Objective: We describe the case of a 59-year-old man who was evaluated for abnormal imaging and subacute parkinsonism.

Background: Secondary parkinsonism can be caused by a variety of conditions including medications, toxins, tumors, and vascular lesions. Metformin has been thought to cause parkinsonism in those with renal impairment but has rarely been reported.

Method: Relevant medical history, physical examination, laboratory findings, neuroimaging, and clinical course are described.

Results: On initial presentation, a 59-year-old man with history of type II diabetes and end stage renal disease presented to the Emergency Room with a two-day history of speech and difficulty walking. Ancillary data disclosed a mild lactic acidosis and symmetric bilateral putaminal T2 FLAIR (fluid-attenuated inversion recovery) hyperintensities; toxidrome workup was unrevealing. He experienced some clinical improvement after hemodialysis and was discharged with outpatient follow-up arranged. One month later, the patient was admitted for hypertensive crisis and lactic acidosis with an exam consistent with marked parkinsonism. Repeat imaging demonstrated diffuse symmetric T2 FLAIR hyperintensities within the bilateral basal ganglia. Extensive metabolic workup was normal. Prompted by additional history, serum metformin levels were measured and found to be elevated to a degree consistent with the development of lactic acidosis. The patient continued to receive scheduled hemodialysis while in the hospital and metformin was discontinued. He experienced dramatic improvement in extrapyramidal symptoms within 14 days.

Conclusion: Metformin use in those with advanced renal impairment may cause a reversible secondary parkinsonism associated with lactic acidosis and MR FLAIR changes within the basal ganglia.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/reversible-secondary-parkinsonism-attributed-to-metformin-induced-lactic-acidosis/