Electromagnetic shield may stop phantom limb pain

NEW YORK (Reuters Health) - A "stump stocking" consisting of a silicone liner interwoven with an electromagnetic shield (Umbrellan) appears to reduce amputees' phantom pain, according to a study by German researchers, published in the Journal of Pain and Symptom Management.

According to the Web page for the manufacturers of the Medipro Liner RELAX stocking -- Medi Ltd in Bayreuth, Germany -- electromagnetic influences from power lines or similar devices may be the cause of phantom limb pain. "As a result of the amputation one can imagine the severed nerve endings as cables with free ends; electromagnetic influences irritate the nerve endings and produce pain."

The company further asserts that the liner "interrupts the transmission of sensations which stimulate the nerve endings of the residual limb" and "also helps to avert further static charge in the prosthesis socket that results from movement or walking."

Dr. Uwe Kern, from the Center of Pain Management and Palliative Care in Wiesbaden, and co-investigators conducted a trial with 30 leg amputees. For 2-week periods, the subjects wore the liner with the electromagnetic shield in place, and for 2 weeks they wore the same stocking but without the shield. During both test periods, the subjects recorded the degree of phantom pain six times a day.

According to the report by Kern and his associates, the 22 subjects who completed the trial were adults whose phantom pain was rated as 3 or higher on a 0-10 pain scale on at least 10 days per month.

Patient reports showed that both liners reduced pain, indicating that the silicone stocking alone relieves pain. However, the liner with Umbrellan significantly reduced pain and maximum pain compared with the stocking lacking the electromagnetic shield.

The active device was also associated with greater "improvement in well-being" reported by the subjects.

The researchers suggest that "trials to deliberately provoke phantom pain by low-amplitude electromagnetic impulses" might help clarify exactly how the electromagnetic shield works.

This study was supported by Medi Ltd.

SOURCE: Journal of Pain Symptom Management, October 2006.