Challenging the Safety Threshold: Neurotoxicity in Bipolar Disorder Treatment with Lithium at Therapeutic Serum Levels

Bipolar disorder is a complex mental disorder that often requires long-term medication management. Lithium carbonate is widely used to prevent and treat the recurrence of bipolar disorder. However, even with normal serum lithium levels, some rare but serious side effects may occur. This case report describes a 42-year-old female patient with bipolar disorder who experienced "electrical shock-like" convulsions after taking lithium carbonate sustained-release tablets, despite having normal serum lithium concentrations. The patient had a history of emotional instability for 27 years, and no obvious psychotic symptoms such as hallucinations or delusions were found upon psychiatric examination at admission. On the 33rd day of medication, the patient began to experience frequent rapid convulsions in the head, neck, and upper body. Considering the possibility of drug side effects, lithium carbonate was discontinued, and the convulsions subsequently subsided. Electroencephalogram (EEG) examination showed no abnormalities. After 10 days of treatment, the convulsions had essentially disappeared. This case reminds clinicians that even with normal serum lithium levels, toxic symptoms may occur, and close monitoring of the patient's clinical manifestations and serum lithium levels is essential. Additionally, poor diet and reduced sodium intake may increase the risk of lithium toxicity, so these factors should also be taken into consideration.