Vessel wall perforation mechanism of the excimer laser-assisted non-occlusive anastomosis technique.

The excimer laser assisted non-occlusive anastomosis (ELANA) technique is used to make anastomoses on intracerebral arteries. This end-to-side anastomosis is created without temporary occlusion of the recipient artery using a 308-nm excimer laser with a ring-shaped multi-fiber catheter to punch an opening in the arterial wall. Over 500 patients have received an ELANA bypass. However, the vessel wall perforation mechanism of the laser catheter is not known exactly and not 100 % successful. In this study, we aimed to understand the mechanism of ELANA vessel perforation using specialized imaging techniques to ultimately improve its effectiveness. High-speed imaging, high-contrast imaging, and high-sensitivity thermal imaging were used to study the laser wall perforation mechanism and reveal the mechanical and thermal effects involved. In vitro, rabbit arteries were exposed with the special designed laser catheter in a setup representative for the clinical setting, in which blood was replaced with a transparent UV absorbing liquid for visualization. We observed that laser vessel wall perforation was caused by explosive vapor bubbles tearing through the vessel wall, mostly within the first 20 of the total 200 pulses. Thermal effects were minimal. Unsymmetrical tension in the vessel wall inducing migration of the flap during laser exposure was observed in case of unsuccessful wall perforations. The laser wall perforation mechanism in the ELANA technique is primarily mechanical. Symmetric tension in the recipient vessel wall is essential and should be trained by neurosurgeons.

High-flow extracranial-to-intracranial excimer laser-assisted nonocclusive anastomosis bypass for symptomatic carotid artery occlusion.

BACKGROUND: A high-flow bypass is theoretically more effective than a conventional low-flow bypass in preventing strokes in patients with symptomatic carotid artery occlusion and a compromised hemodynamic state of the brain. OBJECTIVE: To study the results of excimer laser-assisted nonocclusive anastomosis (ELANA) high-flow extracranial-to-intracranial (EC-IC) bypass surgery in these patients. METHODS: Between August 1998 and May 2008, 24 patients underwent ELANA EC-IC bypass surgery because of transient ischemic attacks or minor ischemic stroke associated with carotid artery occlusion. We retrospectively collected information. Follow-up data were updated by structured telephone interviews between May and September 2008. RESULTS: In all patients, the ELANA EC-IC bypass was patent at the end of surgery with a mean flow of 106 ± 41 mL/min. Within 30 days after the operation, 22 patients (92%) had no major complication, whereas 2 patients (8%) had a fatal intracerebral hemorrhage. During follow-up of a mean 4.4 ± 2.4 years, the bypass remained patent in 18 of the 22 surviving patients (82%) with a mean flow of 141 ± 59 mL/min. All patients with a patent bypass remained free of transient ischemic attacks and ischemic stroke. In 4 patients, the bypass occluded, accompanied by ipsilateral transient ischemic attacks in 2 patients, ipsilateral ischemic stroke in 1 patient, and contralateral ischemic stroke in another patient. CONCLUSION: ELANA EC-IC bypass surgery in patients with carotid artery occlusion is technically feasible and results in cessation of ongoing transient ischemic attacks and minor ischemic strokes, but carries a risk of postoperative hemorrhage.

Experimental simplification of the excimer laser-assisted nonocclusive anastomosis (ELANA) technique.

BACKGROUND: The excimer laser-assisted nonocclusive anastomosis (ELANA) technique facilitates the construction of an end-to-side anastomosis between a donor vessel and a recipient artery without the need to temporarily occlude the recipient artery. OBJECTIVE: To test whether the surgically difficult ELANA technique can be simplified. METHODS: In 42 rabbits, with the aorta as the recipient artery and human saphenous veins as donor grafts, we made 30 conventional ELANAs with 8 microsutures, 90 ELANAs with 4 microsutures (ELANA-4s), 40 ELANAs with 2 microsutures (ELANA-2s), and 90 sutureless ELANAs (SELANAs). SELANA involved a new ring design with 2 pins. ELANA-4, ELANA-2, and SELANA were each combined with 3 different sealants (Bioglue, Tachoseal, and Tisseel) and compared regarding application time, complications, and burst pressure. RESULTS: The conventional ELANA was constructed in a mean of 14.8 +/- 2.6 minutes. All experimental anastomoses were constructed significantly faster; the ELANA-4 in a mean of 10.9 +/- 1.3 minutes, the ELANA-2 in a mean of 5.4 +/- 1.7 minutes, and the SELANA in a mean of 2.5 +/- 1.8 minutes. All ELANA and ELANA-4 anastomoses were sufficiently strong with a burst pressure > 200 mm Hg, except for 1 insufficiently sealed ELANA-4 anastomosis. ELANA-2 was sufficiently strong only with Bioglue, showing a burst pressure > 280 mm Hg. SELANA was sufficiently strong with Bioglue or TachoSil, showing a burst pressure > 260 mm Hg. CONCLUSION: The ELANA technique can be simplified by reducing or even abandoning microsutures. Of the experimental anastomoses tested, we consider the SELANA technique combined with TachoSil of most potential benefit. Long-term survival studies will be performed in animals before we consider using any of these new techniques in patients.

The sutureless excimer laser assisted non-occlusive anastomosis (SELANA); a feasibility study in a pressurized cadaver model.

OBJECTIVE: To compare intracranial feasibility of the conventional Excimer laser assisted non-occlusive anastomosis (ELANA) with the new experimental sutureless ELANA (SELANA). METHODS: Four pressurized human cadaver heads were bilaterally trepanated, using a combined pterional/pretemporal/transcavernous approach. In each head, seven ELANA anastomoses and seven contralateral SELANA anastomoses were constructed on (1) the proximal PCA/basilar artery (P1 segment/basilar artery; BA), (2) the distal posterior cerebral artery (PCA, P2 segment), (3) the supraclinoidal internal carotid artery (ICA), (4) the ICA bifurcation, (5) the proximal anterior cerebral artery (ACA, A1 segment), (6) the proximal middle cerebral artery (MCA, M1 segment), and (7) the distal MCA (M2 segment). RESULTS: In total, 26 of 28 ELANA anastomoses (93%) and 22 of 28 SELANA anastomoses (79%) could be completed. Two ELANA anastomoses on the BA could not be finished because of limited space. Six SELANA anastomoses could not be attached because the applicator did not facilitate an angulated anastomosis spot. Of the remaining anastomoses, more ELANA (eight) than SELANA (two) anastomoses could not be realized without manipulation of surrounding structures. The SELANA anastomoses were completed significantly faster than the ELANA, mean difference ranging from 11 min on the M2 to 107 min on the P1/BA. CONCLUSION: This comparative study shows potential advantages of the SELANA anastomosis over the ELANA anastomosis because during application, it causes less manipulation of surrounding structures while it is faster and easier. Further preclinical research should be performed in order to improve SELANA feasibility on angulated anastomosis spots and to assess long-term SELANA patency and endothelialization.

Optimization of the excimer laser assisted non-occlusive anastomosis (ELANA) flap retrieval rate.

BACKGROUND AND OBJECTIVES: A key element in the Excimer Laser Assisted Non-occlusive Anastomosis (ELANA) technique is the retrieval of a disc ("flap") of artery wall from the anastomosis by the laser catheter tip. We assessed if the flap retrieval rate could be optimized. METHODS: We used a specially designed in vitro model using rabbit aortas. We tested three essential elements of the technique: (1) laser energy (10, 13, 15, or 18 mJ), (2) pressure on the catheter (0, 0.1, 0.2, or 0.4 N), and (3) number of lasing episodes (1 or 2). We made 2,280 anastomoses using different combinations of settings. With a logistic regression model we assessed the influence of each parameter. Current clinical settings (10 mJ, 0.2 N, 1 episode) were reference categories. RESULTS: Flap retrieval rate using conventional settings was 86.7%, equivalent to earlier reported clinical data. A significantly higher flap retrieval appeared when laser energy was increased to 13 mJ (OR 3.0, 95% CI 1.8-4.8), 15 mJ (OR 3.2, 95% CI 1.9-5.3), and 18 mJ (OR 3.7, 95% CI 2.2-6.2). A second lasing episode also significantly increased flap retrieval (OR 2.1, 95% CI 1.4-3.0). However, if we increased energy to 15 or 18 mJ, the effect of a second laser episode was insignificant. When the catheter was pushed down with 0.4 N, flap retrieval decreased significantly in all subgroups (OR 0.07, 95% CI 0.04-0.14). CONCLUSION: The flap retrieval of the ELANA anastomosis technique can be optimized to 100% by setting the laser energy at 15 mJ. However, safety studies are necessary before clinical application. A second lasing episode of 10 mJ is a good alternative to increase the flap retrieval. Moreover, the surgeon should be trained to apply not more than 0.2 N on the catheter.

Skull base tumor model.

OBJECT: Resident duty-hours restrictions have now been instituted in many countries worldwide. Shortened training times and increased public scrutiny of surgical competency have led to a move away from the traditional apprenticeship model of training. The development of educational models for brain anatomy is a fascinating innovation allowing neurosurgeons to train without the need to practice on real patients and it may be a solution to achieve competency within a shortened training period. The authors describe the use of Stratathane resin ST-504 polymer (SRSP), which is inserted at different intracranial locations to closely mimic meningiomas and other pathological entities of the skull base, in a cadaveric model, for use in neurosurgical training. METHODS: Silicone-injected and pressurized cadaveric heads were used for studying the SRSP model. The SRSP presents unique intrinsic metamorphic characteristics: liquid at first, it expands and foams when injected into the desired area of the brain, forming a solid tumorlike structure. The authors injected SRSP via different passages that did not influence routes used for the surgical approach for resection of the simulated lesion. For example, SRSP injection routes included endonasal transsphenoidal or transoral approaches if lesions were to be removed through standard skull base approach, or, alternatively, SRSP was injected via a cranial approach if the removal was planned to be via the transsphenoidal or transoral route. The model was set in place in 3 countries (US, Italy, and The Netherlands), and a pool of 13 physicians from 4 different institutions (all surgeons and surgeons in training) participated in evaluating it and provided feedback. RESULTS: All 13 evaluating physicians had overall positive impressions of the model. The overall score on 9 components evaluated--including comparison between the tumor model and real tumor cases, perioperative requirements, general impression, and applicability--was 88% (100% being the best possible achievable score where the evaluator strongly agreed with the proposed factor). Individual components had scores at or above 80% (except for 1). The only score that was below 80% was related to radiographic visibility of the model for adequate surgical planning (score of 74%). The highest score was given to usefulness in neurosurgical training (98%). CONCLUSIONS: The skull base tumor model is an effective tool to provide more practice in preoperative planning and technical skills.