Neurophysiological evaluation of late paraphrenia: Comparison with chronic schizophrenia and dementia of the Alzheimer type

Abstract

Background: Late paraphrenia (LP) is a clinical entity first proposed by Roth in 1955. Recently, neuroimaging studies have described the organic changes in the brain that are associated with LP. We performed a neurophysiological study on patients with LP, chronic schizophrenics and patients with dementia of the Alzheimer type (DAT) to examine the cognitive function of patients with LP and to differentiate LP patients from these other groups. Methods: We investigated somatosensory‐evoked response (SER), contingent negative variation (CNV) and P300 in 30 LP patients, 22 chronic schizophrenics and 31 patients with DAT. Thirty‐four age‐matched healthy volunteers served as a control group. SER was performed by applying a mechanical stimulus to the right or left palm. CNV was performed by presenting a clicking sound (S1) and a flash of light (S2) to the subjects, with an interval between S1 and S2 of 2 s. P300 was performed using an auditory oddball paradigm. Results: The mean N3 peak latency of SER was significantly prolonged in patients with LP and in patients with DAT, compared with the control group. The mean CNV amplitude was significantly decreased in schizophrenics compared with the control group, but it did not decrease in patients with LP. The mean N200 and P300 latencies were significantly prolonged in patients with DAT compared with the control group, LP patients and schizophrenics, but the latencies of patients with LP were not prolonged compared with the control group. Conclusion: Based on these results, we propose that patients with LP have impaired cerebral reactivity to the stimulus, but their attention, motivation, recognition and differentiation are relatively intact. The present findings are consistent with former investigations, indicating that patients with LP are less likely to show negative symptoms, such as personality deterioration, and more likely to show organic changes in the brain relative to schizophrenics arising in early life.