Etiology

Introduction and incidence

The Guillain–Barré syndrome (GBS) is a subacute immune-mediated disorder of the peripheral nerves. The diagnosis is primarily clinical, the essential features being a more or less symmetrical paresis, decrease of myotatic reflexes and a typical time course (1,2). In addition, other causes for polyneuropathy should be excluded. The paresis reaches its nadir by definition within 4 weeks, but usually it is seen within 2 weeks. In 20–30% of the patients the muscle weakness is so severe that artificial respiration is needed. Based upon clinical and laboratory arguments subpatterns or variants have been described. They will be discussed in more detail below.

Several studies have been published reporting incidence rates (IR) from 0.4 to 2.2 cases per 100,000 persons per year (Table 16.1). The variation in the reported IR may be more related to differences in methodology than to true differences in incidence. The data suggest that the occurrence of the disease does not change consistently over time and is not restricted to specific areas nor related to factors as race, standard of living or climate. GBS affects people from all ages but a clear increase in incidence with age has been reported in most studies (3–6). Some studies show a bimodal age distribution with a peak around 20–30 years (7–10). In most studies men are more frequently affected than women, but in only three studies was this difference statistically significant (3,6,11).

Two-thirds of GBS patients suffer from an infection approximately one to three weeks before the onset of weakness. These infections mostly involve the upperrespiratory and the gastrointestinal tract (12,13). Although some of these infections tend to show a seasonal preponderance, there is hardly ever a significant difference between seasons reported in the occurrence of GBS.