PSSD: Assessing Its Value And Potential
The pursuit of a better testing method for diabetic peripheral neuropathy has spurred the re-emergence of the Pressure Specified Sensory Device (PSSD) and accompanying debate over its potential utility.
Yes, the NCV test and the Semmes-Weinstein monofilament allow you to test for the presence of neuropathy. However, in his article, “Restoring Sensation In Diabetic Patients” (see page 38), Stephen Barrett, DPM, says the monofilament does not “quantify or stage the level of peripheral neuropathy” and neither test enables you to assess “early stages of isolated peripheral nerve compression and peripheral neuropathy.”
Yet the PSSD can give you greater specificity and sensitivity in detecting these early stages, according to the September 2002 Ostomy/ Wound Management article, “Preventing Foot Ulceration And Amputation By Decompressing Peripheral Nerves In Patients With Diabetic Neuropathy,” written by A. Lee Dellon, MD.
The PSSD can help you identify “the earliest degree of chronic nerve compression...” notes Dr. Dellon. Early detection of neuropathy is critical, according to Dr. Barrett, who emphasizes that using a more specific and sensitive testing method allows you to “potentially initiate earlier intervention before severe axonopathy occurs.”
While this device has amazing potential, there are a few drawbacks to consider. One leading surgeon cautions that results can be skewed as there are limited nerves in the foot and ankle with normative data from which one can draw comparisons when using the PSSD.
There is a learning curve with the device and it can be expensive as well. Renting or leasing the PSSD device can cost between $1,200 and $1,400 a month. The company who manufactures the device says this price includes technical support. It also points out that performing one test with this device will net $300 in reimbursement and that it will assist physicians with “medical letters of necessity.” However, one surgeon I spoke with noted that “reimbursement (for the device) is all over the board” for some insurers in his state while other insurers will only pay for it “if a neurologist performs the test.”
Still, it’s hard to resist the device’s potential. While the PSSD has other uses (helping to identify and confirm cases of the oft-misdiagnosed tarsal tunnel syndrome, for example), it can also be employed to help identify diabetic patients with peripheral neuropathy who may benefit from nerve decompression surgery.
In reviewing four studies of nerve decompression in patients with diabetic neuropathy (Dellon (1992), Weimann, (1995), Chafee (1999) and Azmann (2000)), Dr. Dellon writes in his Ostomy/ Wound Management article that in all of these studies, “pain was relieved in 86 percent of patients and 72 percent recovered useful two-point discrimination.”
However, Dr. Dellon notes that two of these studies included patients who had a history of ulceration. While the percentage of pain relief in these patients was the same, he does note that “many of these patients recovered just protective sensation (no two-point discrimination).”
Those who have performed decompression surgery recommend reserving it for those who have painful neuropathy or have specific pain at a nerve entrapment site. While they believe in the procedure’s ability to provide pain relief, there still seem to be doubts about restoring sensation. One surgeon, citing inconsistent results, says “the jury is still out on restoring protective threshold.”
It’s hard not to be excited about the early studies and the potential of the device and decompression surgery in mitigating the damaging effects of neuropathy. Still, in order to overcome the cost barrier and some skepticism over proprietary interests, clearly more studies by a variety of independent authors are needed.