PSSD Testing: a more accurate and noninvasive replacement test for nerve conduction studies. The most common use in foot and ankle exams is for the diagnosis of Tarsal Tunnel syndrome. We are finding that many difficult plantar fasciitis patients actually have Tarsal Tunnel concerns that might be part of the diagnosis. When the nerve is compressed and/or damaged within the Tarsal Tunnel it manifests as decreased sensitivity to the skin which can be tested and compared to normal age appropriate values. We are finding that this test is superior to EMG or nerve conduction studies which appear to have a higher level of false negative results.