Brain metabolism after recurrent insulin induced hypoglycaemic episodes: a PET study

Neuropsychological testing was carried out and the rate of oxygen metabolism in the brain was measured by PET in 15 highly selected patients with type 1 diabetes. The aim was to investigate the impact on the brain of hypoglycaemic comas resulting from insulin treatment. No significant difference was found between nine patients with a history of more than 10 hypoglycaemic comas and six others who denied any history of such events. These data suggest that intensified insulin treatment, although increasing the frequency of hypoglycaemic coma, may not always be harmful for the brain. This may be explained by the limited duration of hypoglycaemic coma induced by conventional insulin treatment.

Cerebral infarction due to painless thoracic aortic and common carotid artery dissections

BACKGROUND

Aortic arch dissection is usually lethal unless emergency surgery is performed. The dissection rarely may have a benign outcome or may occur without pain and be revealed by cerebral infarction. It is then likely to be seen primarily by a neurologist. In such cases, the value of new noninvasive diagnostic testing has not been reported.

CASE DESCRIPTION

A 51-year-old man had a sudden left-sided hemiplegia due to hemorrhagic capsular and caudate infarcts on the right side. Cervical ultrasound examination with color flow imaging showed a bilateral common carotid artery dissection extending up to the bifurcation. Transesophageal echocardiography showed an aortic arch dissection, involving the innominate and left common carotid artery origins, which was confirmed by magnetic resonance imaging and aortography. The patient spontaneously fully recovered and is still alive 24 months after the stroke onset.

CONCLUSIONS

This case emphasizes the usefulness of new noninvasive techniques such as transesophageal echocardiography and color-coded Doppler echocardiography in the diagnosis and follow-up of painless dissection of aortic and common carotid arteries. This cause of stroke may be underestimated.

[Role of electroencephalography in the diagnosis of acute cerebral diseases]

It appears from a study of 100 cases of acute cerebral disease that electroencephalography is valuable as part of the diagnosis strategy and not only to establish the correct final diagnosis. This examination therefore plays a non-negligible role in neurological practice. In a number of diseases it provides information that no other examination can provide, being a dynamic, functional method of brain tissue analysis.

Local cerebral glucose utilisation in treated and untreated patients with Parkinson's disease

Using the 18f-fluoro-2-deoxy-d-glucose technique and positron emission tomography (PET), the local cerebral glucose utilisation (1CMRGlc) was measured in four non-demented patients with early-onset, bilateral Parkinson's disease characterised by the predominance of akinesia. The study was done twice, first in the untreated condition, and then after levodopa had been resumed. Despite a marked clinical improvement, we found no alteration in 1CMRGlc between the first and second studies in any of the brain structure analysed. Compared to control values, 1CMRGlc in the basal ganglia was moderately increased in both studies. These essentially negative findings agree with most previous human or animal studies, and indicate that the functional alterations in the central dopaminergic systems of patients with Parkinson's disease have metabolic correlates that are too small to be demonstrated by current PET devices.

Local interrelationships of cerebral oxygen consumption and glucose utilization in normal subjects and in ischemic stroke patients: a positron tomography study

With the use of positron emission tomography (PET) and the 15O steady-state-[18F]fluorodeoxyglucose combined method, the local interrelationships between the cerebral metabolic rate for oxygen (CMRO2) and the cerebral metabolic rate for glucose ( CMRGlc ) were investigated in control subjects and in stroke patients. In addition to the classic in vivo autoradiographic approach, a kinetic method was used to measure CMRGlc because it was expected to be more reliable in cerebral ischemia. In control subjects local coupling between CBF, CMRO2, and CMRGlc was confirmed, and acceptable values for the CMRO2/ CMRGlc ratio were found; the latter, however, was lower in white matter than in gray. Uncoupling between CMRO2 and CMRGlc was observed in all stroke patients, suggesting that (1) enhanced anaerobic glycolysis occurred both in reperfused recent infarcts and in chronically ischemic tissue, and (2) substrates other than blood-borne glucose were being oxidized at the borders of recent infarcts. However, methodological uncertainties presently make such observations only tentative. Finally, a coupled depression of CMRO2 and CMRGlc was found in the contralateral cerebellum.

[Positron emission tomography in the physiopathological study of cerebral ischemia in man]

The development of positron emission tomography now allows the local study of cerebral blood flow, oxygen consumption and glucose utilization in ischemic stroke patients. In recent cerebral infarction, a disruption of the normal couple between flow and metabolism is almost constantly observed: in the first few days cerebral blood flow is either inadequate (persistent ischemia) or over-abundant ("luxury perfusion"), whereas a late "luxury perfusion" is almost constant within the necrotic area between the 10th and the 40th day. Threshold values for cerebral blood flow and oxygen consumption that are ultimately associated with necrosis or tissue integrity have been determined. A metabolic depression without C.T. Scan counterpart has been observed in various brain structures remote from the infarcted area per se. Lastly, the hemodynamic and metabolic effects the superficial-temporal-middle-cerebral-artery anastomosis have been studied.

Tissue acid-base balance and oxygen metabolism in human cerebral infarction studied with positron emission tomography

Nine patients who had suffered strokes were examined between 10 and 34 days after onset using positron emission tomography. DMO labeled with carbon 11 was used to evaluate brain acid-base balance, and the oxygen-15 inhalation technique was used to measure regional cerebral blood flow, the oxygen extraction fraction, and cerebral metabolic rate for oxygen. [11C]DMO concentration and oxygen metabolism variables were measured in the infarcted area and in the symmetrical region in the contralateral cerebral hemisphere. [11C]DMO concentration was found to be unchanged or slightly increased in five cases and markedly increased in four cases. The apparent increase in tissue pH can be explained by the presence of a large extracellular fluid space with a pH nearly identical to that of brain plasma, or by an increase in intracellular pH, or by both phenomena. The change in [11C]DMO concentration in the infarcted area relative to that in the normal tissue was independent of the change in blood flow. Cerebral metabolic rate for oxygen was decreased in all cases. The increase in [11C]DMO concentration in the infarcted area was linearly correlated with the decrease in the oxygen extraction fraction in the same region; that is, it was correlated with the occurrence of perfusion in excess of metabolic demand. The overabundant local perfusion could play a role in the decreased H+ content.

[A 15oxygen positron study of relative local perfusion and oxygen extraction of the brain in lacunar hemiparesis (author's transl)]

The oxygen-15 non-invasive continuous inhalation technique coupled with positron emission tomography (PET) allows the local study of cerebral blood flow and oxygen metabolism. Recent PET studied have demonstrated the frequent occurrence of widespread metabolic depression remote from the site of middle cerebral artery territory infarct per se, especially over the cortical mantle and thalamus ipsilaterally, and over the cerebellar hemisphere contralaterally. These phenomena have been taken as indicative of a transneural depression (i.e. diaschisis). We thought interesting to study the possible occurrence of such abnormalities in patients with lacunar syndromes. We have applied the 15O technique to seven patients (2 with pure motor hemiplegia, 5 with ataxic hemiparesis) in whom no large causal ischemic lesion could be demonstrated on CT Scans; in only one patient was a lacunar lesion, presumably responsible for the clinical deficit, evidenced. Compared to a set of 19 patients without brain disease, the semi-quantitative results (analyzed in terms of asymmetry indices between homologous brain regions) in our patients did not disclose any pathophysiologically significant abnormality. More specifically, no evidence of physiological dysfunction similar to that reported in internal carotid artery territory infarcts, was detected over the cerebral or the cerebellar cortices. These original findings are commented upon in view of the presumably small size and the uncertain topography of the causal lesion.