1. Computer Architecture and Networks Lab. 컴퓨터 구조 및 네트워크 연구실 Auditory Brainstem Response : Differential Diagnosis(3/3) 2009. 4. 29 윤준철

2. Computer Architecture and Networks Lab. Contents Limitations of the Stacked ABR Other Retrocochlear Pathologies –Auditory Neuropathy Cochlear Pathologies Recommended Protocols Case Studies Summary and Comments CAN Lab. INHA University.

3. Computer Architecture and Networks Lab. Limitations of the Stacked ABR A major limitation of the stacked ABR is that it must be obtained with click levels no greater than 60 to 65 dB. The main use of the stacked ABR is to detect small tumors missed by standard ABR measures. Typically, patients with small tumors do not have average hearing losses that exceed 60 dB. Cochlear hearing loss will reduce the stacked ABR amplitude. CAN Lab. INHA University.

4. Computer Architecture and Networks Lab. Other Retrocochlear Pathologies A number of early studies explored the effects of structural brain lesions on the ABR. The lesions can cause prolongation of interpeak latencies and abnormal peak amplitude ratios. Thus, ABR abnormalities are not specific to any retrocochlear neurologic disease. The one exception is the recently discovered auditory neuropathy. CAN Lab. INHA University.

5. Computer Architecture and Networks Lab. Auditory Neuropathy Patients with auditory neuropathy present with hearing loss for puretones. Reported on 10 young patients with hearing impairments that, by behavioral and physiologic testing, suggested a disorder of the auditory nerve. All 10 patients showed evidence of normal cochlear outer hair cell function as determined by otoacoustic emissions and cochlear microphonic testing. CAN Lab. INHA University.

6. Computer Architecture and Networks Lab. Auditory Neuropathy The configuration of the puretone loss varied across subjects –Predominantly low frequency in 5 patients. –Flat in 3 patients. –Predominantly high frequency in 2 patients. Speech intelligibility tests were conducted in 8 patients. The diagnosis of auditory neuropathy requires ABR tests and tests of cochlear function. CAN Lab. INHA University.

7. Computer Architecture and Networks Lab. Cochlear Pathologies Any cochlear pathology that causes hearing loss can affect ABR measures. ABR abnormalities cannot provide diagnosis of a specific cochlear pathology, with the possible exception of Meniere’s disease with cochlear hydrops. A vast amount of literature documents attempts to diagnose Meniere’s disease with various measures of evoked electrical activity, particularly ECochG. CAN Lab. INHA University.

8. Computer Architecture and Networks Lab. Cochlear Pathologies Abnormal interpeak latencies are usually associated with retrocochlear problems because the delay is presumable due to a problem after activation of the auditory nerve. Abnormal I-V delays in standard ABRs may not be due to retrocochlear problems. Abnormal I-V delays in derived-band ABRs are almost certainly due to a retrocochlear problem. CAN Lab. INHA University.

9. Computer Architecture and Networks Lab. Recommended Protocols CAN Lab. INHA University.

10. Computer Architecture and Networks Lab. Case 1 : Small Tumor Detected by Standard ABR IT5 Measure This 31 year old male experienced tinnitus and sudden total hearing loss in the right ear. The patient’s preoperative audiogram after recovery from the sudden hearing loss is noted in Table 16.2. Audiometric testing in the operated ear a year after the tumor was removed revealed only about 5dB of additional loss in the high frequencies. CAN Lab. INHA University.

11. Computer Architecture and Networks Lab. Case 1 : Small Tumor Detected by Standard ABR IT5 Measure The IT5 was 0.9 ms This small tumor probably affected the high-frequency fibers CAN Lab. INHA University.

12. Computer Architecture and Networks Lab. Case 2 : Mid-Size Tumor Detected by Standard I-V ABR Measure This 36 year old male noticed a progressive loss of hearing in the right ear. The patient’s preoperative audiogram after partial recovery from the sudden hearing loss is noted in Table 16.3. Audiometric testing a week after surgery revealed 15 to 40dB of additional loss in the right ear and little change in the normal left ear. CAN Lab. INHA University.

13. Computer Architecture and Networks Lab. Case 2 : Mid-Size Tumor Detected by Standard I-V ABR Measure CAN Lab. INHA University.

14. Computer Architecture and Networks Lab. Case 3 : Small Eighth Nerve Tumor This 51 year old male had a history of mild hearing loss in the right ear and some dizziness for a 6 month period. The origin of the tumor was the inferior vestibular nerve. The patient’s preoperative audiogram is noted in Table 16.4. CAN Lab. INHA University.

15. Computer Architecture and Networks Lab. Case 3 : Small Eighth Nerve Tumor CAN Lab. INHA University.

16. Computer Architecture and Networks Lab. Case 3 : Small Eighth Nerve Tumor CAN Lab. INHA University.

17. Computer Architecture and Networks Lab. Case 4 : Very Small Eighth Nerve Tumor This 47 year old female, at the suggestion of a psychiatrist the results showed a 3 to 4 mm intracanalicular eighth nerve tumor in the left ear. The patient’s preoperative audiogram is shown in Table 16.5. CAN Lab. INHA University.

18. Computer Architecture and Networks Lab. Case 4 : Very Small Eighth Nerve Tumor CAN Lab. INHA University.

19. Computer Architecture and Networks Lab. Case 4 : Very Small Eighth Nerve Tumor CAN Lab. INHA University.

20. Computer Architecture and Networks Lab. Summary and Comments The major focus of our discussions is on the detection of eighth nerve tumors. The advancement in imaging techniques such as MRIs with contrast, it was discovered that standard ABR measures were not sufficiently sensitive to small tumors. CAN Lab. INHA University.