Cold‐evoked potentials in clinical practice: A head‐to‐head contrast with laser‐evoked responses

Abstract

BackgroundInnocuous cooling of the skin activates cold‐specific Aδ fibres, and hence, the recording of cold‐evoked potentials (CEPs) may improve the objective assessment of human thermo‐nociceptive function. While the feasibility of CEP recordings in healthy humans has been reported, their reliability and diagnostic use in clinical conditions have not been documented.MethodsHere, we report the results of CEP recordings in 60 consecutive patients with suspected neuropathic pain, compared with laser‐evoked potentials (LEPs) which are the gold standard for thermo‐algesic instrumental assessment.ResultsCEP recording was a well‐tolerated procedure, with only ~15 min of surplus in exam duration. The reproducibility and signal‐to‐noise ratio of CEPs were lower than those of LEPs, in particular for distal lower limbs (LLs). While laser responses were interpretable in all patients, CEPs interpretation was inconclusive in 5/60 because of artefacts or lack of response on the unaffected side. Both techniques yielded concordant results in 73% of the patients. In 12 patients, CEPs yielded abnormal values while LEPs remained within normal limits; 3 of these patients had clinical symptoms limited to cold sensations, including cold‐heat transformation.ConclusionsCEPs appear as a useful technique for exploring pain/temperature systems. Advantages are low cost of equipment and innocuity. Disadvantages are low signal‐to‐noise ratio for LL stimulation, and sensitivity to fatigue/habituation. Joint recording of CEPs and LEPs can increase the sensitivity of neurophysiological techniques to thin fibre‐ spinothalamic lesions, in particular, when abnormalities of cold perception predominate.SignificanceRecording of cold‐evoked potentials is a well‐tolerated, inexpensive and easy‐to‐use procedure that can be helpful in the diagnosis of abnormalities in the thin fibre‐ spinothalamic pathways. Supplementing LEPs with CEPs allows consolidating the diagnosis and, for some patients suffering from symptoms limited only to cold, CEPs but not LEPs may allow the diagnosis of thin fibre pathology. Optimal CEP recording conditions are important to overcome the low signal‐to‐noise ratio and habituation phenomena, which are less favourable than with LEPs.

Cold-evoked potentials in Fabry disease and polyneuropathy

“…However, due to the small cohort, it is not possible to conclude mechanistic conclusions about ongoing spontaneous NP from our data and further studies with larger patient cohorts are necessary. Nonetheless, the following considerations can be made: CEPs allow for the examination of specialized, cool-sensitive Aδ- and C-fibers ( 60 – 62 ) and their central pathways ( 26 , 28 , 30 , 31 ). While the conduction velocity offers insights into the state of the myelin sheaths, changes in the amplitudes can be due to axonal dysfunction or, as shown for nociceptive pathways ( 63 ), sensitization processes.…”

“…Recently, Perchet et al reported on CEPs in patients with suspected NP compared to LEPs. They concluded that “for some patients suffering from symptoms limited only to cold, CEPs but not LEPs may allow the diagnosis of thin fiber pathology” ( 30 ).…”

Low-intensity focused ultrasound to the insula and dorsal anterior cingulate has site-specific and pressure dependent effects on pain during measures of central sensitization

“…This device is capable of delivering rapid cooling or heating up to 300°C/s. This device has been validated in previous reports in both healthy volunteers [67][68][69][70][71] and clinical pain patients [72,73]. At each formal testing visit (sessions 2-5) participants were familiarized with the thermal probe prior to heat pain thresholding.…”