Bleed

Abstract: To determine the natural history of brain cavernous malformations, the authors entered patients referred to their center into a prospective registry between 1987 and 1993. All patients underwent magnetic resonance imaging, which showed the typical appearance of this lesion, and conservative management was recommended in all. Patients or their referring physicians were contacted for follow-up data. The purpose of the study was to define the rate of symptomatic hemorrhage and to determine the outcome in those patients who had suffered seizures. Follow-up data were available for 122 patients with a mean age at entry of 37 years (range 4-82 years). The malformation was located in the brainstem in 43 cases (35%), the basal ganglia/thalamus in 20 (17%), and a hemispheric area in 59 (48%). Fifty percent of patients had never had a symptomatic hemorrhage, 41% had one bleed, 7% had two, and 2% had three. Seizures were reported in 23% of patients and headaches in 15%. Lesions were solitary in 80% of patients and multiple in 20%. The retrospective annual hemorrhage rate (61 bleeds/4550.6 patient-years of life) was 1.3%. The mean prospective follow-up period was 34 months. There were nine bleeds during this time, six with new neurological deficits. In patients without a prior bleed, the prospective annual rate of hemorrhage was 0.6%. In contrast, patients with prior hemorrhage had an annual bleed rate of 4.5% (p = 0.028). Patient sex (p = 0.97) or the presence of seizures (p = 0.11), headaches (p = 0.06), or solitary versus multiple lesions (p = 0.15) were not significant predictors of later hemorrhage. There was no difference in the rate of bleeds between brain locations. Four patients with seizures became seizure-free and four patients without seizures later developed seizures; only one patient developed intractable seizures. Fourteen had radiosurgery. No patient died in the follow-up period. This study indicates that conservative versus operative management strategies may need to be redefined, especially in patients who present with hemorrhage and who appear to have a significantly increased risk of subsequent rehemorrhage.

Abstract: It is difficult to assess the natural history of intracranial vascular malformations because they are varied in nature, they are frequently silent clinically, they are often treated when they are discovered, and untreated lesions are not often followed in an organized way. Capillary telangiectasias are usually occult lesions of no clinical significance. Cavernous hemangiomas may cause seizures and may bleed, but the approximate yearly risks of bleeding and of death have not been determined. Venous angiomas seldom cause symptoms, with the exception that those in the cerebellum seem to have a propensity to bleed. Intracranial dural arteriovenous malformations (AVMs) may bleed and may cause brain injury if there is insufficient outflow into a dural venous sinus. The dural AVMs that drain into the cavernous sinus have a more benign course than those that drain into the transverse or sigmoid sinus. The aneurysm of the vein of Galen presents a different clinical picture and threat to health according to whether the patient is a neonate, an infant, or an older child. The AVM of the brain encountered in the adult usually presents with hemorrhage or seizures. An unruptured AVM has approximately a 2 to 3% risk of bleeding per year, with about a 1% risk of death per year. The mortality rate of the first hemorrhage is about 10%. Among the survivors, there is about a 6% chance of rebleeding during the 1st year and then approximately a 2 to 3% risk of bleeding per year subsequently. The mortality rate associated with a second hemorrhage is about 13%, and for subsequent hemorrhages the mortality is roughly 20%.

Abstract: Background and Purpose Arteriovenous malformations (AVMs) have an overall 2% to 4% annual risk of hemorrhage. The purpose of this study was to determine whether specific clinical and radiographic factors predispose AVMs to bleed and to predict the bleeding risk for individual AVM patients. Methods We reviewed the clinical histories and cerebral angiograms of 315 AVM patients who underwent stereotactic radiosurgery at our center. One half of the patient data (analysis cohort) was used to determine risk factors for bleeding and to construct AVM hemorrhage risk groups. These risk groups were then tested with the second half of the patient data (test cohort). Results The mean AVM volume was 4.0±3.4 mL (approximate maximum diameter of 2 cm). One hundred ninety-six initial hemorrhages occurred in 10 348 patient-years for an annual initial bleed rate of 1.89%; 44 of these 196 patients had a repeat bleed in 591 patient-years for an annual rebleed rate of 7.45%. The overall crude annual hemorrhage rate was 2.40%. ...

Abstract: The effects of base bleed on the flow about a two-dimensional model with a blunt trailing edge were examined at Reynolds numbers, based on model base height, between 1·3×104 and 4·1×104. The ratio of boundary layer thickness at the trailing edge to half the model base height was approximately 0·4. Measurements were made of base pressure, vortex shedding frequency and the distance to vortex formation. With a sufficiently large bleed quantity the regular vortex street pattern disappeared and the base drag of the section was reduced to about a third of its value without bleed. The base pressure was found to vary linearly with the inverse of the vortex formation distance. Results of a previous splitter plate investigation were found to agree closely with those of the present experiments.