Lithium-induced cognitive dysfunction assessed over 1-year hospitalisation: A case report.

Introduction: Lithium-induced neurotoxicity is almost always reversible but can cause irreversible neurological sequelae, namely the syndrome of irreversible lithium-effectuated neurotoxicity (SILENT). As there is no definitive treatment for SILENT, caution is required when administering lithium. Reports on the effect of lithium-effectuated neurotoxicity on cognitive function are limited. We report a case in which high cognitive function was lost after lithium overdose and hardly recovered, as evaluated using multiple neuropsychological tests during a 1-year hospitalisation period.

Patient presentation: A 52-year-old man on lithium medication with bipolar disorder was admitted to the intensive care unit because of lithium overdose. The patient achieved lucid consciousness after continuous haemodiafiltration. However, he could not move his body as desired or produce appropriate verbal expressions; thus, he was moved to our psychiatric ward, where his treatment continued.

Management and outcome: After several months, the patient was diagnosed with SILENT owing to persistent motor and cognitive dysfunctions. Multiple neuropsychological tests were performed, and cognitive function was evaluated. The Neurobehavioural Cognitive Status Examination showed a worsening trend, and the full intelligence quotient of the Wechsler Adult Intelligence Scale-Third Edition was in the mild intellectual disability range.

Conclusion: This is a clear case of cognitive dysfunction due to SILENT and is difficult to treat. Thus, it is crucial to prevent the onset of SILENT.

Contribution: This report is valuable because it is one of the few to track changes in cognitive function over time in a patient with SILENT using objective measures over 1 year of hospitalisation.