Yutaka Hirata

Age-related decline of cerebral oxygen metabolism in normal population detected with positron emission tomography

Using positron emission tomography (PET), cerebral blood flow (CBF) and cerebral metabolic rate of oxygen (CMRO2) were measured in 32 healthy volunteers aged from 27 to 67 years. In bilateral putamen, left supratemporal, left infrafrontal and left parietal cortices, CMRO2 showed a significant decline during aging. The age-related decline of CBF was seen only at the left superior temporal cortex. The mean CMRO2 was significantly lower in the elder group (over 51 years old) than in the younger group (under 50 years old), whereas no significant difference in mean CBF between the two groups. The poor correlation of CBF to the age could be explained partly by the fact that CBF is easily influenced by the physiological, psychological and/or environmental factors. The age-related changes of CMRO2 were more marked in the association cortices of the left hemisphere than in that of the right hemisphere.

Evolution of Crossed Cerebellar Diaschisis in Middle Cerebral Artery Infarction

To elucidate the evolution of crossed cerebellar diaschisis, cerebral oxygen metabolism was measured repeatedly by positron emission tomography (PET) in 35 consecutive patients with unilateral cerebral infarction within the territory of middle cerebral artery. The crossed cerebellar diaschisis was defined as significant when the laterality ratio of cerebral oxygen metabolism between the left and right cerebellar hemispheres exceeded the control range (mean ± 2 standard deviations) as derived from 27 age‐matched normal volunteers. Significant crossed cerebellar diaschisis was observed in 31 patients (89%) on the initial PET studies. Of these 31 patients, 23 with infarcts involving the frontal sensorimotor cortex persistently had crossed cerebellar diaschisis up to 5 years after onset, whereas the diaschisis disappeared in 8 patients with smaller infarcts mainly in the frontal or parietal lobe without recovery of oxygen metabolism in the infarcted areas. These present results suggest that crossed cerebellar diaschisis can exist persistently even in the late stage in those having a lesion involving the cortical pontine‐cerebellar pathways.

Long-Term Angiotensin-Converting Enzyme Inhibitor Perindopril Therapy Improves Cerebral Perfusion Reserve in Patients With Previous Minor Stroke

Background and Purpose— Angiotensin-converting enzyme (ACE) inhibitor–based therapy reduces the recurrence of stroke. The present study assessed the effects of long-term ACE inhibitor therapy on cerebral circulation in patients with previous minor stroke. Methods— After a run-in period, 19 patients were randomized to ACE inhibitor therapy (n=9; 4 mg of perindopril daily; mean age, 64±8 years; mean systolic/diastolic blood pressure [BP]±SD, 133±12/77±9 mm Hg) or placebo therapy (n=10; mean age, 66±9 years; mean BP, 139±10/78±8 mm Hg). Cerebral blood flow (CBF) was measured during hypercapnia, normocapnia, and hypocapnia using a positron emission tomography with H215O at entry into the study and after 3 to 12 months. Cerebral perfusion reserve (CPR) was defined as percent CBF response to a 1 mm Hg change in arterial partial pressure of CO2 between hypercapnia and hypocapnia. Results— Systolic/diastolic BP and CBF during normocapnia showed no significant changes between entry and completion of the trial in the perindopril and placebo groups. Mean value of CPR showed a significant increase in the perindopril group (from 3.7±1.7%/mm Hg to 4.8±1.7%/mm Hg; P <0.05) but not in the placebo group (from 4.1±0.8%/mm Hg to 4.2±0.6%/mm Hg; NS). Statistical parametric mapping analysis also showed global and significant increase (P <0.01, uncorrected) in CPR in the perindopril group alone. Conclusions— Long-term ACE inhibitor–based therapy had a beneficial effect on the cerebral circulation by improving CPR in patients with previous minor stroke.

Effects of fasudil hydrochloride on cerebral blood flow in patients with chronic cerebral infarction

Summary: To evaluate the effect of the novel intracellular calcium antagonist fasudil hydrochloride, cerebral blood flow (CBF) was measured quantitatively with positron emission tomography following the intravenous administration of fasudil in five patients with chronic cerebral infarction. The hemispheric mean CBF increased significantly on both hemispheres 30, 60, and 90 min after the administration of fasudil when the CBF values were corrected according to Paco2 level, although there was no significant change in raw CBF data. A significant increase of CBF was seen in the cerebellar hemisphere and thalamus at 30 min and in the occipital cortex at 90 min. There was no significant fall in the systemic blood pressure after the administration of fasudil.

Correlation of EEG activities between slow-wave sleep and wakefulness in patients with supra-tentorial stroke

SummaryUsing topographic EEG mapping, we studied the relationships between delta activity during slow-wave sleep (SWS) and the background EEG activity during wakefulness, in 11 normal subjects and 35 stroke patients with unilateral supra-tentorial lesions. Delta-1 power during SWS showed a significant positive correlation with alpha-1 power during wakefulness, in both hemispheres. Delta-1 and delta-2 power during SWS correlated positively not only with alpha-2 power, but also with delta-1 and delta-2 power during wakefulness in the affected hemisphere. These figures indicate that the amount of delta activity during SWS can be associated with that of alpha activity during wakefulness. A close negative correlation was observed between delta power during SWS and the age of the subjects in the patient group. The Barthel index showed no significant correlation with delta-1 or delta-2 power in either hemisphere in patient group. Our results suggest that delta activity during SWS may be associated with dysfunction of the cerebral cortex in stroke patients as well as in normal aged subjects.

Infratentorial infarction: Correlation of MR findings with neurological and angiographical features

Using magnetic resonance imaging, we reviewed 141 infratentorial infarcts in 81 consecutive cases: 65 infarcts were seen in the paramedian pons, while 18 in the posterior inferior cerebellar artery (PICA) territory and 17 in the watershed area between PICA and superior cerebellar artery. No comparable sign or symptom was observed for 44 (31.2%) infarcts, whereas 66 (46.8%) infarcts appeared symptomatic and 31 (22.0%) infarcts were regarded as equivocal mainly due to the coexisting supratentorial lesions or non-localizing symptoms. The frequent coexistence of basal ganglionic small infarcts in those with infratentorial small (< 15 mm) infarcts implicated their common pathogenetic background. The fact that atrial fibrillation was seen in 33.3% of those with large (> 15 mm) infarcts whereas it was seen in only 6.5% of those with small infarcts may suggest a cardiogenic embolism as a possible cause of infratentorial large infarcts. Major artery occlusive lesion was seen in 15 of 22 cases with cerebellar infarction, whereas no occlusive lesion was seen in the majority of cases with pontine small infarcts. With MR imaging, infratentorial infarcts were detected more frequently than in the previous studies based on X-ray CT, and they can be considered as a benign condition.

Accumulation of L-[2-(F-18)]fluorophenylalanine in peri-infarct area in a patient with acute cerebral infarction.

We studied the brain uptake of amino acid in a patient with acute cerebral infarction with L-[2-(F-18)] fluorophenylalanine and positron emission tomography. The increased accumulation of the ligand was specifically found in the peri-infarct area where oxygen metabolism was still maintained but decreased later in the 72-day follow-up period. The kinetic analysis revealed that increased accumulation was not due to increased transport from the blood to the brain but to delayed washout from the brain to the blood. Although the mechanism is still unknown, abnormally high accumulation of L-[F-18]fluorophenylalanine may predict delayed neuronal changes after ischemic insults of the brain.

Scalp topography of SEP late components in patients with supra-tentorial lesions

SummarySomatosensory evoked potentials (SEP) to simultaneous bilateral median nerve stimulation were recorded in 7 patients with unilateral brain lesions, 8 patients with degenerative dementia, and 5 normal volunteers. Right-left amplitude difference was compared from serial topographic images and the amplitude was compared at homologous electrodes. In patients with unilateral lesions, the amplitude from the frontopolar, frontal, anterior-temporal, and/or occipital electrodes was smaller on the affected side at 240 and 360 msec, regardless of whether the subjects showed sensory deficit or not. No significant laterality was seen in the primary sensorimotor areas. Distribution obtained from the patients with degenerative dementia was quite symmetrical. A significant right-left amplitude difference was seen at the anterior temporal site at 180 and 240 msec in normal controls, although an almost symmetrical distribution was obtained on the topographic images. The late components of SEP are not associated with the primary somatosensory function, but possibly with other cortical pathways.