ORL 2014;76:70–75 DOI: 10.1159/000360997 Received: January 11, 2014 Accepted: February 27, 2014 Published online: April 23, 2014
© 2014 S. Karger AG, Basel 0301–1569/14/0762–0070$39.50/0 www.karger.com/orl
Original Paper
Effect of KTP Laser Cochleostomy on Morphology in the Guinea Pig Inner Ear Digna M.A. Kamalski a, b Jeroen P.M. Peters a Tjeerd de Boorder c Franco Trabalzini d Sjaak F.L. Klis a, b Wilko Grolman a, b a Department
of Otorhinolaryngology and Head and Neck Surgery, b Brain Center Rudolf of Medical Technology and Clinical Physics, University Medical Magnus, and Center Utrecht, Utrecht, The Netherlands; d Otology and Skull Base Surgery Unit, Department of Sense Organs, Siena University Hospital, Siena, Italy c Department
Key Words Cochleostomy · Guinea pig · Histology · KTP laser Abstract Background: The main advantage of using the KTP (potassium-titanyl-phosphate) laser for stapedotomy instead of the conventional micropick instrument is the smaller risk for mechanical damage. However, the KTP laser could theoretically inflict damage to inner ear structures. We hypothesize that KTP laser light [wavelength (λ) = 532 nm] is hardly absorbed in perilymph but well absorbed in solid structures. The aim of this pilot study was to assess if damage occurred after KTP laser cochleostomy in an animal model and, if so, to what extent and at which settings. Materials and Methods: In six guinea pigs, a KTP laser cochleostomy at the basal turn was created. Laser settings of 1, 3 and 5 W and 100 ms pulse time (n = 2 each) were used. Histological preparations were studied for damage to neuroendothelial cells and intrascalar blood. Results: No damage to inner ear neuroendothelial cells was observed, even at the highest power. Blood clots in the scala tympani from vessels in the cochlear wall were seen. The effects were minimal in the lowest, currently clinically used settings. Conclusion: KTP laser cochleostomy gives no damage to inner ear neuroendothelial cells but may cause intra© 2014 S. Karger AG, Basel scalar hemorrhages.
Introduction
Traditionally, in otosclerosis surgery, a fenestration in the footplate is made by a micropick instrument or a microburr. These contact methods entail risks, e.g. bleeding, acoustic trauma to the inner ear or fracture of the stapes footplate [1]. To minimize these risks, a laser can be D.M.A. Kamalski, MD Department of Otorhinolaryngology and Head and Neck Surgery University Medical Center Utrecht, Heidelberglaan 100, G05.129 NL–3584 CX, Utrecht (The Netherlands) E-Mail d.m.a.kamalski @ umcutrecht.nl
71
ORL 2014;76:70–75 © 2014 S. Karger AG, Basel www.karger.com/orl
DOI: 10.1159/000360997
Kamalski et al.: Effect of KTP Laser Cochleostomy on Morphology in the Guinea Pig Inner Ear
Table 1. KTP laser settings
Power, W
Pulse time, ms
Spot diameter, μm
Fluency, J/cm2
1 3 5
100 100 100
200 200 200
318 955 1,592
used for fenestration. Different lasers are available, e.g. argon [wavelength (λ) = 480 nm] laser, KTP (potassium-titanyl-phosphate, λ = 532 nm) laser, erbium:YAG (erbium:yttriumaluminum-garnet, λ = 2,940 nm) laser and CO2 (λ = 10,600 nm) laser. In practice, the choice depends mainly on the surgeons’ preference and availability. Side effects of using a laser are predominantly linked to the heating of inner ear structures. If the laser energy is mainly absorbed in water, which is the case with the CO2 laser, heating of the perilymph may occur. The KTP and argon lasers seem preferable for laserassisted stapedotomy as their wavelength is hardly absorbed in water, minimizing the risk of heating [1–3]. However, theoretically, when using a KTP laser, there is the risk of direct damage to neuroendothelial cells. The transmission of the laser light through the perilymph may result in the absorption of residual energy in the neuroendothelium in the vestibule. Authors have suggested that this could explain the (temporary) vertigo complaints in patients after KTP laser-assisted stapedotomy [1, 4–6]. The aim of this study is to determine whether in vivo application of KTP laser light causes inner ear damage in an animal model, as assessed in histological preparations, and, if so, to what extent and at what power settings. Materials and Methods Animals Six albino female guinea pigs (weight: 350–500 g; strain: Dunkin Hartley; supplier: Harlan Laboratories, Horst, The Netherlands) were used. The study protocol was approved by the Animal Ethical Committee of the University Medical Center Utrecht under the number 2011.I.09.091. A guinea pig model was used because the thickness of the bone of the basal turn of the guinea pig cochlea is comparable to the thickness of a human stapes footplate (150–200 μm). Furthermore, the cross-sectional diameter of the guinea pig cochlear basal turn corresponds to the depth of a human vestibule. Finally, the guinea pig cochlea is easily accessible in surgery [7, 8]. Anesthesia Anesthesia was initiated with 0.5 ml/kg Hypnorm® (0.315 mg/ml fentanyl + 10 mg/ml fluanisone) administered intramuscularly. Further anesthesia was induced with a gas mixture of N2O (2 liter/min), O2 (1 liter/min) and 2% isoflurane using a mouth cap. To prevent bradycardia following anesthesia, 0.1 ml/kg atropine was administered intramuscularly. The animal was subsequently tracheostomized and artificially ventilated with a gas mixture of N2O and O2 (2:1) and 1–1.5% isoflurane (±35 cycles/min respiration rate, 2–2.3 kPa) throughout the experiment. The heart rate was monitored and body temperature was maintained with a heating pad. After surgery, the animals were kept under general anesthesia for 4 h to be able to see late effects of inner ear damage (e.g. edema) in the histological preparations. Surgery After local analgesia with Xylocaine® (1% lidocaine, 2% epinephrine), a retroauricular incision was made to expose the right bulla. The bulla was opened and a clear overview of the middle ear was created. The basal turn of the cochlea was identified. A 532-nm KTP laser (IDAS; Quantel Derma, Erlangen, Germany) coupled to a fiber hand piece (EndoENT, diameter: 200 μm; Biolitec, East Longmeadow, Mass., USA) was used to make the fenestration. For a
72
ORL 2014;76:70–75 DOI: 10.1159/000360997
© 2014 S. Karger AG, Basel www.karger.com/orl
Bulla
Round window
Color version available online
Kamalski et al.: Effect of KTP Laser Cochleostomy on Morphology in the Guinea Pig Inner Ear
Basal turn Cochleostomy
Fig. 1. Intraoperative view of the laser area. The right bulla was opened and the basal turn of the cochlea is visible. A rosette of laser fenestrations was created at a power of 3 W. At the rim of each laser fenestration, carbonization can be seen.
Tympanic membrane
stapedotomy, a setting of 1 W for 100 ms is used clinically. The power of laser pulses used in these experiments was 1, 3 or 5 W for 100 ms (table 1). One watt corresponds to the current, clinically used power [9–11]. At the basal turn of the cochlea, a rosette of four fenestrations was created (fig. 1). Left (untreated) cochleas functioned as controls. Four hours after fenestration, the animals were euthanized with an intracardial injection of 0.5 ml Nembutal® (pentobarbital). Histology The cochleas were fixed by intracardial perfusion with a fixative consisting of 3% glutaraldehyde, 2% formaldehyde, 1% acrolein and 2.5% DMSO in 0.08 M sodium cacodylate buffer (pH 7.4), followed by immersion in the same fixative for minimally 3 h at 4 ° C. Further processing of the cochleas was performed according to a standard protocol [12]. For histology, fixated cochleas were cut into 1-μm slices. Every twentieth section was collected for staining with methylene blue and azure II in sodium tetraborate and used for light microscopic evaluation and quantitative analyses. Analysis of Histology All preparations were reviewed by two observers (D.M.A.K. and J.P.M.P.). In case of discussion, a third observer was consulted to reach consensus. Each preparation was reviewed for damage to the organ of Corti, to vascular structures (stria vascularis) and to the cochlear wall. Photographs were taken using a microscope-mounted camera (Leica DC300F; Leica Microsystems GmbH, Wetzlar, Germany).
Results
In this experiment, three groups (1, 3 and 5 W; n = 2 each) were used to determine whether in vivo application of KTP laser light causes inner ear damage and, if so, to what extent and at what power. As expected, bone ablation was more extensive at higher laser power, i.e. fenestrations that were created with 1 W were smaller than the fenestrations created with 5 W. Representative preparations of a cochlea, fenestrated at different laser settings, are shown in figure 2.
73
ORL 2014;76:70–75 © 2014 S. Karger AG, Basel www.karger.com/orl
DOI: 10.1159/000360997
500 μm
100 μm
ST
1W
SV
a
b
Color version available online
Kamalski et al.: Effect of KTP Laser Cochleostomy on Morphology in the Guinea Pig Inner Ear
ST
3W
ST
SV
ST c
d
5W
ST SV ST e
f
Fig. 2. Detailed images of cochleostomies at different power settings (ST = scala tympani; SV = scala vestibuli).
At a power of 1W, the laser was hardly able to fenestrate the wall of the basal turn of the cochlea (fig. 2a, b). At a power of 3 W, fenestration was possible (fig. 2c, d). Finally, in the 5 W mode, large parts of the cochlear wall were ablated and substantial smoke arose (fig. 2e, f). In none of the cochleas, light microscopic signs of damage to the organ of Corti were visible. The stria vascularis was intact in all cases. No thermal signs were seen opposite to the irradiation holes, not even at the highest settings. All treated cochleas, however, showed blood in the scala tympani of the basal turn. This intrascalar blood extravasated from vessels in the cochlear wall close to the area where the laser fenestrated the bone of the basal turn (fig. 2b, d and fig. 3).
74
ORL 2014;76:70–75 © 2014 S. Karger AG, Basel www.karger.com/orl
DOI: 10.1159/000360997
Cochlear wall
Ablation
Color version available online
Kamalski et al.: Effect of KTP Laser Cochleostomy on Morphology in the Guinea Pig Inner Ear
Blood vessel 100 μm
Hemorrhage
Fig. 3. Details of the laser fenestration.
Discussion
The aim of this study was to show whether damage to inner ear tissue occurred during laser-assisted cochleostomy. We expected to see damage to the organ of Corti in histological preparations when applying substantial power. This damage was not observed, not even at settings five times higher than those clinically used. In addition, no thermal effects were seen opposite to the irradiation site. A possible explanation for the absence of neuroendothelial damage is that the energy of the laser light is absorbed in the hemoglobin molecules of the blood vessels in the cochlear wall, and therefore the laser does not inflict damage at deeper structures [13]. Additionally, the excessive energy might be absorbed in the bone of the cochlear wall, generating heat [14]. We found intrascalar blood in all treated animals. There was no correlation between laser power and blood clot size. Large variances in volumes of blood clots were observed. This is probably due to factors that have no relation with laser power, such as vascular anatomy. It is not clear whether these intrascalar blood clots also occur when using a different laser. After CO2 laser cochleostomy in guinea pigs, no damage to the organ of Corti or intrascalar blood were observed [15]. A CO2 laser fenestration in cats, however, showed reactive hemorrhage in the saccular wall [16, 17]. The clinical relevance of blood in the inner ear remains unclear. Autologous blood of guinea pigs (3 μl) in the scala tympani showed that hearing thresholds deteriorated in the high-frequency range [18]. Part of the threshold shift was permanent, and therefore it was concluded that intrascalar blood might cause harmful effects to the cochlea. In stapedotomy, the blood is located in the vestibule, possibly causing vertigo. Several authors report (transient) vertigo following KTP or argon laser stapedotomy in patients, ranging from 6.6 to 39% [1, 4–6]. As blood in the vestibule could be absorbed in time, clinical symptoms of vertigo subside. Especially, regarding the minimal blood clots seen in the 1-watt group, this seems plausible. Further research on histology, in combination with functional outcome, could help us to better understand the clinical meaning of these blood clots.
75
ORL 2014;76:70–75 DOI: 10.1159/000360997
© 2014 S. Karger AG, Basel www.karger.com/orl
Kamalski et al.: Effect of KTP Laser Cochleostomy on Morphology in the Guinea Pig Inner Ear
Conclusion
The application of a KTP laser-assisted cochleostomy causes no damage to tissues in the cochlea. Intrascalar blood clots were observed extravasating from vessels in the cochlear wall, which might be related to vertiginous spells in patients after laser-assisted stapedotomy. Acknowledgments Ferry Hendriksen is acknowledged for performing histological procedures.
Disclosure Statement The authors declare that they have no conflicts of interest.
References 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18
Buchman CA, Fucci MJ, Roberson JB Jr, De La Cruz A: Comparison of argon and CO2 laser stapedotomy in primary otosclerosis surgery. Am J Otolaryngol 2000;21:227–230. Gherini S, Horn KL, Causse JB, McArthur GR: Fiberoptic argon laser stapedotomy: is it safe? Am J Otol 1993; 14:283–289. Kamalski DM, Verdaasdonk RM, de Boorder T, Vincent R, Trabelzini F, Grolman W: Comparison of KTP, Thulium, and CO laser in stapedotomy using specialized visualization techniques: thermal effects. Eur Arch Otorhinolaryngol 2013, Epub ahead of print. Silverstein H, Rosenberg S, Jones R: Small fenestra stapedotomies with and without KTP laser: a comparison. Laryngoscope 1989;99:485–488. Hodgson RS, Wilson DF: Argon laser stapedotomy. Laryngoscope 1991;101:230–233. Rauch SD, Bartley ML: Argon laser stapedectomy: comparison to traditional fenestration techniques. Am J Otol 1992;13:556–560. Kiefer J, Tillein J, Ye Q, Klinke R, Gstoettner W: Application of carbon dioxide and erbium:yttrium-aluminumgarnet lasers in inner ear surgery: an experimental study. Otol Neurotol 2004;25:400–409. Ren DD, Chi FL: Experimental study on thermic effects, morphology and function of guinea pig cochlea: a comparison between the erbium:yttrium-aluminum-garnet laser and carbon dioxide laser. Lasers Surg Med 2008;40:407–414. Antonelli PJ, Gianoli GJ, Lundy LB, LaRouere MJ, Kartush JM: Early post-laser stapedotomy hearing thresholds. Am J Otol 1998;19:443–446. Gerlinger I, Toth M, Bako P, Nemeth A, Pytel J: KTP-laser stapedotomy with a self-crimping, thermal shape memory Nitinol SMart piston: 1 year follow-up results: how we do it. Clin Otolaryngol 2008;33:475–480. Pudel EI, Briggs RJ: Laser-assisted stapedotomy with a Nitinol heat-crimping prosthesis: outcomes compared with a platinum fluoroplastic prosthesis. Otolaryngol Head Neck Surg 2008;139:51–54. de Groot JC, Veldman JE, Huizing EH: An improved fixation method for guinea pig cochlear tissues. Acta Otolaryngol 1987;104:234–242. Broadhurst MS, Akst LM, Burns JA, Kobler JB, Heaton JT, Anderson RR, Zeitels SM: Effects of 532 nm pulsedKTP laser parameters on vessel ablation in the avian chorioallantoic membrane: implications for vocal fold mucosa. Laryngoscope 2007;117:220–225. Wong BJ, Neev J, van Gemert MJ: Surface temperature distributions in carbon dioxide, argon, and KTP (Nd:YAG) laser ablated otic capsule and calvarial bone. Am J Otol 1997;18:766–772. Ren D, Sun J, Wan G, Yang F, Shen F: Influence of carbon dioxide laser irradiation on the morphology and function of guinea pig cochlea. J Laryngol Otol 2005;119:684–692. Coker NJ, Ator GA, Jenkins HA, Neblett CR: Carbon dioxide laser stapedotomy: a histopathologic study. Am J Otolaryngol 1986;7:253–257. Lundy L: The effect of CO(2) and KTP laser on the cat saccule and utricle. Laryngoscope 2009;119:1594–1605. Radeloff A, Unkelbach MH, Tillein J, Braun S, Helbig S, Gstottner W, Adunka OF: Impact of intrascalar blood on hearing. Laryngoscope 2007;117:58–62.
Copyright: S. Karger AG, Basel 2014. Reproduced with the permission of S. Karger AG, Basel. Further reproduction or distribution (electronic or otherwise) is prohibited without permission from the copyright holder.
© 2014 S. Karger AG, Basel 0301–1569/14/0762–0070$39.50/0 www.karger.com/orl
Original Paper
Effect of KTP Laser Cochleostomy on Morphology in the Guinea Pig Inner Ear Digna M.A. Kamalski a, b Jeroen P.M. Peters a Tjeerd de Boorder c Franco Trabalzini d Sjaak F.L. Klis a, b Wilko Grolman a, b a Department
of Otorhinolaryngology and Head and Neck Surgery, b Brain Center Rudolf of Medical Technology and Clinical Physics, University Medical Magnus, and Center Utrecht, Utrecht, The Netherlands; d Otology and Skull Base Surgery Unit, Department of Sense Organs, Siena University Hospital, Siena, Italy c Department
Key Words Cochleostomy · Guinea pig · Histology · KTP laser Abstract Background: The main advantage of using the KTP (potassium-titanyl-phosphate) laser for stapedotomy instead of the conventional micropick instrument is the smaller risk for mechanical damage. However, the KTP laser could theoretically inflict damage to inner ear structures. We hypothesize that KTP laser light [wavelength (λ) = 532 nm] is hardly absorbed in perilymph but well absorbed in solid structures. The aim of this pilot study was to assess if damage occurred after KTP laser cochleostomy in an animal model and, if so, to what extent and at which settings. Materials and Methods: In six guinea pigs, a KTP laser cochleostomy at the basal turn was created. Laser settings of 1, 3 and 5 W and 100 ms pulse time (n = 2 each) were used. Histological preparations were studied for damage to neuroendothelial cells and intrascalar blood. Results: No damage to inner ear neuroendothelial cells was observed, even at the highest power. Blood clots in the scala tympani from vessels in the cochlear wall were seen. The effects were minimal in the lowest, currently clinically used settings. Conclusion: KTP laser cochleostomy gives no damage to inner ear neuroendothelial cells but may cause intra© 2014 S. Karger AG, Basel scalar hemorrhages.
Introduction
Traditionally, in otosclerosis surgery, a fenestration in the footplate is made by a micropick instrument or a microburr. These contact methods entail risks, e.g. bleeding, acoustic trauma to the inner ear or fracture of the stapes footplate [1]. To minimize these risks, a laser can be D.M.A. Kamalski, MD Department of Otorhinolaryngology and Head and Neck Surgery University Medical Center Utrecht, Heidelberglaan 100, G05.129 NL–3584 CX, Utrecht (The Netherlands) E-Mail d.m.a.kamalski @ umcutrecht.nl
71
ORL 2014;76:70–75 © 2014 S. Karger AG, Basel www.karger.com/orl
DOI: 10.1159/000360997
Kamalski et al.: Effect of KTP Laser Cochleostomy on Morphology in the Guinea Pig Inner Ear
Table 1. KTP laser settings
Power, W
Pulse time, ms
Spot diameter, μm
Fluency, J/cm2
1 3 5
100 100 100
200 200 200
318 955 1,592
used for fenestration. Different lasers are available, e.g. argon [wavelength (λ) = 480 nm] laser, KTP (potassium-titanyl-phosphate, λ = 532 nm) laser, erbium:YAG (erbium:yttriumaluminum-garnet, λ = 2,940 nm) laser and CO2 (λ = 10,600 nm) laser. In practice, the choice depends mainly on the surgeons’ preference and availability. Side effects of using a laser are predominantly linked to the heating of inner ear structures. If the laser energy is mainly absorbed in water, which is the case with the CO2 laser, heating of the perilymph may occur. The KTP and argon lasers seem preferable for laserassisted stapedotomy as their wavelength is hardly absorbed in water, minimizing the risk of heating [1–3]. However, theoretically, when using a KTP laser, there is the risk of direct damage to neuroendothelial cells. The transmission of the laser light through the perilymph may result in the absorption of residual energy in the neuroendothelium in the vestibule. Authors have suggested that this could explain the (temporary) vertigo complaints in patients after KTP laser-assisted stapedotomy [1, 4–6]. The aim of this study is to determine whether in vivo application of KTP laser light causes inner ear damage in an animal model, as assessed in histological preparations, and, if so, to what extent and at what power settings. Materials and Methods Animals Six albino female guinea pigs (weight: 350–500 g; strain: Dunkin Hartley; supplier: Harlan Laboratories, Horst, The Netherlands) were used. The study protocol was approved by the Animal Ethical Committee of the University Medical Center Utrecht under the number 2011.I.09.091. A guinea pig model was used because the thickness of the bone of the basal turn of the guinea pig cochlea is comparable to the thickness of a human stapes footplate (150–200 μm). Furthermore, the cross-sectional diameter of the guinea pig cochlear basal turn corresponds to the depth of a human vestibule. Finally, the guinea pig cochlea is easily accessible in surgery [7, 8]. Anesthesia Anesthesia was initiated with 0.5 ml/kg Hypnorm® (0.315 mg/ml fentanyl + 10 mg/ml fluanisone) administered intramuscularly. Further anesthesia was induced with a gas mixture of N2O (2 liter/min), O2 (1 liter/min) and 2% isoflurane using a mouth cap. To prevent bradycardia following anesthesia, 0.1 ml/kg atropine was administered intramuscularly. The animal was subsequently tracheostomized and artificially ventilated with a gas mixture of N2O and O2 (2:1) and 1–1.5% isoflurane (±35 cycles/min respiration rate, 2–2.3 kPa) throughout the experiment. The heart rate was monitored and body temperature was maintained with a heating pad. After surgery, the animals were kept under general anesthesia for 4 h to be able to see late effects of inner ear damage (e.g. edema) in the histological preparations. Surgery After local analgesia with Xylocaine® (1% lidocaine, 2% epinephrine), a retroauricular incision was made to expose the right bulla. The bulla was opened and a clear overview of the middle ear was created. The basal turn of the cochlea was identified. A 532-nm KTP laser (IDAS; Quantel Derma, Erlangen, Germany) coupled to a fiber hand piece (EndoENT, diameter: 200 μm; Biolitec, East Longmeadow, Mass., USA) was used to make the fenestration. For a
72
ORL 2014;76:70–75 DOI: 10.1159/000360997
© 2014 S. Karger AG, Basel www.karger.com/orl
Bulla
Round window
Color version available online
Kamalski et al.: Effect of KTP Laser Cochleostomy on Morphology in the Guinea Pig Inner Ear
Basal turn Cochleostomy
Fig. 1. Intraoperative view of the laser area. The right bulla was opened and the basal turn of the cochlea is visible. A rosette of laser fenestrations was created at a power of 3 W. At the rim of each laser fenestration, carbonization can be seen.
Tympanic membrane
stapedotomy, a setting of 1 W for 100 ms is used clinically. The power of laser pulses used in these experiments was 1, 3 or 5 W for 100 ms (table 1). One watt corresponds to the current, clinically used power [9–11]. At the basal turn of the cochlea, a rosette of four fenestrations was created (fig. 1). Left (untreated) cochleas functioned as controls. Four hours after fenestration, the animals were euthanized with an intracardial injection of 0.5 ml Nembutal® (pentobarbital). Histology The cochleas were fixed by intracardial perfusion with a fixative consisting of 3% glutaraldehyde, 2% formaldehyde, 1% acrolein and 2.5% DMSO in 0.08 M sodium cacodylate buffer (pH 7.4), followed by immersion in the same fixative for minimally 3 h at 4 ° C. Further processing of the cochleas was performed according to a standard protocol [12]. For histology, fixated cochleas were cut into 1-μm slices. Every twentieth section was collected for staining with methylene blue and azure II in sodium tetraborate and used for light microscopic evaluation and quantitative analyses. Analysis of Histology All preparations were reviewed by two observers (D.M.A.K. and J.P.M.P.). In case of discussion, a third observer was consulted to reach consensus. Each preparation was reviewed for damage to the organ of Corti, to vascular structures (stria vascularis) and to the cochlear wall. Photographs were taken using a microscope-mounted camera (Leica DC300F; Leica Microsystems GmbH, Wetzlar, Germany).
Results
In this experiment, three groups (1, 3 and 5 W; n = 2 each) were used to determine whether in vivo application of KTP laser light causes inner ear damage and, if so, to what extent and at what power. As expected, bone ablation was more extensive at higher laser power, i.e. fenestrations that were created with 1 W were smaller than the fenestrations created with 5 W. Representative preparations of a cochlea, fenestrated at different laser settings, are shown in figure 2.
73
ORL 2014;76:70–75 © 2014 S. Karger AG, Basel www.karger.com/orl
DOI: 10.1159/000360997
500 μm
100 μm
ST
1W
SV
a
b
Color version available online
Kamalski et al.: Effect of KTP Laser Cochleostomy on Morphology in the Guinea Pig Inner Ear
ST
3W
ST
SV
ST c
d
5W
ST SV ST e
f
Fig. 2. Detailed images of cochleostomies at different power settings (ST = scala tympani; SV = scala vestibuli).
At a power of 1W, the laser was hardly able to fenestrate the wall of the basal turn of the cochlea (fig. 2a, b). At a power of 3 W, fenestration was possible (fig. 2c, d). Finally, in the 5 W mode, large parts of the cochlear wall were ablated and substantial smoke arose (fig. 2e, f). In none of the cochleas, light microscopic signs of damage to the organ of Corti were visible. The stria vascularis was intact in all cases. No thermal signs were seen opposite to the irradiation holes, not even at the highest settings. All treated cochleas, however, showed blood in the scala tympani of the basal turn. This intrascalar blood extravasated from vessels in the cochlear wall close to the area where the laser fenestrated the bone of the basal turn (fig. 2b, d and fig. 3).
74
ORL 2014;76:70–75 © 2014 S. Karger AG, Basel www.karger.com/orl
DOI: 10.1159/000360997
Cochlear wall
Ablation
Color version available online
Kamalski et al.: Effect of KTP Laser Cochleostomy on Morphology in the Guinea Pig Inner Ear
Blood vessel 100 μm
Hemorrhage
Fig. 3. Details of the laser fenestration.
Discussion
The aim of this study was to show whether damage to inner ear tissue occurred during laser-assisted cochleostomy. We expected to see damage to the organ of Corti in histological preparations when applying substantial power. This damage was not observed, not even at settings five times higher than those clinically used. In addition, no thermal effects were seen opposite to the irradiation site. A possible explanation for the absence of neuroendothelial damage is that the energy of the laser light is absorbed in the hemoglobin molecules of the blood vessels in the cochlear wall, and therefore the laser does not inflict damage at deeper structures [13]. Additionally, the excessive energy might be absorbed in the bone of the cochlear wall, generating heat [14]. We found intrascalar blood in all treated animals. There was no correlation between laser power and blood clot size. Large variances in volumes of blood clots were observed. This is probably due to factors that have no relation with laser power, such as vascular anatomy. It is not clear whether these intrascalar blood clots also occur when using a different laser. After CO2 laser cochleostomy in guinea pigs, no damage to the organ of Corti or intrascalar blood were observed [15]. A CO2 laser fenestration in cats, however, showed reactive hemorrhage in the saccular wall [16, 17]. The clinical relevance of blood in the inner ear remains unclear. Autologous blood of guinea pigs (3 μl) in the scala tympani showed that hearing thresholds deteriorated in the high-frequency range [18]. Part of the threshold shift was permanent, and therefore it was concluded that intrascalar blood might cause harmful effects to the cochlea. In stapedotomy, the blood is located in the vestibule, possibly causing vertigo. Several authors report (transient) vertigo following KTP or argon laser stapedotomy in patients, ranging from 6.6 to 39% [1, 4–6]. As blood in the vestibule could be absorbed in time, clinical symptoms of vertigo subside. Especially, regarding the minimal blood clots seen in the 1-watt group, this seems plausible. Further research on histology, in combination with functional outcome, could help us to better understand the clinical meaning of these blood clots.
75
ORL 2014;76:70–75 DOI: 10.1159/000360997
© 2014 S. Karger AG, Basel www.karger.com/orl
Kamalski et al.: Effect of KTP Laser Cochleostomy on Morphology in the Guinea Pig Inner Ear
Conclusion
The application of a KTP laser-assisted cochleostomy causes no damage to tissues in the cochlea. Intrascalar blood clots were observed extravasating from vessels in the cochlear wall, which might be related to vertiginous spells in patients after laser-assisted stapedotomy. Acknowledgments Ferry Hendriksen is acknowledged for performing histological procedures.
Disclosure Statement The authors declare that they have no conflicts of interest.
References 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18
Buchman CA, Fucci MJ, Roberson JB Jr, De La Cruz A: Comparison of argon and CO2 laser stapedotomy in primary otosclerosis surgery. Am J Otolaryngol 2000;21:227–230. Gherini S, Horn KL, Causse JB, McArthur GR: Fiberoptic argon laser stapedotomy: is it safe? Am J Otol 1993; 14:283–289. Kamalski DM, Verdaasdonk RM, de Boorder T, Vincent R, Trabelzini F, Grolman W: Comparison of KTP, Thulium, and CO laser in stapedotomy using specialized visualization techniques: thermal effects. Eur Arch Otorhinolaryngol 2013, Epub ahead of print. Silverstein H, Rosenberg S, Jones R: Small fenestra stapedotomies with and without KTP laser: a comparison. Laryngoscope 1989;99:485–488. Hodgson RS, Wilson DF: Argon laser stapedotomy. Laryngoscope 1991;101:230–233. Rauch SD, Bartley ML: Argon laser stapedectomy: comparison to traditional fenestration techniques. Am J Otol 1992;13:556–560. Kiefer J, Tillein J, Ye Q, Klinke R, Gstoettner W: Application of carbon dioxide and erbium:yttrium-aluminumgarnet lasers in inner ear surgery: an experimental study. Otol Neurotol 2004;25:400–409. Ren DD, Chi FL: Experimental study on thermic effects, morphology and function of guinea pig cochlea: a comparison between the erbium:yttrium-aluminum-garnet laser and carbon dioxide laser. Lasers Surg Med 2008;40:407–414. Antonelli PJ, Gianoli GJ, Lundy LB, LaRouere MJ, Kartush JM: Early post-laser stapedotomy hearing thresholds. Am J Otol 1998;19:443–446. Gerlinger I, Toth M, Bako P, Nemeth A, Pytel J: KTP-laser stapedotomy with a self-crimping, thermal shape memory Nitinol SMart piston: 1 year follow-up results: how we do it. Clin Otolaryngol 2008;33:475–480. Pudel EI, Briggs RJ: Laser-assisted stapedotomy with a Nitinol heat-crimping prosthesis: outcomes compared with a platinum fluoroplastic prosthesis. Otolaryngol Head Neck Surg 2008;139:51–54. de Groot JC, Veldman JE, Huizing EH: An improved fixation method for guinea pig cochlear tissues. Acta Otolaryngol 1987;104:234–242. Broadhurst MS, Akst LM, Burns JA, Kobler JB, Heaton JT, Anderson RR, Zeitels SM: Effects of 532 nm pulsedKTP laser parameters on vessel ablation in the avian chorioallantoic membrane: implications for vocal fold mucosa. Laryngoscope 2007;117:220–225. Wong BJ, Neev J, van Gemert MJ: Surface temperature distributions in carbon dioxide, argon, and KTP (Nd:YAG) laser ablated otic capsule and calvarial bone. Am J Otol 1997;18:766–772. Ren D, Sun J, Wan G, Yang F, Shen F: Influence of carbon dioxide laser irradiation on the morphology and function of guinea pig cochlea. J Laryngol Otol 2005;119:684–692. Coker NJ, Ator GA, Jenkins HA, Neblett CR: Carbon dioxide laser stapedotomy: a histopathologic study. Am J Otolaryngol 1986;7:253–257. Lundy L: The effect of CO(2) and KTP laser on the cat saccule and utricle. Laryngoscope 2009;119:1594–1605. Radeloff A, Unkelbach MH, Tillein J, Braun S, Helbig S, Gstottner W, Adunka OF: Impact of intrascalar blood on hearing. Laryngoscope 2007;117:58–62.
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