Diffusion-weighted imaging in methanol poisoning: beyond the lentiform fork sign

INTRODUCTION

Methanol poisoning is a life-threatening emergency, in which the presence of a lentiform fork sign on magnetic resonance imaging, although not exclusive to methanol poisoning, can be of diagnostic assistance. This report highlights the additional value of diffusion-weighted imaging in methanol poisoning.

CASE SUMMARY

A 38-year-old man was admitted to the hospital with severe metabolic acidosis, coma and visual disturbances due to methanol poisoning.

IMAGES

Initial computed tomography of the brain was unremarkable. However, magnetic resonance imaging revealed the lentiform fork sign, with diffusion-weighted imaging changes in the lentiform nuclei.

CONCLUSION

Diffusion-weighted imaging sequences provide additional information compared to traditional magnetic resonance imaging in assessing methanol poisoning. Systematic evaluation is needed to fully understand and utilize the potential predictive value of diffusion-weighted imaging in this context.

Extrapyramidal syndromes of chronic kidney disease and dialysis (diabetic uremic syndrome) with reversible parkinsonism and lentiform fork sign: A case report and literature review including metformin-induced encephalopathy

Diabetic uremic syndrome has been rarely reported in patients on maintenance dialysis for diabetic nephropathy who present subacutely with neurological symptoms and bilateral basal ganglia lesions. There are also a few reports on metformin-induced encephalopathy, which is clinically similar to diabetic uremic syndrome. Because some patients with each of these diseases also have metabolic acidosis, it is speculated that these two diseases may have the same pathology. Recently, the term "extrapyramidal syndromes of chronic kidney disease and dialysis" (EPS-CKDD), with associated diagnostic criteria, has been proposed to describe these conditions, and metformin use is considered a risk factor for developing these syndromes. We report a case of a patient on maintenance hemodialysis for diabetic nephropathy who was taking metformin and developed subacute parkinsonism and bilateral basal ganglia lesions that rapidly improved after discontinuation of metformin with continued maintenance hemodialysis. We should ascertain whether patients with EPS-CKDD are taking metformin because it may be inappropriately prescribed for end-stage renal disease. If metformin has been prescribed, it should be discontinued immediately; its discontinuation may lead to rapid symptom recovery and improved prognosis.

Focal brain lactate accumulation in metformin-induced encephalopathy without systemic lactic acidosis: A case report suggesting mitochondrial vulnerability in lentiform fork sign

Metformin causes metabolic encephalopathy in some patients with end-stage chronic kidney disease, resulting in impaired consciousness and parkinsonism. This encephalopathy has a very characteristic magnetic resonance imaging feature in lentiform nuclei known as the “lentiform fork sign”. However, the mechanism is unknown. Here, we report a case of metformin-induced encephalopathy with a novel observation of lactate accumulation in the lentiform nuclei on magnetic resonance spectroscopy without systemic lactic acidosis. Since metformin is an inhibitor of mitochondrial complex-I, this focal brain lactate accumulation implies that a part of the pathogenesis of metformin-induced encephalopathy is the focal vulnerability of mitochondria to metformin in the lentiform nuclei. When metformin causes encephalopathy, not only testing for serum lactic acidosis and performing routine magnetic resonance imaging but also evaluation of brain lactate accumulation by magnetic resonance spectroscopy should be required to elucidate the etiology.

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Metformin-induced encephalopathy with lactate accumulation in lentiform fork sign was reported.

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Lentiform nuclei might be more vulnerable to metformin than other organs.

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This case suggested an etiology for the lentiform fork sign because metformin is a mitochondrial inhibitor.

Metformin-associated Encephalopathy in Hemodialysis

Metformin-associated encephalopathy in maintenance hemodialysis is very rare in literature, till now only three to four cases are published. We report a patient on maintenance hemodialysis from standalone unit presented to us with abnormal neurological signs and symptoms. His medication chart included metformin, which he was taking for quite a long time. Computed tomography brain showed hypointensity in bilateral basal ganglia. Magnetic resonance imaging (MRI) brain showed hyperintensity in T2/fluid-attenuated inversion recovery sequences suggestive of Lentiform fork sign. We stopped metformin, and he was continued on regular hemodialysis. He showed dramatic improvement in neurological manifestations. Two months later, we repeated MRI brain, which showed resolution of basal ganglia changes. We should suspect the possibility of this when a diabetic end-stage renal disease presents with unknown etiology of encephalopathy.