1. Guillain-Barre syndrome (GBS) has been the subject of over 30 population studies during the past 50 years, most of which have shown an annual incidence in the range 1 0 to 2 0 per 100 000 population. The condition seems to be reasonably evenly distributed throughout the world and incidence rates are probably fairly stable over time.26 The annual incidence seemed to rise from 1-2 per 100 000 in 1953-6 to 2-7 per 100 000 in 1970-80 in Olmsted county, Rochester, USA.27 Similarly the annual incidence rose from about 1-3 per 100 000 in the triennium 1981-3 to 2-7 per 100 000 in 1991-3 when surveyed in Ferrara, northern Italy.28 These apparent increases in incidence were based on few cases and may be explained by increasing awareness and ascertainment of the disease.28
2. The disease occurs from infancy to extreme old age. There is a more or less linear increase in incidence with advancing years which would be compatible with lessening of immune suppressor mechanisms in old age and consequent increased susceptibility to autoimmune disease. In the largest series, collected in an active surveillance programme in the United States from 1979 to 1981, there was a small peak in the age distribution for young adults, especially women.32 This might be explained by exposure to infections which are more common in that age group, which include Campylobacter jejuni and cytomegalovirus
3. relation between the onset of symptoms and However, there are also other explanations for cytomegalovirus infection. Neuropathies in the association between a paraprotein and the other patients were more heterogenous. neuropathy including amyloid, vasculitis, and They included multiple mononeuropathy, isocoincidence. Peripheral neuropathy is somelated mononeuropathies, and lumbosacral times a feature of multiple myeloma, and is polyradiculopathy
4. Organisation surveillance programmes are plasm. Conversely between 2 5 and 5 5% of having a major impact. Between 1990 and patients with lung or breast cancer have clinical
5. there was a 55% fall in the worldwide evidence of a peripheral neuropathy.74 Focal or prevalence although part of the decrease may multifocal radiculopathies, plexopathies, and be due to changes in case definition. The highneuropathies are usually due to infiltration or est prevalence of leprosy