Organophosphate poisoning case with atypical clinical survey and magnetic resonance imaging findings

Evaluation of MR perfusion abnormalities in organophosphorus poisoning and its correlation with SPECT

AIM

Acute organophosphate (OP) pesticide poisoning causes substantial morbidity and mortality worldwide. Many imaging modalities, such as computerized tomography (CT), magnetic resonance imaging (MRI), and single photon emission computed tomography (SPECT) of the brain, have been used for quantitative assessment of the acute brain insult caused by acute OP poisoning. Perfusion defects on SPECT in acutely poisoned patients with OPs have been described, however, MR perfusion abnormalities have not been described in the literature. MR perfusion Imaging has the advantage of having higher spatial resolution, no radiation, and better availability.

MATERIALS AND METHODS

In this prospective study, 20 patients who ingested OP compounds were included. All the patients underwent brain SPECT on a dual head SPECT gamma camera and MRI brain on a 1.5T MR system. Neurocognitive tests were performed for all patients.

RESULTS

SPECT showed perfusion defects in 7 patients and total number of perfusion defects were 29. On MR perfusion, based on the cut-off values of normalized cerebral blood volume (nCBV) ratios and normalized cerebral blood flow (nCBF) ratios, the total number of patients showing perfusion defects were 6 and 8; and the total number of perfusion defects were 29 and 45, respectively. There was significant difference of the nCBV ratios and nCBF ratios between the control group (n = 20) and positive patients group (n = 6 and n = 8, respectively) (P > 0.05). All the defects seen on SPECT were well appreciated on nCBF maps (MRI perfusion) suggestive of 100% correlation.

CONCLUSION

MR perfusion imaging can be used as an effective modality for evaluation in acute OP poisoning.

Role of magnetic resonance imaging in diagnosing neurological complications in intermediate syndrome of organophosphate poisoning

Organophosphate poisoning (OP) is a very common mode of suicide in rural and urban areas due to the wide availability of pesticides. The identification of OP and timely referral for appropriate supportive care can be lifesaving. Injury to the central nervous system is a serious entity in acute OP. Application of modern imaging techniques like diffusion weighted imaging increases the diagnostic rate of brain injury in the early period and can provide evidence for medical treatment. We present the imaging features in the intermediate syndrome of OP.

Inherited or acquired metabolic disorders

This chapter starts with a description of imaging of inherited metabolic disorders, followed by a discussion on imaging of acquired toxic-metabolic disorders of the adult brain. Neuroimaging is crucial for the diagnosis and management of a number of inherited metabolic disorders. Among these, inherited white-matter disorders commonly affect both the nervous system and endocrine organs. Magnetic resonance imaging (MRI) has enabled new classifications of these disorders that have greatly enhanced both our diagnostic ability and our understanding of these complex disorders. Beyond the classic leukodystrophies, we are increasingly recognizing new hereditary leukoencephalopathies such as the hypomyelinating disorders. Conventional imaging can be unrevealing in some metabolic disorders, but proton magnetic resonance spectroscopy (MRS) may be able to directly visualize the metabolic abnormality in certain disorders. Hence, neuroimaging can enhance our understanding of pathogenesis, even in the absence of a pathologic specimen. This review aims to present pathognomonic brain MRI lesion patterns, the diagnostic capacity of proton MRS, and information from clinical and laboratory testing that can aid diagnosis. We demonstrate that applying an advanced neuroimaging approach enhances current diagnostics and management. Additional information on inherited and metabolic disorders of the brain can be found in Chapter 63 in the second volume of this series.

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.

Parkinsonism with organophosphate poisoning

Parkinsonism is a primary neurotoxic manifestation of organophosphate pesticide intoxication. We report here the case of a 67-year-old man who developed acute parkinsonism with tremors and rigidity following exposure to fenitrothion, an organophosphate pesticide. His parkinsonism disappeared, and 2 months later he was able to walk alone without antiparkinsonian drug treatment. To identify particular lesions in the brain, Z score images were obtained from SPECT (single photon emission computed tomography) scans of the patient during the acute poisoning and a follow-up scan performed 2 months later. We indicate that reversible parkinsonism correlated with putaminal hyperperfusion as observed in the Z score images obtained during the acute event; this condition resolved later in concert with resolution of the clinical parkinsonism. We believe that the SPECT scan Z score images in this study are an important find in elucidating parkinsonism manifestations due to organophosphate poisoning.

Aspects électrophysiologiques du syndrome intermédiaire au cours des intoxications aux organophosphorés

Acute organophosphate poisoning, whether accidental or suicidal, is frequent in developing countries and produces significant morbidity and mortality. Organophosphates inhibit cholinesterase activity at the neuromuscular junction and cause extensive muscle paralysis, particularly for respiratory function. Poisonings evolve in three stages: cholinesterase crisis, intermediate syndrome and delayed neuropathy. Electrophysiological aspects have been poorly studied. We report the case of a 25-year-old woman admitted to intensive care unit with muscarinic signs and respiratory failure after attempted suicidal organophosphate poisoning. Cholinesterase activity was low and the electrophysiological study disclosed the characteristic aspect of intermediate syndrome. The patient died due to septic complications. This syndrome is exceptional with a poorly understood pathophysiology. The electrophysiological study is essential for diagnosis.

Aspects cliniques et électrophysiologiques de l’intoxication aiguë aux organophosphorés

INTRODUCTION

Acute organophosphate (OP) intoxications, accidental or voluntary, are responsible for a high mortality. They cause extensive muscular paralysis by acetyl cholinesterase activity inhibition at the neuromuscular junction level.

AIM

To underline the rarity and the characteristic electrophysiological pattern during cholinergic crisis.

OBSERVATION

A 28-year-old woman was admitted to the medical intensive care unit for Malathion acute intoxication with signs of glandular hypersecretion, complicated tetraparesis, and respiratory distress. The cholinesterase activity was 17%. The electroneuromyography showed multiple motor responses to the same stimulation, which is characteristic of the cholinergic crisis. Other electrophysiological parameters, in particular low-frequency repetitive stimulations, were normal. The evolution was favourable after symptomatic treatment and respiratory assistance.

DISCUSSION AND CONCLUSIONS

Organophosphate intoxications evolve in three phases: acute cholinergic crisis, intermediate syndrome, and delayed neuropathy. While the electrophysiological aspects of delayed neuropathy are best characterized, those of crisis and intermediate syndrome remain very little studied. The persistence of acetylcholine in the synaptic slit would explain the multiple motor responses to single stimulation during the crisis.