Pretreatment ipsilateral regional cortical blood flow influences vessel recanalization in intra-arterial thrombolysis for MCA occlusion.

BACKGROUND AND PURPOSE: The aim of acute stroke interventions is to achieve recanalization of the target occluded artery. We sought to determine whether pretreatment cortical cerebral blood flow (CBF) was associated with vessel recanalization in patients undergoing intra-arterial therapy. METHODS: This is a retrospective analysis of patients who underwent a quantitative xenon CT blood flow study and were noted to have a documented M1 middle cerebral artery (MCA) or carotid terminus occlusion less than 6 hours from symptom onset between January 1997 and April 2001. Twenty-three patients who underwent intra-arterial thrombolysis were included in the analysis. Univariate and multivariate analyses were performed to determine whether pretherapy CBF was correlated to the likelihood of recanalization. RESULTS: A total of 23 patients were studied in this analysis with a median age of 69 (range 32-81) and median National Institutes of Health Stroke Score of 19 (range, 8-22). Twelve patients (52%) underwent combined intravenous/intra-arterial therapy, and 11 patients (48%) were treated with intra-arterial thrombolytics alone. Successful vessel recanalization (Thrombolysis in Myocardial Infarction classification 2 or 3 flow) occurred in 13 patients (57%). The only variable associated with recanalization in multivariate modeling was mean ipsilateral MCA CBF (odds ratio, 1.25; 95% confidence interval, 1.01-1.54; P = .035). A receiver operating characteristic curve was generated, and a mean ipsilateral MCA CBF threshold of 18 mL/100 g/min was found to be the threshold for successful recanalization. CONCLUSIONS: Our study suggests that patients with higher mean ipsilateral MCA CBF are more likely to recanalize. The threshold for successful revascularization may be 18 mL/100 g/min. Further study is required to determine whether pretreatment CBF is related to recanalization success.

The bioceramic orbital implant: a new generation of porous implants.

PURPOSE: The authors describe a new generation of porous orbital implant made of aluminum oxide (Al2O3) and compare it with the hydroxyapatite orbital implants (Bio-Eye and FCI hydroxyapatite). METHODS: The authors examined the new implant macroscopically, with chemical analysis and microscopically with scanning electron microscopy. Animal implantation studies were performed using six adult male New Zealand albino rabbits. Implant vascularization was evaluated by means of magnetic resonance imaging and histopathologic sectioning. RESULTS: The Bioceramic orbital implant was found to have very uniform pore structure with an average pore size of 500 microm. The implant was 99.9% aluminum oxide on x-ray diffraction. Magnetic resonance imaging in vivo vascularization studies demonstrated enhancement of the implant to its center by 4 weeks after implantation in the rabbit. Histopathologically, fibrovascularization occurred uniformly throughout the implant and was noted by 4 weeks. CONCLUSIONS: The Bioceramic orbital implant represents a new porous orbital implant that has a very regular and extensive interconnected pore system, is as biocompatible as hydroxyapatite, is easy to manufacture, structurally strong, and free of contaminants. It is manufactured with no disruption to marine life ecosystems as may occur in the harvesting of coral for other orbital implants. It is less expensive than currently available hydroxyapatite implants and was approved by the U.S. Food and Drug Administration in April 2000.

Hydroxyapatite implant wrapping materials: analysis of fibrovascular ingrowth in an animal model.

PURPOSE: To compare the influence of seven currently available spherical orbital implant wraps on host fibrovascularization of a hydroxyapatite (HA) orbital implant. METHODS: Five groups of 3 (15 total) adult male New Zealand albino rabbits underwent enucleation with placement of a 12-mm HA implant wrapped in high-porosity expanded polytetrafluoroethylene (e-PTFE), processed bovine pericardium, or processed human pericardium, sclera, or fascia lata. Magnetic resonance imaging before and after the intravenous administration of gadolinium-diethylenetriamine pentaacetic acid (DTPA, 0.1 mol/kg) was performed immediately before exenteration. Five rabbits (one with each of the different implant wraps) were killed at 4, 8, and 12 weeks, and the operated socket was exenterated. Histopathologic sections of the implants were then compared with the results of our previous study using polyglactin 910 mesh and autologous sclera as HA orbital implant wraps. RESULTS: Complete fibrovascularization of all the implants occurred by 12 weeks; however, HA implants wrapped with sclera, polyglactin mesh, and e-PTFE appeared to undergo more rapid fibrovascularization than spheres wrapped with other materials. CONCLUSIONS: Although all of the implant wraps studied may be suitable substitutes for donor sclera, we prefer polyglactin mesh because it is readily available, inexpensive, and without risk of transmissible diseases.

A new variety of hydroxyapatite: the Chinese implant.

PURPOSE: This study was designed to evaluate a new type of hydroxyapatite (HA) implant (produced in China) in a rabbit model. METHODS: Three New Zealand white rabbits underwent enucleation of one eye followed by implantation of a 12-mm Chinese HA implant wrapped in Vicryl mesh (polyglactin 910). Magnetic resonance imaging was performed to assess host fibrovascularization of the implant 4, 8, and 12 weeks after implantation. One animal was sacrificed at each of these times for histopathologic examination. The Chinese implant was also examined chemically and by scanning electron microscopy. It was compared to the original BioEye and the third generation synthetic HA implant produced in France by FCI (FCI3). RESULTS: This new variety of HA implant from China is heavier than the FCI3 implant but lighter than the original BioEye. The Chinese implant was easy to work with and not fragile. The pore size was more uniform than the FCI3 implant and similar to the BioEye implant clinically and by scanning electron microscopy. The pores in this implant are unidirectional. Analysis for impurities revealed a calcium oxide (CaO) content of 4.4%. Histopathologically, central vascularization occurred by 4 weeks and was similar in extent to the vascularization seen with the FCI3 implant and the BioEye. CONCLUSIONS: The Chinese implant is less expensive then the BioEye and the FCI3 implants, and appears to be a viable alternative to the BioEye. Further refinements are in progress to eliminate the CaO contaminant.

A synthetic hydroxyapatite implant: the so-called counterfeit implant.

This article evaluates three generations of synthetic hydroxyapatite implants in a rabbit model. Fourteen New Zealand white rabbits received synthetic hydroxyapatite orbital implants (first, second, and third generation). The rabbits underwent enucleation of one eye and then received a 12-mm synthetic hydroxyapatite implant wrapped in Vicryl (polygalactin 910; Ethicon, Inc.) mesh or sclera. Magnetic resonance imaging was conducted to assess host fibrovascularization of the implant 4 and 12 weeks after implantation. Animals were killed at each of these times and the implant was removed for histopathologic examination. Enhancement on magnetic resonance imaging and extent of fibrovascularization by histopathologic examination were assessed. The first-generation synthetic hydroxyapatite (FCI, Issy-Les-Moulineaux, France) was not 100% hydroxyapatite as is the Bio Eye (Integrated Orbital Implants, Inc., San Diego, CA, U.S.A.). It contained 3.2% calcium oxide. The implant was heavier and much less porous than the original Bio Eye implant. Central vascularization eventually occurred but was not extensive. The second-generation implant was more porous than the first, with rapid central vascularization to the center of the implant by 4 weeks. However, the second-generation implant was very fragile and crumbled easily. The second-generation synthetic implant was chemically identical to the original Bio Eye implant with no calcium oxide. The third-generation implant was more porous than its predecessors. When compared side by side with the Bio Eye, a difference in pore uniformity and interconnectivity seems apparent. However, an early extensive vascularization pattern to the center of the implant is seen histopathologically, similar to that with the Bio Eye. Magnetic resonance imaging also shows extensive enhancement as is the case with the Bio Eye. The third-generation synthetic implant is not fragile as was the second-generation implant, and chemically it is identical to the Bio Eye with no calcium oxide present. The third-generation implant is approximately half the price of the original Bio Eye implant.

The synthetic hydroxyapatite implant: a report on 65 patients.

Sixty-five patients receiving the FCI synthetic hydroxyapatite implant (FCI3, FCI, Issy-Les-Moulineaux, France) after enucleation, evisceration, or as a secondary implant were studied under human trial guidelines established by Health and Welfare Canada. The implant is chemically identical to the original coralline Bio Eye (Integrated Orbital Implants Inc., San Diego, CA, U.S.A.), is easy to work with, and was implanted without difficulty using a wrap of polygalactin 910 (Vicryl mesh, Ethicon, Inc.) in the majority of patients. Postoperative drilling was carried out at approximately 6 months and found to be much easier than drilling of the Bio Eye. The implant could be hand drilled using drill bits rolled between the thumb and index finger. Postoperatively, patients were followed-up from 7 to 24 months and did not have any problems different from those associated with the original hydroxyapatite implant derived from sea coral (Bio Eye). One case of conjunctival dehiscence occurred at 4 weeks and required a temporalis fascia patch graft to repair. One implant became infected after drilling and had to be removed. The motility obtained with the third-generation FCI implant (FCI3) was similar to that seen with the Bio Eye, in comparable patients. That is, those receiving implants after an evisceration, on the whole, had better motility than those receiving an implant after primary enucleation or secondary implantation. The FCI3 hydroxyapatite implant is a viable alternative to the original Bio Eye hydroxyapatite implant. It's advantages are: 1) reduced cost, and 2) ease of drilling (a motorized drill is not required). The implant was given Health and Welfare approval in Canada on February 26, 1997.

Vicryl-mesh wrap for the implantation of hydroxyapatite orbital implants: an animal model.

OBJECTIVE: To evaluate host fibrovascularization of hydroxyapatite orbital implants wrapped in sclera or in Vicryl (polyglactin 910) mesh in a rabbit model. NUMBERS: Eight adult New Zealand white rabbits that received hydroxyapatite orbital implants wrapped in homologous donor sclera (four animals) or Vicryl mesh (four animals). INTERVENTIONS: The rabbits had one eye enucleated and then received a 12-mm hydroxyapatite implant wrapped in sclera or Vicryl mesh. Magnetic resonance imaging (MRI) and bone scintigraphy were done to assess host fibrovascularization of the implant 4, 8, 12 and 20 weeks after implantation. Two animals (one in each group) were killed at each of these times, and the implant was removed for histopathological examination. MAIN OUTCOME MEASURES: Enhancement on MRI, uptake on bone scintigraphy, fibrovascularization seen on histopathological examination. RESULTS: The degree of fibrovascularization was substantial in all the specimens but appeared greater in the Vicryl-mesh-wrapped implants in the first 12 weeks after implantation on both histopathological and MRI studies. At 20 weeks these findings were similar in the two groups. A granulomatous foreign-body giant-cell reaction to both the Vicryl mesh and the implant itself was present up to 8 weeks after implantation. Bone scans showed only grade 1+ activity in all the implants. CONCLUSIONS: Host fibrovascularization in the rabbit appears to occur to a greater degree in Vicryl-mesh-wrapped hydroxyapatite implants than in those wrapped in donor sclera during the first 12 weeks after implantation. Vicryl mesh appears to be an acceptable alternative wrap for the hydroxyapatite implant, eliminating the need for donor sclera and its potential risks of transmissible diseases.

CT and MR imaging findings in adults with cerebellar medulloblastoma: comparison with findings in children.

The goal of this study was to determine if certain imaging features suggest the diagnosis of cerebellar medulloblastoma in adults and to determine how often the classic CT appearance seen in children is present in adults. The study included 28 adult patients with proved cerebellar medulloblastoma. The tumor was located in the cerebellar vermis in 14 patients and in a cerebellar hemisphere in 14 patients. Thirteen patients had unenhanced CT of the brain, all patients had contrast-enhanced CT, and eight patients had unenhanced MR imaging. The imaging features in adults were compared with those in children, as described in the literature. In our adult patients, all tumors were hyperdense compared with gray matter on unenhanced CT and showed a slight to moderate increase in density after injection of contrast medium. Thirteen lesions had well-defined margins, and 15 had poorly defined margins. Low-density areas consistent with cystic and necrotic degeneration were detected in 23 (82%) of the 28 tumors. By comparison, in children, medulloblastoma usually originates in the vermis. As in adults, the mass is hyperdense on unenhanced CT, but enhances markedly and homogeneously after injection of contrast medium. Usually no evidence of cyst formation or necrosis is seen, and the tumor margins are well defined. This classic CT appearance of medulloblastoma in children was identified in only three (11%) of the 28 adult patients. Medulloblastoma has a variable MR appearance in both children and adults. On T2-weighted images, lesions are hypo-, iso-, or hyperintense compared with normal gray matter. The CT findings of medulloblastoma in adults usually differ from those of medulloblastoma in children. The tumor has a variable and nonspecific appearance in adults and should always be considered in the differential diagnosis of a mass in the posterior fossa.