Correlation of defects in regional cerebral blood flow determined by 99mTc SPECT with residual neurocognitive testing abnormalities during and 3 months post exposure in acutely poisoned patients with organophosphates.

Introduction: Following acute organophosphate exposure, morphological changes in certain regions of the brain have been reported to develop within a few hours and involve neuronal degeneration. Single photon emission computed tomography (SPECT) has been used to determine changes in the regional cerebral blood flow and attempts have been made to correlate these changes with long-term neurological sequelae.

Purpose Of Study: The aim of the study was to determine changes in the regional cerebral blood flow by 99mTc-ECD SPECT following acute organophosphate poisoning and to correlate these defects with abnormalities in neurocognitive testing carried out during admission and at 3 months post exposure, in order to determine whether any changes in the cerebral blood flow could help in predicting future development of neurocognitive deficit.

Patients And Methods: Twenty-eight patients with acute organophosphorous poisoning were included in the study. The inclusion criteria were a history of ingestion or accidental exposure, clinical features of cholinergic crises, and low serum acetylcholinesterase (AChE). Twenty age- and sex-matched patients from a previous study were used as controls for the neurocognitive tests. There were no controls for SPECT.

Results: Of the 28 patients studied, 27 had abnormalities in the regional cerebral blood flow on SPECT with men having significantly higher abnormalities than women (p < 0.05). The right side of the brain had more defects than the left, with the occipital lobes being the most commonly involved. Of seven neurocognitive function tests carried out on patients who had regional cerebral blood flow defects during admission, abnormalities were observed in six tests. In 18 of 26 patients who could be tested at 3 months post exposure, improvement was observed in Trail B and Visual retention tests. However, others tests remained significantly abnormal.

Conclusion: We conclude that a single episode of clinically significant organophosphate intoxication can lead to persistent residual neurocognitive deficits. Detection of regional cerebral blood flow defects on 99mTc-ECD SPECT can possibly help in predicting long-term deficits in neurocognitive functions in such patients.