After the hand in hot water, the feet in ice water may be a test for Small Fiber Neuropathy


Senior Member
The wrinkling fingers test in water is cheap and simple test to screen for SFN

It can be done with the feet or hands.

Another test caught my attention. the one sided face vasodilation (temple) following 10 mn of the ipsilateral foot or hand.

This article suggests a failure to this test could be a kind of C-fibers neuropathy.

A Human Sensory Pathway Connecting the Foot to Ipsilateral Face That Partially Bypasses the Spinal Cord - PMC (


Figure 6
Schematic model of ipsilateral vasodilation occurring following ice water foot immersion. We suggest that the preferred pathway for ipsilateral extracranial vasodilation following foot immersion is via a series of antidromic-orthodromic cutaneous connections (top of Figure). As this pathway partially bypasses the spinal cord, it remains intact following spinal cord injury (bottom of Figure).
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