Lentiform Fork Sign Secondary To Metformin-Induced Encephalopathy

The Lentiform Fork sign is an imaging finding on brain MRI described by bilateral, symmetric hyperintensities in the basal ganglia. It is described in the setting of metabolic acidosis of many etiologies and is a sign of vasogenic edema. Both imaging findings and symptoms are often reversible with correction of the acidosis and removal of any identifiable triggers. We report a case of confusion and ataxic gait in a patient with end stage renal disease and ongoing metformin use. The mechanism of metformin-induced encephalopathy remains unclear, but could be due to vulnerability of mitochondria to metformin within the lentiform nuclei.