Abstract

Basal ganglia lesions showing an expansile high signal intensity on T2-weighted MRI are termed the lentiform fork sign. This specific finding is mainly observed in diabetic patients with uremic encephalopathy with metabolic acidosis, although there are also reports in patients with ketoacidosis, dialysis disequilibrium syndrome, intoxication, and following drug treatment (e.g., metformin). A 57-year-old Japanese man on chronic hemodialysis for 4 years because of diabetic nephropathy was admitted to our hospital for relatively rapid-onset gait disturbance, severe dysarthria, and consciousness disturbance. Brain T2-weighted MRI showed the lentiform fork sign. Hemodialysis was performed the day before admission, and laboratory tests showed mild metabolic (lactic) acidosis, but no uremia. Surprisingly, metformin, which is contraindicated for patients with end-stage kidney disease, had been prescribed for 6 months in his medication record, and his sluggish speaking and dysarthria appeared gradually after metformin treatment was started. Thus, the encephalopathy was considered to be related to metformin treatment. He received hemodialysis treatment for 6 consecutive days, and his consciousness disturbance and dysarthria improved in 1 week. At the 8-month follow-up, the size of the hyperintensity area on MRI had decreased, while the mild gait disturbance remained. Considering the rapid onset of gait and consciousness disturbance immediately before admission, diabetic uremic syndrome may also have occurred with metformin-related encephalopathy, and resulted in the lentiform fork sign, despite the patient showing no evidence of severe uremia on laboratory data.

Highlights

  • Basal ganglia lesions showing an expansile high signal intensity on T2weighted MRI are termed the lentiform fork sign

  • Any further responses from the reviewers can be found at the end of the article Introduction Metabolic encephalopathy with abnormal basal ganglia lesions has been reported in hemodialysis patients

  • In addition to diabetic uremic syndrome (DUS)4,5, the lentiform fork sign can be observed in severe metabolic acidosis11–13, dialysis disequilibrium syndrome14, and metformin-associated encephalopathy (ME)6,7

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Summary

11 Aug 2020 report report report

Brain MRI showed bilateral symmetrical basal ganglia lesions with an expansile high signal intensity (lentiform fork sign) on T2-weighted sequences (Figure 1b), which was not seen on MRI taken one-year prior when he developed a right thalamic lacunar infarction. In his medication history, he had taken metformin for six months. We stopped metformin treatment, and immediately performed intensive hemodialysis (four hours daily; blood flow, 200 mL/min; dialysate flow, 500 mL/min; 1.5 m2-dialysis membrane, polymer alloy (polyarylate/polyethersulfone) for six days after hospitalization to remove metformin and uremic toxin, and to correct metabolic acidosis. Brain lesions were still evident on CT scan (Figure 1e)

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