Selective intracranial magnification angiography of the rabbit: basic techniques and anatomy

Variations in the morphology of lagomorph confluence sinuum on contrast enhanced CT

Knowledge of lagomorph confluence sinuum anatomy on contrast-enhanced CT may prevent the misdiagnoses of intracranial, extra-axial masses. The purpose of this retrospective, observational, descriptive study was to describe the characteristics of the confluence sinuum in rabbits on contrast-enhanced CT. Images of 24 rabbits who had pre- and postcontrast CT sequences of the skull were reviewed by an American College of Veterinary Radiology-certified veterinary radiologist and third-year radiology resident. Degree of contrast enhancement within the region of the confluence sinuum was graded based on consensus as no (0), mild (1), moderate (2), or marked (3) contrast enhancement. Hounsfield units (HU) of the confluence sinuum was measured in three different regions of interest, averaged for each patient, and divided into each group for comparison using one-way ANOVA analysis. Contrast enhancement was mild in 45.8% (11/24) rabbits, moderate in 33.3% (8/24), marked in 20.8% (5/24), and none in 0.0% (0/24). There were significant differences (P < 0.05) between the average HU of the mild and marked group (P-value = 0.0001) and moderate and marked groups (P-value = 0.0010). Two rabbits with marked contrast enhancement were initially misdiagnosed with an intracranial, extra-axial mass along the parietal lobe based on contrast-enhanced CT. On necropsy, no gross or histopathological abnormalities were identified in the brain for these rabbits. In summary, contrast enhancement was identified in all rabbits (24/24) on contrast-enhanced CT imaging . This normal structure can be variable in size should not be mistaken for a pathological lesion in the absence of mass effect, secondary calvarial lysis, or hyperostosis.

Monitoring cardiovascular disease severity using near-infrared mechanoluminescent materials as a built-in indicator

Artificial vascular grafts (AVGs) are widely used to treat cardiovascular diseases (CVDs). But none of the reported AVGs can also monitor the CVD severity. Because CVDs affect the blood pressure, we proposed to employ a force-sensing material that emits near-infrared (NIR) light upon force loading, a NIR mechanoluminescent (ML) material (CaZnOS:Nd³⁺), as an indicator in AVGs to tackle this challenge. Specifically, we used a polydimethylsiloxane AVG modified with this ML material, termed ML-AVG, to achieve the rapid and convenient monitoring of two CVD models (vascular occlusion and hypertension) in real time. The NIR ML material showed good blood and tissue compatibility without causing an inflammatory response. By implanting the ML-AVGs into the common carotid artery (CCA) of rats, we observed the NIR ML signals emitted from the AVGs by a thermal camera, a NIR spectrometer, and a NIR camera. The NIR ML signal was linearly correlated with the degree of vascular opening (in the vascular occlusion model) or the degree of hypertension (in the hypertension model). Our work suggests that NIR ML materials can monitor the severity of diseases with force or pressure as biomarkers.

Superselective Arterial Hyaluronidase Thrombolysis Is Not an Effective Treatment for Hyaluronic Acid-Induced Retinal Artery Occlusion: Study in a Rabbit Model

BACKGROUND

Worldwide application of hyaluronic acid has brought about severe complications, including central retinal arterial occlusion, which leads to a deleterious effect on vision. The current study explored the efficacy of superselective arterial hyaluronidase thrombolysis in rabbit retinal artery occlusion induced by hyaluronic acid.

METHODS

Occlusion of the internal/external ophthalmic artery in New Zealand White rabbits was induced with superselective injection of hyaluronic acid. Superselective subtraction angiography and fundus examination were conducted to confirm and evaluate the artery embolism. After 30 minutes of embolism, hyaluronidase was injected in the occluded artery through superselective arterial intubation.

RESULTS

Compared with preoperative and contralateral eyes, the postoperative eyes showed the symptoms of central retinal arterial occlusion and embolization, confirmed by digital subtraction angiography. After intraarterial hyaluronidase thrombolysis, the embolization failed to dissolve as shown on funduscopic and angiographic examinations.

CONCLUSIONS

Superselective ophthalmic artery intervention could accurately and successfully establish the animal models of retinal artery occlusion induced by hyaluronic acid. The precise occlusion site of the retinal artery and complete embolism were confirmed by ophthalmologic examinations. Intraarterial hyaluronidase thrombolysis might not be an effective method to treat retinal artery occlusion induced by hyaluronic acid.

Cerebral angiography using transauricular access in a rabbit model: a new technique

BACKGROUND

Cerebral angiography in a rabbit model is widely used in the field of interventional radiology. Conventionally, the femoral artery is used for cerebral angiography in radiology departments. However, angiographic studies require surgical cutdown of the femoral artery, which is technically difficult.

PURPOSE

To evaluate a new cerebral angiography technique involving a transauricular approach in a rabbit model.

MATERIAL AND METHODS

In each of 10 rabbits, central auricular arteries were punctured in the right or left ear with a 20-gauge i.v. catheter. A microcatheter (2.0 F) with a 0.016-inch guide wire was introduced through the i.v. catheter and advanced to the aortic arch. The microcatheter and guide wire were advanced selectively into cerebral arteries and angiography was performed.

RESULTS

Central auricular arteries were successfully punctured with 20-gauge i.v. catheters. After approaching the aortic arch, microcatheter tips and guide wires were advanced manually to cerebral arteries on both sides. Difficulties in selecting the carotid arteries were resolved by using a looping technique within the cardiac chamber. Microcatheter loops within the cardiac chamber disappeared or remained during artery superselection.

CONCLUSION

Transauricular cerebral angiography appears to be a feasible technique for brain or carotid intervention studies in rabbits. In addition, vertebral angiography using a transauricular approach is possible using the looping technique. Selection of carotid or vertebral arteries on each side was not difficult when the microcatheter and guide wire were looped within the cardiac chamber. The ear chosen for the initial puncture does not appear to be important.

Angiographic investigation of orbital vascular variations in the rabbit and implications for endovascular intra-arterial chemotherapy models

BACKGROUND

The New Zealand White rabbit (NZWR) is the first small-animal experimental model of intra-arterial chemotherapy (IAC) for retinoblastoma treatment. The NZWR has dual ophthalmic arteries (OA): the external OA (EOA) arises from the external carotid artery and the internal OA (IOA) from the internal carotid artery. We describe the technique that we have refined for OA catheterization in rabbits, and describe the angioanatomical variations in the OA supply to the NZWR eye and implications for IAC delivery, which were identified as part of a larger project exploring IAC effects in a rabbit retinoblastoma model.

METHODS

We developed techniques to perform angiography of the external and internal carotid arteries and superselective angiography of the EOA and IOA in NZWR using transfemoral access and a microwire/microcatheter system. EOA and IOA supply to the eye was determined angiographically and recorded before selective OA catheterization and angiography.

RESULTS

114 rabbits underwent carotid angiographic evaluation and OA catheterization (161 total eyes evaluated, 112 right, 49 left). Most eyes had a single dominant arterial supply; either IOA or EOA. EOA was dominant in 73% (118/161), and IOA was dominant in 17% (27/161). Co-dominant supply was seen in 10% (16/161). Of the rabbits with bilateral OA catheterization, 25/47 (53%) had bilateral dominant EOA.

CONCLUSION

Successful catheterization of the OA in the NZWR can be readily accomplished with nuanced technique. The external OA is the dominant arterial supply in the majority of NZWR eyes. These findings allow for successful reproduction of OA catheterization studies of IAC for retinoblastoma in NZWR.

Selective middle cerebral artery occlusion in the rabbit: Technique and characterization with pathologic findings and multimodal MRI

BACKGROUND

A reliable animal model of ischemic stroke is vital for pre-clinical evaluation of stroke therapies. We describe a reproducible middle cerebral artery (MCA) embolic occlusion in the French Lop rabbit characterized with multimodal MRI and histopathologic tissue analysis.

NEW METHOD

Fluoroscopic-guided microcatheter placement was performed in five consecutive subjects with angiographic confirmation of MCA occlusion with autologous clot. Multimodal MRI was obtained prior to occlusion and up to six hours post after which repeat angiography confirmed sustained occlusion. The brain was harvested for histopathologic examination.

RESULTS

Angiography confirmed successful MCA catheterization and durable (>6 h) MCA occlusion in all animals. There was increase of ADC volume over time and variable final core volume presumably related to individual variation in collateral flow. FLAIR hyperintensity indicative of cytotoxic edema and parenchymal contrast enhancement reflective of blood brain barrier disruption was observed over time. Tissue staining of the ischemic brain showed edema and structural alterations consistent with infarction.

COMPARISON WITH EXISTING METHODS

This study describes a technique of selective catheterization and embolic occlusion of the MCA in the rabbit with MRI characterization of evolution of ischemia in the model.

CONCLUSIONS

We demonstrate the feasibility of a rabbit model of embolic MCA occlusion with angiographic documentation. Serial MR imaging demonstrated changes comparable to those observed in human ischemic stroke, confirmed histopathologically.

Accurate and continuous ultrasonography evaluation of small diameter vascular prostheses in vivo

There is a large clinical requirement for novel vascular grafts; however, the development of novel vascular grafts has not been extremely successful to date. The most successful method for the continuous evaluation of vascular grafts in vivo remains unclear. Therefore, an optimal successive, non-invasive imaging modality is necessary for the study of vascular transplantation. In the present study, a common rabbit model of carotid artery defect was utilized. The patency and hemodynamic characteristics of implanted grafts was examined following surgery by color Doppler ultrasound in three modes, including B-mode, color flow map and pulse-Doppler examination. The results revealed that ultrasound had sufficient spatial resolution to generate clear images of the carotid artery of rabbits with or without the implanted grafts. Color Doppler ultrasound may be applied to evaluate and differentiate the patent, stenosis and occlusion of carotid arteries in rabbits with different vascular grafts implanted. Furthermore, color Doppler ultrasound is an optimal imaging modality for continuous evaluation in vivo. It is also possible for some quantitative analyses to be performed, including measuring the diameter of vascular lumens and the flow velocity of the region of interest. The present study suggests vascular ultrasound as the optimum choice for continuous surveillance of vascular prostheses in vivo, which may provide valuable information about the grafts in order to greatly shorten the experimental period.

Dynamic EPR Oximetry of Changes in Intracerebral Oxygen Tension During Induced Thromboembolism

Cerebral tissue oxygenation (oxygen tension, pO₂) is a critical parameter that is closely linked to brain metabolism, function, and pathophysiology. In this work, we have used electron paramagnetic resonance oximetry with a deep-tissue multi-site oxygen-sensing probe, called implantable resonator, to monitor temporal changes in cerebral pO₂ simultaneously at four sites in a rabbit model of ischemic stroke induced by embolic clot. The pO₂ values in healthy brain were not significantly different among the four sites measured over a period of 4 weeks. During exposure to 15% O₂ (hypoxia), a sudden and significant decrease in pO₂ was observed in all four sites. On the other hand, brief exposure to breathing carbogen gas (95% O₂ + 5% CO₂) showed a significant increase in the cerebral pO₂ from baseline value. During ischemic stroke, induced by embolic clot in the left brain, a significant decline in the pO₂ of the left cortex (ischemic core) was observed without any change in the contralateral sites. While the pO₂ in the non-infarct regions returned to baseline at 24-h post-stroke, pO₂ in the infarct core was consistently lower compared to the baseline and other regions of the brain. The results demonstrated that electron paramagnetic resonance oximetry with the implantable resonator can repeatedly and simultaneously report temporal changes in cerebral pO₂ at multiple sites. This oximetry approach can be used to develop interventions to rescue hypoxic/ischemic tissue by modulating cerebral pO₂ during hypoxic and stroke injury.

Three variations in rabbit angiographic stroke models

PURPOSE

To develop angiographic models of embolic stroke in the rabbit using pre-formed clot or microspheres to model clinical situations ranging from transient ischemic events to severe ischemic stroke.

MATERIALS AND METHODS

New Zealand White rabbits (N=151) received angiographic access to the internal carotid artery (ICA) from a femoral approach. Variations of emboli type and quantity of emboli were tested by injection into the ICA. These included fresh clots (1.0-mm length, 3-6h), larger aged clots (4.0-mm length, 3 days), and 2 or 3 insoluble microspheres (700-900 μm). Neurological assessment scores (NAS) were based on motor, sensory, balance, and reflex measures. Rabbits were euthanized at 4, 7, or 24h after embolization, and infarct volume was measured as a percent of total brain volume using 2,3,5-triphenyltetrazolium chloride (TTC).

RESULTS

Infarct volume percent at 24 h after stroke was lower for rabbits embolized with fresh clot (0.45±0.14%), compared with aged clot (3.52±1.31%) and insoluble microspheres (3.39±1.04%). Overall NAS (including posterior vessel occlusions) were positively correlated to infarct volume percent measurements in the fresh clot (r=0.50), aged clot (r=0.65) and microsphere (r=0.62) models (p<0.001).

CONCLUSION

The three basic angiographic stroke models may be similar to human transient ischemic attacks (TIA) (fresh clot), major strokes that can be thrombolysed (aged clot), or major strokes with insoluble emboli such as atheromata (microspheres). Model selection can be tailored to specific research needs.

High-intensity focused ultrasound (HIFU) for dissolution of clots in a rabbit model of embolic stroke

It is estimated that only 2-6% of patients receive thrombolytic therapy for acute ischemic stroke suggesting that alternative therapies are necessary. In this study, we investigate the potential for high intensity focused ultrasound (HIFU) to initiate thrombolysis in an embolic model of stroke. Iron-loaded blood clots were injected into the middle cerebral artery (MCA) of New Zealand White rabbits, through the internal carotid artery and blockages were confirmed by angiography. MRI was used to localize the iron-loaded clot and target the HIFU beam for treatment. HIFU pulses (1.5 MHz, 1 ms bursts, 1 Hz pulse repetition frequency, 20 s duration) were applied to initiate thrombolysis. Repeat angiograms and histology were used to assess reperfusion and vessel damage. Using 275 W of acoustic power, there was no evidence of reperfusion in post-treatment angiograms of 3 rabbits tested. In a separate group of animals, 415 W of acoustic power was applied and reperfusion was observed in 2 of the 4 (50%) animals treated. In the last group of animals, acoustic power was further increased to 550 W, which led to the reperfusion in 5 of 7 (∼70%) animals tested. Histological analysis confirmed that the sonicated vessels remained intact after HIFU treatment. Hemorrhage was detected outside of the sonication site, likely due to the proximity of the target vessel with the base of the rabbit skull. These results demonstrate the feasibility of using HIFU, as a stand-alone method, to cause effective thrombolysis without immediate damage to the targeted vessels. HIFU, combined with imaging modalities used to identify and assess stroke patients, could dramatically reduce the time to achieve flow restoration in patients thereby significantly increasing the number of patients which benefit from thrombolysis treatments.

Dodecafluoropentane emulsion decreases infarct volume in a rabbit ischemic stroke model

PURPOSE

To assess the efficacy of dodecafluoropentane emulsion (DDFPe), a nanodroplet emulsion with significant oxygen transport potential, in decreasing infarct volume in an insoluble-emboli rabbit stroke model.

MATERIALS AND METHODS

New Zealand White rabbits (N = 64; weight, 5.1 ± 0.50 kg) underwent angiography and received embolic spheres in occluded internal carotid artery branches. Rabbits were randomly assigned to groups in 4-hour and 7-hour studies. Four-hour groups included control (n = 7, embolized without treatment) and DDFPe treatment 30 minutes before stroke (n = 7), at stroke onset (n = 8), and 30 minutes (n = 5), 1 hour (n = 7), 2 hours (n = 5), or 3 hours after stroke (n = 6). Seven-hour groups included control (n = 6) and DDFPe at 1 hour (n = 8) and 6 hours after stroke (n = 5). DDFPe dose was a 2% weight/volume intravenous injection (0.6 mL/kg) repeated every 90 minutes as time allowed. After euthanasia, infarct volume was determined by vital stains on brain sections.

RESULTS

At 4 hours, median infarct volume decreased for all DDFPe treatment times (pretreatment, 0.30% [P = .004]; onset, 0.20% [P = .004]; 30 min, 0.35% [P = .009]; 1 h, 0.30% [P = .01]; 2 h, 0.40% [P = .009]; and 3 h, 0.25% [P = .003]) compared with controls (3.20%). At 7 hours, median infarct volume decreased with treatment at 1 hour (0.25%; P = .007) but not at 6 hours (1.4%; P = .49) compared with controls (2.2%).

CONCLUSIONS

Intravenous DDFPe in an animal model decreases infarct volumes and protects brain tissue from ischemia, justifying further investigation.

Microbubble-augmented ultrasound sonothrombolysis decreases intracranial hemorrhage in a rabbit model of acute ischemic stroke

OBJECTIVES

Increasing evidence confirms that microbubble (MB)-augmented ultrasound (US) thrombolysis enhances clot lysis with or without tissue plasminogen activator (tPA). Intracranial hemorrhage (ICH) is a major complication militating against tPA use in acute ischemic stroke. We quantified the incidence of ICH associated with tPA thrombolysis and MB + US therapy and compared infarct volumes in a rabbit model of acute ischemic stroke.

MATERIALS AND METHODS

Rabbits (n = 158) received a 1.0-mm clot, angiographically injected into the internal carotid artery causing infarcts. Rabbits were randomized to 6 test groups including (1) control (n = 50), embolized without therapy, (2) US (n = 18), (3) tPA only (n = 27), (4) tPA + US (n = 22), (5) MB + US (n = 27), and (6) tPA + MB + US (n = 14). US groups received pulsed wave US (1 MHz, 0.8 W/cm) for 1 hour; rabbits with tPA received intravenous tPA (0.9 mg/kg) over 1 hour. Rabbits with MB received intravenous MB (0.16 mg/kg) given over 30 minutes. Rabbits were killed 24 hours later and infarct volume and incidence, location, and severity of ICH were determined by histology and pathologic examination.

RESULTS

Percentage of rabbits having ICH outside the infarct area was significantly decreased (P = 0.004) for MB + US (19%) rabbits compared with tPA + US (73%), US only (56%), tPA (48%), tPA + MB + US (36%), and control (36%) rabbits. Incidence and severity of ICH within the infarct did not differ (P > 0.39). Infarct volume was significantly greater (P = 0.002) for rabbits receiving US (0.97% ± 0.17%) than for MB + US (0.20% ± 0.14%), tPA + US (0.15% ± 0.16%), tPA (0.14% ± 0.14%), and tPA + MB + US (0.10% ± 20%) rabbits; these treatments collectively, excluding US only, differed (P = 0.03) from control (0.45% ± 0.10%).

CONCLUSIONS

Treatment with MB + US after embolization decreased the incidence of ICH and efficacy was similar to tPA in reducing infarct volume.

Variations in the circle of Willis in the New Zealand white rabbit

PURPOSE

The New Zealand White rabbit (NZWR) serves an important role as an experimental model for vascular research, specifically in the area of stroke. Here the authors document vascular variations in the circle of Willis (COW).

MATERIALS AND METHODS

Subselective internal carotid digital subtraction angiography was performed in 100 NZWRs.

RESULTS

Important variations include hypoplasia in 36%, duplication of the middle cerebral artery in 29%, asymmetries of the posterior region in 19%, and multiple variations in 28%. The complete classical symmetric COW without significant variation is present in fewer than 30% of animals.

CONCLUSIONS

With recognition of the variations, the NZWR becomes an improved research model.

Successful microbubble sonothrombolysis without tissue-type plasminogen activator in a rabbit model of acute ischemic stroke

BACKGROUND AND PURPOSE

Microbubbles (MB) combined with ultrasound (US) have been shown to lyse clots without tissue-type plasminogen activator (tPA) both in vitro and in vivo. We evaluated sonothrombolysis with 3 types of MB using a rabbit embolic stroke model.

METHODS

New Zealand White rabbits (n=74) received internal carotid angiographic embolization of single 3-day-old cylindrical clots (0.6 × 4.0 mm). Groups included: (1) control (n=11) embolized without treatment; (2) tPA (n=20); (3) tPA+US (n=10); (4) perflutren lipid MB+US (n=16); (5) albumin 3 μm MB+US (n=8); and (6) tagged albumin 3 μm MB+US (n=9). Treatment began 1 hour postembolization. Ultrasound was pulsed-wave (1 MHz; 0.8 W/cm²) for 1 hour; rabbits with tPA received intravenous tPA (0.9 mg/kg) over 1 hour. Lipid MB dose was intravenous (0.16 mg/kg) over 30 minutes. Dosage of 3 μm MB was 5 × 10⁹ MB intravenously alone or tagged with eptifibatide and fibrin antibody over 30 minutes. Rabbits were euthanized at 24 hours. Infarct volume was determined using vital stains on brain sections. Hemorrhage was evaluated on hematoxylin and eosin sections.

RESULTS

Infarct volume percent was lower for rabbits treated with lipid MB+US (1.0%± 0.6%; P=0.013), 3 μm MB+US (0.7% ± 0.9%; P=0.018), and tagged 3 μm MB+US (0.8% ± 0.8%; P=0.019) compared with controls (3.5%± 0.8%). The 3 MB types collectively had lower infarct volumes (P=0.0043) than controls. Infarct volume averaged 2.2% ± 0.6% and 1.7%± 0.8% for rabbits treated with tPA alone and tPA+US, respectively (P=nonsignificant).

CONCLUSIONS

Sonothrombolysis without tPA using these MB is effective in decreasing infarct volumes. Study of human application and further MB technique development are justified.

Decreased Serum Levels of S-100B Protein Reflect Successful Treatment Effects in a Rabbit Model of Acute Ischemic Stroke

Serum levels of S-100B were investigated as a marker for infarct volume and response to treatment following acute ischemic stroke in rabbits. Following subselective angiography, rabbits (n=31) were embolized by injection of a 3-day-old blood clot (0.6x4.0-mm) into the internal carotid artery. Treatment began 1-hr post-embolization, groups included: Control (n=8, embolization only), tissue plasminogen activator (tPA, n=12, 0.9mg/kg), and perflutren lipid microbubbles with transcranial ultrasound (MB+US, n=11, MB at 0.16mg/kg, US at 1-MHz pulsed-wave, 0.8 W/cm² for 1-hr). Serum S-100B levels were significantly increased (P<0.01) 24-hours following embolization in control (3.1-fold over baseline) and tPA (2.9-fold) groups, while treatment with MB+US resulted in an attenuated, non-significant (P=0.221) increase (1.6-fold). Twenty-four hour infarct volumes averaged 4.76%±1.16% for controls, 2.25%±0.95% for rabbits treated with tPA (P=0.32 vs. control), and 0.79%±0.99% for rabbits treated with MB+US (P=0.04 vs. control). Twenty-four hour concentrations of S-100B were positively correlated with infarct volume (r=0.59, P=0.0004).

Microbubbles improve sonothrombolysis in vitro and decrease hemorrhage in vivo in a rabbit stroke model

INTRODUCTION

Tissue plasminogen activator (tPA) is the thrombolytic standard of care for acute ischemic stroke, but intracerebral hemorrhage (ICH) remains a common and devastating complication. We investigated using ultrasound (US) and microbubble (MB) techniques to reduce required tPA doses and to decrease ICH.

MATERIALS AND METHODS

Fresh blood clots (3-5 hours) were exposed in vitro to tPA (0.02 or 0.1 mg/mL) plus pulsed 1 MHz US (0.1 W/cm²), with or without 1.12 × 10⁸/mL MBs (Definity or albumin/dextrose MBs [adMB]). Clot mass loss was measured to quantify thrombolysis. New Zealand white rabbits (n = 120) received one 3- to 5-hour clot angiographically delivered into the internal carotid artery. All had transcutaneous pulsed 1 MHz US (0.8 W/cm²) for 60 minutes and intravenous tPA (0.1-0.9 mg/kg) with or without Definity MBs (0.16 mL/mg/kg). After killing the animals, the brains were removed for histology 24 hours later.

RESULTS

In vitro, MBs (Definity or adMB) increased US-induced clot loss significantly, with or without tPA (P < 0.0001). At 0 and 0.02 mg/mL, tPA clot loss was greater with adMBs compared with Definity (P ≤ 0.05). With MB, the tPA dose was reduced 5-fold with good efficacy. In vivo, both Definity MB and tPA groups had less infarct volume compared with controls at P < 0.0183 and P = 0.0003, respectively. Definity MB+tPA reduces infarct volume compared with controls (P < 0.0001), and ICH incidence outside of strokes was significantly lower (P = 0.005) compared with no MB. However, infarct volume in Definity MB versus tPA was not different at P = 0.19.

CONCLUSION

Combining tPA and MB yielded effective loss of clot with very low dose or even no dose tPA, and infarct volumes and ICH were reduced in acute strokes in rabbits. The ability of MBs to reduce tPA requirements may lead to lower rates of hemorrhage in human stroke treatment.

Stroke location and brain function in an embolic rabbit stroke model

PURPOSE

Current rabbit stroke models often depend on symptoms as endpoints for embolization and produce wide variation in location, size, and severity of strokes. In a further refinement of an angiographic embolic stroke model, localized infarctions were correlated to neurologic deficits with the goal to create a rabbit model for long-term studies of therapies after stroke.

MATERIALS AND METHODS

New Zealand White rabbits (4-5 kg; N = 71) had selective internal carotid artery (ICA) angiography and a single clot was injected. At 24 hours, neurologic assessment score (NAS) was measured on an 11-point scale (0, normal; 10, dead). Brains were removed and stained to identify stroke areas. All animals with single strokes (n = 31) were analyzed by specific brain structure involvement, and NAS values were correlated.

RESULTS

Stroke incidence differed by location, with cortex, subcortical, and basal ganglia regions highest. The middle cerebral artery (MCA), at 52%, and anterior cerebral artery (ACA), at 29%, were most commonly involved, with the largest stroke volumes in the ACA distribution. Brainstem and cerebellum strokes had disproportionately severe neurologic deficits, scoring 2.25 +/- 1.0 on the NAS, which represented a significant (P < .02) difference versus cortex (0.5 +/- 0.2), subcortical (1.3 +/- 0.4), and basal ganglia (0.5 +/- 0.3), all in the frontal or parietal regions.

CONCLUSIONS

MCA and ACA distributions included 81% of strokes. These sites were relatively silent (potentially allowing longer-term survival studies) whereas others in the posterior circulation produced disproportionately severe symptoms. Symptoms were not reliable indicators of stroke occurrence, and other endpoints such as imaging may be required. These are important steps toward refinement of the rabbit stroke model.