Encephalopathy associated with rapid decrease of high levels of lithium

A case is described in which a highly detailed time course of serum lithium levels and mental status observations was consistent with neurotoxicity from the rapid decrease in high lithium levels rather than from the high lithium levels alone. The highest lithium level observed was 4.89 mEq/L; the patient remained oriented until about 40 h after hospital admission and the serum lithium level fell below 1.65 mEq/L. An EEG taken during the 2-day period of gross disorientation showed focal sharp epileptiform waves and paroxysmal bursts of slowing without full seizure. In view of these and previous complementary observations, and a rationale of similarity between hyperlithemia and hyponatremia, the potential toxicities of dialysis and abrupt lithium dose discontinuation should be considered in patients who develop high lithium levels after taking regular doses.