Occlusion of the middle cerebral artery Guidance by screen imaging using an EDA-H portable medium-soft electronic endoscope☆

Xingbao Zhu, Junli Luo, Song Liu, Dongping Li, Min Li, Quanshui Fan

1Department of Neurosurgery, Kunming General Hospital, Chengdu Military Command of Chinese PLA, Kunming 650032, Yunnan Province,China

2Disease Prevention & Control Centre, Chengdu Military Command of Chinese PLA, Kunming 650032, Yunnan Province, China

INTRODUCTION

The indications for endoscopic neurosurgery have recently gradually extended from intracranial cystic lesions[1-8]to intracranial non-cystic lesions[9-20]. Rigid and soft endoscopes are currently available. However, the viewing angles of rigid endoscopes cannot be changed, and the eye lens-digital microscope camera requires a special stand for support. The viewing angles of soft endoscopes are changeable,but cannot be automatically maintained.

The EDA-H portable medium-soft electronic endoscope (EDA-H pmsEE) was designed and manufactured based on the WCM-II portable electronic endoscope, to complete the new task of intracranial endoscopy[21].

The intraluminal thread model of middle cerebral artery occlusion (MCAO) is a recognized surgical procedure for microsurgical training and for verifying navel surgical operations. We therefore verified the practicability of performing screen-based surgical operations using an EDA-H pmsEE real-time viewing and recording system (EDA-H pmsEE RTVRS)to guide the performance of MCAO to reproduce an animal model of human cerebral infarction.

RESULTS

Quantitative analysis of experimental animals

A total of 54 rats were randomly assigned to two groups. MCAO models were produced in the two groups by lens-operative surgery using an operating microscope(lens-operative surgery group) or by screen-operative surgery using an EDA-H pmsEE RTVRS (screen-operative surgery group), respectively. All 54 rats were included in the final analysis.

Guidance by screen imaging using the EDA-H pmsEE RTVRS facilitated the surgical procedure during MCAO modeling

The branches of the common carotid artery(CCA) and internal carotid artery (ICA) were easily dissected under screen-imaging guidance using the EDA-H pmsEE RTVRS.

The bifurcations of the CCA and ICA were clearly exposed, and the suture was gently inserted into the external carotid artery (ECA)passing the bifurcations of the CCA into the ICA and advancing to the origin of the middle cerebral artery (MCA).

Surgical efficacy of screen-operative surgery using EDA-H pmsEE RTVRS was similar to lens-operative surgery using an operating microscope

Time of model establishment

Screen-operative surgery using the EDA-H pmsEE RTVRS was accurate, stable, minimally invasive,and comparatively easy. Quantitative analysis of the average operating times showed no significant difference between the two groups (lens-operative surgery group:30 (25-35) minutes vs. screen-operative surgery group:31 (27-35) minutes, P ＞ 0.05).

Success rate of model establishment

Neurological function was evaluated using the modified neurological score system (mNSS): high scores represent severe injury. mNSS ≥ 7 was considered to indicate successful injury[22]of the MCAO. There was no significant difference in success rates between the two groups(lens-operative surgery group: 76.68% vs.screen-operative surgery group: 75.16%, P ＞ 0.05).

Neurological function scores

Quantitative analysis of the results of behavioral tests confirmed no significant difference in sensorimotor deficit between two groups (lens-operative surgery group:13.41 (12.37-13.41) vs. screen-operative surgery group:13.33 (12.76-13.90), P ＞ 0.05).

Infarct volume

Normal brain tissue became purple, while infarcted foci remained white after staining with 2, 3, 5-triphenyl-2H-tetrazolium chloride (TTC). Quantitative analysis of the infarct volume percentage showed no significant difference between the two groups (lens-operative surgery group: 22.84% (14.47-31.21%) vs.

screen-operative surgery group: 22.82% (14.14-31.50%),P ＞ 0.05).

DISCUSSION

This study used an EDA-H pmsEE medium-soft endoscope, based on the WCM-II portable electronic endoscope (Wise Digital Hangzhou, China)[21]. The intraluminal thread model of MCAO in rats is a recognized microsurgical training technique, as well as being used to verify navel surgical operations. This model was selected to confirm the suitability of an EDA-H pmsEE RTVRS for guiding screen-based micrological (minimally invasive)operative surgery. The results of preliminary experiments indicated that rats weighing 180-250 g were appropriate for this surgical operation and were able to survive for a prolonged period.

MCAO in rats has been achieved using a number of methods. Among these, the intraluminal thread model,which was first introduced by Koizumi et al[23]in 1986 and later modified by Longa et al[24]in 1989, has become the most widely used model to study the pathophysiology and therapeutic approaches in permanent and transient focal cerebral ischemia. The model is easy to establish,minimally invasive, and omits the need for craniectomy.

Application of the intraluminal thread model of MCAO in rats involves exposure of the bifurcation of the CCA and the ICA and insertion of a suture bypassing the bifurcation and advancing to the origin of the MCA. These surgical procedures are usually performed with the assistance of an operating microscope. The current study represents the first time that the surgical procedure has been performed with the assistance of an endoscope(EDA-H pmsEE RTVRS).

Previous results showed that EDA-H pmsEE RTVRS screen imaging produced images that were clear, life-like,stereoscopic and synchronous with the actual operation[21]. The present study showed that accurate,stable, minimally invasive and comparatively easy MCAO could be performed under screen-imaging guidance using an EDA-H pmsEE RTVRS, and that the average operating time, surgical success rate,sensorimotor deficit and infarct volume percentage were similar to those associated with microscopic operative surgery. Screen-based surgery under guidance by an EDA-H pmsEE RTVRS therefore represents a practicable, simple, comfortable and cost-effective approach to establishing the intraluminal thread model of MCAO.

MATERIALS AND METHODS

Design

A randomized, controlled, animal experiment.

Time and setting

The experiment was performed at the Animal Experimental Centre, Department of Clinical Research, Kunming General Hospital, Chengdu Military Command of Chinese PLA, Yunnan Province, China from April to June 2010.

Materials

Fifty-four healthy, adult male Sprague-Dawley rats, aged 45-120 days, weighing 180-250 g, were provided by the Animal Experimental Centre, Department of Clinical Research, Kunming General Hospital, Chengdu Military Command of Chinese PLA, Yunnan Province, China (No.SYXK (Dian) 2008-0005). The experimental procedures were performed in accordance with the Guidance Suggestions for the Care and Use of Laboratory Animals,formulated by the Ministry of Science and Technology of the People’s Republic of China[25].

EDA-H pmsEE[21]was designed by our group and manufactured by Wise Digital, Hangzhou, China (Figure 1). The main technical parameters were as follows: direct viewing; viewing angle: 95°; viewing depth: 10-200 mm;fixed focus; diameter of probe: 8 mm; plastic-coated fixable shaft; the smallest curve radius: 6 cm; working distance: 700 mm; video signal: PAL; video/USB 2.0; manual white-balancing; light source: LED; power source:AC IN 100-240 V; ambient temperature: -20 to 80°C.

EDA-H pmsEE was linked to a Dell laptop computer using a USB cable to provide the EDA-H pmsEE RTVRS.

Methods

MCAO model establishment

The surgical procedure was performed as lens-operative surgery using an operating microscope, or screen-operative surgery using an EDA-H pmsEE RTVRS (Figure 2). Serial perioperative measurements were routinely performed. Atropine sulfate (0.5 mg/kg of body mass; Sigma, St. Louis, MO, USA) was intraperitoneally injected 10 minutes before anesthesia, which was introduced by intraperitoneal administration of chloral hydrate (3.6 g/kg of body mass; Sigma). A longitudinal incision was made in the midline of the ventral cervical skin. Follow-up surgical procedures were performed under the operating microscope or guided by screen imaging using the EDA-H pmsEE RTVRS. The bifurcation of the CCA and the ICA on the left side was carefully dissected and clearly exposed, and the distal portion of the ECA and the proximal portion of the pterygopalatine artery were ligated with 5.0 silk sutures. The CCA and the ICA were temporarily clamped using microvascular clips. A 5.0 silk suture was then tied loosely around the origin of the ECA, a small puncture was made on the wall of the ECA with a pair of spring scissors, and a 20-mm long blunted and coated 4-0 monofilament nylon suture(Harvard Apparatus, Holliston, Massachusetts, USA)was inserted through the proximal ECA into the ICA and advanced into the circle of Willis to effectively occlude the MCA. Prior to use, the suture tip was blunted by heating it near a flame and a 20-mm distal segment of the suture was then coated with poly-L-lysine solution(0.1% (w/v), in deionized water; Sigma) and dried in a 60°C oven for 1 hour. The suture was inserted 18-20 mm from the bifurcation of the CCA, according to the animal's body mass[26-27]. Local cerebral blood flow was monitored in the cerebral cortex of each hemisphere in the supply territory of the MCA by laser-Doppler flowmetry (Laserflo BPM2; Vasamedics, St. Poul, MN, USA)according to a previously described method[27]. Local cerebral blood flow was continuously measured (2-Hz sampling rate) 30 minutes before and after the suture was placed. The ipsilateral laser-Doppler signal decreasing to 20% of baseline while the contralateral one maintained the baseline level represented the completion of MCAO[27].

Figure 1 EDA-H portable medium-soft electronic endoscope. The main technical parameters were as follows: direct-viewing; viewing angle: 95°; viewing depth:10-200 mm; fixed focus; diameter of probe: 8 mm;plastic-coated fixable shaft; the smallest curve radius:6 cm; working distance: 700 mm; video signal: PAL;video/USB 2.0; manual white-balancing; light source: LED;power source: AC IN 100-240 V; ambient temperature:-20 to 80°C.

Figure 2 Establishment of middle cerebral artery occlusion (MCAO) model under the guidance of an EDA-H portable medium-soft electronic endoscope real-time viewing and recording system (pmsEE RTVRS).Screen-based surgical procedure using an EDA-H pmsEE RTVRS to establish the MCAO model (A). Arrows show the bifurcation of the common carotid artery (B) and suture insertion into the external carotid artery (C).

mNSS evaluation

The mNSS was evaluated on the third day before and after MCAO to identify sensorimotor deficits[28]. The mNSS was composed of motor, sensory, reflex, and balance tests and graded on a scale of 0-18, i.e. normal score was 0, maximal deficit score was 18, and 1 point was awarded for the inability to perform the tasks or the lack of a tested reflex. The behavioral tests were conducted between 14: 00 and 17: 00 by two investigators blinded to the experiments, with a 5-minute rest period between each type of motor test. The sequence of testing animals was randomized.

TTC staining

After the behavioral tests, animals were sacrificed and the fresh brains were removed and stained with TTC(Sigma) to observe the infarct foci[29]. The infarct volume was calculated according to a previously published method[30].

Statistical analysis

Data were expressed as mean with 95% confidence intervals. Statistical analysis was performed using SPSS Windows Version 12.0 (SPSS, Chicago, IL, USA). The average operating time, surgical success rate (mNSS ≥7), sensorimotor deficit and infarct volume percentage were compared between the lens-operative surgery and screen-operative surgery groups using t-tests. A value of P ＜ 0.05 was considered statistically significant.

Author contributions:Xingbao Zhu and Junli Luo participated in lens-operative surgery and screen-operative surgery. Song Liu participated in TTC staining and infarct volume calculation.Dongping Li and Min Li participated in the behavioral tests.Quanshui Fan participated in data collection, analysis and interpretation.

Conflicts of interest:None declared.

Ethical approval:This study received permission from the Animal Care and Research Committee of Kunming General Hospital, Chengdu Military Command of Chinese PLA, China.

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