The effect of antipsychotic medication on relative cerebral blood perfusion in schizophrenia: assessment with technetium-99m hexamethyl-propyleneamine oxime single photon emission computed tomography.

Functional neuroimaging studies in schizophrenia have often been confounded by various factors including medication status. To explore the effects of antipsychotic medications on relative regional cerebral perfusion, we scanned a group of 33 persons with schizophrenia twice, while receiving a stable dose of antipsychotic and after being off antipsychotics for 3 weeks, using technetium-99m hexamethyl-propyleneamine oxime single photon emission computed tomography (Tc-99m HMPAO-SPECT. We found that antipsychotic significantly increased the mean relative cerebral perfusion in the left basal ganglia. Additionally, patients receiving thiothixene (n = 9) had a significantly greater increase in relative cerebral perfusion in the basal ganglia than patients receiving haloperidol (n = 12). These findings indicate that antipsychotics lead to regional increases in cerebral perfusion and that antipsychotic status must be controlled for in functional neuroimaging studies. Functional neuroimaging techniques such as SPECT may be useful in furthering our understanding of the mechanism of antipsychotics.

Assessment of the CO2 response by means of non diffusible contrast media and angio-CT in patients with cluster headache.

We analyzed the possibility of assessing functional vasomotor changes by means of Arm-Brain Circulation Time (rABCT) and Vascular volume images (Vv) obtained with Angio-CT, in basal condition and following CO2 inhalation, in a sample of 48 patients with cluster headache. CO2 inhalation resulted in the appearance of local changes, which were detected in 28 regions. Analysis by indicator images of Vv-dependent rABCT distribution showed two main patterns: abnormal rABCT mostly evident at the smallest Vv pixels and abnormal rABCT dependent on abnormal Vv distribution. The former pattern was linked to abnormality at the circle of Willis; the latter to abnormal local vasomotor responses. Patients with cluster headache showed both patterns, which prompted us to conclude for the presence of low-degree stenosis in carotid arteries and vasomotor instability in peripheral brain vessels.

Assessment of local cerebral blood flow in neonates with N-isopropyl-P-[123I]iodoamphetamine and single photon emission computed tomography.

Local cerebral blood flow was measured in 10 high-risk infants with neonatal episodic neurological events at 41-44 post-conceptional weeks using N-isopropyl-p-[123I]iodoamphetamine (IMP) and single photon emission computed tomography (SPECT). In 5 of the 7 infants with normal neurological outcome, prominent cerebral perfusion was found in the basal ganglia, brainstem, cerebellum, parietal white matter, and sensory motor cortex. The frontal lobes showed poor relative perfusion. In 3 infants with severe neurological deficits, SPECT demonstrated severe hypoperfusion of all parts of the brain except the basal ganglia, brainstem and sensorimotor cortex. However, MRI revealed non-specific changes, such as poor myelination and ventricular dilatation. SPECT, when performed in the first weeks of life, can be useful and may be more sensitive than MRI in predicting the occurrence of major neurological handicaps. However, because of the relatively invasive character and high cost of SPECT, SPECT should not necessarily be performed in all high-risk neonates.