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Biomedical subjects

R Leblanc

Publications and source records attributed to R Leblanc.

At least 91 records · Page 5Linked to original sources
PubMed1985

Cerebral amyloid angiopathy.

We studied 24 patients with autopsy-proven cerebral amyloid angiopathy. Eight patients were demented or had some other medical problem and died of pneumonia or systemic disease. Sixteen patients died of intracranial hemorrhage. Amyloid was found in cortical arteries and arterioles of all patients. CT showed diffuse atrophy in demented patients and intracerebral hematomas in the others. The location and size of the hematoma, with cortical and subarachnoid extension, help to differentiate amyloid angiopathy from other causes of intracranial hemorrhage in the elderly.

Age Factors↗
PubMed1984

The warning leak in subarachnoid hemorrhage and the importance of its early diagnosis.

A 40-year-old man had a severe headache of sudden onset and progressive palsy of the third cranial nerve from a minor subarachnoid hemorrhage. Despite assessment by two primary care physicians the possibility of serious neurologic disease was not raised and the urgency of the situation not appreciated. Two weeks after the onset of the headache the patient was urgently admitted to hospital at the request of a neuro-ophthalmologist. Cerebral angiography revealed an aneurysm of the posterior communicating artery, which was surgically occluded with a clip. The patient had a satisfactory recovery, with almost complete return of nerve function by the time of discharge from hospital. Such "warning leaks" in subarachnoid hemorrhage are discussed, and a protocol for their assessment is recommended.

Adult↗
PubMed1984

Reversal of acute experimental cerebral vasospasm by calcium antagonism with verapamil.

Acute vasospasm of the transclivally exposed basilar artery of anesthetised cats was produced by the subarachnoid injection of platelet-rich plasma (PRP) treated with enough adenosine diphosphate (ADP) to induce platelet aggregation and secretion. Vasorelaxation was produced by the topical application of the calcium antagonist verapamil. Changes in the internal diameter of the basilar artery were determined by measuring the blood column diameter from photomicrographs taken sequentially, at 5 minute intervals, through the operating microscope. Changes in blood vessel diameter are expressed as a plus or minus percentage of the pretreatment diameter. Arterial blood pressure and blood gas values were kept in the physiological range for the cat. The subarachnoid injection of PRP-ADP produced severe constriction of the basilar artery (mean constriction at 5 minutes after injection: -40.7% +/- 2.8 SEM). Platelet-free plasma, ADP alone and Elliott's A solution had no spasmogenic effect when injected into the subarachnoid space. The topical application of the calcium channel blocker verapamil (0.1 mg per kg) 30 minutes after the injection of PRP-ADP, with the basilar artery still in spasm (mean constriction: -23% +/- 3.5 SEM), produced prompt and dramatic vasodilation (mean dilation at 5 minutes after application: +52.7% +/- 18.1 SEM). This spasmolytic effect persisted in a decremental fashion for the 60 minute period of observation, by which time the previously constricted vessel had returned to its normal size. These observations indicate that the platelet fraction of whole blood may be involved in the genesis of acute vasospasm following subarachnoid hemmorrhage and that this phenomenon can be readily reversed by calcium antagonism.

Acute Disease↗
PubMed1983

Epilepsy from cerebral arteriovenous malformations.

Twenty-seven patients with epilepsy as the only manifestation of a cerebral AVM were seen at the MNI/MNH from 1973 to 1981. The nine females and eighteen males between the ages of fourteen and fifty-four years (mean 25.2 years) had epilepsy for an average of 3.5 years prior to the diagnosis of AVM. Seven patients had primarily generalized seizures, ten patients had partial seizures with complex symptoms, fourteen patients had partial seizures with elementary symptoms, and thirteen patients had secondarily generalized seizures. Although there was no history of intracranial hemorrhage, seven patients had negative hemispheric signs (hemiatrophy, hemianopia, dysphasia, hemiparesis), two had impaired mentation, and two were ataxic. The EEG, normal in ten cases,showed non-epileptiform activity in six cases, and focal epileptiform activity in eleven cases. Angiographic and/or histological examination revealed eight small (less than 2 cm in diameter) and nineteen large lesions. Fifteen AVMs involved the frontal lobe, ten the temporal lobe five the parietal lobe, and one the occipital lobe. Angiography failed to demonstrate three frontal and three temporal AVMs. Plain CT scanning demonstrated a high or low density lesion without a mass effect in sixteen cases, enlargement of the ipsilateral ventricle or Sylvian fissure in seven cases, and diffuse ventricular enlargement in three cases. CT scanning was performed after the intravenous injection of contrast material in nineteen cases and demonstrated vascular enhancement in fifteen cases and an abnormal blood vessel in six cases. Two angiographically occult AVMs demonstrated vascular enhancement with infusion CT scanning, thereby demonstrating the vascular nature of the lesion where angiography had failed to do so.

Adolescent↗
PubMed1981

The computerized tomographic appearance of angiographically occult arteriovenous malformations of the brain.

Eight patients with a histologically proven angiographically occult arteriovenous malformation of the brain had plain and infused computed tomographic (CT) examinations. In five cases angiography revealed a hypovascular mass in three cases the angiogram was normal. On CT examination a high density lesion (six cases) and ventricular asymmetry (five cases) were demonstrated. In three patients presenting with intracerebral hemorrhage, the high density appearance and ventricular compression were accounted for by the presence of hematoma. In three of five seizure patients the high density lesion was associated with calcification while ipsilateral (one case) and contralateral (one case) enlargement of the lateral ventricle was seen. In five of the eight cases the vascular nature of the lesion was suggested by vascular enhancement of the infused CT scan. Glioma was a common misdiagnosis.

Adolescent↗
PubMed1981

Tuberculous brain abscess: report of a case with computed tomography correlation.

A 27 year-old Vietnamese male immigrant to Canada developed a hemispheric cerebellar abscess. The patient presented at the hospital with osteomyelitis of the 5th finger of the left hand. He complained of lassitude, weight loss, and early morning headache, nausea, and vomiting, and he developed a left facial weakness. A computed tomographic scan demonstrated the distinctive appearance of an abscess of the left cerebellar hemisphere. Aspiration of the abscess afforded immediate relief of obstructive hydrocephalus and provided pus from which Mycobacterium tuberculosis was grown, thus permitting specific antituberculous chemotherapy. The cerebrospinal fluid obtained at the time of operation was sterile. The patient recovered fully. A primary site of infection was not conclusively identified.

Adult↗
PubMed1980

Neonatal intracranial hemorrhage. A clinical and serial computerized tomographic study.

Forty-six neonates with intracranial hemorrhage were classified into three groups on the basis of the major computerized tomography (CT) scan findings: Group I consisted of 24 cases of subarachnoid hemorrhage, Group II 20 cases of intracerebral and/or intraventricular hemorrhage, and Group III two cases of subdural hemorrhage. The initial scans in Group I showed blood in the interhemispheric fissure and the supratentorial recess. Sixty percent had an associated hypodensity in the frontal and/or parietal areas, thought to be an indication of ischemia. Changes in the configuration of the ventricular system were infrequent. Initial scans in Group II showed hematomas as follows: one in the brain stem, five in the basal ganglia, 10 in the temporal lobes, and 11 in the ventricles. In 70% of these cases, changes in the configuration of the ventricular system were seen, including compression of a lateral ventricle by mass effect, ventricular dilatation with blood, and obstructive hydrocephalus. Subarachnoid blood was an associated finding in 55% of cases, and focal and diffuse cerebral edema in 40%. Scans in both Group III patients initially showed a mass effect from a subdural clot. In all, 30 patients had one or more follow-up CT scans, and 13 of these were scanned at regular intervals. None of the Group I patients developed hydrocephalus, but 85% of Group II patients with intraventricular blood extending from an intracerebral hemorrhage had this complication. A seizure disorder occurred in 31% of Group I patients and 20% of Group II patients, where it was seen exclusively in those with an intralobar hematoma. A major motor disturbance occurred in 16% of patients; their Ct scans showed evidence of brain destruction involving enlargement of a lateral ventricle, porencephaly, or focal atrophy. Computerized tomography is a useful adjunct to the diagnosis, management, and follow-up study of neonatal intracranial hemorrhage, and correlates well with the clinical findings.

Birth Weight↗
PubMed1976

A theory of the mechanism of cerebral vasospasm and its reversal, the role of calcium and cyclic AMP.

It is proposed that the basic mechanism of vasospasm which sometimes follows subarachnoid hemorrhage is dependent on increased free intracellular calcium ion produced by spasmogens from closely applied extravasated blood. Relaxation of this spasm occurs when the intracellular cyclic AMP levels are raised, resulting in sequestration of calcium ion by the vascular smooth muscle cell sarcoplasmic reticulum.

Blood Platelets↗
PubMed1975

Cyclic adenosine monophosphate antagonism of prostaglandin induced vasospasm.

Prostaglandin F2alpha was applied topically to the transclivally exposed basilar artery of the cat. The resultant vasoconstriction and its reversal by dibutyryl cyclic adenosine monophosphate was recorded photographically and measured, and the results analyzed statistically. Arterial BP, pCO2' pO2 and pH were determined to insure that the vascular responses were not due to any general physiological disturbance. The results indicated that Prostaglandin F2alpha is a powerful vasoconstrictive substance and that its effects are readily reversible by dibutyryl cyclic adenosine monophosphate.

Animals↗
PubMedDate not supplied

Using pattern analysis of in vivo proton MRSI data to improve the diagnosis and surgical management of patients with brain tumors.

We have used pattern analysis of proton magnetic resonance spectroscopic imaging (1H MRSI) data in a variety of situations related to the clinical management of patients with brain tumors and other cerebral space-occupying lesions (SOLs). Here, we review how 'leave-one-out' linear discriminant analyses (LDAs) of in vivo 1H MRSI spectral patterns have enabled us to quickly, accurately, and non-invasively: (1) discriminate amongst tissue arising from the five most common types of supratentorial tumors found in adults, and (2) use the metabolic heterogeneity of cerebral SOLs to predict certain pathological characteristics that are useful in guiding stereotaxic biopsy and selective tumor resection. These findings suggest that pattern analysis of 1H MRSI data can significantly improve the diagnostic specificity and surgical management of patients with certain cerebral SOLs.

Aged↗