an update on sensory testing

1. An update on sensory testing
Dr. Sanjeev Kelkar M.D.
1st
National Foot Group Meeting
Bangalore – 22nd
July 2001

2. Diabetic Sensory Neuropathy:1
• 85% of Diabetic Foot problem is neuropathic.
• It is the insensate foot that causes considerable morbidity.
• Repetitive, unnoticed trauma results in inflammation and
ulceration.

3. Diabetic Sensory Neuropathy:2
• Variety of trauma known.
• Diagnosis of sensory neuropathy often late when trauma
has already resulted in foot ulcer

4. Diabetic Sensory Neuropathy:3
• Late Diagnosis due to:
• Patient factors.
• No pain, no complaint
• Ulcer but no pain, no complaint
• Physician:
• No complaint, no examination 7% of patients were ever
examined in one of the Bangalore study in all years of
diabetes.

5. Diabetic Sensory Neuropathy:4
• Clinical examination (when done)
• Reveals evidence of neuropathy as
- Loss of reflexes
- Loss of pain, touch heat and cold sensation or
decrease
- Loss of proprioception
- Loss of vibration sense

6. Diabetic Sensory Neuropathy:5
• Clinically: Positive symptoms
• Dysesthesia
• Paresthesia
• Hyperesthesia
Examination:
Could still be insensate to touch, pain, temperature – The
painless – Painful foot.

7. Diabetic Sensory Neuropathy:6
Clinical Examination depends upon –
Clarity of communication by the physician.
Clarity of understanding of patient and clear response.
Difficult to quantify.

8. Diabetic Sensory Neuropathy:5
Quantifying the loss of function useful to correlate –
Degree of loss to the likelihood of developing morbidity
Important for early diagnosis of foot at risk develop
preventive strategies.

9. Diabetic Sensory Neuropathy:8
What sensations can vibration sense
Pain on analog scale – (suffers most on account subjective
variation of pain threshold, severity perception pressure:
force/area sense of pressure - quantifiable

10. Instruments for quantification:I
• Quantification needs instrumentation.
• Available or:
• Light touch + pressure
• SW monofilaments
• A nylon fiber, held again a foot and bent,
• Gives 10 gms of weight / pressure

11. Instruments for Quantification:2
• Simple, well tested method
• Identifies easily foot at risk if the patient cannot sense the
10 gm pressure.
• Correlates well with other tests.

13. Instruments for Quantification:3
• To test vibration sense
• Tuning fork – frequency of 128
• Diagnoses per sense or absence of vibration sense but does
not indicate quantifiable severity of loss.

14. Instruments for Quantification:2
• Graduated tuning fork:
• Weighted and graduated for 0 – 10
• The apex of the triangle rises from 0 – 10
• If vibrations are perceived beyond 6, vibration sense
considered normal.
• At best semi quantitative.

15. Instruments for Quantification:5
• Biothesiometer:
• Delivers vibrations in micron displacements increasing
with increasing voltage applied.
• Loss of vibration sense quantifiable well in terms of
voltage applied,
• V read off simply on the panel.

16. Instruments for Quantification:2
• Indian version available.
• Normal range on 300 normal, non diabetic Indian doctors
and nurses, across the country
• 4 to 9 volts
• Much higher thresholds in diabetics with neuropathy upto
48 volts, vibrations not perceived.

17. Instruments for Quantification:7
• Indian version tested in 75 patients by Dr. Vijay
Viswanathan against an English Biothesiometer.
• P value for inter instrumental interpersonal variation, on
first analysis – not significant
• Correlates well, needs more stringent analyses – under
way.

18. Instruments for Quantification:8
• Heat and cold perception thresholds
• Foreign instruments available but difficult to get Indian
version being developed by NNEF.

19. Correlations: 1
• “If any one sensation tested is abnormal, then the
possibility that there will be at least one more abnormal
sensation is high”.
Dyke - Thomas

20. Correlations: 2
• Abnormality detected on Monofilaments has equal
sensitivity and specificity with an abnormality detected on
biothesiometer.
• Quantifiable accuracy of course is greater with
biothesiometer.

21. Correlations: 3
• Biothesiometer voltage value on insensate vibration, of 25
volts, exposes the foot to risk of ulceration 43 times more
than a normal foot.
• Proportionate increase in risk is present with lower but
above normal voltage measurements.

22. Achievements
• Monofilaments in Indian version also available
• Biothesiometer available
• Heat and cold perception threshold under development.
• Materials tested for taking foot impressions for castes –
available graduated tuning fork developed, more
refinement under way.