of vagal integrity (<1.05 - abnormal in young adults)

TILT TABLE TESTING FOR SYNCOPE : 

TILT TABLE TESTING FOR SYNCOPE To diagnose vasovagal syncope Standardized protocol followed Positive nitroglycerine-stimulated test (procedure for provocation of vasodilatation) predicts recurrence of syncope

OTHER TESTS OF VASOMOTOR CONTROL : 

OTHER TESTS OF VASOMOTOR CONTROL

QSART (Quantitative Sudomotor Axon Reflex Test) : 

QSART (Quantitative Sudomotor Axon Reflex Test) Measures regional autonomic function mediated by Ach-induced sweating 10% solution of Ach iontophoresed onto skin using 2 mA for 5 min --sweat output in adjacent skin by sophisticated circular cells that detect the sweat water ? or absent response– lesion in postganglionic sudomotor axon

TST (Thermoregulatory Sweat Test) : 

TST (Thermoregulatory Sweat Test) Qualitative measure of regional sweat production with ? body temperature Indicator powder (starch or quinizarin) placed on anterior surface of body changes color with sweat production Pattern of color changes- measure of regional sweat secretion

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Postganglionic lesion- both QSART and TST show absent sweating Preganglionic lesion- QSART intact, but TST shows anhidrosis Galvanic skin-resistance test– easy, but not entirely reliable for sweat measuring

SCHIRMER TEST : 

SCHIRMER TEST Roughly estimates tearing, thus lacrimal function 5mm-wide, 25mm-long strip of thin filter paper inserted into lower conjunctival sac Normal response- moistened area extends for 15mm, after 5 min Hypolacrimia- <10mm

BLADDER FUNCTION : 

BLADDER FUNCTION Best assessed by cystometrogram --500ml NS introduced into bladder, emptying contractions of detrusor and volume at sensation of bladder fullness recorded by manometer Measuring residual volume --by catheterization, immediately after voluntary voiding --by IVP

G I MOTILITY : 

G I MOTILITY Demonstrated radiologically Barium swallow- atonic dilatation of esophagus, gastric atony and distension, delayed gastric emptying, small bowel pattern of rapid intestinal transit Barium enema- colonic distention, ? propulsive activity Sophisticated manometric techniques now available

PENILE ERECTILE FUNCTION : 

PENILE ERECTILE FUNCTION Nocturnal penile tumescence recorded in sleep laboratories May be used as ancillary test of sacral autonomic function

TESTS OF PUPILLARY INNERVATION : 

TESTS OF PUPILLARY INNERVATION

PHARMACOLOGIC TESTS : 

PHARMACOLOGIC TESTS Measuring plasma NE, first supine, then standing for 5 min --Supine value ? in postganglionic disorder (e.g. autonomic neuropathy or pure autonomic failure), --May fail to ? in pre/post ganglionic disorders. Postganglionic lesion- --? response to tyramin (normally release NE from PG terminals). --Excessive response to subthreshold doses of phenylephrin (a1 agonist), due to denervation supersensitivity.

PHARMACOLOGIC TESTS : 

PHARMACOLOGIC TESTS Infusion of pressor drugs- NE or angiotensin-2 cause exaggerated BP surge in dysautonomia -- inadequate muting of HTN by baroreceptors, than denervation hypersensitivity Ganglionic blockade with trimethophan- greater fall in BP with preganglionic lesion Evaluation of afferent central pathways by arginine vasopressin

SUMMARY OF AUTONOMIC TESTINGS : 

SUMMARY OF AUTONOMIC TESTINGS Quantitative tests are emphasized At bedside, most convenient are -orthostatic pulse and BP -BP response to Valsalva -HRDB -pupillary responses -rough estimate of sweating of palms and soles These tests and clinical situation determines further test necessity

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