there is a variation in the rate and extent of recovery. the prognosis of guillain–barré syndrome is determined mainly by age (those over 40 may have a poorer outcome), and by the severity of symptoms after two weeks. furthermore, those who experienced diarrhea before the onset of disease have a worse prognosis. on the nerve conduction study, the presence of conduction block predicts poorer outcome at 6 months. in those who have received intravenous immunoglobulins, a smaller increase in igg in the blood two weeks after administration is associated with poorer mobility outcomes at six months than those whose igg level increased substantially. if the disease continues to progress beyond four weeks, or there are multiple fluctuations in the severity (more than two in eight weeks), the diagnosis may be chronic inflammatory demyelinating polyneuropathy, which is treated differently.