译丨脑干听觉诱发反应

Brain-Stem Auditory Evoked Response

来源丨《Blackwell’s Five-Minute Veterinary Consult》

翻译丨宠物神经科医生高健 

BASICS 基础

TYPE OF PROCEDURE 检查类型

Electrodiagnostic 电诊断

PROCEDURE EXPLANATION AND RELATED PHYSIOLOGY
检查解释和相关生理学

The brain-stem auditory evoked response (BAER) is a graphic record- ing of the evoked response in brain-stem activity elicited by an auditory stimulus. The test is performed by providing a repetitive auditory stimulus to 1 ear while providing a masking noise to the other ear.

脑干听觉诱发反应（BAER）是对听觉刺激引起的脑干活动的诱发反应的图形记录。

该检查通过向一只耳朵提供重复的听觉刺激，
同时向另一只耳朵提供噪声屏蔽来进行。

The sounds are transmitted by earphones placed in the ear canal. The evoked potentials are recorded from subdermal scalp electrodes; because these potentials are relatively small, the waveforms are averaged to eliminate extraneous electrical activity. A normal BAER consists of 4–5 highly reproducible, time-locked waves obtained within 10 ms of the stimulus and represent activation of structures along the auditory pathway in the brain stem. The first large wave (wave I) is generated by action potentials in the cochlear division of the vestibulocochlear nerve (cranial nerve VIII). Subsequent waves are generated by brain-stem nuclei and tracts that comprise the auditory pathway, including the cochlear nucleus, rostral olivary nucleus, lateral lemniscus, and caudal colliculus.

声音通过放置在耳道中的耳机传播。

诱发电位由头皮皮下的电极进行记录;
由于这些电位相对较小，
所以对波形进行平均以消除外来的电活动。

一个正常的BAER由4-5个高度可重复的、时间锁定（time-locked）的波组成，
这些波在刺激后10ms内获得，
代表了脑干中听觉通路结构的激活。

第一个大波（I波）是由前庭耳蜗神经（第 VIII 对脑神经）的耳蜗分支的动作电位产生的。

随后的波是由构成听觉通路的脑干神经核和神经束产生的，
包括耳蜗核（cochlear nucleus）、前侧橄榄核（rostral olivary nucleus）、外侧丘系（lateral lemniscus）和后丘（caudal colliculus）。

The BAER is an objective, noninvasive method of assessing the functional integrity of the inner ear and cochlear nerve, as well as the auditory pathways within the brain stem. In addition, disease of the external or middle ear can be evaluated to a limited extent, particularly in cases in which the disease limits the transmission of normal sound waves to the receptors in the inner ear.

BAER是一种客观、无创的方法，
用于评估内耳和耳蜗神经，
以及脑干内听觉通路的功能完整性。

此外，
外耳或中耳疾病可以在有限程度上进行评估，
特别是在某些疾病限制了正常声波向内耳受体传递的情况。

INDICATIONS 适应症

 To screen animals for congenital deafness 

  To assess for acquired deafness

  To evaluate brain-stem function

  筛查动物先天性耳聋

  评估获得性耳聋

  评估脑干功能

CONTRAINDICATIONS 禁忌症

None 无

POTENTIAL COMPLICATIONS 潜在并发症

None 无

CLIENT EDUCATION 宠主教育

 As a test for hearing, the BAER evaluates each ear for the expected response to auditory stimulation, and animals with unilateral deafness can be identified. Animals with unilateral hearing loss may appear clinically normal to their owner.

作为一项听力检查，
BAER评估每只耳朵对听觉刺激的预期反应，
可以识别出单侧耳聋的动物。

在其宠主看来，
单侧听力丧失的动物在临床上可能表现是正常的。

 Partial hearing loss is more difficult to assess and is often not recognized. Similarly, a BAER cannot discriminate an animal’s ability to hear only certain frequencies or tones, because these characteristics of the stimulus are not varied during testing.

部分性听力丧失更难评估，而且常常无法被识别。

同样，
BAER也不能分辨出动物只听到某些频率或音调的能力，
因为这些刺激的特征在检查过程中是不会变化的。

BODY SYSTEMS ASSESSED 评估的身体系统

Nervous 神经系统

PROCEDURE 检查

PATIENT PREPARATION 病患预备

Preprocedure Medication or Preparation 检查所需药物或预备

None 无

Anesthesia or Sedation 麻醉或镇静

Animals that object to either the electrodes being placed subdermally on the scalp or the earphones inserted into the ear canals can be sedated for the procedure. Neither sedation nor anesthesia will affect the test results.

对于那些难以将电极置于头皮皮下或将耳机插入耳道的动物，
可以在检查过程中给它们镇静。

镇静和麻醉都不会影响检测结果。

Patient Positioning 病患摆位

 The animal is placed in sternal recumbency.
 If the animal is not heavily sedated or anesthetized for the procedure, its head should be gently restrained to prevent the animal’s movement from dislodging the earphones or electrodes. Excessive movement will also cause electrical interference, and the elicited responses will not be averaged into the final waveform. This prolongs the time required to perform the test.

动物俯卧位。

如果动物在检查过程中没有深度镇静或麻醉，
那么它的头部应该被轻轻地保定好，
以避免动物的运动导致耳机或电极脱落。

过度的运动也会引起电干扰，
引起的反应不会被平均到最终的波形当中。

这还会延长执行检查所需的时间。

Patient Monitoring 病患监测

None 无

Equipment or Supplies 设备或耗材

 An electrodiagnostic unit capable of performing BAER, which also has the auditory stimulator and transducer needed to create the audible clicks

 Scalp electrodes

   Specially designed, disposable tubal insert earphones

  一个能够执行BAER的电诊断设备，同时还有听觉刺激器和产生可听到咔哒声的换能器

  头皮上的电极

  特别设计的一次性管式耳机

TECHNIQUE 技术

 The earphones are placed securely in the external ear canals.
 Subdural electrodes are placed at specific sites on the scalp; the recording electrode is placed at the vertex, the reference electrode at the mastoid just rostral to the base of the ear, and the ground electrode on the dorsal midline of the midcervical region.

 A 70- to 90-decibel click stimulus is applied to the test ear at a rate of 10 Hz while a masking noise of 30–40 decibels less than the test stimulus is applied to the opposite ear. Typically, 500–1,000 repetitions are averaged to produce the final waveform.

耳机确实地放置在外耳道中。

硬膜下电极被放置在头皮的特定部位;
记录电极（recording electrode）放置在头顶点（vertex），
参考电极（reference electrode）放置在正好耳基部前侧的乳突部，
接地电极（ground electrode）放置在颈中央区的背侧中线处。

以10 Hz 的频率将70- 90 分贝（decibel）的咔哒声刺激施加到测试耳内，
同时将比检查刺激低 30-40分贝（DB）的掩蔽噪声施加到另一只耳内。

通常，需要平均500-1,000次重复波形来产生最终的波形。

SAMPLE HANDLING 采样处置

N/A 无

APPROPRIATE AFTERCARE 恰当的检查后护理

Postprocedure Patient Monitoring 检查后病患监测

None 无

Nursing Care 医疗护理

None 无

Dietary Modification 饮食调整

None 无

Medication Requirements 药物需求

None 无

Restrictions on Activity 活动限制

None 无

Anticipated Recovery Time 所需恢复时间

None 无

INTERPRETATION 判读

NORMAL FINDINGS OR RANGE 正常发现或范围

A BAER is evaluated with respect to the number of waveforms present, as well as the latency and relative amplitude of the waveforms. The BAER normally results in 4–5 waveforms; expected latencies for each of the generated waveforms have been established for dogs and cats. As a general rule, wave I appears at a latency of approximately 1 ms, with each successive peak occurring at <1-ms intervals (Figure 1).

BAER是根据所出现的波形的数量，
以及波形的时长和相对振幅来评估的。

BAER通常产生4-5个波形;

对于犬猫，
已经建立了每种产生的波形的预期时长。

一般来说，
I波出现的时长约为1ms，
每个连续的峰值间隔为<1-ms（图1）。

ABNORMAL VALUES 异常值

 When used as an assessment of hearing, the absence of any identifiable waveforms (a flat line) is indicative of deafness in the ear being tested.

当用作听力评估时，
缺失所有可识别的波形（一条平坦的线）时，表明被检查那只耳朵耳聋。

 An increase in the latency of all waveforms and an increase in the stimulus intensity necessary to obtain a detectable response are suggestive of conductive hearing loss. This disturbance of transmission through the external or middle ear can be caused by otitis externa, tympanic membrane rupture, otitis media, or disease of the bony ossicles.

所有波形时长的延长，和获得可检测出的反应所必需的刺激强度的增加，
均表明传导性听力损失（conductive hearing loss）。

外耳炎、鼓膜破裂、中耳炎或骨性听小骨的疾病，
均可引起外耳或中耳的传播障碍。

 Increased latency between waveform peaks is indicative of a brainstem lesion causing delayed conduction along the auditory pathway. Similarly, a ratio of wave V amplitude to wave I amplitude of <0.5 indicates brain-stem disease. However, brain-stem disease can be present without alterations in the BAER if the auditory pathways are not involved in the disease process.

波形峰值之间的时长延长，
提示脑干病变，
从而导致沿听觉通路的传导延迟。

同样，
V波振幅与I波振幅之比为<0.5时，
提示存在脑干疾病。

然而，
如果听觉通路没有被疾病过程所波及，
那么脑干疾病可以不引起BAER改变。

 An animal with a severe, irreversible brain lesion compatible with brain death will have complete loss of all waves or a preservation of wave I with an absence of all subsequent waves.

伴有与脑死亡相关的严重、不可逆的脑损伤的动物，
将会出现所有脑波的完全丧失，
或保留I波，而没有所有后续脑波。

CRITICAL VALUES 临界值

None 无

INTERFERING FACTORS 干扰因素

Drugs That May Alter Results of the Procedure

可能影响检查结果的药物

None 无

Conditions That May Interfere with Performing the Procedure

可能影响实施检查结果的情况

None 无

Procedure Techniques or Handling That May Alter Results

可能影响检查结果的检查技术或处置

None 无

Influence of Signalment on Performing and Interpreting the Procedure

动物特征对检查执行和解释的影响

Species 物种
None 无

Breed 品种

None 无

Age 年龄

 Studies have demonstrated that the BAER thresholds mature in dogs and cats by approximately 3 weeks of age.

研究表明，犬猫的BAER阈值在大约3周龄时才成熟。

Hereditary deafness associated with the white or merle coat color is due to cochlear agenesis or early degeneration. Animals of predisposed breeds can be screened for congenital deafness as early as 5–6 weeks of age. If the results of initial screening are equivocal, it is recommended that the test be repeated in 1 month.

遗传性耳聋与白色或陨石色（merle）的被毛有关，
可能是由于耳蜗发育不全（cochlear agenesis）或早期变性/退变（early degeneration）所致。

好发品种的动物可在5-6周龄时进行先天性耳聋筛查（congenital deafness）。

如果初步筛查的结果仍然不明确，建议1个月后再复查。

Gender 性别

None 无

Pregnancy 怀孕

None 无

CLINICAL PERSPECTIVE 临床意义

 BAER testing is most commonly performed to screen for deafness in certain breeds of dogs that are predisposed to hereditary hearing loss, the most notable of which is the dalmatian. Hearing loss in these animals can be unilateral or bilateral.

BAER检查最常用于筛查某些易患遗传性听力丧失的犬种的耳聋，
其中最著名的就是斑点犬（dalmatian）。

这些动物的听力丧失可能是单侧的或双侧的。

 In a specialty-practice setting, BAER testing may be used as a tool to evaluate animals for brain-stem disease. This is most commonly performed in animals with vestibular disease, where differentiation of central from peripheral vestibular disease is important from diagnostic and prognostic standpoints.

在专科临床实践环境中，
BAER检查可作为评估动物脑干疾病的工具。

这在患有前庭疾病的动物中最常见，
从诊断和预后的角度来看，
区分中枢性前庭疾病和外周性前庭疾病是很重要的。

 BAER testing can also be used to assess prognosis in animals with severe brain disease that has caused a comatose state. In these animals, an absence of waveforms is suggestive of irreversible brain injury. However, this assessment can be performed only in animals known to have normal hearing.

BAER检测也可用于评估患有严重脑病并导致昏迷状态的动物的预后。

在这些动物中，
某些波形的缺失提示着可能存在不可逆的脑损伤。

然而，
这种评估只能在已知听力正常的动物中进行。

MISCELLANEOUS 其他

ANCILLARY TESTS 附加检查

 A thorough otoscopic exam should be performed in any animal with an abnormal BAER (particularly when the animal fails to respond to a normal stimulus intensity or the latency of all waveforms is increased) to determine whether debris in the ear canal, severe canal stenosis, or rupture of the tympanic membrane is contributing to the hearing loss.

任何BAER异常的动物（特别是当动物对正常刺激强度没有反应，或所有波形的时长延长时）都应进行全面的耳镜检查，
以确定是否有导致听力丧失的耳道内的碎屑、严重的耳道狭窄或鼓膜破裂等疾病。

 Animals with evidence, based on BAER testing, of brain-stem disease should undergo imaging of the brain and possible analysis of cerebrospinal fluid to assess for potential causes of the dysfunction.

根据BAER检查，
有脑干疾病证据的动物应进行脑部成像和可能需要脑脊液分析，
以评估功能障碍的潜在原因。

SYNONYMS 同义词

 BAER
 Brain-stem auditory evoked potential 脑干听觉诱发电位

SEE ALSO

Blackwell’s Five-Minute Veterinary Consult: Canine and Feline Topics

 Deafness
 Otitis Externa and Media Otitis Media and Interna

Related Topics in This Book

None

ABBREVIATIONS 缩写

BAER = brain-stem auditory evoked response = 脑干听觉诱发反应

Suggested Reading 推荐阅读

- Eger CE, Lindsay P. Effects of otitis on hearing in dogs characterized by brainstem auditory evoked response testing. J Small Anim Pract1997; 38: 380–386.

- Fischer A, Obermaier G. Brainstem auditory-evoked potentials and neuropathologic correlates in 26 dogs with brain tumors. J Vet Intern Med 1994; 8: 363–369.

- Holliday TA, Nelson HJ, Williams DC, Willits N. Unilateral and bilateral brainstem auditory-evoked response abnormalities in 900 Dalmatian dogs. J Vet Intern Med 1992; 6: 166–174.

- Steiss JE, Cox NR, Hathcock JT. Brain stem auditory-evoked response abnormalities in 14 dogs with confirmed central nervous system lesions. J Vet Intern Med 1994; 8: 293–298.

INTERNET RESOURCES 网络资源

Strain GM. Deafness in dogs & cats. Louisiana State University School of Veterinary Medicine, http://www.lsu.edu/deafness/deaf.htm.

AUTHOR NAME 作者名字

Karen R. Mun ̃ana

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