A neuroimmunologic evaluation of 200 symptomatic patients with breast implants and 100 symptomatic patients with chronic fatigue tabulates only laboratory data and provides an extensive methodological description. Antibodies to myelin basic protein, myelin associated glycoprotein (MAG), asialoganglioside GM1, and sulfatide were measured, and lymphocyte subsets were defined. The absence of demographic or clinical information limits any meaning that might be assigned to these laboratory data (Vojdani, 1995a). An abstract by Shanklin and Smalley (1996a) reports their examination of sural nerve biopsies from women with silicone breast implants using polarizing microscopy. These authors reported detection of quartzite silica scattered throughout the nerve at the outer surface of the myelin and speculated on how silicone might be transformed to silica in the body (Shanklin and Smalley, 1996a). However, there is no credible evidence that silicone is degraded to crystalline silica under physiologic conditions. There is also no credible evidence that crystalline silica originates from breast implants or is found near implants (see Chapter 5 of this report). Furthermore, polarizing microscopy is not a reliable technology for detection of crystalline silica (IRG, 1998; see Young, IOM Scientific Workshop), and examination of sural nerves in cadavers of women with silicone breast implants did not reveal elevated silicon concentrations (Evans et al., 1996).
The available studies suggesting neurologic disease, with the exception of obvious local problems due to the physical presence of silicone gel which can compress nerves following implant rupture and migration of the gel, have defects that limit any conclusions to be drawn from them. Furthermore, basic toxicological and animal experimental studies do not find pathology that would support a causation of human neurologic disease by silicone breast implants. Two epidemiological studies suggest that there is no elevated relative risk for neurological disease in large cohorts of women with silicone breast implants. The committee finds that the evidence for a general neurologic disease or syndrome caused by, or associated with, silicone breast implants is insufficient or flawed.