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Biomedical subjects

R Leblanc

Publications and source records attributed to R Leblanc.

At least 73 records · Page 4Linked to original sources
PubMed1988

Neurobehavioral effects of intrathecal somatostatinergic treatment in subhuman primates.

We infused somatostatin and its long-acting analogue (SMS 201-995) into the intracranial subarachnoid space of eight monkeys. Chronic infusions of SMS 201-995 produced marked neurotoxic effects characterized by truncal ataxia, dysmetria, and severe bradykinesia, with normal level of consciousness. Subcutaneous injection of apomorphine, a dopaminergic agonist, promptly reversed these effects. Further studies are required before intrathecal somatostatin replacement therapy can be offered to patients with Alzheimer's disease.

Animals↗
PubMed1988

Excitatory amino acids are elevated in human epileptic cerebral cortex.

We used intraoperative electrocorticography to identify and compare specimens from two groups of patients undergoing temporal lobectomy: (1) spiking cortex (12 patients)--epileptic activity recorded over much of the temporal convexity; and (2) nonspiking cortex (9 patients)--temporal convexity free of interictal spiking, epileptic activity confined to the hippocampus and/or amygdala. Comparative amino acid levels were (mumol/g protein, mean +/- SEM): glutamate--spiking 109.8 +/- 1.8, nonspiking 87.4 +/- 2.0 (p less than 0.001); aspartate--spiking 15.2 +/- 0.9, nonspiking 12.2 +/- 0.5 (p less than 0.05); GABA--spiking 15.0 +/- 1.0, nonspiking 13.9 +/- 1.4 (NS); taurine--spiking 14.5 +/- 0.8, nonspiking 12.2 +/- 0.8 (NS); and glycine--spiking 11.5 +/- 0.8, nonspiking 7.4 +/- 0.6 (p less than 0.01). Cortical epileptic activity appears to be associated with elevated concentrations of glutamate, aspartate, and glycine, but not GABA and taurine, perhaps indicating a relative imbalance between putative excitatory and inhibitory amino acid neurotransmitters.

Adolescent↗
PubMed1987

Borderzone ischemia.

Positron emission tomography was used to measure cerebral perfusion and metabolism in 7 patients with severe carotid stenosis. None of the patients had sustained a major stroke, and all had a normal neurological examination except 1 patient with a mild neurological deficit from a capsular lacuna. Cerebral blood flow (CBF), cerebral blood volume, the cerebral blood flow/cerebral blood volume ratio, oxygen metabolism, and the fractional extraction of oxygen by the brain were measured in the cerebral cortex of both hemispheres in the anterior and middle cerebral artery distributions, in the borderzone regions between the anterior and middle cerebral arteries (anterior borderzone), and between the middle cerebral and posterior cerebral arteries (posterior borderzone). Results obtained in patients were compared, using Student's t test, to those obtained in 6 neurologically normal, elderly volunteers. Cerebral blood flow and the cerebral blood flow/cerebral blood volume ratio were both significantly decreased (p less than 0.025 and p less than 0.05, respectively) in the anterior borderzone ipsilateral to the carotid stenosis. In the same region there was a tendency toward a rising fractional extraction of oxygen with the oxygen metabolism maintained in the low-normal range. Cerebral blood flow was also significantly decreased (p less than 0.05) in the contralateral anterior borderzone. Hemodynamic and metabolic variables in other vascular territories were not significantly different from values obtained in the control group.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1987

Thalamic abscess: a stereotactically treatable lesion.

A 69-year-old man developed abdominal pain, fever, shaking chills and acute hemiplegia. Computed tomography (CT) scanning demonstrated a hematoma within a thalamic space-occupying lesion having the radiological characteristics of a malignant glioma. Low-grade fever and leukocytosis persisted and follow-up CT scanning showed ring enhancement of the thalamic lesion and ependymitis suggesting a cerebral abscess. Stereotactic aspiration achieved drainage of the abscess and relief of mass effect and provided pus from which a causative organism was identified and treated with appropriate antibiotics. Contrast-enhanced CT scan should be obtained in cases of hemorrhage within mass lesions and tissue diagnosis should be achieved even in deep brain regions, as this can be accomplished safely using stereotactic techniques.

Aged↗
PubMed1987

Selective neuromuscular blockade for intraoperative electrocorticography.

Local anesthesia is advocated for cortical mapping in certain neurological procedures. Occasionally, however, a modified general anesthetic is necessary. We describe a technique of balanced anesthesia in which the arm opposite to the craniotomy is selectively isolated from the effect of the neuromuscular blocking agent and hence preserves its motor response to cortical stimulation. The technique secures complete immobility of the patient during mapping of the brain, shortens the stimulation time, facilitates the localization of the motor cortex, precludes the development of full-blown seizures, increases safety and is well tolerated.

Adolescent↗
PubMed1987

Magnetic resonance imaging of cerebral arteriovenous malformations.

Magnetic resonance imaging (MRI) was performed in 15 patients with small to very large supratentorial arteriovenous malformations (AVMs). Unlike non-contrast infused computed tomographic (CT) scanning, MRI demonstrated the AVM in all cases. The nidus had a characteristic honeycomb appearance, and in all cases feeding arteries and deep or superficial draining veins were demonstrated without intervening bone artifact. The relationship of the AVM to surrounding cortical areas, deep nuclei, important white matter tracts, and the ventricular system was well appreciated. These characteristics make MRI useful for the diagnosis of cerebral AVMs and add to the accuracy of systems that grade operability on the basis of the angiographic demonstration of size, location, depth, arterial supply, and venous drainage. In many cases, based on the MRI appearance of the AVM and its relationship to important brain structures, the lesion can be deemed inoperable or unsuitable for other forms of treatment, making angiography unnecessary. Thus, the superior anatomical and morphological resolution of MRI, the lower false-negative rate, and the independence from x-ray and contrast material make MRI more useful than CT scanning for the diagnosis of AVMs and as an aid in the management of specific cases.

Adult↗
PubMed1987

The minor leak preceding subarachnoid hemorrhage.

Thirty-four of 87 consecutive patients with subarachnoid hemorrhage from a cerebral aneurysm had a premonitory minor leak. There were 12 men and 22 women, aged 25 to 73 years (mean 44.4 years). Twenty-two had a small and 12 had a large aneurysm located on the internal carotid artery (17 cases), anterior communicating artery (10 cases), middle cerebral artery (five cases), and pericallosal artery (two cases). Fifty-two percent of patients with a minor leak from an internal carotid artery aneurysm had ipsilateral, hemicranial, hemifacial, or periorbital pain. Half of the patients initially saw a physician, but in no case was the correct diagnosis made. Twenty-five patients had a major rupture within 24 hours to 4 weeks after findings suggesting a minor leak, with a mortality rate of 53%. Nine other patients were diagnosed by lumbar puncture or computerized tomography (CT) scanning after initial misdiagnosis and were operated on, without mortality, before a major rupture could occur. The CT scans were negative in 55% of patients with a minor leak, but lumbar puncture, when performed, was always positive. A minor leak prior to major aneurysmal rupture is a common occurrence and, if unrecognized, is associated with a high mortality. Computerized tomography scanning is unreliable in diagnosing this event, and lumbar puncture is the examination of choice once intracranial hypertension has been ruled out.

Adult↗
PubMed1987

Familial intracranial aneurysms.

The authors report seven individuals from two families, all of whom had aneurysmal subarachnoid hemorrhage. These cases and all reported cases of familial aneurysms (243 aneurysms in 177 patients from 74 families) were submitted to computer-aided multivariate analysis to determine if the aneurysms or the patients who harbor them differ from sporadic aneurysm cases. Familial aneurysms rupture at a smaller size (mean diameter 10.5 mm), and when the patient is younger (mean age 42.3 years and decennial age at peak incidence 40 to 49 years). There is a similar sex distribution (male to female ratio 48:52), a similar incidence of multiple aneurysms (21.5%), and a similar predominance of females over males with multiple aneurysms (2.2:1). Anterior communicating artery aneurysms occur less often in familial cases (19%) than in sporadic cases. In sibling pairs the aneurysms occur at the same or at mirror sites, and rupture within the same decade twice as frequently as randomly selected nonfamilial aneurysm patient pairs. The occurrence of aneurysms at identical and mirror sites is more frequent in familial cases and appears to be a function of the degree of kinship between affected individuals. These observations suggest a genetic basis for the pathogenesis of familial intracranial aneurysms.

Adult↗
PubMed1987

Hemodynamic and metabolic effects of cerebral revascularization.

Pre- and postoperative positron emission tomography (PET) was performed in six patients undergoing extracranial to intracranial bypass procedures for the treatment of symptomatic extracranial carotid occlusion. The six patients were all men, aged 52 to 68 years. Their symptoms included transient ischemic attacks (five cases), amaurosis fugax (two cases), and completed stroke with good recovery (one case). Positron emission tomography was performed within 4 weeks prior to surgery and between 3 to 6 months postoperatively, using oxygen-15-labeled CO, O2, and CO2 and fluorine-18-labeled fluorodeoxyglucose. Cerebral blood flow (CBF), cerebral blood volume (CBV), cerebral metabolic rates for oxygen and glucose (CMRO2 and CMRGlu), and the oxygen extraction fraction (OEF) were measured in both hemispheres. Preoperatively, compared to five elderly control subjects, patients had increased CBV, a decreased CBF/CBV ratio, and decreased CMRO2, indicating reduced cerebral perfusion pressure and depressed oxygen metabolism. The CBF was decreased in only one patient who had bilateral carotid occlusions; the OEF, CMRGlu, and CMRO2/CMRGlu and CMRGlu/CBF ratios were not significantly different from control measurements. All bypasses were patent and all patients were asymptomatic following surgery. Postoperative PET revealed decreased CBV and an increased CBF/CBV ratio, indicating improved hemodynamic function and oxygen hypometabolism. This was associated with increased CMRO2 in two patients in whom the postoperative OEF was also increased. The CMRGlu and CMRGlu/CBF ratio were increased in five patients. Changes in CBF and the CMRO2/CMRGlu ratio were variable. One patient with preoperative progressive mental deterioration, documented by serial neuropsychological testing and decreasing CBF and CMRO2, had improved postoperative CBF and CMRO2 concomitant with improved neuropsychological functioning. It is concluded that symptomatic carotid occlusion is associated with altered hemodynamic function and oxygen hypometabolism. Cerebral revascularization results in decreased CBV, indicating improved hemodynamic reserve, but does not consistently improve oxygen metabolism.

Aged↗
PubMed1987

Graves' disease and subarachnoid hemorrhage: a possible familial association.

We report the occurrence of cerebral aneurysms and subarachnoid hemorrhage (SAH) in a family with Graves' disease (GD). Nine affected individuals across three generations have GD alone; three in the same generation have SAH without GD; and three others in the same sibship have both conditions. The familial association of GD and SAH has not been previously described. The occurrence of these disorders in individuals of the same family and their coexistence in the same individuals suggests a possible genetic determination for some cerebral aneurysms and may imply a genetic locus related to that of Graves' disease.

Adult↗
PubMed1986

Antemortem laboratory diagnosis of Alzheimer's disease.

The accuracy of diagnosis for AD by conventional clinical and laboratory means is in the order of 80%. Neurophysiological techniques (EEG, evoked potentials) show abnormalities in AD that could prove to be useful for diagnosis after pharmacological challenges. CSF analysis show a reduction of the concentration of various neuropeptides, reduction shared by other types of dementias. Among the existing imaging techniques PET using 18F-fluorodeoxyglucose is the most diagnostic in AD because of the early and often asymmetrical decrease in parietotemporal metabolic activity. Cortical biopsy with histological and biochemical analysis can provide an accurate in vivo diagnosis of AD.

Alzheimer Disease↗
PubMed1986

Transmitter-replacement therapy in Alzheimer's disease using intracerebroventricular infusions of receptor agonists.

Neurotransmitter replacement therapy in Alzheimer's Disease is currently being attempted using bethanechol chloride (Urecholine) infused intracerebroventricularly with an Infusaid continuous infusion pump. The rationale of this therapy is based on the severe cortical pre-synaptic cholinergic deficit in the presence of relatively normal post-synaptic muscarinic receptor density. Patients are selected on the basis of strict clinical criteria at a functional stage 4 or 5 of Reisberg. A cortical biopsy at the time of pump and catheter implantation confirms the diagnosis by histological and biochemical examination. Pre-operative, post-operative and serial mental status assessments combined with functional ADL assessments monitor changes in behavior. A 6 months double-blind treatment period is done in every patient, who is then free to continue if he has improved on active treatment. This specific study is part of a multi-centre trial. Other therapeutic trials using somatostatin analogs, such as Sandostatin, could then be done. The biological effects of the latter compound are being studied currently in adult Green Vervet monkeys, prior to its use in Alzheimer patients. Furthermore autoradiography of bethanechol and peptides labeled with 14C administered in these animals by intracerebroventricular infusion will allow a better knowledge of their pharmacological site of action.

Alzheimer Disease↗
PubMed1986

Neurocysticercosis: surgical and medical management with praziquantel.

Eight cases of neurocysticercosis were encountered at the two major neurological centers affiliated with McGill University in Montreal in 4 years. All patients were immigrants who had been in Canada for a period of 1 to 18 years and came from South America (three cases), Haiti (three cases), and Greece (two cases). Five patients had parenchymal cysts and presented with epilepsy; three had the racemose form and presented with hydrocephalus. Four patients with parenchymal cysts were treated by removal of the cysticercus and did well. One patient with numerous cysts was treated with praziquantel with good clinical and radiological results. Two patients with the racemose form were treated by cyst aspiration, cerebrospinal fluid (CSF) diversion, and praziquantel and did well. Another patient with the racemose form, seen before the advent of praziquantel, died of cysticercosis infection. Neurocysticercosis is not uncommon in the immigrant population of large North American cities. Single symptomatic cysts can be evacuated surgically with good results; multiple parenchymatous cysts can be treated with praziquantel. Patients with the racemose form who are treated with CSF diversion and praziquantel do well, although those who are only treated surgically die of their disease.

Adult↗
PubMed1986

Familial mixed oligodendrocytic-astrocytic gliomas.

We present the first reported cases of mixed oligodendrocytic-astrocytic gliomas to occur in two members of the same family, a father and a son. These tumors had common biological and histological characteristics, and their occurrence supports the concept of genetic determination in some gliomas.

Adult↗
PubMed1985

Akinetic mutism and parkinsonism associated with obstructive hydrocephalus.

We report the case of a patient with idiopathic aqueductal stenosis and hydrocephalus who had several episodes of akinetic mutism, each preceded by shunt malfunction, that resolved with shunt revision. She also developed a parkinson's syndrome resistant to shunt revision but responsive to antiparkinsonian medications. The parkinson's syndrome and the episodes of akinetic mutism may be related to a reduction of dopaminergic input to the striatum and to the cingulate and frontal cortex brought about or worsened by ventricular dilatation.

Adult↗
PubMed1985

Wall motion in expiratory flow limitation: choke and flutter.

Limitation of expiratory airflow from mammalian airways is currently understood to be due to choking at wave speed (S. V. Dawson and E. A. Elliott. J. Appl. Physiol. 43: 498-515, 1977). A critical weakness of the theory is the lack of a mechanism for the dissipation of energy when effort exceeds that needed for maximal flow. We have observed substantial wall motion with flow limitation in a physical model of a trachea. Therefore we have examined a simple two-dimensional mathematical model, designed to approximate the behavior of the physical model of the trachea, to try to identify a relationship between flow limitation and wall oscillation. The model matches wave-speed predictions when only long waves are considered. The model predicts that aerodynamic flutter will occur in the zone of supercritical flow described in wave-speed theory. Aerodynamic flutter in the zone of supercritical flow provides a potential mechanism for the energy dissipation necessary for transition from supercritical to subcritical flow and explains the high-frequency pure tone heard with flow limitation.

Airway Obstruction↗
PubMed1985

Meningioma cysts.

We studied six cases of intracranial meningioma with cyst formation. Manifestations included focal neurologic signs (four cases), seizures (three cases), headache (three cases), and personality changes (two cases). CT revealed a cystic enhancing supratentorial lesion in five cases. Angiographic changes of meningioma were observed in only three cases, and correct preoperative diagnosis was made in only half the cases so studied. Histologically, all lesions were syncytial meningiomas. Cyst fluid was always xanthochromic, acellular, and highly proteinaceous. The variety of anatomic configurations suggests several pathophysiologic mechanisms in formation of the cysts that are commonly misdiagnosed preoperatively. Tissue analysis is needed for all cystic, enhancing lesions of the brain.

Adult↗