Volume 107 Number 3 september 1992
Letters to the Editor
495
REFERENCE
REFERENCES
I. Mangham CA. Hearing threshold difference between earsandrisk of acoustic tumor. OTOLARYNGOL HEAD NECK SURG 1991;105: 814-7.
I. JergerJ, JergerS. Acoustic reflex decay: IO-second or 5-second
• AUTHOR'S REPLY
I gratefully accept Dr. Bartel's praise of our work. He accurately restated the message we were trying to convey in our discussion.
Charles A. Mangham, Jr., MD Seattle, Washington
Role of Audiology In Identification of Acoustic Tumors
To the Editor: We read the article entitled, "Hearing threshold difference between ears and risk of acoustic tumor," by Dr. Charles A. Mangham (OTOLARYNGOL HEAD NECK SURGERY 1991;105:814-7) with much interest. As audiologists, we are equally concerned about detecting as many acoustic neuromas as early as possible. Dr. Mangham's suggestions for balancing the degree of pure-tone asymmetry vs. the need for ABR and MRI in detecting tumors is very interesting. However, it appears to us that Dr. Mangham has overlooked the valuable and relatively inexpensive diagnostic information to be derived from the complete audiological test battery. AfteralI, audiological testing extends beyond pure-tone thresholds. A complete audiological test battery, including speech audiometry and impedance measurement, should be a minimal starting point. Beyond that, site of lesion tests, such as PIPB rollover functions, tone decay testing, acoustic reflex threshold, and acoustic reflex decay testing would increase the accuracy of tumor detection significantly beyond the capability of pure-tone asymmetry alone, and at a significantly lower cost than ABR or MRI. For example, Jerger and Jerger, I reporting in Ear and Hearing, have shown acoustic reflex decay to be an effective early screening procedure for eighth nerve tumors. A second example can be found in Gelfand et al.,? reporting in the Journal of Speech and Hearing Disorders, that elevated acoustic reflex thresholds at more than one frequency occur with such low probability among normal and cochlear-impaired ears that such an observation implied considerable risk for retrocochlear pathology. A third example is reported in Silman's' The Acoustic Reflex, in which the accuracy of acoustic reflex thresholds in identifying eighth nerve tumors can be as high as 95%, with other studies showing false-negative rates of 0% to 20.8%. Although we do not suggest that the audiological test battery is infallible, we do believe that, before rushing to ABR and MRI, complete audiological evaluations could routinely provide valuable diagnostic information, significantly more than pure-tone audiometry alone. Those patients who manifest evidence of retrocochlear pathology would then benefit from ABR and MRI. Arthur Podwall, PhD Toni G. Gordon, PhD Paula Lamendola, MS Syosset, New York
criterion? Ear Hear 1983;4:70-1. 2. Gelfand SA, Schwander T, Silman S. Acoustic reflex thresholds in normal andcochlear impaired ears:effectsof no-response rates on 90th percentiles in a large sample. J Speech Hear Dis 1990;55: 198-205. 3. Silman S. The acoustic reflex. NewYork: Academic Press, Inc., 1984.
To the Editor: We enjoyed reading the article by von Glass et al., "Falsepositive MR imaging in the diagnosis of acoustic neurinomas (OTOLARYNGOL HEAD NECK SURG 1991;104:863-6). We would like to inform the readers, however, of our experience with one middle cranial fossa exploration of the internal auditory canal, which might have been misconstrued as a "falsepositive" incident. A 58-year-old woman manifested progressive dizziness that was described as mostly Iightheadedness, but with rare episodes of true rotary vertigo. She noted no other otologic or neurologic symptoms and specifically denied hearing loss, tinnitus, or aural pressure. She was evaluated by a neurologist who obtained an auditory brainstern recording that was interpreted as normal, and a gadolinium-enhanced MRI scan that showed an 8-mm lesion at the lateral aspect of the left internal auditory canal. Her electronystagmogram showed only a mild (21%) caloric weakness on the left. Her audiogram was normal. Because the lesion on MRI scan was small and because of the paucity of other symptoms, the patient was followed conservatively. A half year later, the MRI scan showed little change. When her dizziness became more severe, the left internal auditory canal was explored through a middle fossa craniectomy. On initial exploration, the internal auditory canal appeared completely normal, prompting us to consider that this was our first "false-positive" MRI scan. However, because of her dizziness, we proceeded with a vestibular neurectomy. On avulsing the lateral-most aspect of the inferior vestibular nerve, we encountered a small acoustic neuroma. Its size and location being inferior and far lateral toward the fundus had precluded identification of this tumor. The neoplasm was then completely removed and the patient awoke with normal hearing and normal facial function. This single case report would suggest that small, laterally based tumors of the internal auditory canal may be missed, unless the vestibular nerves are sectioned. Jack M. Kartush, MD Michael D. Graham, MD, FACS Michael J. Lakouere, MD Farmington Hills, Michigan
Letters to the Editor
495
REFERENCE
REFERENCES
I. Mangham CA. Hearing threshold difference between earsandrisk of acoustic tumor. OTOLARYNGOL HEAD NECK SURG 1991;105: 814-7.
I. JergerJ, JergerS. Acoustic reflex decay: IO-second or 5-second
• AUTHOR'S REPLY
I gratefully accept Dr. Bartel's praise of our work. He accurately restated the message we were trying to convey in our discussion.
Charles A. Mangham, Jr., MD Seattle, Washington
Role of Audiology In Identification of Acoustic Tumors
To the Editor: We read the article entitled, "Hearing threshold difference between ears and risk of acoustic tumor," by Dr. Charles A. Mangham (OTOLARYNGOL HEAD NECK SURGERY 1991;105:814-7) with much interest. As audiologists, we are equally concerned about detecting as many acoustic neuromas as early as possible. Dr. Mangham's suggestions for balancing the degree of pure-tone asymmetry vs. the need for ABR and MRI in detecting tumors is very interesting. However, it appears to us that Dr. Mangham has overlooked the valuable and relatively inexpensive diagnostic information to be derived from the complete audiological test battery. AfteralI, audiological testing extends beyond pure-tone thresholds. A complete audiological test battery, including speech audiometry and impedance measurement, should be a minimal starting point. Beyond that, site of lesion tests, such as PIPB rollover functions, tone decay testing, acoustic reflex threshold, and acoustic reflex decay testing would increase the accuracy of tumor detection significantly beyond the capability of pure-tone asymmetry alone, and at a significantly lower cost than ABR or MRI. For example, Jerger and Jerger, I reporting in Ear and Hearing, have shown acoustic reflex decay to be an effective early screening procedure for eighth nerve tumors. A second example can be found in Gelfand et al.,? reporting in the Journal of Speech and Hearing Disorders, that elevated acoustic reflex thresholds at more than one frequency occur with such low probability among normal and cochlear-impaired ears that such an observation implied considerable risk for retrocochlear pathology. A third example is reported in Silman's' The Acoustic Reflex, in which the accuracy of acoustic reflex thresholds in identifying eighth nerve tumors can be as high as 95%, with other studies showing false-negative rates of 0% to 20.8%. Although we do not suggest that the audiological test battery is infallible, we do believe that, before rushing to ABR and MRI, complete audiological evaluations could routinely provide valuable diagnostic information, significantly more than pure-tone audiometry alone. Those patients who manifest evidence of retrocochlear pathology would then benefit from ABR and MRI. Arthur Podwall, PhD Toni G. Gordon, PhD Paula Lamendola, MS Syosset, New York
criterion? Ear Hear 1983;4:70-1. 2. Gelfand SA, Schwander T, Silman S. Acoustic reflex thresholds in normal andcochlear impaired ears:effectsof no-response rates on 90th percentiles in a large sample. J Speech Hear Dis 1990;55: 198-205. 3. Silman S. The acoustic reflex. NewYork: Academic Press, Inc., 1984.
To the Editor: We enjoyed reading the article by von Glass et al., "Falsepositive MR imaging in the diagnosis of acoustic neurinomas (OTOLARYNGOL HEAD NECK SURG 1991;104:863-6). We would like to inform the readers, however, of our experience with one middle cranial fossa exploration of the internal auditory canal, which might have been misconstrued as a "falsepositive" incident. A 58-year-old woman manifested progressive dizziness that was described as mostly Iightheadedness, but with rare episodes of true rotary vertigo. She noted no other otologic or neurologic symptoms and specifically denied hearing loss, tinnitus, or aural pressure. She was evaluated by a neurologist who obtained an auditory brainstern recording that was interpreted as normal, and a gadolinium-enhanced MRI scan that showed an 8-mm lesion at the lateral aspect of the left internal auditory canal. Her electronystagmogram showed only a mild (21%) caloric weakness on the left. Her audiogram was normal. Because the lesion on MRI scan was small and because of the paucity of other symptoms, the patient was followed conservatively. A half year later, the MRI scan showed little change. When her dizziness became more severe, the left internal auditory canal was explored through a middle fossa craniectomy. On initial exploration, the internal auditory canal appeared completely normal, prompting us to consider that this was our first "false-positive" MRI scan. However, because of her dizziness, we proceeded with a vestibular neurectomy. On avulsing the lateral-most aspect of the inferior vestibular nerve, we encountered a small acoustic neuroma. Its size and location being inferior and far lateral toward the fundus had precluded identification of this tumor. The neoplasm was then completely removed and the patient awoke with normal hearing and normal facial function. This single case report would suggest that small, laterally based tumors of the internal auditory canal may be missed, unless the vestibular nerves are sectioned. Jack M. Kartush, MD Michael D. Graham, MD, FACS Michael J. Lakouere, MD Farmington Hills, Michigan
