Evaluation of brainstem function in patients with spasmodic dysphonia using vestibular evoked myogenic potentials and auditory brainstem responses

CONCLUSION: The vestibular area is closer than the auditory region to nucleus ambiguus. If a 'shared' lesion involves regions of adjacent nuclei of the brainstem in patients with spasmodic dysphonia then vestibular area involvement is more possible than that of the auditory region. OBJECTIVES: The authors hypothesize that lower brainstem lesions and involvement of descending pathways of the spinal tract may be the site of lesion in patients with spasmodic dysphonia. PATIENTS AND METHODS: Ten patients with spasmodic dysphonia were tested using the auditory brainstem response (ABR) and vestibular evoked myogenic potentials (VEMPs). RESULTS: No ABR abnormalities were found in right ears. Results of ABR on the left ear showed that one patient had abnormal ABR. This patient had severe sensorineural hearing loss on the left side. VEMPs displayed normal response in two patients bilaterally. First positive (p13) and second negative (n23) waves of VEMP could not be recorded in three cases unilaterally and in five patients bilaterally.     

听神经病106例听力学分析

目的 分析106例听神经病患者的临床特点和听力学测试结果.探讨听神经病纯音听力图和听性脑干反应(ABR)的特点.方法 回顾性分析2001年12月至2007年5月就诊的106例(212耳)听神经病患者的症状及纯音听阈、声导抗图及镫骨肌反射、ABR、畸变产物耳声发射(DPOAE)和颅脑影像学检查的结果.结果 患者中男54例,女52例;年龄11～37岁,以青少年居多(75例,70.8%).伴有其他外周神经病者8例,伴视神经病者4例,未查出明确病因者94例.患者均为双耳发病.在212耳中,有173耳(81.6%)听力下降最多的频率为0.25 kHz和0.5 kHz.轻至中度听力损失共209耳(98.6%),均为感音神经性听力损失.按WHO(1997)听阈的均值计算法统计,本组有49耳(23.1%)的听阈≤25 dB,按WHO推荐的听力减退分级标准,使这些有听力障碍的病耳列入了正常范围.212耳听性脑干反应的测试中,各波形皆未引出者124耳(58.5%),余88耳有1或2个波未引出,而可引出的波的波幅很小,但有重复性.在1或2个可引出小波病例中,有23例其另1侧耳各波皆缺失.另有2例伴其他周围神经病和1例伴视神经病的患者,其双耳均有1或2个小波可引出.畸变产物耳声发射除1例左侧3～6 kHz,右侧5～6 kHz未引出外,余均可引出.结论 听神经病在青少年中并不罕见.因听神经病大多以低频听力下降为主,对听神经病患者平均听阈的计算方法值得讨论.     

Brainstem auditory-evoked potentials and electrocochleography: comparison of different criteria for the detection of acoustic neuroma and other cerebello-pontine angle tumours

Different means of identifying the presence of cerebello-pontine angle (CPA) tumours using brainstem auditory-evoked potentials (BAEP) were evaluated. The results from 33 ears affected by tumours were compared with BAEP from 50 normal ears and 23 ears affected by Menière's disease. Measurement of inter-aural latency differences correctly identified 97% of tumours from the normal group, but only 81% of tumours from the Menière group. Comparison of different interwave interval measures showed that the NI to NV interval was the best criterion and correctly identified 90% of the tumours from both the normal and the Menière groups. The use of transtympanic electrocochleography (ECochG) is discussed. Used alone, ECochG was of limited value in detecting CPA tumours except in five out of nine deaf ears where no BAEP were recorded but 'disconnection' action potentials were encountered. By combining BAEP and ECochG, the NI to NV interval could be identified with certainty. Combined BAEP and ECochG recordings were only undertaken when NI was unclear on BAEP recordings or when the ECochG was indicated clinically for the identification of endolymphatic hydrops. In this series, the combined use of BAEP and ECochG resulted in a tumour detection rate of 100% with a false positive rate of zero. The BAEP from the unaffected ear recorded from the ipsilateral and contralateral sides were compared. Significant NI to NV delay was noted, especially on recording from the contralateral side, when there was distortion of the brainstem due to a large tumour. The article concludes with an appendix of six illustrative case reports.     

以突发性聋为首发表现的斜坡脊索瘤1例

1病例报告患者,女,55岁,右耳突发听力下降伴耳鸣1d于2010年2月23日入院。患者无眩晕、耳痛及耳溢液。既往有糖尿病史20余年,高血压病史10余年。体检:BP 150/90 mm Hg(1 mm Hg=0.133kPa),双耳廓无畸形,外耳道通畅,鼓膜完整,内陷。纯音测听示:右耳全聋,左耳语言频率轻     

Audiological and electrocochleography findings in hearing-impaired children with connexin 26 mutations and otoacoustic emissions

We recorded cochlear potentials by transtympanic electrocochleography (ECochG) in three hearing-impaired children with GJB2 mutation who showed otoacoustic emissions. Pure tone thresholds, distortion product otoacoustic emissions (DPOAEs) and, auditory brainstem responses (ABRs) were also obtained. Subjects 1 (35delG/35delG) and 3 (M34T/wt) had profound hearing loss and showed the picture of auditory neuropathy (AN) as DPOAEs were detected with absent ABRs in both ears. The hearing impairment found in subject 2 (35delG/35delG) was profound in the right ear and moderate in the left ear. Both DPOAEs and ABRs with normal latencies and morphology were recorded only from the left ear. On the ECochG recording the cochlear microphonic was obtained from all children. No compound action potential (CAP) was detected in subject 1. A neural response was recorded only from the left ear in subject 2 with a threshold corresponding to the audiometric threshold while no CAP was detected on the right side. The ECochG obtained from subject 3 showed a low-amplitude broad negative deflection which was identifiable down to low stimulus levels. This response decreased in amplitude and duration when utilizing a high-rate stimulation paradigm. The amount of amplitude reduction was close to that calculated for normal ears, thus revealing the presence of an adapting neural component. These findings indicate that patients with GJB2 mutations and preserved outer hair cells function could present with the picture of AN. The hearing impairment is underlain by a selective inner hair cell loss or a lesion involving the synapses and/or the auditory nerve terminals. We suggest that neonatal hyperbilirubinemia may play a role in protecting outer hair cells against the damage induced by GJB2 mutations.     

The order of testing effect in otoacoustic emissions and its consequences for sex and ear differences in neonates

The amplitude values of transient-evoked otoacoustic emissions, recorded from a large sample of neonates, were used to examine the asymmetry between ears tested and the differences due to the sex of the subject. Whilst the sex difference, with females having larger responses than males, has been a consistent finding in previous reports, the right/left ear difference, with the right ear giving a larger response than the left, has produced variable results that differed between laboratories. In this study, the sex difference was confirmed with females giving a 1.2 dB greater response than males. It was not affected by the age of the neonate. A significant effect of test order was found. The measured right/left difference was enhanced when the right ear was tested first but was diminished when the left ear was tested first. If the left ear is tested first then the measured right/left difference would be about 0.5 dB whereas, if the right ear is tested first, the measured right/left difference would be about 1.5 dB. When male/female comparisons were made for right and left ears separately and for the same ear tested first, the sex differences were the same for all four conditions. The sex and right/left differences have been confirmed as statistically significant effects and the order effect could explain the discrepancies and variability of the right/left differences reported in the literature.     

听神经病听力学分析

目的 探讨听神经病的听觉电生理特点。方法 总结了10例听神经病患者的病史、纯音测听、镫骨肌反射、听性脑干反应（auditory brainstem response,ABR)、耳蜗电图、畸变产物耳声发射（distortion product otoacoustic emission,DPOAE)及对侧白噪声抑制试验、中潜伏期反应和慢皮层反应。5例患者作了颅脑CT或磁共振成像（magnetic resonance imaging,MRI)。结果 患者男女兼有，平均年龄为20．3岁，10余岁的青少年占多数。9例主诉双耳听力下降，1例双耳鸣。纯音测听示19耳为轻度至中度的低频下降型感音神经性听力损失，听力损失最严重的频率为0．5kHz或（和）0．25kHz；1耳听力正常。19耳镫骨肌反射消失，1耳纯音测听为上升型曲线者反射阈提高。ABR不能引出或仅出现波V和（和）波1。全部病例均可记录到DPOAE，但不能被对侧噪声抑制。耳蜗电图示大部分病例动作电位（action potential,AP)消失或振幅很小，负总和电位（negative summating potential,-SP)振幅绝对平均值为0．595μV，慢皮层反应皆正常，6例测中潜伏期反应5例正常。CT或MRI无异常发现。结论 听神经病早期纯音测听可正常，但其镫骨肌反射和ABR消失或阈值升高，其确切病变部位尚不明了，可能位于脑干平面以下的听觉系统。     

Abnormal timing delays in auditory brainstem responses evoked by bilateral cochlear implant use in children.

HYPOTHESIS: A period of unilateral implant use before bilateral implantation affects timing of brainstem processes measured by the electrically evoked auditory brainstem response (EABR). BACKGROUND: EABR latencies decrease with unilateral implant use potentially disrupting binaural timing cues important in auditory brainstem processing of bilateral input. METHODS: EABRs were evoked by electrical pulses from the left, right, and both implants simultaneously in 3 groups of children. All were initially implanted at ages younger than 3 years and had the following: 1) a long delay (>2 yr [n = 16]), 2) a short delay (<1 yr [n = 15]), or 3) no delay (n = 15) between left and right ear implantation. Responses were recorded on the first day of bilateral implant use and 3 and 9 months thereafter. RESULTS: Relative to responses evoked in the experienced ear, the naive ear showed prolonged latency in both the EABR peaks and the binaural difference response. After 3 and 9 months of bilateral implant use, the relative prolongation decreased in the long and short delay groups, but significant differences persisted in the former. No clear differences in latencies evoked by the left versus right implant were found at any time point in children receiving bilateral implants simultaneously. CONCLUSION: Results suggest potential disruptions to binaural brainstem processing based on timing cues in children receiving a second cochlear implant after more than 2 years of unilateral implant use that persist through at least the first 9 months of bilateral implant use.     

Bilateral electrical stimulation of a congenitally-deaf ear and of an acquired-deaf ear

Two identical multichannel intracochlear prostheses were implanted in the same patient. The first prosthesis, implanted in the congenitally-deaf right ear, elicited clear sound perception but no speech recognition. After 2 years, a second prosthesis, implanted in the acquired-deaf left ear, enabled the patient to understand speech without lip-reading. Brainstem and middle-latency evoked potentials were similar with electrical stimulation of both ears and resembled those evoked by acoustic stimuli in subjects with normal hearing. Cortical electric and magnetic responses differed for right- and left-sided electrical stimulation suggesting that stimulation of the congenitally-deaf ear elicited an abnormal activation of the auditory cortex. These results suggest that only cortical responses were affected by the different histories of deafness of the ears.     

颞叶癫痫患者的中枢听功能初探

目的采用汉语最低听觉功能测试（minimal auditory capabilities inchina，MACC）中背景噪声下言语测听法（speech-perception-in-noise test，SPIN），评价颞叶癫痫患者的中枢听觉功能。方法对9例经脑电图和MRI、CT检查后神经内科确诊的颞叶癫痫患者，进行SPIN、听性脑干反应（auditory brainstem response，ABR）测试。选择19例年龄、性别相匹配的健康人做对照组，进行SPIN测试。所有受试者均经询问病史、耳科检查及纯音测听、声导抗测定除外传导、感音神经性及混合性聋，且纯音听阈均在25dB以内。SPIN测试材料中测试言语和噪声材料，采用独立声道录制，通过预实验选择测试信噪比（S／N）为-25dB。测试时，每受试句均朗读2次，并对2次的结果分别进行记录和比较。结果在ABR测试中，癫痫患者仅V波潜伏期左耳较右耳延长，且差异有统计学意义（P〈0．05），余各波潜伏期及波间期差异均无统计学意义（P〉0．05）；在SPIN测试中，健康对照组第1次聆听左右耳间得分比较，差异无统计学意义（P〉0．05），第2次聆听时，差异有统计学意义（P〈0．05）；颞叶癫痫患者左右耳间得分比较，第1次和第2次聆听的差异均无统计学意义（P〉0．05），而颞叶癫痫患者无论在单耳、双耳聆听以及第1次和第2次聆听的SPIN得分，与健康对照组相比，差异均有统计学意义（P〈0．01）。由于9例癫痫患者中有3例为右侧颞叶病变，余为双侧颞叶病变，故未对左、右侧颞叶病变与左、右利手的关系可能对实验造成的影响进行统计分析。结论本组颞叶癫痫患者在纯音测听、ABR检查无明显异常，而SPIN测试言语识别率明显低于对照组，差异有统计学意义，证明颞叶癫痫患者具有中枢听功能障碍，同时提示SPIN是一项敏感、无创的中枢听觉功能检查方法，建议临床上将其作为听处理套查方法之一。     

Hemodynamic differences in children with dichotic listening deficits: preliminary results from an fMRI study during a cued listening task

Functional magnetic resonance images were acquired while children with and without dyslexia identified incongruous words embedded within fairy tale segments in a quasidichotic listening task. All children produced greater activation in the left hemisphere than in the right hemisphere during the binaural separation listening task. Children with dyslexia, who had a higher incidence of a dichotic left ear deficit from prescanning behavioral tests, produced fewer hits and more misses than control children while monitoring their left ears in the scanner. Control children produced stronger left hemispheric activation for ipsilateral left ear input than right hemispheric activation for ipsilateral right ear input, but ipsilateral activation patterns in children with dyslexia were symmetrical. Children with dyslexia who monitored their right ears first produced the lowest left hemispheric activation overall, suggesting that priming of the right ear may have inhibited the ability of children with a left ear deficit to adequately identify target words presented toward their left ears while in the scanner.     

双耳感音神经性聋患儿合并分泌性中耳炎的临床诊治

目的 探讨双耳感音神经性聋并发分泌性中耳炎患儿的症状特点, 为及时诊治此类患者提供临床依据。方法 收集经手术治疗的双耳感音神经性聋并发分泌性中耳炎患儿(A组)17例(34耳)的病历资料, 分析其误诊原因、临床特点及并发症发生率, 并与同期行手术治疗的单纯双耳单纯分泌性中耳炎患儿(B组)17例(34耳)进行鼓室粘连发生率的比较。手术前后应用听性脑干反应(ABR)检查随诊听力变化。结果 A组均以家属发现听力下降为首诊症状, 在当地首诊曾诊断为突发性聋7例, 耳闷塞感、耳鸣、耳痛等症状叙述不清, 均无法采集到确切的分泌性中耳炎发病时间;行双耳鼓膜置管时发现中耳粘连5例(7耳), 手术前后ABR检查Ⅴ波阈值改善0～30 dB nHL, 平均17.3 dB nHL, 手术前后Ⅴ波阈值改善, 差异有统计学意义(P < 0.05)。B组患儿无1例误诊, 首诊诉耳痛或耳鸣、耳闷塞感等耳部不适症状15例, 发病时间明确, 首诊诉听力下降2例, 鼓膜置管时中耳粘连1例(1耳)。A组并发症发生率高于B组, 差异有统计学意义(P < 0.05)。结论 双耳感音神经性聋并发分泌性中耳炎患儿临床病史采集困难, 易误诊, 临床并发症发生率高, 应及时干预;鼓膜置管对听力改善效果明显。     

Does the use of radiofrequency myringotomy for insertion of a ventilation tube reduce the incidence of myringosclerosis?

The aim of the present study was to determine the rate of myringosclerosis after radiofrequency (RF) myringotomy and ventilation tube (VT) insertion and compare it with that after the incisional myringotomy and VT insertion. Thirty children (60 ears), 2–16 years old (mean age 7.06 ± 2.77 years) who were planned to undergo surgical intervention for bilateral otitis media with effusion (OME), were included in this study. The children were treated by RF myringotomy of the right ear, incisional myringotomy of the left ear, and insertion of VTs into both ears. Both ears were examined intraoperatively for bleeding, and patients were evaluated for myringosclerosis formation with otomicroscopy at the end of the ninth month. Myringosclerosis was observed in 22 of the 60 ears. The overall incidence was 36.6 %. Fifteen (50 %) left ears showed myringosclerosis by otomicroscopy, and seven (23.3 %) right ears showed myringosclerosis. The rate of myringosclerosis of the right ear was significantly lower than that of the left ear (p < 0.05). In addition, intraoperative tympanic membrane bleeding was observed in 24 (40 %) of the 60 ears: 21 (70 %) left ears and three (10 %) right ears were perforated by RF. The tympanic membrane bleeding rate of the right ear was significantly lower than that of the left ear (p < 0.01). The present study is the first to determine the myringosclerosis rate after RF myringotomy and VT insertion. Our results indicate that VT insertion with RF myringotomy decreased the incidence of myringosclerosis.     

Lateral asymmetry in the ABR of neonates: evidence and mechanisms

Lateralized processing of auditory stimuli occurs at the level of the auditory cortex but differences in function between the left and right sides are not clear at lower levels of the auditory system. The current study is designed to (1) investigate asymmetric auditory function at the ear and brainstem in human infants and (2) investigate possible mechanisms for asymmetry at these levels. Study 1 evaluated auditory brainstem responses (ABRs) in response to high and low-level clicks presented to the right and left ears of neonates. Wave V was significantly larger in amplitude and waves III and V were shorter in latency when the ABR was generated in the right ear. Study 2 investigated two possible mechanisms of such asymmetry by (a) using contralateral white noise masking to activate the medial olivocochlear system and (b) increasing stimulus rate to reveal neural conduction and synaptic mechanisms. ABR wave V, evoked by clicks to the left ear, showed a greater reduction in amplitude with contralateral noise than the response evoked from the right ear. No systematic asymmetries in ABR latencies or amplitudes were found with increased stimulus rate. We conclude that (1) the click-evoked ABR in neonates demonstrates asymmetric auditory function with a small but significant right ear advantage and (2) asymmetric activation of the medial olivocochlear system, specifically greater contralateral suppression of ABR produced by the left ear, is a possible mechanism for asymmetry.     

Evaluation of the effect of dexamethasone in experimentally induced endolymphatic hydrops in guinea pigs

PURPOSE: The aim of this study was to investigate the audiological and histopathologic effects of dexamethasone in the treatment of experimentally induced endolymphatic hydrops. MATERIALS AND METHODS: Thirty mature, male guinea pigs weighing 400 +/- 50 g were operated on to induce experimental endolymphatic hydrops in their right ear. Left ear served as control. Subjects were separated into control and dexamethasone groups, with the latter receiving dexamethasone 5 mg/(kg d) intraperitoneally for 10 days. Electrocochleography and auditory brainstem response were applied to all subjects at preoperation, on the second postoperative day and also on the 15th postoperative day in animals that lived for a long time. The histopathologic examination of the inner ear in all animals was done at the end of the study. RESULTS: The summating potential and the ratio of the summating potential to the action potential measured on the second postoperative day were found to be increased in both groups, but more significantly in the control one. When the left and right ears were compared, significant difference was found in the control group; however, no significant difference was found between the ears in the dexamethasone group. Histopathologic examination revealed varying degrees of hydrops in the control group, but showed only normal findings or minor changes in the dexamethasone group. CONCLUSIONS: Dexamethasone can prevent the audiological and histopathologic findings of experimentally induced endolymphatic hydrops. However, these results must be supported by clinical and experimental studies designed with a large number of subjects.     

Observations on bilateral symmetry of the stapedial footplate lesion and narrowing of the oval window niche in otosclerosis

OBJECTIVES: We consider whether patients with bilateral otosclerosis who have surgery on their second ear show symmetry in the degree of severity of their footplate otosclerosis. METHODS: The severity of the stapedial otosclerotic lesion and the degree of narrowing of the oval window niche by exostoses were recorded for each ear of 269 patients who elected to undergo operation on the second ear. The severities and similarities of the otosclerotic lesion affecting the oval window niche were compared between the ears. RESULTS: The majority of oval window niches were normal in width in both ears. A niche narrowed to less than 0.8 mm in diameter was rare and tended to affect both ears (5.6% first ears and 5.95% second ears; chi2 = 134.6 on 4 df, p < .0001). The degree of footplate otosclerosis was classified and amalgamated into 3 broad categories: minor (47.2%), moderate (21.6%), and severe (31.2%). A high degree of bilateral symmetry of the stapedial footplate lesion was found (chi2 = 162.2 on 4 df; significant at .0001 level). CONCLUSIONS: The findings at the oval window of the first ear in regard to the severity of otosclerotic involvement of the stapes footplate and narrowing of the niche by exostoses do allow a fair prediction of the pathological findings in the second ear, if that ear is suitable for stapes surgery and the patient elects to have an operation. The surgeon is forewarned of possible difficulties and technical challenges if an operation has been performed on the first ear.     

The influence of ototoxic drugs on brainstem auditory evoked potentials in man

To examine the short- and long-term consequences of ototoxic drug administration, the brainstem auditory evoked potentials (BAEP) have been recorded in patients undergoing treatment with aminoglycosides antibiotics. It appears that the rapidity of the i.v. injection influences the short-term consequences of the drug administration. The long-term consequences may be reversible. Their reversibility could depend on the status of the ear before the first injection of ototoxic drug. In conclusion, BAEP may be useful as a means of atraumatic monitoring of the auditory function of patients treated with aminoglycosides antibiotics, the non-invasive character of this technique allowing it to be repeatedly used in both adult and young patients.     

Case report: "auditory neuropathy" in a newborn caused by a cerebellopontine angle arachnoid cyst

We present a 6-week-old girl, referred because of failed newborn hearing screening in the right ear. Click-evoked oto-acoustic emissions were present in both ears, auditory brainstem responses (ABR) were present in the left but totally absent in the right ear. A magnetic resonance imaging (MRI) study revealed a large arachnoid cyst in the right cerebellopontine angle (CPA) and a diagnosis of “auditory neuropathy/auditory dyssynchrony” was established. A microsurgical resection of the cyst wall and fenestration was performed by a retro sigmoid approach. This is the first case in the literature of auditory neuropathy (AN) in an infant caused by a cerebellopontine angle arachnoid cyst.     

Detailed Analysis of Auditory Brainstem Responses in Patients with Noise-induced Tinnitus

The role of the auditory brainstem in tinnitus is questionable. This study aimed comprehensively to assess auditory brainstem responses (ABRs) in patients suffering from noise-induced tinnitus (NIT). ABRs were recorded from 13 chronic NIT patients (21 ears) and 11 (21 ears) age and hearing matched control subjects without tinnitus. ABRs were recorded with scalp electrodes placed ipsilateral and contralateral to the stimulated ear, and in three orthonormal differential configurations. The ABRs were analyzed as a function of time, frequency and voltage space. A significantly enhanced ipsilaterally recorded, time domain wave III amplitude was observed for the tinnitus patients. This finding was not confirmed by any of the other ABR measures, which were indistinguishable between subject groups. Although this may be a spurious result, it nonetheless may point to an alteration in the functioning of the putative wave III auditory brainstem generator, which deserves further study.     

Transient evoked otoacoustic emissions (TEOAEs) in new-borns: normative data.

OBJECTIVE: Early diagnosis and rehabilitation of congenital hearing loss are mandatory in order to achieve a satisfactory linguistic and cognitive development. A universal hearing screening in order to identify congenital hearing losses before 3 months of age is required. METHODS: TEOAEs are an easy to perform, short lasting, not invasive and low-cost test with a high sensitivity. 320 at term new-borns (640 ears) without any risk factor for hearing loss underwent TEOAEs. The new-borns were screened 3 days after birth. Those who failed the first test were retested when possible before the discharge from the hospital. ABR was performed 3 months later in cases who failed TEOAE. RESULTS: The median TEOAE sampling time was 98 s, the median test duration was 14 min. The mean stimulus amplitude was 80 dB peSPL in the left ear and 81 dB peSPL in the right ear, noise levels within the external meatus during sampling were 44 dB SPL on the right ear and 43 dB SPL on the left one, noise contained within the response (A-B difference) was 8.65 dB SPL in the left ear and 8.74 dB SPL in the right ear, mean TEOAEs amplitudes were 21.49 dB SPL and 21.78 dB SPL in the right and left ear respectively, the mean lower and upper limit of the spectrum being 678 and 5720 Hz. According to these criteria 494/640 ears (77.2%) passed the test at the first recording, while TEOAEs resulted to be absent in 146/640 ears (22.8%). A retest was performed successfully before the discharge from the Hospital in 30/640 ears (4.7%). An ABR recording within the third month of life was scheduled as out-patient in the 58 new-borns (116 ears, 18.2%) who failed the test. 18 of them (36 ears, 5.6%) did not complete the program, 19 new-borns (38 ears, 11.8%) showed a normal ABR, while two new-borns (four ears, 0.6%) failed ABR after 3 months. A second ABR performed after 6 months was normal. CONCLUSIONS: TEOAEs recording seems at now the test of choice for a universal hearing screening. However, a greater standardization of criteria both in performing the test and in evaluating the results is needed.