Topics in transcranial magnetic stimulation.
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Biomedical subjects
Publications and source records attributed to H Sackeim.
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To evaluate the effects of neuroleptic medications on cerebral blood flow (CBF), cortical perfusion was quantified by the 133xenon technique in 8 unmedicated schizophrenics and 9 healthy controls before, and 1 and 3 hours after, administration of haloperidol (5 mg per os). At 3 hours, the normal subjects, but not schizophrenic patients, showed a significant increase in global mean perfusion (17 +/- 13%). Changes in CBF were not associated with plasma haloperidol levels or the presence of extrapyramidal side effects, and remained significant after controlling for pCO2. The lack of change in CBF in schizophrenic patients following acute haloperidol administration may be due to prior neuroleptic exposure, absence of anxiety, or other nonspecific factors, or may reflect a more fundamental feature of underlying pathophysiology in schizophrenia.
An association between negative symptoms and frontal cortex abnormalities has been suggested in schizophrenic patients. We tested whether this association can be found when patients' task performance is good and while controlling for possible cortical atrophy. We investigated regional cerebral blood flow with the xenon-133 inhalation method in 9 unmedicated schizophrenic patients at rest and during performance of the Continuous Performance Test. Negative symptoms were quantified with the Scale for Assessment of Negative Symptoms. All patients could attend to the test and performed it successfully with mean accuracy of 91 +/- 8%. Changes of the left hemisphere hyperfrontality ratio were significantly correlated with severity of negative symptoms, especially for the subscales of attention (r = -0.83) and anhedonia (r = -0.70). These results lend further support to the putative association between negative symptoms and physiological abnormalities of the frontal cortex in schizophrenic patients.
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In a random-assignment trial to unilateral right and bilateral electrode placements, electroconvulsive therapy (ECT) stimulus intensity was titrated to just above seizure threshold for each of 52 depressed patients. Seizure threshold was quantified in units of charge. There was a 12-fold range in the minimum electrical intensity necessary to produce seizure. Sex, age, electrode placement, and the cumulative number of treatments were each associated with seizure threshold. Bilateral ECT had both a higher initial seizure threshold and a greater cumulative increase in seizure threshold compared with unilateral ECT. Clinical and research implications are discussed with respect to dosing strategies in ECT.
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