Related Experiment Videos
Neurological syndromes of organophosphorus compounds
1University Department of Neurology, Institute of Neurological Sciences, Southern General Hospital NHS Trust, Glasgow.
Abstract:
In addition to the acute cholinergic poisoning, organophosphorus (OP) compounds are capable of producing several subacute, delayed and chronic neurological, neurobehavioural and psychiatric syndromes. These include the intermediate syndrome, the organophosphate induced delayed neuropathy (OPIDN) and a number of chronic neurological and psychiatric manifestations lumped in this review under the term chronic organophosphate induced neuropsychiatric disorder (COPIND). A critical review of the concept of the neuropathy target esterase (NTE) inhibition and ageing as a marker of OPIDN and the related hen test is presented. It is concluded that the use of the hen test as an exclusive screening test for neurotoxicity of organophosphorus compounds is flawed. A number of recent studies are presented to demonstrate the unreliability of the test and flaws of scientific concepts underlying the hen test which is used to identify OPs as safe and "non-neurotoxic". The components of this new COPIND syndrome are described and the evidence for its existence is reviewed. Studies are in progress to further determine the profile of this syndrome and to define the overlap between its various components. The review also attempts to determine the clinical features so far described of these components and the investigations or markers used to identify and characterize COPIND and the behaviour of these markers. Evidence for chronic neurological/psychiatric effects of OP compounds have come from case studies, clusters of neurological diseases or from epidemiological investigations. New concepts in neurotoxicology are being produced from recent studies which may necessitate a new radical approach to the assessment of neurotoxicity of pesticides before releasing them for widespread use.
Insights
Organophosphorus compounds cause various neurological and psychiatric syndromes beyond acute poisoning. Current testing methods, like the hen test, are unreliable for detecting neurotoxicity, necessitating a reevaluation of pesticide safety assessments.
Area of Science:
- Neurotoxicology
- Environmental Health
- Occupational Medicine
Background:
- Organophosphorus (OP) compounds are known for acute cholinergic poisoning.
- OPs can also induce subacute, delayed, and chronic neurological, neurobehavioral, and psychiatric syndromes.
- These syndromes include intermediate syndrome, organophosphate-induced delayed neuropathy (OPIDN), and chronic organophosphate-induced neuropsychiatric disorder (COPIND).
Purpose of the Study:
- To critically review the concept of neuropathy target esterase (NTE) inhibition and aging as a marker for OPIDN.
- To evaluate the reliability of the hen test for screening OP neurotoxicity.
- To describe the components and review evidence for the existence of COPIND.
Main Methods:
- Critical literature review of existing concepts and studies.
- Analysis of recent studies challenging the validity of the hen test.
- Synthesis of evidence from case studies, disease clusters, and epidemiological investigations.
Main Results:
- The hen test is an unreliable and flawed screening tool for OP neurotoxicity.
- Recent studies demonstrate the unreliability of the hen test and underlying scientific concepts.
- Evidence suggests the existence of COPIND, a syndrome with distinct neurological and psychiatric components.
Conclusions:
- The current hen test is inadequate for identifying OPs as safe or "non-neurotoxic".
- A new radical approach to pesticide neurotoxicity assessment is required before widespread use.
- Further research is needed to define COPIND's profile, components, and clinical markers.