Functional relationship among brain regions in schizophrenia: evaluation with pearson's product-moment correlation between event-related potentials (ERPs)

S85

conduction studies and in multimodality evoked potentials, including pattern-reversal visual (VEP), brain-stem auditory (BAEP) and somatosensory (SEP) evoked potentials. Evoked potentials were normal in all patients. Thus, evoked potentials may distinguish patients with early onset ataxia and retained tendon reflexes from patients with Friedreich’s ataxia or with late-onset cerebellar ataxia.

sal stimulation with small and large checks. The field distribution of fovea1 and parafoveal evoked responses by half-field stimulation shows different patterns, according to the check size. A pattern-specific topography visual cortex has to be assumed.

of the vectors evoked in the

SENSORY EVOKED POTENTIALS (SEP) EVALUATION OF PATIENTS IN COMA. FUNCTIONAL RELATIONSHIP AMONG BRAIN REGIONS IN SCHIZOPHRENIA: EVALUATION WITH PEARSON’S PRODUCT-MOMENT CORRELATION BETWEEN EVENT-RELATED POTENTIALS (ERPs). M.R. LOI_& K. Maurer (University

and B. Neuhauser

of SBo Paulo,

SHo Paulo, Brazil)

Thirty medicated schizophrenics (RDC), divided into paranoid (n = 16) and nonparanoid (n = 14) subgroups, and 30 healthy subjects were examined using a somatosensory version of the odd-ball P300 paradigm (LouzI Neto: Z. EEG-EMG, 1989) by stimulating the right (1st run) and then the left (2nd run) median nerve at the wrist. Electrodes: F3, F4, P3 and P4 referred to (Al + A2). Similarity between waveforms was measured by correlating the digital values comprising the O-900 msec segment of each recording site with the corresponding values from other recording sites; coefficients of correlation were transformed to Fisher’s z-coefficients for statistical analysis. There was no significant difference among the correlations of the three groups after stimulation of the right and the left median nerve. The lack of disruption of the functional interand intrahemispheric interaction of brain areas did not support the laterality and the hypofrontality hypothesis of schizophrenia. However, these negative results could be due to the fact that the whole ERP segments were correlated, not parts of them. Volume-conducted activity from a distant (subcortical?) generator or the synchronization of two neuronal populations through a third population could also produce these negative results.

(Hospital

(Hospital F.R.G.)

Pattern-reversal visual evoked potentials (VEP) to half-field stimulation were elicited by 15’ and 50’ checks via mirror movement (Digitimer D-112) according to Halliday (1972) and Lowitzsch et al. (1976). Mapping was performed via a 28-channel registration using the Brain Imager System (Neuroscience, Madaus) against combined-ears reference. The 25’ visual field was stimulated with the central fovea (3O ) included and excluded, applying half-field pattem-rever-

Albert

Einstein,

SBo Paulo, Brazil)

REFRACTORY STATUS EPILEFwCUS (SE) MONITORING WITH EEG COMPRESSED SPECTRAL ARRAY (CSA).

K. Lowitzsch

of Mainz, Ludwigshafen,

lsraelita

Non-invasive SEP performed at the bedside of more than 150 patients in coma from different causes has proved to have both diagnostic and prognostic value. Combining information generated in 3 modalities: somatosensory (SSEP, on its own the most important), flash visual (FVEP). and brain-stem auditory (BAEP), allows the evaluation of patients with CNS diffuse lesions through a ‘vertical’, a ‘horizontal’ and a brain-stem view. SEPs contribute to the diagnosis of pathway lesions, neurophysiological level of lesion, brain death (in association with EEG). Establishing prognosis is perhaps the best contribution of SEP in coma: (1) abnormal BAEP (brain-stem lesion) reserved prognosis; a normal BAEP does not allow precise definition, depending on other SEP; (2) bilaterally normal or only slightly altered SSEP, good prognosis; bilaterally absent Pl4 together with absent BAEP. may be compatible with brain-stem death, or with brain death if accompanied by absent FVEP and electrocerebraf silence in the EEG; bilateral absence of thalamo-cortical (N20 and P23) components, bad prognosis, since the best outcome (in younger patients) was to a persistent vegetative state; adults and older patients died; intermediate SSEP corresponded to intermediate prognosis; (3) FVEP has shown the same prognostic tendency as SSEP, but with a lesser degree of precision.

F.J.C.

(University

THE

F. J. C. Luccas

MAPPING OF PA’ITERN-REVERSAL VISUAL EVOKED POTENTIALS BY HALF-FIELD STIMULATION. and E. Guth

IN

Luccas, J.A. Lopes, V.A. Gomes lsraelita

Albert

Einstein,

and F.R.T.

Plastino

Sao Paulo. Brazil)

Chnical and experimental data emphasize the importance of treating SE as a medical emergency. Ictal EEG abnormalities and motor phenomena represent different expressions of the same problem. As more information can be obtained with the help of EEG instrumentation there are concrete advantages of SE monitoring. If antiepileptic drugs fail, and a refractory SE exists, general anesthetics are recommended in doses capable of producing EEG burst suppression. We monitored 20 patients (12 males), age range 3 months-67 years in SE from different causes. Monitoring lasted 1-22 days. Whenever possi-