1362578115 vpt assessment in neuropathy

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Quantitative tests for Quantitative tests for neuropathic assessment - 1neuropathic assessment - 1

Quantitative sensory testing (QST) is the Quantitative sensory testing (QST) is the determination of the absolute sensory determination of the absolute sensory threshold, defined as the minimal energy threshold, defined as the minimal energy required to reliably stimulate the required to reliably stimulate the particular modality of sensation to be particular modality of sensation to be detected.detected.

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The higher the level of the minimal The higher the level of the minimal energy energy

required the greater is the deficit of required the greater is the deficit of function function

of the particular modality of sensation.of the particular modality of sensation.

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In vibration threshold measurement the energy is In vibration threshold measurement the energy is delivered as voltage converted in the vibration of delivered as voltage converted in the vibration of the probe. On VPT sensitometer, both voltage and the probe. On VPT sensitometer, both voltage and vibration ie spatial disfigurement to and fro of the vibration ie spatial disfigurement to and fro of the skin can be measured. skin can be measured.

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The higher the deficit of function the The higher the deficit of function the greater voltage is required, ie greater greater voltage is required, ie greater displacement for the limb to sense displacement for the limb to sense

vibration. vibration.

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The higher the deficit of function the The higher the deficit of function the greater voltage is required, ie greater greater voltage is required, ie greater displacement for the limb to sense displacement for the limb to sense

vibration.vibration.Has great implications in prognosis and Has great implications in prognosis and therapy. therapy.

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QST is a relatively simple procedure that is QST is a relatively simple procedure that is both noninvasive and nonabrasive. both noninvasive and nonabrasive.

In assessing diabetic neuropathy, the In assessing diabetic neuropathy, the paramount concern is to detect the paramount concern is to detect the integrity of the axons forming the integrity of the axons forming the peripheral nervous system and their distal peripheral nervous system and their distal receptors. receptors.

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Measurable Modalities:Measurable Modalities: Vibration Vibration ThresholdsThresholds

This measure is the most widely studied This measure is the most widely studied QST procedure. It principally assesses QST procedure. It principally assesses function in Meissner and Pacinian function in Meissner and Pacinian corpuscles and their associated large-corpuscles and their associated large-diameter fibers. diameter fibers.

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Vibration PerceptionVibration PerceptionThreshold is the indirectly made Threshold is the indirectly made detection of loss of protective pain detection of loss of protective pain sensation that would render a patient sensation that would render a patient susceptible to foot ulceration.susceptible to foot ulceration.

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Other Measurable Modalities Other Measurable Modalities

Light Touch:Light Touch: This measure tests the integrity of Merkel touch This measure tests the integrity of Merkel touch

domes and Meissner corpuscles and their domes 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 Perception The new system: Heat and Cold Perception

ThresholdThreshold

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What do we have for Assessing What do we have for Assessing NeuropathyNeuropathy

Need to assess associated risk

of ulceration in a neuropathic

Need to distinguishNeuropathic and non neuropathic patients

Need to establishwide range of quantitated

gradation of sensory deficitsfor comparison on

Follow up

Simple test equipments

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Have it nowHave it now

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• The ability to identify feet at risk of The ability to identify feet at risk of ulceration has been demonstrated ulceration has been demonstrated prospectively in two studies using the prospectively in two studies using the biothesiometer.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].

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Detection of neuropathyDetection of neuropathy• The role of impaired vibratory perception in the The role of impaired vibratory perception in the

pathogenesis of foot ulceration has been well pathogenesis 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 Objective measurement of this sensory parameter with a biothesiometer has been used parameter with a biothesiometer has been used to identify those at risk at developing ulceration.to identify those at risk at developing ulceration.

[Young MJ et al. Diabet Care 1994][Young MJ et al. Diabet Care 1994]

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The SensitometerThe Sensitometer An Answer An Answer

• Sensory deficits of vibration perception Sensory deficits of vibration perception thresholds is measured as micron thresholds is measured as micron displacement of the vibrator tip or as displacement of the vibrator tip or as the voltage applied to the tip. the voltage applied to the tip.

• These can be read off the control panelThese can be read off the control panel

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Wide ranging gradationsWide ranging gradations

• The meter has two scales as shown in the voltage The meter has two scales as shown in the voltage panel. Lower one is in Microns. This is the actual panel. Lower one is in Microns. This is the actual scale, with a large range of measurement from scale, 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 accepted The 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 of This helps establish wide ranging differentiation of Vibratory Perception Threshold ( VPT )Vibratory Perception Threshold ( VPT )

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Sensitometer - MSensitometer - Measures accurately the easures accurately the Vibration Perception Threshold, in an Vibration Perception Threshold, in an upgraded, validated and endorsed upgraded, validated and endorsed instrument. instrument.

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SensitometerSensitometer is a simple to is a simple to operate, easy to use equipment. The operate, easy to use equipment. The simplicity does not lower the simplicity does not lower the accuracy nor affects reliability.accuracy nor affects reliability.

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Hold the probe in hand and apply Hold the probe in hand and apply it’s button on any these points on it’s button on any these points on both the feet systematically. both the feet systematically. • These are 6 points for testing on the footThese are 6 points for testing on the foot1.1. The big toeThe big toe2.2. First meta tarsal headFirst meta tarsal head3.3. Third meta tarsal headThird meta tarsal head4.4. Fifth meta tarsal headFifth meta tarsal head5.5. In stepIn step6.6. HeelHeelRecord VoltagesRecord Voltages

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How to use the How to use the Sensitometer?Sensitometer?

• Apply the tip to the Apply the tip to the points one by one points one by one as aboveas above

• Slowly rotate the Slowly rotate the knob clock wise to knob clock wise to increase the increase the voltage / vibration.voltage / vibration.

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• Record at what level Record at what level of vibrations, patient of vibrations, patient respondsresponds

• Slowly lower the Slowly lower the voltage / vibration till voltage / vibration till the patient says nothe patient says no

• Raise again to reach Raise again to reach the point of first the point of first sensation & recordsensation & record

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• The turn around The turn around way:way:

• Raise the voltage by Raise the voltage by 8 quickly, if there is 8 quickly, if there is no response raise by no response raise by 8 till the response is 8 till the response is generated generated

• Then make a turn Then make a turn around by lowering around by lowering the voltagesthe voltages

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• The turn around The turn around way:way:

• Lower the voltage by Lower the voltage by installments of 4 till installments of 4 till the sensation is lost.the sensation is lost.

• Now we have two Now we have two points of first points of first detection and first detection and first loss of sensation.loss of sensation.

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• Now raise the Now raise the voltages by 2 volts voltages by 2 volts till a response is till a response is obtained.obtained.

• Now lower the Now lower the voltage by 1 till voltage by 1 till you reach the point you reach the point of just detectable. of just detectable.

• This is a faster This is a faster methodmethod

• Compare it with Compare it with reference value, reference value,

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If you find inconsistent If you find inconsistent readings readings • Use the silent buttonUse the silent button• It’s just bellow the It’s just bellow the

power on/off switchpower on/off switch• On pressing it the On pressing it the

vibrations ceasevibrations cease• But the meter But the meter

reading dose not reading dose not changechange

• One can thus verify One can thus verify the reliability of the the reliability of the patient responsepatient response

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The SensitometerThe Sensitometer Implications of a study Implications of a study• The Indian normal on field testing appears The Indian normal on field testing appears

to be between 8 to 11 volts on feet of non to be between 8 to 11 volts on feet of non diabetic men and women. diabetic men and women.

• There seems to be a rise in the baseline There seems to be a rise in the baseline commonly among diabetics, compared to commonly among diabetics, compared to normal in a clinic based study. normal in a clinic based study.

• The deficits detected can be linked to the The deficits detected can be linked to the excess risk of ulceration of a diabetic footexcess risk of ulceration of a diabetic foot

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Prospective Foot Ulcer Prospective Foot Ulcer StudyStudy

Results — Foot UlcersResults — Foot Ulcers VPT<15 VPT 16-24 VPT>25VPT<15 VPT 16-24 VPT>25Total ulcers 1988-92 Total ulcers 1988-92 66 2 41 2 41Risk 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

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The SensitometerThe Sensitometer Implications of a study - 1 Implications of a study - 1

• The risks compared to a normal The risks compared to a normal diabetic foot go up as voltages go diabetic foot go up as voltages go beyond 11.beyond 11.

• 25 volts is a critical value - Risk of 25 volts is a critical value - Risk of ulceration rises three to fourfold ulceration rises three to fourfold

• Above 42 volts – it rises to 23 foldAbove 42 volts – it rises to 23 fold

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The SensitometerThe Sensitometer Implications of a study - 2 Implications of a study - 2• Repeat Study after 6 months or 1 year is Repeat Study after 6 months or 1 year is

useful. It will tell if - useful. It will tell if - • Any intervention for improvement has Any intervention for improvement has

reduced the voltages required, maintained reduced the voltages required, maintained the same or has increased, indicating that the same or has increased, indicating that the neural damage has not haltedthe neural damage has not halted

• Rethink about what we are doing is a must Rethink about what we are doing is a must thenthen

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1362578115 vpt assessment in neuropathy