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Thermal Pain Stimulation
on 09 Mar 2021 10:12 AM

Dr. Dominic A. Hegarty.

BSc., BMedSc., MB., MSc. (Pain Management), PhD. FCARSCI, FFPMCAI, FIPP
Consultant in Pain Management & Neuromodulation, Mater Private Hospital, Cork
Clinical Director Pain Relief Irelandwww.painreliefireland.ie

Do you suffer from “burning sensation” in your hands and feet? Do you experience tingling or pins and needle sensations especially at night? Have all your investigations drawn a blank? The you may be suffering from Small Fiber Neuropathy. Perhaps a simple computer test might help. Pain Relief Ireland are delight to be able to launch this new service.

Small fiber peripheral neuropathy (SFN) is recognised as an expanding public health problem with 40 million individuals identified in the United States. Painful Small fibre neuropathy (SFN) is characterised by structural injury selectively affecting small diameter sensory and/or autonomic axons dominated by pain.

Diabetic neuropathy is the most common peripheral neuropathy in the United States and globally. With the prevalence of diabetes in adults rising to 10.8% in the United States and 4.3% in the United Kingdom improving the management of peripheral neuropathy has never been more important. Unfortunately the pathogenesis of injury to small nerve fibers is not well understood and therefore treatment can prove challenging.

Pain Relief Ireland are delighted to report that we now have access to a simple office based electronic assessment to identify the present of SFN. Dr. Dominic Hegarty, (Clinical Director at Pain Relief Ireland) highlights the fact that by trying to understand the nature of the painful sensations will help us to propose personalised treatment option for patients.

The symptoms individuals complain of typically are “burning”, “pins and needles”, “hot /cold sensations” usually in hand and feet bit this can be anywhere on the body. Despite extensive diagnostic evaluation, up to 50% of individuals with small fiber neuropathy ultimately may be given a diagnosis of “idiopathic” or cause unknown! Some of the features are outlined in this table.

Table 1 Over view of key symptoms

  • A cold-like pain, tingling or a pins and needles sensation.
  • Burning pain that often is persistent, although it may vary in intensity throughout the day.
  • transient electric shock–like pain, usually lasting only seconds, but quite severe and potentially multiple times per day can be a feature.
  • Symptoms worsen during periods of rest and at night.
  • Reports of increased or pain to light touch (allodynia and hyperesthesia).
  • Small nerve fiber neuropathies also may result in autonomic and enteric dysfunction.

What is Quantitative sensory testing?

Quantitative sensory testing (QST) is an extension of the physical examination that can provide a threshold for detection of thermal sensation, thermal pain, and vibratory sensation. QST has been used in a number of longitudinal studies and clinical trials of neuropathy. In the past it was seen as a research tool but with newer technology and the ability to compare to large baseline databases preforming reliable tests in a busy clinic will become an option. Dr. Hegarty has long standing experience with the technique and has published his work on it several times. “The reason why it has taken this length of time to be available in the clinic” Dr. Hegarty says “ is because the algorithms need to be developed and the quick and easy needle free system needed to be developed”.

Figure 1 illustrates a the lost in small fibers in the skin and Figure 2 shows atypical report where abnormal SFN function is reported.

There are some well-recognized limitations to QST; abnormalities in either the central or peripheral nervous system can result in the same deficit. In addition, QST requires conscious integration from the patient, and in conditions of cognitive impairment (due to disease or medication), the reliability of the test results are in question. Finally, QST is unable to distinguish between feigned and true loss of sensation.

There are few trials utilizing QST in the study of isolated small fiber neuropathies, most trials include patients with large fiber involvement as well. Heat or heat-pain detection thresholds are considered the most useful and specific for evaluation of a small fiber neuropathy. Cold and cold-pain detection are transmitted through lightly myelinated Aδ fibers, while vibration detection thresholds are detected through large myelinated Aα and Aβ sensory fibers. Recent reports of contact heat evoked potentials (CHEPs), a device that provides rapid cycles of heat resulting in evoked potentials measured by electroencephalogram, show a linear correlation between CHEP amplitude and cutaneous nociceptive nerve fiber density.

An advantage of QST testing is the non-invasive and the repeatable nature of the test. Not only can it help assess the baselines status it can be used to assessment the impact treatment is having on the SFN and can guide the pharmacology management options. While further study is required to determine the utility of new variations of QST on the diagnosis of a small fiber neuropathy the use of this device will influence treatment planning.

Will it change our management options?

Yes it may. It will guide the choice of medication, the dose regime and ultimately it may help remove medication. It may also allow us offer other non-invasive and implanted devices to try and regulate and control pain symptoms. It is not a test that is required by all cases of chronic pain but it can give valuable insight into the mechanism of the pain and that has to be positive.

Conclusion

The number of individuals at risk of developing painful SFN is growing  globally. Too often the symptoms are well established before any opportunity to treatment presents itself and reversing the injury is difficult with poor prognosis. The development of practical QST assessment can provide a reliable repeatable and non-invasive assessment tool to not only establish the presence of SFN disease but also to track its pattern and may guide pharmacology dosing regimens. Bioelectric modulation of SFN needs to be considered as an early option in the therapy regimes because it can provide long-term drug free solutions.

 

More information can be found at Dr. Hegarty’s recent medical report in the March 2021 edition of the Medical Independent -

Article: Diagnosing and managing painful small fibre neuropathy

www.medicalindependent.ie

 

Download the PDF :

Advanced Thermosensory Stimulator PDF

If you suffer from the symptoms outline please speak with your GP or contact us for more information.