The Value of Morphological Neuroimaging after Acute Exposure to Toxic Substances

Toxic encephalopathy and peripheral neuropathy of poisoning by Avermectin Pyridine: a case report and a review of the literature

Background

Avermectin Pyridaben (AVP) is an insecticide with extreme neurotoxicity in human, causing critical symptoms such as nausea, vomiting, coma and respiratory failure within a short time after oral ingestion. Neurological sequelae or even death may occur because of delayed treatment or excessive toxic dose.

Case presentation

We report a 15-year-old girl who presented with coma, respiratory failure, limb weakness, ataxia symptoms after ingestion of a toxic dose of AVP. Soon after the poisoning, the patient was treated with life-saving mechanical ventilation and haemodialysis. Subsequently brain Magnetic Resonance Imaging (MRI) and nerve conduction study (NCS) and electromyography (EMG) demonstrated toxic encephalopathy and peripheral nerve injury. Over the next 2 months the patient's limb function gradually recovered under treatment with hyperbaric oxygen, glucocorticoid pulses and neurotrophic drugs.

Conclusion

This case documents a rare presentation of toxic encephalopathy complicated with peripheral neuropathy following AVP poisoning. Seven other similar cases of poisoning in terms of common symptoms and effective treatment have also been summarised for providing clinicians with experience in diagnosis and therapy.

[Damage to the structures of the brain in acute carbon monoxide poisoning]

OBJECTIVE

The aim of the study was to investigate the features of damage to the structures of the brain in acute carbon monoxide (CO) poisoning. The results of forensic, microscopic and morphometric studies of the brain of 78 corpses died from acute carbon monoxide poisoning are presented. The peculiarities of damage to the nervous tissue, the glial complex, as well as changes in the structures of blood vessels and the state of intravascular blood with the formation of aggregates, sludge, and blood clots were revealed. These changes along with perivascular and pericellular edema indicate the agonal death of the victims. When the carboxyhemoglobin concentration in the blood is about 30% the brain structures' lesions begin to appear; their intensity increases when the carboxyhemoglobin concentration is more than 60%. According to the authors, the substantiation of the thanatogenesis of various types of carbon monoxide poisoning requires further research taking into account the age of the victims, the carboxyhemoglobin concentration in the blood, the duration of the agonal period, as well as possible (competing) conditions: for example, acute alcohol intoxication, thermal injury, etc. Still urgent the studies of structures of other target organs of CO - heart and lungs.

Delayed brain injury post carbon monoxide poisoning

A 66-year-old male was found unresponsive and diagnosed with acute carbon monoxide poisoning, with pathognomonic findings on radiological imaging. During his first day's the patient underwent acute neurological deterioration; however, this was followed 2 weeks later with a subsequent improvement to near baseline. The improvement back to baseline was short-lived, and the patient quickly worsened and underwent neurological decompensation. These findings were consistent with delayed post hypoxic leukoencephalopathy, serious sequelae of carbon monoxide poisoning. This case report shows the importance of recognition of carbon monoxide toxicity and aims to improve accurate diagnosis of the sequelae that may follow using computed tomography and magnetic resonance imaging sequences, magnetic resonance spectroscopy in order to prevent or ameliorate further neurological decline.

Neurologic complications of electrolyte disturbances and acid-base balance

Electrolyte and acid-base disturbances are common occurrences in daily clinical practice. Although these abnormalities can be readily ascertained from routine laboratory findings, only specific clinical correlates may attest as to their significance. Among a wide phenotypic spectrum, acute electrolyte and acid-base disturbances may affect the peripheral nervous system as arreflexic weakness (hypermagnesemia, hyperkalemia, and hypophosphatemia), the central nervous system as epileptic encephalopathies (hypomagnesemia, dysnatremias, and hypocalcemia), or both as a mixture of encephalopathy and weakness or paresthesias (hypocalcemia, alkalosis). Disabling complications may develop not only when these derangements are overlooked and left untreated (e.g., visual loss from intracranial hypertension in respiratory or metabolic acidosis; quadriplegia with respiratory insufficiency in hypermagnesemia) but also when they are inappropriately managed (e.g., central pontine myelinolisis when rapidly correcting hyponatremia; cardiac arrhythmias when aggressively correcting hypo- or hyperkalemia). Therefore prompt identification of the specific neurometabolic syndromes is critical to correct the causative electrolyte or acid-base disturbances and prevent permanent central or peripheral nervous system injury. This chapter reviews the pathophysiology, clinical investigations, clinical phenotypes, and current management strategies in disorders resulting from alterations in the plasma concentration of sodium, potassium, calcium, magnesium, and phosphorus as well as from acidemia and alkalemia.

The role of MR imaging in assessment of brain damage from carbon monoxide poisoning: a review of the literature

SUMMARY

The aim of this article is to review how MR imaging and associated imaging modalities provide clinicopathologic information on brain damage after carbon monoxide poisoning. Initially, many authors documented typical findings of conventional MR imaging in the gray matter structures such as the globus pallidus and in various regions of cerebral white matter. The focus of investigation has since shifted to observation of cerebral white matter areas that are more frequently detected on MR imaging and are more responsible for chronic symptoms than the gray matter. DWI has dramatically contributed to the ability to quantitatively assess cerebral white matter damage. Subsequently, DTI has enabled more sensitive evaluation than DWI and can demonstrate progressive pathologic changes in the early stage, allowing prediction of chronic conditions. In addition, MR spectroscopy reveals changes in metabolite levels, offering quantitative clinicopathologic information on brain damage after carbon monoxide poisoning.

Toxic encephalopathy

This article schematically reviews the clinical features, diagnostic approaches to, and toxicological implications of toxic encephalopathy. The review will focus on the most significant occupational causes of toxic encephalopathy. Chronic toxic encephalopathy, cerebellar syndrome, parkinsonism, and vascular encephalopathy are commonly encountered clinical syndromes of toxic encephalopathy. Few neurotoxins cause patients to present with pathognomonic neurological syndromes. The symptoms and signs of toxic encephalopathy may be mimicked by many psychiatric, metabolic, inflammatory, neoplastic, and degenerative diseases of the nervous system. Thus, the importance of good history-taking that considers exposure and a comprehensive neurological examination cannot be overemphasized in the diagnosis of toxic encephalopathy. Neuropsychological testing and neuroimaging typically play ancillary roles. The recognition of toxic encephalopathy is important because the correct diagnosis of occupational disease can prevent others (e.g., workers at the same worksite) from further harm by reducing their exposure to the toxin, and also often provides some indication of prognosis. Physicians must therefore be aware of the typical signs and symptoms of toxic encephalopathy, and close collaborations between neurologists and occupational physicians are needed to determine whether neurological disorders are related to occupational neurotoxin exposure.

Pathophysiology, clinics, diagnosis and treatment of heart involvement in carbon monoxide poisoning

The toxicity of carbon monoxide has been recognized for long throughout history and is unquestionably the leading cause of unintentional poisoning deaths in the Western countries. The severity of poisoning is dependent upon environmental and human factor. The leading pathophysiological mechanism resides in the ability of carbon monoxide to bind to hemoglobin molecules with high affinity, displacing oxygen and generating carboxyhemoglobin, which is virtually ineffective to deliver oxygen to the tissues. The organs with the highest demand for oxygen such as the brain and the heart are more vulnerable to injury. Myocardial involvement is commonplace in moderate to severe carbon monoxide poisoning and is associated with a substantially higher risk of mortality. Besides hypoxic damage, carbon monoxide produces myocardium injuries with cardiospecific mechanisms, mostly attributable to direct damage at cellular or subcellular level. The clinical spectrum of heart involvement is broad and encompasses cardiomyopathy, angina attack, myocardial infarction, arrhythmias and heart failure up to myocardial stunning, cardiogenic shock and sudden death. Patients with underlying cardiac disease, especially coronary heart disease, are at greater risk of infarction and arrhythmias. Single photon emission computed tomography (SPECT) is the technique of choice for diagnosing cardiac involvement, whereas the recent introduction of the highly sensitive troponin immunoassays seems promising for the early triage of patients. No specific treatment other than oxygen delivery can be advocated for cardiac toxicity at present, and 100% oxygen therapy should be continued until the patient is asymptomatic and carboxyhemoglobin levels decrease below 5-10%.

Unilateral basal-ganglia involvement likely due to valproate-induced hyperammonemic encephalopathy

A male child suffering from generalized tonic clonic epilepsy, on treatment with valproate, developed fulminant hepatic failure, hyperammonemia and encephalopathy due to drug toxicity. The most extraordinary feature was his MRI (FLAIR image) of brain which showed unilateral hyperintensities in right putamen and caudate nucleus. The patient recovered on withdrawal of valproate with mild residual left sided athetotic movements during remission. Repeat investigation confirmed an improved MRI imaging and normalised blood ammonia levels. The case report is unique because of unilateral involvement of basal ganglia due to valproate-induced encephalopathy.

Thalamofrontal neurodevelopment in new-onset pediatric idiopathic generalized epilepsy

BACKGROUND

Quantitative MRI techniques have demonstrated thalamocortical abnormalities in idiopathic generalized epilepsy (IGE). However, there are few studies examining IGE early in its course and the neurodevelopmental course of this region is not adequately defined.

OBJECTIVE

We examined the 2-year developmental course of the thalamus and frontal lobes in pediatric new-onset IGE (i.e., within 12 months of diagnosis).

METHODS

We performed whole-brain MRI in 22 patients with new-onset IGE and 36 age-matched healthy controls. MRI was repeated 24 months after baseline MRI. Quantitative volumetrics were used to examine thalamic and frontal lobe volumes.

RESULTS

The IGE group showed significant differences in thalamic volume within 1 year of seizure onset (baseline) and went on to show thalamic volume loss at a significantly faster rate than healthy control children over the 2-year interval. The control group also showed a significantly greater increase in frontal white matter expansion than the IGE group. In contrast, frontal lobe gray matter volume differences were moderate at baseline and persisted over time, indicating similar developmental trajectories with differences early in the disease process that are maintained.

CONCLUSIONS

Brain tissue abnormalities in thalamic and frontal regions can be identified very early in the course of IGE and an abnormal trajectory of growth continues over a 2-year interval.

Hyperintensity of the basal ganglia and cortex on FLAIR and diffusion-weighted imaging: self-assessment module

The educational objectives for this self-assessment module are for the participant to exercise, self-assess, and improve his or her understanding of the hyperintensity of the basal ganglia and cortex on FLAIR and diffusion-weighted imaging and the key imaging characteristics of various causes of the hyperintensity of the basal ganglia and cortex.

Features of Neurotoxicity on Brain CT of Acutely Intoxicated Unconscious Patients

Diagnostic imaging is a valuable device in clinical management of poisoned patients presenting to emergency units in a comatose state. Some toxic agents have adverse effects on the central nervous system (CNS). Non-contrast computed tomography (CT) of the brain, as an available diagnostic method with a high resolution, can provide useful information about structural disturbances of unconscious patients with suspected drug or chemical intoxication. The authors would describe various presentations of toxic substances detected on the brain CT scans of ten patients with acute intoxication. While non-specific, CT findings of low-attenuation lesions in the basal ganglia, infarctions in young patients, or diffuse edema should raise suspicion for poisoning or overdose.

[Severe ethylene glycol intoxication by skin absorption]

Ethylene glycol is present predominantly in antifreeze,and in industrial solvents. Accidental ingestion of ethylene glycol is relatively rare, but may be potentially lethal. It results in a depression of the central nervous system, a severe metabolic acidosis and an acute renal failure by tubular precipitation of calcium oxalate crystals. We report a case of ethylene glycol poisoning by through skin absorption.

OBSERVATION

A 38-year-old man, working in a cement factory, with a history of cutaneous psoriasis for 10 years, was admitted to our hospital due to acute nausea, vomiting and diffuse abdominal pain, followed by generalized convulsive status epilepticus and worsening of his mental status. Biologic analysis showed severe metabolic acidosis and acute renal failure which required hemodialysis. On renal biopsy, there were intratubular crystals of calcium oxalate. Cerebral magnetic resonance imaging showed posterior encephalitis. Evolution was marked by normalization of renal function at two weeks and improvement of the mental status. Retrospectively, the patient's history-taking revealed that he manipulated ethylene glycol without gloves.

CONCLUSION

Cutaneous contact with ethylene glycol may cause poisoning in presence of skin lesions. The triad neurologic involvement, renal failure due to oxalate crystals deposits and metabolic acidosis leads to the diagnosis of ethylene glycol intoxication. In the case of acute renal failure with oliguria, haemodialysis is the treatment of choice. It allows the removal of the toxic substance and its metabolites with correction of the metabolic acidosis. The precocity of the treatment may improve the prognosis.

The value of brain CT findings in acute methanol toxicity

OBJECTIVE

Due to depressant effects of methanol on the central nervous system, brain computed tomography (CT) scan has been introduced as a diagnostic device in methanol intoxication. The authors aimed to present brain CT findings in patients with acute methanol intoxication and to determine signs associated with death.

MATERIALS AND METHODS

This cohort study involved 42 consecutive patients with acute methanol intoxication. Inclusion criteria were consisted of characteristic clinical presentation of methanol poisoning, and metabolic acidosis with increased anion and osmolar gaps. Brain CT scans without contrast medium were obtained. To determine the association between the CT findings and death, the chi-square test or the Fisher's exact test, odds ratio (OR) and its 95% confidence interval (95% CI) were calculated.

RESULTS

Twenty-eight patients (66.6%) had a total of 55 abnormal findings on brain CT, in which bilateral putaminal hypodense lesions was the most common manifestation (27 cases, 96.4%). Putaminal hemorrhage with varying degrees was observed in 7 patients (25%). Six patients (21.4%) had low attenuation lesions in the subcortical white matter of the insula. A significant association was observed between putaminal hemorrhage (OR=8, 95% CI=1.187-53.93, P=0.018) and subcortical necrosis of the insula (OR=11, 95% CI=1.504-80.426, P=0.007) with death.

CONCLUSION

In addition to clinical and laboratory findings, presence of putaminal hemorrhage and insular subcortex white matter necrosis are associated with a poor clinical outcome in patients with methanol poisoning.

Pyramidal and extrapyramidal dysfunction as a sequela of hypoxic injury: case report

Background

The clinical and radiological aspects of hypoxic brain injury without ischemia are not well characterized. A spectrum of clinical manifestations have been observed in patients that recover from hypoxic brain injury, including a subset that demonstrate persistent motor system disturbances. Early Magnetic Resonance Imaging (MRI) studies have shown abnormalities in basal ganglia, cerebral and cerebellar cortex.

Case presentation

A 23-year-old man was affected by acute respiratory failure after drug overdose. His clinical condition progressed from coma to partial recovery with persistent lack of control and stiffness in the lower extremities. MRI of the brain showed evolving lesions in the cerebellum, globus pallidus and motor cortex that correlated with neurological signs.

Conclusion

A careful analysis of this case and a review of the relevant literature indicate that the clinical residua after recovery from hypoxic injury to the brain is predominantly disorders of the motor system, and the MRI manifestations as well as the clinical presentation can evolve over time. Understanding more of the factors that affect hypoxic brain injury can be helpful in determining the clinical outcome and management of these patients.