The Water Induced Skin Wrinkling (WISW) has been found to be useful in assessment of autonomic nerves for more than seven decades1. Recently developed ultrasound imaging technique of the distal phalanx in both fingers and toes has reviled dynamic changes in the digital pulp after WISW2,3 allowing its more accurate scaling.
This study aimed to explore Ultrasound digital pulp imaging changes in patients with peripheral neuropathy and to assess their usefulness as markers for small fibre peripheral nerve dysfunction.
11 consecutive patients referred for electrophysiological assessment of peripheral neuropathy with nerve conduction studies (who also underwent sympathetic skin response and thermal threshold studies) were included in this study (6 male, 5 female; age 48-80)4. High frequency (22 MHz) ultrasound imaging was performed of the distal finger and toe phalanxes before and after WISW.
The ultrasound imaging measurements showed a reduction in the pulp hypo-echogenic areas after WISW in this patient population with electrophysiologically confirmed large fibre polyneuropathy (40% for the fingers and 30% for the toes). No significant changes were noted for the epidermal thickness or pulp hyper-echogenic areas before and after WISW. The mean number of finger wrinkles (2nd, 3rd and 4th digits) was borderline abnormal 3.9 (SD=3.4); however significantly lower than the mean number of hyper-echogenic areas number 5.3 (SD=0.9), p=0.035, Wilcoxon signed-rank test.
The hypo-echogenic cross-sectional area reduction was abnormal according to the previous pilot study2 in both fingers and toes, more pronounced for the latter. The mean visually assessed wrinkling score vs. ultrasound imaging predicted wrinkling score was significantly different.
It is concluded the US imaging could provide more reliable scoring system of WISW and might increase the diagnostic yield in assessment of length dependent neuropathies. Further studies are needed to assess US distal finger (toe) phalanx imaging sensitivity and specificity in cases of small fibre peripheral neuropathy.
We are grateful to Dr. Tom Tidswell and Dr. Alex Hadjipourou for their contribution in neurophysiological assessment of the patients, constructive discussions and comments whilst crafting the manuscript. We would also like to extend our thanks to Dr. Marsha Morgan for her advices and co-devising this project. We express our thanks to all the colleagues of the Department of Clinical Neurophysiology at the Royal Free Hospital.