The course of organophosphate-induced delayed polyneuropathy (OPIDP) in humans 
has not been quantitatively measured in epidemiologic studies. This study 
evaluated the association of acute OP poisonings with motor neurologic 
impairment. Hand grip and pinch strength were evaluated among 62 Nicaraguan men 
hospitalized for acute OP poisoning between 1992 and 1996; 39 cattle ranchers 
and fishermen who had never experienced pesticide poisoning were controls. 
Exposure categories were moderate and severe poisonings with neuropathic and 
non-neuropathic OPs. Strength was measured at hospital discharge and seven weeks 
after poisoning. Grip and pinch strength were impaired among all OP-poisoned 
subjects at both examinations, more noticeably among those poisoned with OPs 
with suspected neuropathic effects, methamidophos and chlorpyrifos. In those 
with severe poisonings with neuropathic OPs, impairments were more marked among 
intentional than among occupational poisonings. The performances of suicidal 
subjects worsened at the second examination, consistent with OPIDP. Early motor 
impairment at the time of hospital discharge is consistent with cholinergic 
depolarization blockade after acute poisoning. The persistence of deficits in 
motor strength in all severely poisoned patients regardless of pesticide type 
was unexpected, and may reflect persistent cholinergic blockade or intermediate 
syndrome, neuropathy, or a combination of these.