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Nd∶YAG激光照射鼓膜对豚鼠内耳影响的实验研究
http://www.100md.com 《中国激光医学杂志》 2000年第2期
     作者:吴玉珍 肖伯奎 吴展元 刘剑锋

    单位:湖北医科大学附属第一医院耳鼻咽喉头颈外科,武汉市,430060

    关键词:激光;鼓膜;耳蜗;听性脑干反应

    中华激光医学杂志000226摘要 目的 探讨不同功率Nd∶YAG激光照射鼓膜对内耳功能和结构的影响。方法 45只豚鼠分3组,每组15只。分别以光纤末端功率为8、6、4 W的Nd∶YAG激光针对鼓膜作接触式照射,照射时间均为2 s。激光照射前、照射后即刻及2周,分别测试听性脑干反应(ABR)阈值,并应用光镜和扫描电镜技术观察耳蜗形态学变化。结果 激光照射后即刻3组ABR阈值均升高(P<0.01),8 W组较4 W组升高明显(P<0.05);照射后2周8、6 W组ABR阈值虽然较照射后即刻有所降低,但仍高于照射前(P<0.05),而4 W组则恢复至照射前水平。照射后即刻,8、6 W组耳蜗外毛细胞出现肿胀,硝酸银浓染,血管纹血管扩张,4 W组无明显改变;照射后2周,8 W组外毛细胞平均损失达45%,6 W组平均损失20%,内毛细胞也均有少量缺失,4 W组内、外毛细胞形态基本正常。
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    结论 应用Nd∶YAG激光治疗中耳疾病时,光纤末端输出功率应控制在4 W,照射时间以2 s为宜,否则可能会导致不可逆的听力下降。

    中图分类号: TN240;R332.9+22 文献标识码: A

    文章编号: 1003-9430(2000)02-0089-04

    Experimental Study on Effects of Nd∶YAG Laser Irradiation to Tympanic

    Membrane on Inner Ear in Guinea Pig

    WU Yuzhen, XIAO Bokui, WU Zhanyuan, LIU Jianfeng
, 百拇医药
    (First Affiliated Hospital of Hubei Medical University, Wuhan 430060, China)

    ABSTRACT Objective To explore the effect of Nd∶YAG laser irradiation to tympanic membrane on the structure and function of inner ear.Methods Guinea pigs were equally divided into 3 groups. Their tympanic membrane were irradiate for 2 seconds by Nd∶YAG laser with output power of 4 W, 6 W or 8 W, respectively for each group. The ABR thresholds was measured before, immediately after and two weeks after irradiation. Cochlear sections were prepared. Light and scanning electron microscopies were performed to observe the morphological alteration.Results The experiment elucidated that impairment of inner ear was correlated with laser output power and the thresholds of ABR were elevated after irradiation. Although the ABR threshold 2 weeks after irradiation in 8 W and 6 W group respectively was lower than that immediately after irradiation, but was still higher than that before irradiation(P<0.05). No significance was noted in group 4 W. Immediately after irradiation, swelling and deeply staining of outer hair cells and dilation of stria vascularis were present in cochlea in group 8 W and group 6W, without obvious injurg in group 4 W. Two weeks later, the outer hair cells loss rates were 45% and 20% in group 8 W and group 6 W, respectively. There were also some loss of inner hair cells. The hair cells of group 4 W were intact.Conclusions In the Nd∶YAG laser treatment of middle ear disease, the appropriate output power is 4 W and appropriate irradiation duration 2 seconds to protect inner hair cells from injury.
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    Key words Lasers; Tympanic membrane; Cochleas; Auditory brainstem response

    近年来,Nd∶YAG激光已被广泛应用于耳鼻咽喉疾病的手术治疗,如汽化外耳道新生物,鼓膜打孔治疗渗出性中耳炎,汽化乳突腔、中耳腔的肉芽组织等,取得一定的疗效。但Nd∶YAG激光有较强的热辐射作用,激光剂量掌握不当,会导致内耳不可逆的热损伤。为探讨不同功率Nd∶YAG激光照射鼓膜对内耳功能和结构的影响,我们以豚鼠为对象进行了实验研究。

    材料与方法

    一、实验动物及分组

    健康杂色豚鼠45只,雌雄不拘,体重250~400 g,平均350 g。耳廓反射均灵敏,外耳道检查无异物及耵聍栓塞。按激光照射功率分8、6、4 W 3组,每组15只豚鼠。
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    二、实验方法

    每只豚鼠腹腔注射1%戊巴比妥钠40 mg/kg麻醉后,测试听性脑干反应(auditory brainstem response, ABR)。以右耳为实验耳。清洁外耳道,将Nd∶YAG激光光纤(半径0.5 mm)对准鼓膜前下象限,按既定功率行接触式照射,照射时间均为2 s,孔径为1.0~1.5 mm。功率密度8 W组为10.19 W/mm2,6 W组为7.64 W/mm2,4 W组为5.09 W/mm2。照射后即刻每组处死3只豚鼠,取听泡作光镜观察;另12只测试ABR后饲养2周,于2周后再行ABR测试,并取听泡作光镜和扫描电镜观察。

    三、ABR阈值检测

    在隔声静电屏蔽室内,用MEM 3202型(日本光电公司产)诱发电位仪行右耳ABR测试,短声(click)刺激,刺激重复率20次/s,叠加128次。针型记录电极置于豚鼠头顶正中,对侧外耳道后壁为参考电极,鼻尖为地极,以III波反应阈为ABR阈值判断标准。
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    四、光镜和扫描电镜观察

    参照文献[1],取耳蜗全程基底膜,分回封片,光镜下观察,并记录内外毛细胞数量,计算平均缺失率。耳蜗切片及扫描电镜标本制作也参照文献[1]。

    结 果

    一、大体观察

    Nd∶YAG激光照射鼓膜后2周观察,3组豚鼠鼓室及耳蜗表面均正常,无凝固、汽化等损伤。

    二、ABR测试

    结果见表1。激光照射后即刻,3组豚鼠ABR阈值均升高,与照射前比较,差异均有显著性(P<0.05),但8 W和6 W组升高幅度高于4 W组,且8 W组与4 W组比较,差异有显著性(P<0.05)。激光照射后2周,3组豚鼠ABR阈值与照射后即刻比较均有所降低,但8 W和6 W组ABR阈值与照射前比较,差异仍有显著性(P<0.05),4 W组则基本恢复到照射前水平。
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    表1 Nd∶YAG激光照射鼓膜前后3组豚鼠ABR阈值测试结果(dBnHL, xx1.gif (49 bytes)±s)

    Tab.1 The thresholds of ABR before and after irradiation (dBnHL, xx1.gif (49 bytes)±s) 组别

    Groups

    耳数

    Ear

    number
, 百拇医药
    照射前

    Before

    irradiation

    照射后即刻

    Immediately after

    irradiation

    照射后2周

    Two weeks after

    irradiation

    8 W

    12

    12.78±5.65
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    38.89±11.40*△

    28.32±6.61*

    6 W

    12

    6.67±2.58

    41.67±14.38*

    30.00±4.47*

    4 W

    12

    11.54±5.16

    24.62± 6.28*
, 百拇医药
    15.62±5.58

    * 与照射前比较 Compared with before irradiation,P<0.05 △ 与4 W组比较 Compared with 4 W group,P<0.05

    三、光镜观察

    照射后即刻每组各3耳、照射后2周每组各5耳取听泡,行耳蜗基底膜铺片。光镜观察显示,照射后即刻8 W和6 W组耳蜗外毛细胞部分出现肿胀,硝酸银浓染,表皮板破裂;4 W组毛细胞形态正常。照射后2周,8 W组耳蜗底回内毛细胞基本正常,外毛细胞少量缺失,浓染,第2回内毛细胞及外1基本正常,外2、外3缺失增加,第3回内毛细胞损伤、缺失,部分结构不清,外1、外2、外3缺失,3回平均缺失45%;6 W组各回内毛细胞基本正常,极少量缺失,第2、3回外毛细胞部分结构不清,3回平均缺失20%;4 W组内外毛细胞数量、形态基本正常。
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    照射后2周,每组各5耳取听泡制备耳蜗石蜡切片,光镜观察显示8 W和6 W组毛细胞以外毛细胞损害为主,胞体溶解,核萎缩,毛细胞变性、坏死,血管纹毛细血管扩张;4 W组无明显改变。

    四、扫描电镜观察

    照射后2周,每组各2耳取听泡制片行扫描电镜观察。8 W组耳蜗3排外毛细胞部分消失,静纤毛排列紊乱、倒伏、形态不规则(图1);6 W组耳蜗外1基本正常,外2、外3纤毛紊乱(图2);4 W组耳蜗内外毛细胞形态正常,纤毛排列规则,无紊乱或倒伏(图3)。t9101.gif (9624 bytes)t9102.gif (11709 bytes)t9103.gif (9511 bytes)
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    图1 8 W组豚鼠Nd∶YAG激光照射鼓膜后2周耳蜗扫描电镜观察,外毛细胞部分缺失,纤毛形态不规则,部分成簇状或倒伏,内毛细胞正常 ×1 200 图2 6 W组豚鼠Nd∶YAG激光照射鼓膜后2周耳蜗扫描电镜观察,外1基本正常,外2、外3纤毛紊乱,内毛细胞正常 ×1 200 图3 4 W组豚鼠Nd∶YAG激光照射鼓膜后2周耳蜗扫描电镜观察,内外毛细胞排列整齐,形态规则,外毛细胞静纤毛成“V”字形 ×1 200

    Fig.1 SEM picture of the cochlea of guinea pig with 8 W irradiation. The outer hair cells were partially lost. The cilia were irregular, partially dustering and bending down. The inner hair cells were normal. ×1 200 Fig.2 SEM picture of the cochlea of guinea pig with 6 W irradiation. The first array of outer hair cells were roughly normal. The 2nd and 3rd arrays outer hair cells cilia were disordered. The inner hair cells were normal. ×1 200 Fig.3 SEM picture of the cochlea of guinea pig with 4 W irradiation. Both the outer and inner hair cells were normal. ×1 200
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    讨 论

    渗出性中耳炎鼓室积液,可用激光行鼓膜切开术以排液。有报道应用CO2激光行鼓膜切开术不置通气管,治疗渗出性中耳炎获得良好效果[2,3]。CO2激光穿透能力弱,对周围组织的热损伤较轻,行鼓膜造孔比较安全,但CO2激光必须有特制的显微调聚焦装置,结合内镜传输,且仪器价格昂贵。Nd∶YAG激光是一种固体激光,波长为1.06 μm,激光通过细长光纤输出,进入外耳道达到鼓膜或中耳等深在部位非常方便,能精确定位,而且Nd∶YAG激光可封闭组织中小血管,鼓膜打孔处不出血,术野清晰,因此已越来越多地用于中耳疾病的治疗。但

    Nd:YAG激光易被组织吸收,在一定的条件下,其热能穿透组织的深度约4 mm[4]。用于治疗中耳疾病时,如鼓膜打孔治疗渗出性中耳炎,汽化、凝固富含血管的鼓膜血管瘤和毛细血管扩张等,过高的热能通过中耳腔直接辐射到内耳组织,有可能损伤耳蜗毛细胞。
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    为了探讨不同功率Nd∶YAG激光照射鼓膜对内耳功能和结构的影响,我们选用8、6、4 W 3种功率的Nd∶YAG激光,分别照射3组豚鼠的鼓膜,照射时间均为2 s,发现照射后即刻3组豚鼠ABR阈值即明显升高,与照射前比较差异有显著性(P<0.05);照射后2周,8 W和6 W组豚鼠ABR阈值与照射后即刻比较虽然有所降低,但与照射前比较差异仍有显著性(P<0.05),即均不能恢复到原有的阈值,4 W组ABR阈值则恢复到照射前水平。形态学观察显示,8 W和6 W组豚鼠鼓膜激光照射后即刻耳蜗外毛细胞肿胀,血管纹毛细血管扩张,2周后以外毛细胞损伤为主,胞体溶解,核萎缩,细胞变性、坏死,毛细胞静纤毛散乱、倒伏;4 W组耳蜗毛细胞形态基本正常。本实验结果提示,用Nd∶YAG激光治疗鼓膜及中耳疾患,选择适当的激光功率是十分重要的,并为临床应用选择适宜的激光功率提供了参考依据。当激光功率为4 W、照射时间为2 s时,对内耳结构和功能均无明显影响。

    作者简介:吴玉珍(1947-),女,湖北人,湖北医科大学附属第一医院耳鼻咽喉头颈外科副教授,从事耳鼻咽喉激光医学研究。
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    参考文献

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    [2] Silverstein H, Kuhu J, Choo D, et al. Laser-assisted tympanostomy[J]. Laryngoscope, 1996, 106:1067-1074.

    [3] Goode R, Alto P. CO2 laser myringotomy[J]. Laryngoscope, 1982, 92:420-423.

    [4] 杨绪霞. 头颈部激光外科. 见:王正敏,主编. 耳鼻喉科学新理论与新技术[M]. 上海:上海科技教育出版社, 1997, 292-297.

    (收稿日期:2000-01-28), 百拇医药