The effects of cryosurgery and cryoprotectants on peripheral nerve function

Cryosurgery has many advantages in the treatment of musculoskeletal tumors, but complications can occur, with injuries to the peripheral nerves. Cryoprotectants such as dimethylsulfoxide (DMSO) and glycerol enhance the in vitro survival of cultured Schwann cells, but they have not been studied in vivo. In vitro, 10 percent DMSO provided the maximal survival after freezing to -80 degrees C. The neurologic recovery of a peripheral nerve, following cryoinjury and using liquid nitrogen, was evaluated both with and without pretreatment of the nerve with 10 percent DMSO. There were three experimental groups: 1) one sham operation; 2) with freezing of the sciatic nerve; and 3) with freezing of the sciatic nerve after treatment with DMSO. Gait analyses (sciatic function index, SFI), muscle weights, and histologic evaluations were performed in order to follow the neurologic recovery over a ten-week period. The freezing-only group and the sham-operated control had an excellent functional recovery in terms of the SFI following surgery (-4.2 percent +/- 4.0 percent and -2.4 percent +/- 5.7 percent, respectively), in contrast to the freezing group with DMSO (-34.1 percent +/- 5.5 percent, p less than .01). The average tibialis anterior muscle weight, reported as the ratio of the operated to the unoperated limb (88.2 percent +/- 1.0 percent) in the freezing-only group, was greater than the average for the freezing-with-DMSO-treated group (70.6 percent +/- 3.9 percent, p less than .01). Cryoprotectants are routinely used to optimize the survival of cells in tissue culture. However, DMSO not only failed to protect peripheral nerves from cryoinjury, but it also inhibited functional recovery.