MRI findings in methanol intoxication: a report of two cases

Höffding step and beyond: The impact of visual sensory impairment on cognitive performance in neuropsychological testing of survivors of acute methanol poisoning

BACKGROUND

Sensory deficits can result in limitations regarding how well neuropsychological test findings can be interpreted. Only a few studies have investigated the influence of vision alteration on neuropsychological tests. In 2012 the Czech Republic experienced mass methanol poisoning. Methanol metabolites cause histotoxic hypoxia to the optic nerve.

OBJECTIVE

In the current study, the effect of the toxic damage on the parts of the visual pathway on visual and non-visual neuropsychological measures was investigated using electrophysiological methods (visual evoked potential (VEP) and optical coherence tomography (OCT) with retinal nerve fibre layer (RNFL) thickness measurement.

METHODS

53 individuals who experienced methanol poisoning participated in this research (76% men; ages 24 to 74 years, mean = 43.8±14.6 years; education 11.9±1.4 years). Each participant underwent comprehensive neurological, ophthalmological, and neuropsychological examinations.

RESULTS

The results of mixed-effect models revealed significant small to a medium association between the Stroop test weak interference and Grooved Pegboard with the left eye global, nasal and temporal RNFL thickness. Also, medium associations between the Finger Tapping test and the Stroop test weak interference and OS temporal RNFL, right eye temporal RNFL, and the latency P1 of VEP in the left eye were significant.

CONCLUSION

The results of this study found a small to medium association (r = .15- .33; p = .010- .046) between RNFL thickness and cognitive visual test performance. Careful interpretation is suggested regarding results obtained from visual tests of the executive or motor functioning with participants with RNFL decrease or other types of early visual processing damage.

Neuroimaging for differential diagnosis of transient neurological attacks

BACKGROUND

Rapid yet comprehensive neuroimaging protocols are required for patients with suspected acute stroke. However, stroke mimics can account for approximately one in five clinically diagnosed acute ischemic strokes and the rate of thrombolyzed mimics can be as high as 17%. Therefore, to accurately determine the diagnosis and differentiate mimics from true transient ischemic attacks, acute ischemic stroke is a challenge to every clinician.

DISCUSSION

Medical history and neurological examination, noncontract head computed tomography, and routine magnetic resonance imaging play important roles in the assessment and management of patients with transient neurological attacks in the emergency department. This review attempts to summarize how neuroimaging can be utilized to help differentiate the most common mimics from transient ischemic attack and acute ischemic stroke.

CONCLUSION

Although imaging can help direct critical triage decisions for intravenous thrombolysis or endovascular therapy, more detailed medical history and neurological examination are crucial for making a prompt and accurate diagnosis for transient neurological attack patients.

Biochemical mechanism underlying the pathogenesis of diabetic retinopathy and other diabetic complications in humans: the methanol-formaldehyde-formic acid hypothesis

Hyperglycemia in diabetic patients is associated with abnormally-elevated cellular glucose levels. It is hypothesized that increased cellular glucose will lead to increased formation of endogenous methanol and/or formaldehyde, both of which are then metabolically converted to formic acid. These one-carbon metabolites are known to be present naturally in humans, and their levels are increased under diabetic conditions. Mechanistically, while formaldehyde is a cross-linking agent capable of causing extensive cytotoxicity, formic acid is an inhibitor of mitochondrial cytochrome oxidase, capable of inducing histotoxic hypoxia, ATP deficiency and cytotoxicity. Chronic increase in the production and accumulation of these toxic one-carbon metabolites in diabetic patients can drive the pathogenesis of ocular as well as other diabetic complications. This hypothesis is supported by a large body of experimental and clinical observations scattered in the literature. For instance, methanol is known to have organ- and species-selective toxicities, including the characteristic ocular lesions commonly seen in humans and non-human primates, but not in rodents. Similarly, some of the diabetic complications (such as ocular lesions) also have a characteristic species-selective pattern, closely resembling methanol intoxication. Moreover, while alcohol consumption or combined use of folic acid plus vitamin B is beneficial for mitigating acute methanol toxicity in humans, their use also improves the outcomes of diabetic complications. In addition, there is also a large body of evidence from biochemical and cellular studies. Together, there is considerable experimental support for the proposed hypothesis that increased metabolic formation of toxic one-carbon metabolites in diabetic patients contributes importantly to the development of various clinical complications.

Cognitive changes after methanol exposure: Longitudinal perspective

BACKGROUND

From 2012 to 2013, there was a mass methanol poisoning outbreak in the Czech Republic. Methanol metabolites can cause specific lesions in the basal ganglia, subcortical white matter, and optic nerve. However, long-term sequelae of methanol poisoning on cognitive functioning have not yet been explored. The current study aimed to delineate the cognitive changes observed in methanol poisoning survivors in the seven years since 2012.

METHODS

We conducted longitudinal research with repeated measurements in 2013, 2015, 2017 and 2019 to evaluate the development of cognitive changes after acute methanol poisoning. A complex neuropsychological battery consisted of tests of global cognitive performance, auditory and visual attention, executive functioning, learning and memory, working memory and language. Motor performance measures and depression scale were also included.

RESULTS

Repeated measures ANOVA of four measurements with post-hoc tests showed a significant decline in the Mini-Mental State Examination (p = 0.007); however, other parameters were not significantly decreasing. In comparison to normative values, the z-scores for each test measure, in the memory domain, in particular, ranged from 43 to 60 % of participants below 1.5 SD. Mild to severe depression levels from the onset of poisoning improved during the seven years, returning to normal in up to 27 % of participants.

CONCLUSION

In the longitudinal perspective, methanol poisoning survivors manifest progressive global cognitive decline and overall persistent below-average cognitive performance with some improvements in the frequency of depressive symptoms.

Methanol poisoning as a new world challenge: A review

BACKGROUND

Methanol poisoning (MP) occurs often via ingestion, inhalation, or dermal exposure to formulations containing methanol in base. Clinical manifestations of MP include gastrointestinal symptoms, central nervous system (CNS) suppression, and decompensated metabolic acidosis occurred with blurred vision and early or late blindness.

OBJECTIVE

This study reviewed the clinical manifestations, laboratory and radiology findings, and treatment approaches in MP.

DISCUSSION

Methanol is usually rapidly absorbed after ingestion and metabolized by alcohol dehydrogenase (ADH), then distributed to the body water to reach a volume distribution approximately equal to 0.77 L/kg. It is also eliminated from the body as unchanged parent compounds. Clinical manifestations of MP alone initiate within 0.5-4 h after ingestion and include gastrointestinal symptoms and CNS suppression. After a latent period of 6-24 h, depending on the absorbed dose, decompensated metabolic acidosis occurs with blurred vision and early or late blindness. Blurred vision with normal consciousness is a strong suspicious sign of an MP. The mortality and severity of intoxication are well associated with the severity of CNS depression, hyperglycemia, and metabolic acidosis, but not with serum methanol concentration. After initial resuscitation, the most important therapeutic action for patients with known or suspected MP is correction of acidosis, inhibition of ADH, and hemodialysis.

CONCLUSION

Since MP is associated with high morbidity and mortality, it should be considered seriously and instantly managed. Delay in treatment may cause complications, permanent damage, and even death.

Tongue fasciculations with denervation pattern in osmotic demyelination syndrome: a case report of diagnostic dilemma

Background

The pathogenesis of osmotic demyelination syndrome is not completely understood and usually occurs with severe and prolonged hyponatremia, particularly with rapid correction. It can occur even in normonatremic patients, especially who have risk factors like alcoholism, malnutrition and liver disease. Bilateral tongue fasciculations with denervation pattern in electromyogram is a manifestation of damage to the hypoglossal nucleus or hypoglossal nerves. Tongue fasciculations were reported rarely in some cases of osmotic demyelination syndrome, but the exact mechanism is not explained.

Case presentation

A 32-year-old Sri Lankan male, with a history of daily alcohol consumption and binge drinking, presented with progressive difficulty in walking, dysphagia, dysarthria and drooling of saliva and alteration of consciousness. On examination he was akinetic and rigid resembling Parkinsonism with a positive Babinski sign. Clinical features were diagnostic of osmotic demyelination syndrome and MRI showed abnormal signal intensity within the central pons and basal ganglia. He also had tongue fasciculations. The electromyogram showed denervation pattern in the tongue with normal findings in the limbs. Medulla and bilateral hypoglossal nerves were normal in MRI.

Conclusion

We were unable to explain the exact mechanism for the denervation of the tongue, which resulted in fasciculations in this chronic alcoholic patient who developed osmotic demyelination syndrome. The hypoglossal nuclei are located in the dorsal medulla and radiologically undetected myelinolysis of the medulla is a possibility. Hypoglossal nerve damage caused by methanol or other toxic substances that can contaminate regular ethyl alcohol is another possibility, as it is known to cause neurological and radiological features similar to osmotic demyelination syndrome with long-term exposure. So these toxic substances might play a role in chronic alcoholic patients with central pontine myelinolysis.

Electronic supplementary material

The online version of this article (10.1186/s13104-018-3287-8) contains supplementary material, which is available to authorized users.

Cognitive sequelae of methanol poisoning involve executive dysfunction and memory impairment in cross-sectional and long-term perspective

Methanol poisoning leads to lesions in the basal ganglia and subcortical white matter, as well as to demyelination and atrophy of the optic nerve. However, information regarding cognitive deficits in a large methanol sample is lacking. The principal aim of the present study was to identify the cognitive sequelae of methanol poisoning and their morphological correlates. A sample of 50 patients (METH; age 48 ± 13 years), 3-8 months after methanol poisoning, and 57 control subjects (CS; age 49 ± 13 years) were administered a neuropsychological battery. Forty-six patients were followed in 2 years' perspective. Patients additionally underwent 1.5T magnetic resonance imaging (MRI). Three biochemical and toxicological metabolic markers and a questionnaire regarding alcohol abuse facilitated the classification of 24 patients with methanol poisoning without alcohol abuse (METHna) and 22 patients with methanol poisoning and alcohol abuse (METHa). All groups were compared to a control group of similar size, and matched for age, education, premorbid intelligence level, global cognitive performance, and level of depressive symptoms. Using hierarchical multiple regression we found significant differences between METH and CS, especially in executive and memory domains. METHa showed a similar pattern of cognitive impairment with generally more severe executive dysfunction. Moreover, all METH patients with extensive involvement on brain MRI (lesions in ≥2 anatomical regions) had a more severe cognitive impairment. From a longitudinal perspective, we did not find any changes in their cognitive functioning after 2 years' follow-up. Our findings suggest that methanol poisoning is associated with executive dysfunction and explicit memory impairment, supposedly due to basal ganglia dysfunction and disruption of frontostriatal circuitry proportional to the number of brain lesions, and that these changes are persistent after 2 years' follow-up.

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.

Uremic Encephalopathy: MR Imaging Findings and Clinical Correlation

BACKGROUND AND PURPOSE

Uremic encephalopathy is a metabolic disorder in patients with renal failure. The purpose of this study was to describe the MR imaging findings of uremic encephalopathy.

MATERIALS AND METHODS

This study retrospectively reviewed MR imaging findings in 10 patients with clinically proved uremic encephalopathy between May 2005 and December 2014. Parameters evaluated were lesion location and appearance; MR signal intensity of the lesions on T1WI, T2WI, and T2 fluid-attenuated inversion recovery images; the presence or absence of restricted diffusion on diffusion-weighted images and apparent diffusion coefficient maps; and the reversibility of documented signal-intensity abnormalities on follow-up MR imaging.

RESULTS

MR imaging abnormalities accompanying marked elevation of serum creatinine (range, 4.3-11.7 mg/dL) were evident in the 10 patients. Nine patients had a history of chronic renal failure with expansile bilateral basal ganglia lesions, and 1 patient with acute renal failure had reversible largely cortical lesions. Two of 6 patients with available arterial blood gas results had metabolic acidosis. All basal ganglia lesions showed expansile high signal intensity (lentiform fork sign) on T2WI. Varied levels of restricted diffusion and a range of signal intensities on DWI were evident and were not correlated with serum Cr levels. All cortical lesions demonstrated high signal intensity on T2WI. Four patients with follow-up MR imaging after hemodialysis showed complete resolution of all lesions.

CONCLUSIONS

The lentiform fork sign is reliable in the early diagnosis of uremic encephalopathy, regardless of the presence of metabolic acidosis. Cytotoxic edema and/or vasogenic edema on DWI/ADC maps may be associated with uremic encephalopathy.

An interesting case of characteristic methanol toxicity through inhalational exposure

Methanol poisoning is rare but carries high risk of morbidity and mortality. Most of the cases witnessed in emergency are due to consumption of adulterated alcohol. Here we are reporting a very rare case of methanol poisoning through inhalational exposure leading to putamen necrosis and decreased visual acuity. He had dyselectrolytemia and metabolic acidosis which was successfully managed with early intervention. Its importance lies in the fact that inhalational methanol poisoning is an entity which if picked up early can prevent long-term neurological sequelae.

Toxic and metabolic encephalopathies: iconographic essay

Generally, toxic-metabolic diseases affecting the central nervous system can hardly be differentiated just on the basis of their clinical presentation. However, some typical neuroradiological features can guide the correct diagnosis. In this context, magnetic resonance imaging is an important tool which, in association with clinical and laboratory data, can establish an early and specific treatment. The present pictorial essay with selected cases from the archives of the authors' institution describes imaging findings which might help in the etiologic diagnosis of toxic-metabolic diseases.

Lentiform fork sign: a magnetic resonance finding in a case of acute metabolic acidosis

We report a 33 year-old woman addicted to chronic unspecified solvents abuse with stupor, respiratory disorders, tetraplegia and severe metabolic acidosis. On admission an unenhanced cranial CT scan showed symmetrical hypodensities of both lentiform nuclei. MR imaging performed 12 hours after stupor demonstrates bilateral putaminal hemorrhagic necrosis, bilateral external capsule, corona radiata and deep cerebellar hyperintensities with right cingulate cortex involvement. DWI reflected bilateral putaminal hyperintensities with restricted water diffusion as to citotoxic edema and development of vasogenic edema in the external capsule recalling a fork. On day twenty, after specific treatments MRI demonstrated a bilateral putaminal marginal enhancement. Bilateral putaminal necrosis is a characteristic but non-specific radiological finding of methanol poisoning. Lentiform Fork sign is a rare MRI finding reported in literature in 22 patients with various conditions characterized by metabolic acidosis. Vasogenic edema may be due to the differences in metabolic vulnerability between neurons and astrocytes. We postulate that metabolic acidosis could have an important role to generate this sign.

A rare presentation of methanol toxicity

Methanol is a highly toxic alcohol resembling ethanol in smell and taste. Methanol poisoning is a lethal form of poisoning that can cause severe metabolic acidosis, visual disturbances, and neurological deficit. Brain lesions typically described in methanol toxicity are in the form of hemorrhagic and non-hemorrhagic necrosis of the basal ganglia and sub-cortical white matter. To our knowledge, lesions in the parietal, temporal, or frontal areas of cerebrum and cerebellar hemispheres have been rarely reported so far. We herewith report this rare presentation.

Lentiform Fork sign: a unique MRI picture. Is metabolic acidosis responsible?

BACKGROUND AND PURPOSE

Bilateral basal ganglia lesions are neither diagnostic nor pathognomonic of uremic encephalopathy (UE). Nonetheless, bilateral basal ganglia T2/FLAIR hyperintensities have been widely reported to be associated with UE. The aim of this study was to describe a unique neuroradiological sign seen on the MRI brain in UE, present a retrospective chart review of patients with UE over the past 10 years for evidence of similar MRI appearance, review literature for evidence of this sign, and generate a hypothesis to explain its pathophysiological basis.

METHODS

We describe a previously unreported and unique MRI picture, the Lentiform Fork sign, in a patient with UE. We conducted a focused retrospective chart review of patients with UE over the past 10 years, for evidence of similar MRI changes. We review literature (through PUBMED, OVID, and CENTRAL) for evidence of this sign and propose a hypothesis to explain the basis of this MRI sign.

RESULTS

We describe the Lentiform Fork sign in a patient with UE. Of our 21 retrospectively reviewed patients with UE who underwent MRI, only one had this sign. Literature review identified 22 patients with this sign who had various conditions, all associated with metabolic acidosis. Fourteen of these patients had documented evidence of severe metabolic acidosis. We propose the hypothesis that metabolic acidosis is the basis of this Lentiform Fork sign.

CONCLUSION

Lentiform Fork sign is a unique, previously unreported MRI picture that is seen not only in patients with UE but also in other conditions that result in metabolic acidosis, helping discriminate a specific etiology from the myriad of conditions that are lumped under the rubric of "basal ganglia hyperintensity." We propose the hypothesis that metabolic acidosis may be the key factor in the pathogenesis of this sign.