the cause is unknown. the underlying mechanism involves an autoimmune disorder in which the body's immune system mistakenly attacks the peripheral nerves and damages their myelin insulation. sometimes this immune dysfunction is triggered by an infection or, less commonly by surgery and rarely by vaccination. the diagnosis is usually made based on the signs and symptoms, through the exclusion of alternative causes, and supported by tests such as nerve conduction studies and examination of the cerebrospinal fluid. there are a number of subtypes based on the areas of weakness, results of nerve conduction studies and the presence of certain antibodies. it is classified as an acute polyneuropathy.