Intracranial Aneurysms: A Clinical, Angiographic and Computerized Tomographie Study

An experimental investigation of the hemodynamic variations due to aplastic vessels within three-dimensional phantom models of the circle of Willis

A complete circle of Willis (CoW) is found in approximately 30-50% of the population. Anatomical variations, such as absent or surgically clamped vessels, can result in undesirable flow patterns. These can affect the brain's ability to maintain cerebral perfusion and the formation of cerebral aneurysms. An experimental test system was developed to simulate cerebral physiological conditions through three flexible 3D patient-specific models of complete and incomplete CoW geometries. Flow visualizations were performed with isobaric dyes and the mapped dye streamlines were tracked throughout the models. Three to seven flow impact locations were observed for all configurations, corresponding to known sites for aneurysmal formation. Uni and bi-directional cross-flows occurred along the communicating arteries. The greatest shunting of flow occurred for a missing pre-communicating anterior (A1) and posterior (P1) cerebral arteries. The anterior cerebral arteries had the greatest reduction (15-37%) in efferent flow rates for missing either a unilateral A1 or bilateral P1 segments. The bi-directional cross-flows, with multiple afferent flow mixing, observed along the communicating arteries may explain the propensity of aneurysm formation at these sites. Reductions in efferent flow rates due to aplastic vessel configurations may affect normal brain function.

[Subarachnoid hemorrhage caused by aneurysm rupture. Initial management of patients]

Subarachnoid haemorrhage is a severe illness with a high mortality and morbidity. Its diagnosis is considered in the case of a brutal, violent and unusual headache. It is confirmed rapidly with the conventional techniques such as CT-scan and lumbar puncture. The main complications (ischaemia, rebleeding, hydrocephalus) occur during the first two weeks and are a usual event in case of a lack of diagnosis or specialised medical, surgical and radiological management. Among the complications, rebleeding badly affects prognosis, and only early surgery or interventional radiology may improve the outcome. Delayed ischaemia may be prevented by medical management with correction of hypovolaemia and administration of calcium antagonists, before and after surgery, particularly between the 4th and the 10th day. When signs of ischaemia occur, aggressive treatment should be administered in order to improve cerebral perfusion pressure and cerebral blood flow. The treatment is aimed to prevent the complications of subarachnoid haemorrhage and to establish optimal conditions for surgical and radiological procedures.

Amount of subarachnoid blood and vasospasm: current aspects. A transcranial Doppler study

Subsequent to admission after aneurysmal subarachnoid haemorrhage (SAH), 120 patients (74 women and 46 men) underwent microsurgical clipping of a total of 158 cerebral aneurysms within 96 hours after the bleed. Their mean age was 46 (20-91) years. Computed tomography (CT) findings were graded according to the modified Fisher scale and all patients had daily transcranial doppler (TCD) recordings of their basal cerebral arteries. In 19% of SAH was grade I on CT, in 44% grade II and in 37% grade III. The rate of patients who developed severe vasospasm as documented by TCD (mean blood flow velocities exceeding 160 cm/s on 2 or more consecutive days) was 39% for grade I patients, 26% for grade II patients and 34% for patients with SAH grade III on the initial CT. There was no difference in the rate of occurrence of severe vasospasm, when the patients were split into 2 groups according to the time of performance of the initial CT scan-within 24 hours, and 48-80 hours after SAH, respectively. It is concluded that the amount of subarachnoid blood on the initial CT scan should no longer be used as the indicator for occurrence and severity of the multifactorial entity vasospasm.

Prevalence of brain atrophy in liver cirrhosis patients with chronic persistent encephalopathy. Evaluation by computed tomography

Brain computerized axial tomography scans were performed in 18 consecutive liver cirrhosis patients with chronic persistent encephalopathy (8 alcoholic and 10 nonalcoholic) in order to evaluate the incidence of brain atrophy in this pathological condition. Fifteen patients of similar age with liver cirrhosis of Child's class B but with acute episodic hepatic encephalopathy were studied in parallel. Brain atrophy was detected in 87.5% of alcoholic and in 50% of nonalcoholic liver cirrhosis patients with chronic persistent encephalopathy, whereas the patients with acute episodic encephalopathy were normal. The high frequency of brain atrophy in alcoholic patients with chronic encephalopathy can be attributed at least in part to the toxic effect of alcohol. The presence of brain atrophy in nonalcoholic liver cirrhosis patients with chronic persistent encephalopathy seems to indicate that the chronic exposure to toxins which are involved in the pathogenesis of hepatic encephalopathy leads to neuronal alterations which develop mainly in the cortex and which can be demonstrated by in vivo imaging only in a long-lasting state of coma. Moreover, alcohol and toxins causing hepatic encephalopathy seem to potentiate each other in inducing brain atrophy.

Computerized tomography and prognosis in early aneurysm surgery

A study of computerized tomography (CT) scans was performed in a consecutive series of 100 patients with ruptured saccular cerebral aneurysms who were admitted, diagnosed, and operated on within 72 hours after subarachnoid hemorrhage (SAH) and treated with calcium antagonists. The aneurysms were in the anterior portion of the circle of Willis in 95% of patients and in the posterior portion in 5%; 12% had multiple aneurysms. Preoperative neurological grades according to Hunt and Hess were I to III in 74% of patients and IV or V in 26%. Subarachnoid hemorrhage as determined by CT scanning was minor in 20%, moderate in 43%, and severe in 37% of patients. All patients received intraoperative and postoperative administration of the calcium antagonist nimodipine. Three days postoperatively, SAH (as measured by CT) was significantly reduced in the majority of patients but was still moderate in 18%. In the postoperative course, 2% of patients developed delayed ischemic neurological symptoms due to vasospasm. In two additional patients, ischemic symptoms were transient and fully reversible. At the 6-month follow-up interval, a significant prognostic difference was found between two patient groups with different CT scan findings. Among the patients with SAH only, the rate of good outcome (no or minimal deficit) was 93% when the preoperative neurological Grade was I or II; but even with a Grade of III to V, there was a good outcome in 84% of patients. By contrast, in patients with additional intracerebral and/or intraventricular hemorrhage, the good-outcome rate was only 44%. From these data it is concluded that morphological preoperative CT findings are of prognostic value and may even be superior to clinical grading in predicting outcome.

Intraventricular hemorrhage from ruptured aneurysm. Retrospective analysis of 91 cases

Intraventricular hemorrhage (IVH) from aneurysm rupture is generally considered to be of grave prognostic significance. Ninety-one cases have been studied retrospectively from seven medical centers. The overall mortality rate was 64%. The dramatically poor condition of these patients leads to their rapid admission to the hospital. Eighty-seven percent were admitted on Day 0 or 1, and more than half were classified neurologically as Grade 4 or 5. A multiple regression analysis explained 56% of the variance in survival, using the variables of ventriculocranial ratio (VCR), day of admission, diastolic blood pressure, location of aneurysm, associated intracerebral hematoma, age, grade on admission, sex, and systolic blood pressure. No patient with a VCR of more than 0.25, as calculated from the initial computerized tomography (CT) scan, survived. No patient whose smallest VCR was 0.23 or more survived. This ratio can be simply measured with a millimeter ruler from the CT scan. Patients with IVH usually had enlarged ventricles, even initially. The overall results suggest that early management of intracranial hypertension should be more generally considered, although even when this was done the prognosis was still guarded. The timing of surgery was not an important determinant of outcome, although a significant number of patients died awaiting surgery.

Clinical - radiological correlates in intracerebral hematomas due to aneurysmal rupture

In this series of intracerebral hematomas from aneurysmal rupture, gathered from several neurosurgical services, certain morphological features were studied in detail. Patients with very large hematomas tended to have poor neurological grades on admission to hospital and their immediate discharge outlook was correspondingly poor. Ruptured middle cerebral and pericallosal artery aneurysms were relatively common causes of intracerebral hematomas. Patients with temporal lobe hematoma did relatively well; those with parietal hematoma did poorly. The larger the hematoma the less chance there was of developing cerebral vasospasm but the more likely was pre-operative brain herniation. The survival was more closely linked to size and location of the hematoma than to the location of aneurysm or the degree of midline shift.

Computer tomographic features of giant intracranial aneurysms

Five cases of giant intracranial aneurysm are reported, all of which presented as intracranial mass lesions. All five aneurysms were visualised by CT scanning as well as angiography. Their CT scan appearances may be sufficiently characteristic to be distinguished from other mass lesions. The poor prognosis when untreated is emphasised, and the results of treatment by carotid ligation discussed.

Giant aneurysm of anterior communicating artery simulating 3rd ventricular tumor

This is a case report of an anterior communicating artery aneurysm simulating a 3rd ventricular tumor with obstructive hydrocephalus demonstrated on CT scan. Angiography showed the "tumor" to be an aneurysm. We believe that giant aneurysms of the anterior communicating artery should be included in the differential diagnosis of suspected 3rd ventricular tumors along with suprasellar masses as seen on CT scans.