Ketter et al1 report on an increase in anterior paralimbic cerebral blood flow (CBF) associated with procaine-induced affective and perceptual symptoms. Changes in CBF and increased activation of left anterior paralimbic structures were associated with procaine-induced fear. Superior temporal activation occurred in the entire group of subjects, most of whom experience "hallucinations." Intense unformed visual hallucinations were associated with greater global CBF.
The clinical psychiatric symptoms of the toxic effects of lidocaine hydrochloride and procaine are similar, both showing dysphoric mood changes with fear of death or doom-related content and hallucinations.2 Based on the work of Post et al,3 it had been previously hypothesized that activation of the amygdala, hippocampus, and related structures might be involved in producing the symptoms of lidocaine toxicity.4-6 The interesting finding by Ketter et al1 that procaine-induced fear is related to activation of the left amygdala in experimental subjects