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1362578115 vpt assessment in neuropathy

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vpt assessment in neuropathy

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1362578115 vpt assessment in neuropathy

  1. 1. 1 Quantitative tests forQuantitative tests for neuropathic assessment - 1neuropathic assessment - 1 Quantitative sensory testing (QST) is theQuantitative sensory testing (QST) is the determination of the absolute sensorydetermination of the absolute sensory threshold, defined as the minimal energythreshold, defined as the minimal energy required to reliably stimulate the particularrequired to reliably stimulate the particular modality of sensation to be detected.modality of sensation to be detected.
  2. 2. 2 Quantitative tests forQuantitative tests for neuropathic assessment - 2neuropathic assessment - 2 The higher the level of the minimal energyThe higher the level of the minimal energy required the greater is the deficit of functionrequired the greater is the deficit of function of the particular modality of sensation.of the particular modality of sensation.
  3. 3. 3 Quantitative tests forQuantitative tests for neuropathic assessment - 3neuropathic assessment - 3 In vibration threshold measurement the energy isIn vibration threshold measurement the energy is delivered as voltage converted in the vibration ofdelivered as voltage converted in the vibration of the probe. On VPT sensitometer, both voltage andthe probe. On VPT sensitometer, both voltage and vibration ie spatial disfigurement to and fro of thevibration ie spatial disfigurement to and fro of the skin can be measured.skin can be measured.
  4. 4. 4 Quantitative tests forQuantitative tests for neuropathic assessment - 4neuropathic assessment - 4 The higher the deficit of function theThe higher the deficit of function the greater voltage is required, ie greatergreater voltage is required, ie greater displacement for the limb to sense vibration.displacement for the limb to sense vibration.
  5. 5. 5 Quantitative tests forQuantitative tests for neuropathic assessment - 5neuropathic assessment - 5 The higher the deficit of function theThe higher the deficit of function the greater voltage is required, ie greatergreater voltage is required, ie greater displacement for the limb to sensedisplacement for the limb to sense vibration.vibration. Has great implications in prognosis andHas great implications in prognosis and therapy.therapy.
  6. 6. 6 Quantitative tests forQuantitative tests for neuropathic assessment - 6neuropathic assessment - 6 QST is a relatively simple procedure that is bothQST is a relatively simple procedure that is both noninvasive and nonabrasive.noninvasive and nonabrasive. In assessing diabetic neuropathy, the paramountIn assessing diabetic neuropathy, the paramount concern is to detect the integrity of the axonsconcern is to detect the integrity of the axons forming the peripheral nervous system and theirforming the peripheral nervous system and their distal receptors.distal receptors.
  7. 7. 7 Quantitative tests forQuantitative tests for neuropathic assessment - 7neuropathic assessment - 7 Measurable Modalities:Measurable Modalities: Vibration ThresholdsVibration Thresholds This measure is the most widely studied QSTThis measure is the most widely studied QST procedure. It principally assesses functionprocedure. It principally assesses function in Meissner and Pacinian corpuscles andin Meissner and Pacinian corpuscles and their associated large-diameter fibers.their associated large-diameter fibers.
  8. 8. 8 Quantitative tests forQuantitative tests for neuropathic assessment - 8neuropathic assessment - 8 Vibration PerceptionVibration Perception Threshold is the indirectly madeThreshold is the indirectly made detection of loss of protective paindetection of loss of protective pain sensation that would render a patientsensation that would render a patient susceptible to foot ulceration.susceptible to foot ulceration.
  9. 9. 9 Other Measurable ModalitiesOther Measurable Modalities Light Touch:Light Touch: This measure tests the integrity of Merkel touchThis measure tests the integrity of Merkel touch domes and Meissner corpuscles and theirdomes and Meissner corpuscles and their associated large-diameter fibers.associated large-diameter fibers. Thermal Sensitivity:Thermal Sensitivity: Known - Marstock ThermodeKnown - Marstock Thermode The new system: Heat and Cold PerceptionThe new system: Heat and Cold Perception ThresholdThreshold
  10. 10. 10 What do we have for AssessingWhat do we have for Assessing NeuropathyNeuropathy Need to assess associated risk of ulceration in a neuropathic Need to distinguish Neuropathic and non neuropathic patients Need to establish wide range of quantitated gradation of sensory deficits for comparison on Follow up Simple test equipments
  11. 11. 11 Have it nowHave it now
  12. 12. 12 • The ability to identify feet at risk of ulceration hasThe ability to identify feet at risk of ulceration has been demonstrated prospectively in two studiesbeen demonstrated prospectively in two studies using the biothesiometer.using the biothesiometer. [Young MJ, et al. Diabet Care 1994][Young MJ, et al. Diabet Care 1994] [Abbott CA, et al. Diabet Care 1998].[Abbott CA, et al. Diabet Care 1998]. • In one study using the monofilament.In one study using the monofilament. [Rith-Najarian SJ, Diabet Care 1992].[Rith-Najarian SJ, Diabet Care 1992].
  13. 13. 13 Detection of neuropathyDetection of neuropathy • The role of impaired vibratory perception in theThe role of impaired vibratory perception in the pathogenesis of foot ulceration has been wellpathogenesis of foot ulceration has been well documented.documented. [Boulton AJM, et al. Diabet Med 1986][Boulton AJM, et al. Diabet Med 1986] • Objective measurement of this sensory parameterObjective measurement of this sensory parameter with a biothesiometer has been used to identifywith a biothesiometer has been used to identify those at risk at developing ulceration.those at risk at developing ulceration. [Young MJ et al. Diabet Care 1994][Young MJ et al. Diabet Care 1994]
  14. 14. 14 The SensitometerThe Sensitometer An AnswerAn Answer • Sensory deficits of vibration perceptionSensory deficits of vibration perception thresholds is measured as micronthresholds is measured as micron displacement of the vibrator tip or as thedisplacement of the vibrator tip or as the voltage applied to the tip.voltage applied to the tip. • These can be read off the control panelThese can be read off the control panel
  15. 15. 15 Wide ranging gradationsWide ranging gradations • The meter has two scales as shown in the voltageThe meter has two scales as shown in the voltage panel. Lower one is in Microns. This is the actualpanel. Lower one is in Microns. This is the actual scale, with a large range of measurement fromscale, with a large range of measurement from “0.025 to 25 microns,” a ratio of nearly 1:1000.“0.025 to 25 microns,” a ratio of nearly 1:1000. • The upper scale is for voltage. It is widely acceptedThe upper scale is for voltage. It is widely accepted ( 0 to 50 Volts) as it is more convenient.( 0 to 50 Volts) as it is more convenient. • This helps establish wide ranging differentiation ofThis helps establish wide ranging differentiation of Vibratory Perception Threshold ( VPT )Vibratory Perception Threshold ( VPT )
  16. 16. 16 Sensitometer - MSensitometer - Measures accurately theeasures accurately the Vibration Perception Threshold, in anVibration Perception Threshold, in an upgraded, validated and endorsedupgraded, validated and endorsed instrument.instrument.
  17. 17. 17 SensitometerSensitometer is a simple to operate,is a simple to operate, easy to use equipment. The simplicityeasy to use equipment. The simplicity does not lower the accuracy nor affectsdoes not lower the accuracy nor affects reliability.reliability.
  18. 18. 18 Hold the probe in hand and apply it’sHold the probe in hand and apply it’s button on any these points on both thebutton on any these points on both the feet systematically.feet systematically. • These are 6 points for testing on the footThese are 6 points for testing on the foot 1.1. The big toeThe big toe 2.2. First meta tarsal headFirst meta tarsal head 3.3. Third meta tarsal headThird meta tarsal head 4.4. Fifth meta tarsal headFifth meta tarsal head 5.5. In stepIn step 6.6. HeelHeel Record VoltagesRecord Voltages
  19. 19. 19 How to use the Sensitometer?How to use the Sensitometer? • Apply the tip to theApply the tip to the points one by one aspoints one by one as aboveabove • Slowly rotate the knobSlowly rotate the knob clock wise to increaseclock wise to increase the voltage /the voltage / vibration.vibration.
  20. 20. 20 How to use the Sensitometer?How to use the Sensitometer? • Record at what levelRecord at what level of vibrations, patientof vibrations, patient respondsresponds • Slowly lower theSlowly lower the voltage / vibration tillvoltage / vibration till the patient says nothe patient says no • Raise again to reachRaise again to reach the point of firstthe point of first sensation & recordsensation & record
  21. 21. 21 How to use the Sensitometer?How to use the Sensitometer? • The turn around way:The turn around way: • Raise the voltage byRaise the voltage by 8 quickly, if there is8 quickly, if there is no response raise byno response raise by 8 till the response is8 till the response is generatedgenerated • Then make a turnThen make a turn around by loweringaround by lowering the voltagesthe voltages
  22. 22. 22 How to use the Sensitometer?How to use the Sensitometer? • The turn around way:The turn around way: • Lower the voltage byLower the voltage by installments of 4 tillinstallments of 4 till the sensation is lost.the sensation is lost. • Now we have twoNow we have two points of firstpoints of first detection and firstdetection and first loss of sensation.loss of sensation.
  23. 23. 23 How to use the Sensitometer?How to use the Sensitometer? • Now raise theNow raise the voltages by 2 volts tillvoltages by 2 volts till a response isa response is obtained.obtained. • Now lower the voltageNow lower the voltage by 1 till you reach theby 1 till you reach the point of justpoint of just detectable.detectable. • This is a fasterThis is a faster methodmethod • Compare it withCompare it with reference value,reference value,
  24. 24. 24 If you find inconsistent readingsIf you find inconsistent readings • Use the silent buttonUse the silent button • It’s just bellow theIt’s just bellow the power on/off switchpower on/off switch • On pressing it theOn pressing it the vibrations ceasevibrations cease • But the meter readingBut the meter reading dose not changedose not change • One can thus verifyOne can thus verify the reliability of thethe reliability of the patient responsepatient response
  25. 25. 25 The SensitometerThe Sensitometer Implications of a studyImplications of a study • The Indian normal on field testing appears to beThe Indian normal on field testing appears to be between 8 to 11 volts on feet of non diabeticbetween 8 to 11 volts on feet of non diabetic men and women.men and women. • There seems to be a rise in the baselineThere seems to be a rise in the baseline commonly among diabetics, compared to normalcommonly among diabetics, compared to normal in a clinic based study.in a clinic based study. • The deficits detected can be linked to the excessThe deficits detected can be linked to the excess risk of ulceration of a diabetic footrisk of ulceration of a diabetic foot
  26. 26. 26 Prospective Foot Ulcer StudyProspective Foot Ulcer Study Results — Foot UlcersResults — Foot Ulcers VPT<15 VPT 16-24 VPT>25VPT<15 VPT 16-24 VPT>25 Total ulcers 1988-92Total ulcers 1988-92 66 2 412 41 Risk per patientRisk per patient 2.9% 3.4% 19.6%2.9% 3.4% 19.6% Risk/patient/yearRisk/patient/year 0.7%0.7% 0.9% 04.9%0.9% 04.9% AJM BoultonAJM Boulton
  27. 27. 27 The SensitometerThe Sensitometer Implications of a study - 1Implications of a study - 1 • The risks compared to a normal diabeticThe risks compared to a normal diabetic foot go up as voltages go beyond 11.foot go up as voltages go beyond 11. • 25 volts is a critical value - Risk of25 volts is a critical value - Risk of ulceration rises three to fourfoldulceration rises three to fourfold • Above 42 volts – it rises to 23 foldAbove 42 volts – it rises to 23 fold
  28. 28. 28 The SensitometerThe Sensitometer Implications of a study - 2Implications of a study - 2 • Repeat Study after 6 months or 1 year is useful.Repeat Study after 6 months or 1 year is useful. It will tell if -It will tell if - • Any intervention for improvement has reducedAny intervention for improvement has reduced the voltages required, maintained the same orthe voltages required, maintained the same or has increased, indicating that the neural damagehas increased, indicating that the neural damage has not haltedhas not halted • Rethink about what we are doing is a must thenRethink about what we are doing is a must then

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