1. BRAINSTEM AUDITORY
EVOKED RESPONSES
(BAER OR ABR)

2.  Auditory pathway
 Cranial VIII nerve
 Nucleus brain
click
 Retrocochlear pathology
Identify for sensorineural hearing loss.

3. Indication
 The main indicate Acoustic neuroma
 Postoperative of cochlear implant
 Who has mental disease
 After illness neuropathy
 The all sensorineural hearing loss

4. Auditory pathway

7. Normative Data
7
Latency (ms)
 Wave I=1.50
 Wave III=3.57
 Wave V=5.53
Interpeak intervals
I-III=2.06
III-V=1.96
I-V=4.02

8. The waveform represents specific
anatomical points along the
auditory neural pathway:
 The cochlear nerve and nuclei (waves I and
II),
 Superior olivary nucleus (wave III)
 Lateral lemniscus (wave IV)
 Inferior colliculi (wave V).

10. AUDITORY BRAINSTEM
RESPONSE THRESHOLD
DIFFERENCES IN PATIENTS
WITH VESTIBULAR
SCHWANNOMA: A NEW
DIAGNOSTIC INDEX
From the Division of Otolaryngology–Head and Neck Surgery,
Department of Surgery, University of Kentucky College of
Medicine, Lexington. Matthew L. Bush, MD, University of
Kentucky College of Medicine,

11.  Auditory brainstem response (ABR) testing is less sensitive in
detecting small vestibular schwannomas than medium-size tumors.
 Magnetic resonance imaging (MRI) is more sensitive than ABR
alone for small and large tumors, but it carries with it increased cost
and issues of unavailability and patient discomfort.
 We conducted a prospective pilot study of 7 patients with untreated
MRI-proven, unilateral vestibular schwannoma to determine if we
could increase the sensitivity of ABR testing in detecting small
tumors.
 Our method involved the use of a new ABR index that is based on
threshold differences.
 All patients underwent pure-tone audiometry followed by a
determination of behavioral threshold and neurodiagnostic threshold
ABR in the normal ear, which was used as a control, and in the
diseased ear. Analysis of results revealed that all 7 patients had an
abnormal ABR threshold difference, and 5 patients displayed
abnormal traditional ABR indices. The mean difference between the
ABR and behavioral click thresholds was 41.4 dB in the diseased
ears (with the ABR threshold being higher than the click threshold)
and 15.8 dB in the normal ears. None of the control ears had a
threshold difference >30 dB.

12. Introduction
 The use of auditory brainstem response (ABR) testing in the screening of
retrocochlear pathology such as vestibular schwannomas is widespread.
 Since ABR testing was first described by Selters and Brackmann in 1977,multiple
studies have shown that its sensitivity exceeds 90%, thus establishing it as the most
sensitive audiologic test for the detection of vestibular schwannomas.
 However, within the past decade, magnetic resonance imaging (MRI) has emerged as
the gold standard for the diagnosis and monitoring of vestibular schwannomas.
 MRI is capable of detecting vestibular schwannomas of any size, while ABR testing
tends to be less sensitive for smaller lesions.
 For example, Schmidt et al reported that ABR testing was only 58% sensitive for
detecting lesions 1 cm or smaller
 The usefulness of ABR testing is also limited by compromised audiologic function,
which is typically seen in the setting of retrocochlear pathology. While MRI is more
sensitive than ABR alone, it is not always readily available and it adds to treatment
costs.6 Moreover, patient discomfort can be an issue.
 Finally, MRI is contraindicated in many patients because of implants or other types of
metal in the body.
 Computed tomography (CT) is an option, but it is less sensitive than MRI and it may
also miss small lesions.

13.  ILD of ≥0.3 msec has been reported to greatly
assist in vestibular schwannoma detection.
 A threshold difference of ≥30 dB in vestibular
schwannomas.

14. Patients and methods
 This prospective pilot study involved patients with
untreated vestibular schwannomas.
 40 patients with unilateral vestibular
schwannomas presented to our clinic. Of these,
33 were excluded on the basis of a PTA >60 dB,
previous treatment, or an unwillingness to
participate.
 The charts of the remaining 7 patients were
reviewed for demographic information and for
information on the site and size of the vestibular
schwannoma.
 Recent MRIs were also reviewed.

15. Parameters
 I-V interval ≥4.4 msec for,
 ILD ≥0.4 msec for,
 absolute latency of V ≥6.2 msec
 Threshold difference ≥30 db

16. Results
 The 7 patients in our study group were aged 49 to 70 years
(mean: 59)
 Five of the patients had at least one abnormal index.
 In 3 of the 7 patients (patients 4, 6, and 7), we were unable
to detect a wave I, and therefore a wave I-V interval could not
be calculated.
 All 3 of these patients had at least one other abnormal
index.
 In 1 of those 3 patients (patient 7), therefore the ILD could
not be calculated;
 this patient had a significant sensorineural hearing loss on
the normal side, which may have accounted for the difficulty
in obtaining normal waveforms. Failure to obtain traditional
indices was considered abnormal in this study.

17. Summary of patient demographic
information and ABR results*
pt ag
e
Tumor
side
Tumor
size
I-V
interval
ms
ILD
ms
Absolute
latency
of V ms
Behavi
oral
thresh
old Db
ABR
thesh
o
Ld
Db
Thres
hold
diffe
1 52 Left 3.0 mm 4.2 0.0 6.0 10/10/ 60/20/ 50/10
2 49 left 4.0 mm 4.6 0.2 6.0 10/25/ 50/30/ 40/5/
3 60 Left 1.1 cm 5.0 0.8 6.7 15/5/ 50/20/ 35/15
4 70 left 1.6 cm cnd 0.4 6.1 35/15/ 90/40/ 55/25/
5 70 rigth 5.0 mm 4.3 0.0 6.1 25/25/ 60/50/ 35/25/
6 58 left 1.2 mm cnd 0.5 6.6 15/15/ 50/30/ 35/15/
7 54 rigth 5.0 mm cnd cnd 6.6 45/35/ 85/cnd 40/cn

20. Discussion
 In this study, we evaluated patients with untreated, MRI-proven unilateral
vestibular schwannomas with the use of a traditional ABR test and a
determination of threshold differences for the purpose of increasing ABR
sensitivity.
 Our goal was not to attempt to replace MRI with ABR. Rather, we advocate
the development of a cost-effective yet accurate algorithm for the diagnostic
evaluation of patients with asymmetrical auditory symptoms.
 The application of the threshold difference is completely dependent on the
examiner's ability to determine a reliable neurodiagnostic threshold; this is
not possible in all patients, but it does hold promise for the development of
new indices in vestibular schwannoma detection.
 The results of ABR testing in patients with significantly diminished auditory
function are typically unreliable, and these patients should be evaluated
radiographically if asymmetrical symptoms exist.
 As reflected in our exclusion criteria, we attempted to examine patients with
PTAs <60 dB in an attempt to gain more reliable ABR results.
 A threshold difference >30 dB may represent an additional index to indicate
suspicion of retrocochlear pathology

21. Criteria for retrocochlear
dysfunction
 Absence of all waves following waves I, II, or
III.
 Abnormal prolongation of I-III, III-V. and I-V
interpeak intervals
 Abnormally increased differences between the
two ears (interaural differences)

24. 24
 Large cerebellopontine angle tumor that was
compressing the brainstem
 I–V and III–V intervals are both abnormally
prolonged
in Large Acoustic Neuroma

26. Thank you