The Laryngoscope C 2015 The American Laryngological, V
Rhinological and Otological Society, Inc.
Classics From The Laryngoscope D. Bradley Welling, MD, PhD “Ganglion Cell Populations in Normal and Pathological Human Cochleae: Implications for Cochlear Implantation” Jorge Otte, MD; Harold F. Schuknecht, MD; Alan G. Kerr, MB, FRCS This classic article1 meticulously detailed the spiral ganglion cell (SGC) populations in 100 patients with variable degrees of hearing loss and known diagnoses to assess the correlation with speech discrimination scores and to hypothesize upon the inherent ability to stimulate the remaining spiral ganglia successfully with cochlear implants. Important observations from this study were that spiral ganglion cell populations in excess of 20,000 had normal or near normal thresholds, whereas losses up to 40 dB had at least 15,000 cells, and those with losses in the range of 50 to 60 dB had at least 10,000 cells. Surprisingly, with counts as low as 10,000 SGCs, some speech discrimination is still possible, and with 20,000 SGCs, normal discrimination was possible. These findings were especially significant at the time of publication because animal studies had shown “Free-Floating Endolymph Particles: A New Operative Finding During Posterior Semicircular Canal Occlusion” Lome S. Parnes, MD; Joseph A. McClure, MD This was also a landmark article.4 Previously, cupulolithiasis had been accepted as the cause of benign paroxysmal positional vertigo (BPPV), based upon the findings of a basophilic deposit on the cupula of the posterior semicircular canal described in Schuknecht’s Pathology of the Ear. Granular deposits have been noted in the posterior canal as well, but there was no way to know if these were fixed or mobile. In the process of occluding the posterior semicircular canal for intractable BPPV, two patients were noted to have freefloating white mater within the endolymphatic compartment of the posterior canal. This material slowly floated
From the Department of Otology and Laryngology, Otology and Neurotology Division, Massachusetts Eye and Ear Infirmary, Boston, Massachusetts, U.S.A. Editor’s Note: This Manuscript was accepted for publication March 4, 2015. The author has no funding, financial relationships, or conflicts of interest to disclose. Send correspondence to D. Bradley Welling, MD, Department of Otology and Laryngology, Massachusetts Eye and Ear Infirmary, 243 Charles St., Boston, MA 02114. E-mail: [email protected]
Laryngoscope 125: May 2015
degeneration of SGCs following deafness. Opponents of cochlear implantation posited that implants would lead to further hair cell damage and subsequent loss of all SPCs, which would lead to failure of the cochlear implant. Following these early studies, much greater detail in understanding neuronal projections to sensory epithelium, survival, and regeneration have come to light. Fayad and Linthicum2 showed that in human temporal bones, hair cell loss did not necessarily correlate with SGC survival out to 3 years. These results did not correlate implant function with the number of surviving SGC counts. In fact, there was curiously an inverse relationship between function and SGCs. Recently, however, it has been shown, in a within-subjects study, that in patients with bilateral cochlear implants, the differences in SGC counts were directly correlated with word recognition scores in patients.3 The variability between different patients did not allow such good controls and accurate assessment. Clearly, we continue to learn much from carefully correlated histories and human histopathologic specimens. The continued studies of the human temporal bone are key in furthering our understanding. downward with gravity and occasionally dispersed, indicating the free-floating nature of the material. Parnes and McClure noted that free-floating, rather than fixed particles, were consistent with the observed findings on performance of the Hall-Pike maneuver in many cases. These free particles induce an endolymph current from their relative hydrodynamic drag as they moved to a more gravitydependent position, but always were associated with the posterior canal in the dependent position. If cupulolithiasis was involved, it would cause the same ampullofugal cupular displacement initially. However, the opposite or upward ear should have been able to cause the same rotatory nystagmus if affected by fixed debris on the superior cupula. This intraoperative finding, also seen in many subsequent other cases as demonstrated in the video at this link5 led to a physiologic understanding of the Semont and Eppley maneuvers for repositioning of the freefloating particulate matter back into the vestibule, greatly simplifying the treatment for many patients with BPPV. A subsequent publication proved the particulate matter to be consistent with degenerating otoconia. I would be surprised if any otolaryngologist has not benefitted significantly from the findings presented in these two classic articles. Likewise, some of my most grateful patients have been those receiving the modern miracle of a cochlear implant or the straightforward cure of their BPPV. Welling: Historical Classics
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BIBLIOGRAPHY 1. Otte J, Schunknecht HF, Kerr AG. Ganglion cell populations in normal and pathological human cochleae. Implications for cochlear implantation. Laryngoscope 1978;88:1231–1246. 2. Fayad JN, Linthicum FH. Multichannel cochlear implants: relation of histopathology to performance. Laryngoscope 2006;116:1310– 1320.
Laryngoscope 125: May 2015
1032
3. Seyyedi M, Viana LM, Nadol JB. Within-subject comparison of word recognition and spiral ganglion cell count in bilateral cochlear implant recipients. Otology Neurotol 2014;35:1446–1450. 4. Parnes LS, McClure JA. Free-floating endolymph particles: a new operative finding during posterior semicircular canal occlusion. Laryngoscope 1992;102:988–992. 5. Parnes LS. Free floating endolymph particles [video]. YouTube. https://youtu.be/qpW98U7MUyc. Published March 24, 2015.
Welling: Historical Classics
Rhinological and Otological Society, Inc.
Classics From The Laryngoscope D. Bradley Welling, MD, PhD “Ganglion Cell Populations in Normal and Pathological Human Cochleae: Implications for Cochlear Implantation” Jorge Otte, MD; Harold F. Schuknecht, MD; Alan G. Kerr, MB, FRCS This classic article1 meticulously detailed the spiral ganglion cell (SGC) populations in 100 patients with variable degrees of hearing loss and known diagnoses to assess the correlation with speech discrimination scores and to hypothesize upon the inherent ability to stimulate the remaining spiral ganglia successfully with cochlear implants. Important observations from this study were that spiral ganglion cell populations in excess of 20,000 had normal or near normal thresholds, whereas losses up to 40 dB had at least 15,000 cells, and those with losses in the range of 50 to 60 dB had at least 10,000 cells. Surprisingly, with counts as low as 10,000 SGCs, some speech discrimination is still possible, and with 20,000 SGCs, normal discrimination was possible. These findings were especially significant at the time of publication because animal studies had shown “Free-Floating Endolymph Particles: A New Operative Finding During Posterior Semicircular Canal Occlusion” Lome S. Parnes, MD; Joseph A. McClure, MD This was also a landmark article.4 Previously, cupulolithiasis had been accepted as the cause of benign paroxysmal positional vertigo (BPPV), based upon the findings of a basophilic deposit on the cupula of the posterior semicircular canal described in Schuknecht’s Pathology of the Ear. Granular deposits have been noted in the posterior canal as well, but there was no way to know if these were fixed or mobile. In the process of occluding the posterior semicircular canal for intractable BPPV, two patients were noted to have freefloating white mater within the endolymphatic compartment of the posterior canal. This material slowly floated
From the Department of Otology and Laryngology, Otology and Neurotology Division, Massachusetts Eye and Ear Infirmary, Boston, Massachusetts, U.S.A. Editor’s Note: This Manuscript was accepted for publication March 4, 2015. The author has no funding, financial relationships, or conflicts of interest to disclose. Send correspondence to D. Bradley Welling, MD, Department of Otology and Laryngology, Massachusetts Eye and Ear Infirmary, 243 Charles St., Boston, MA 02114. E-mail: [email protected]
Laryngoscope 125: May 2015
degeneration of SGCs following deafness. Opponents of cochlear implantation posited that implants would lead to further hair cell damage and subsequent loss of all SPCs, which would lead to failure of the cochlear implant. Following these early studies, much greater detail in understanding neuronal projections to sensory epithelium, survival, and regeneration have come to light. Fayad and Linthicum2 showed that in human temporal bones, hair cell loss did not necessarily correlate with SGC survival out to 3 years. These results did not correlate implant function with the number of surviving SGC counts. In fact, there was curiously an inverse relationship between function and SGCs. Recently, however, it has been shown, in a within-subjects study, that in patients with bilateral cochlear implants, the differences in SGC counts were directly correlated with word recognition scores in patients.3 The variability between different patients did not allow such good controls and accurate assessment. Clearly, we continue to learn much from carefully correlated histories and human histopathologic specimens. The continued studies of the human temporal bone are key in furthering our understanding. downward with gravity and occasionally dispersed, indicating the free-floating nature of the material. Parnes and McClure noted that free-floating, rather than fixed particles, were consistent with the observed findings on performance of the Hall-Pike maneuver in many cases. These free particles induce an endolymph current from their relative hydrodynamic drag as they moved to a more gravitydependent position, but always were associated with the posterior canal in the dependent position. If cupulolithiasis was involved, it would cause the same ampullofugal cupular displacement initially. However, the opposite or upward ear should have been able to cause the same rotatory nystagmus if affected by fixed debris on the superior cupula. This intraoperative finding, also seen in many subsequent other cases as demonstrated in the video at this link5 led to a physiologic understanding of the Semont and Eppley maneuvers for repositioning of the freefloating particulate matter back into the vestibule, greatly simplifying the treatment for many patients with BPPV. A subsequent publication proved the particulate matter to be consistent with degenerating otoconia. I would be surprised if any otolaryngologist has not benefitted significantly from the findings presented in these two classic articles. Likewise, some of my most grateful patients have been those receiving the modern miracle of a cochlear implant or the straightforward cure of their BPPV. Welling: Historical Classics
1031
BIBLIOGRAPHY 1. Otte J, Schunknecht HF, Kerr AG. Ganglion cell populations in normal and pathological human cochleae. Implications for cochlear implantation. Laryngoscope 1978;88:1231–1246. 2. Fayad JN, Linthicum FH. Multichannel cochlear implants: relation of histopathology to performance. Laryngoscope 2006;116:1310– 1320.
Laryngoscope 125: May 2015
1032
3. Seyyedi M, Viana LM, Nadol JB. Within-subject comparison of word recognition and spiral ganglion cell count in bilateral cochlear implant recipients. Otology Neurotol 2014;35:1446–1450. 4. Parnes LS, McClure JA. Free-floating endolymph particles: a new operative finding during posterior semicircular canal occlusion. Laryngoscope 1992;102:988–992. 5. Parnes LS. Free floating endolymph particles [video]. YouTube. https://youtu.be/qpW98U7MUyc. Published March 24, 2015.
Welling: Historical Classics
