The P3 event-related potential in young recent-onset schizophrenic patients

In schizophrenic patients, the amplitude of the P3 event-related potential (ERP) is usually decreased and the latency is often prolonged. Most ERP studies have compared schizophrenic patients with chronic illness or in mixed age groups with age-matched control subjects. However, P3 latency and amplitude change with age, and P3 latency increases more rapidly in schizophrenic patients than in control subjects. To investigate whether mixed age groups and chronic illness have been determining factors in ERP results, P3 was measured in 15 young patients (mean age 21.6 years) with recent-onset schizophrenia and compared with age-matched controls. P3 amplitudes were decreased in the schizophrenic group compared with the control group. P3 latencies were less significantly prolonged in the schizophrenic group than in other studies. Furthermore, in an exploratory study, the ERPs resulting from application of the irrelevant tones in some schizophrenic patients demonstrated ERP activity at latencies of 250-600 ms, while little or no activity was present at these latencies in control subjects. It is hypothesized that a defect in inhibition of incoming sensory information in the nucleus reticularis thalami may play a role in the pathogenesis of schizophrenia. Such a defect could result in a dysfunctional filter function of external stimuli and may therefore affect the social and psychological functioning of the patient. (C) 1998 Rapid Science Lt

The Late Blink Reflex Response Abnormality Due To Lesion Of The Lateral Tegmental Field

We report on a blink reflex abnormality observed in two normal. patients, which provides additional information on the central pathways mediating this reflex. Autopsy was performed in of one patient and MRI in the other. In the first patient there was a small lesion at the dorsal middle third of the lateral tegmental field and in the second patient at the level of the dorsal lower third of the medulla oblongata. In both patients the common finding was the absence of the late response (R2) ipsilateral to the side of the lesion, while the R2 response on the unaffected side was normal regardless of the side of the supraorbital nerve stimulation. The R1 responses were normal.This type of blink reflex abnormality has not beenreported before and is referred to by us as‘tegmental type’ of R2 abnormality. The results led to the conclusions that: (i) the crossed and uncrossed ascending trigeminofacial connections are mediated through the lateral tegmental field; (ii) the uncrossed trigeminofacial connection originates at the level of at least the lower medulla oblongata; (iii) the contralateral R2 response is established by way of an ascending pathway, which crosses the midline at the level of at least the lower third of the medulla oblongata.

Blepharospasm In Association With A Lower Pontine Lesion.

A patient with neurofibromatosis type I and breast carcinoma developed a bilateral but asymmetric blepharospasm and paresis of the left abducens muscle over a 2-week course. MRI disclosed a small lesion in the left dorsomedial lower pontine region. Electrodiagnostic investigations revealed bilateral R1 responses after stimulation of the left supraorbital nerve and enhancement of R1 and R2 recovery curves. We concluded that lesions in the lower porltine tegmentum may cause blepharospasm.