The intermediate syndrome (IMS) appears in the interval between the end of the cholinergic crisis and the onset of OPIDP. Symptoms associated with IMS manifest between 24–96 hours after exposure. The exact etiology, incidence, and risk factors associated with IMS are not well understood, but IMS is recognized as a disorder of neuromuscular junctions. IMS occurs when a person has a prolonged and severe inhibition of AChE. It has been linked to specific OP pesticides such as parathion, methylparathion, and dichlorvos. Patients generally present with increasing weakness in the facial, neck flexor, and respiratory muscles.