Disclaimer: The information contained within the Grand Rounds Archive is intended for use by doctors and other health care professionals. These documents were prepared by resident physicians for presentation and discussion at a conference held at Baylor College of Medicine in Houston, Texas. No guarantees are made with respect to accuracy or timeliness of this material. This material should not be used as a basis for treatment decisions, and is not a substitute for professional consultation and/or peer-reviewed medical literature.Lasers in Otologic Surgery Today, I would like to first briefly discuss the history of science of laser and then briefly review the four common lasers that we use in otolaryngology including argon, KPT, YAG and CO2 lasers and then look at the use of laser in middle ear surgery with particular emphasison the stapedotomy and then the use of laser in inner ear surgery, and following with this some of the useful applications of laser in otology. The word “laser” is an acronym standing for light amplification by stimulated emission of radiation and as with much of the modern physics, the history of laser can be traced back to Albert Einstein back in 1917 when he formulated theory on the quantum mechanics. When he proposed that light is consisting quantumsof energy called protons and although Einstein himself did not develop laser, it is his theory of photo mechanics that really laid a foundation for the development of laser and he was also the first one to speculate that light could be generated by stimulating emission of radiation. In 1958, Townes and Schawlow at Bell Laboratories first made a calculation for laser and a couple of years later Theodore Maimen of Hughes aircraft company asked to produce the first laser, which was a ruby red laser at that time. In 1964 the YAG laser and argon laser were produced and in 1965, a year later CO2 laser was introduced and the use of laser in otolaryngology first began in 1972 when Dr. Jako and Polanyi at Boston University used a CO2 laser for the ablation of respiratory papillomatosis. All lasers are composed of three main components. The first component is the lasing medium, which could be either a solid or a gas. The second component is the excitation source or power source and the most of time it is a flash lamp and finally we have a set of mirrors, which provides the optical feedback. One mirror is a totally reflective mirror and the other mirror on the other side is partially reflective and partially transmitting, therefore, allowing the laser beam to transmit through this particular mirror. The generation of laser is illustrated in these two diagrams here. So, first we have the placement of a lasing medium within the resonant cavity bounded by the two mirrors and then what happens is the power source is used to stimulate the lasing medium and then the atoms within the lasing medium are promoted to a higher energy state. After a given period of time, the atoms start to decay back down to the ground state and in the process they release the energy that they have absorbed in the form of photons and what happens is some of these protons will get reflected back into the lasing medium by this totally reflecting mirror and therefore, amplify the lights and stimulate more atoms within the lasing medium and this is what we call the stimulated emission of radiation. Laser light is distinguished from ordinary light by four properties, it is monochromatic, meaning that one single color of wavelength of light emitted. It is coherent, meaning that individual light waves are in phase with each other and the laser beam is also collimated meaning that non-divergent parallelbeam of light is emitted, therefore, the laser beam can be focused down to a very small point and finally the laser’s high power, however, what we usually really refer to is the power density of laser because the absolute intensity of laser while may be pretty low, perhaps in a range of a few watts or tens of watts, it is the ability of the laser to really focus down to a single point and achieving a high energy density per centimeter square that really makes the laser a useful tool in surgery. When we actually use the laser, there are several parameters then we can control as a surgeon. The first is power, as we discussed earlier and second is a temporal profile, the laser can be used in either a continuous wave or a pulsed mode, therefore, allowing time between the individual pulses of laser for cooling and then the third is the duration and this is expressed in terms of fluence, which is equal to power density x time and that is equal to the units of joules per centimeter squared. Most of the commercial lasers today produce a Gaussian profile beam, meaning that the intensity peaks at a center and then gradually falls off towards periphery as you can see in this diagram here. This is also sometimes referred to as a fundamental mode of laser or a TEM00 mode of laser. The beam waves of laser can be controlled by varying the focal length of the lens and is directly proportional to that. Therefore, if you have a 400-mm lens you end up having a bigger laser spot compared to using a 250 mm lens. The characteristic of laser tissue interaction is characterized by four properties and these four properties always occur in conjunction with each other and first of all is transmission in which we either we want to maximize or minimize. For example, in the case of middle ear surgery, you want to minimize chance of laser transmitting through the perilymph down to the vestibule and also in inner ear surgery versus the ophthalmological surgery this is exactly the opposite, where you want to maximize transmission through the fluids and some of the laser can get down to the retina. The second property is reflection, which can be minimized by minimizing the angle of incidence and this can be achieved by directing the laser beam as perpendicular as possible to the surface cup contact. The third property is scattering, which happens when the laser gets down around the crater of the impact here and then what happens is this causes a larger than expected irradiated area and also limits the depth of penetration of laser as well. The laser is absorbed obviously by the tissue medium as well and what happens is it results in two main processes. The first of which is a photothermal process where the ablation of tissue results in generation of heat and the second of which is photoacoustic process usually happens when the laser impacts on the fluid medium for example like perilymph and then generate a sound or shockwave. The four common lasers that we use in otolaryngology are shown here on this electromagnetic spectrum, first of which is the argon and the KTP lasers, which are in the visible light range and then we have the YAG laser and CO2 laser, which are in the infrared range of the electromagnetic spectrum. The visible lasers include argon laser with the wavelength of 488 and 514 nanometers and also the potassium titanyl phosphate or the KTP lasers at the wavelength of 532 nanometers. Both of these lasers as you saw earlier are in the blue, green color region of the visible spectrum and they can be delivered either via microscope-mounted manipulator or a hand-held fiberoptic probe, neither of which is absorbed by a non-pigmented tissue and they are both transmitted rarely through a clear fluids such as perilymph and collagen and they are selectively absorbed by red hemoglobin and therefore, they can efficiently vaporize just a small amount of vascular tissues such as a granulation tissue, glomus tumor, etc. The infrared YAG lasers, the two main types are the neodymium yttrium-aluminum-garnet or Nd: YAG laser at the wave lengths of 1064 nanometers and then the erbium YAG lasers at the wavelength of 2940 nanometers and Nd: YAG laser is delivered via a hand-held fibrotic probe while the Er: YAG usually is delivered from a microscope-mounted manipulator. Since these are infrared lasers, they require the use of a aiming beam which is usually a krypton beam which are ideal for a collagen and bone vaporization, however, they have poor hemostasis properties secondary to the lack of lateral thermal spread of the laser preventing blood vessel coagulation. The CO2 laser is in the long infrared range at the wavelength of 10600 nanometers and they are delivered via a microscope-mounted micromanipulator system with a flexible arm, which consists of a series of 13 mirrors and lenses and also requires the use of invisible beam usually is a red Helium-Neon in this case. They can be delivered in continuous or pulsed mode. The CO2 laser has a very shallow depth of penetration with average tissue penetration depth of 0.03 nanometers and the CO2 lasers are well absorbed by water and the lateral thermal spread of CO2 laser around the crater allows it to keep a good hemostasis property. Now depending on the type of laser and the type of tissue, the amount of laser light that is being absorbed by the tissue varies and here we can see that the collagen is best absorbed by the infrared lasers, these being YAG and CO2 lasers and for water or perilymph is rapidly absorbed also by the infrared lasers. The concernhere is the heating of the perilymph due to the absorption of laser versus the perilymph is poorly absorbed by the visible lasers and in these cases what you worry about is the risk of damaging inner ear structures from the transmission of the laser through the perilymph down to inner ear structures. Bone is very well absorbed by argon YAG and CO2 lasers. It has a 100% absorption by the average thickness of human stapes bone 150 microns and there is only a 50% absorption by the argon and KTP lasers in the human bone. The history of laser in otology can be traced back to 1967 when Sataloff first conducted experimental use of neodymium laser on four humans otosclerotic footplates and this type of study done by Dr. Sataloff showed that discrete lesions in varying area and depthcan be created. Following that in 1972, Dr. Stahle and Hogberg irradiated inner ears of penguins with a ruby laser and saw that focal epithelial lesions in both the bony and membranous labyrinth was observed and they speculated at that time a biological effect of lasers namely thermal with possible generation of ultrasonic waves, which is the photoacoustic phenomenon and that we talked earlier. Here shows a diagram of the laser use by a Dr. Stahle and Hogberg in 1972. The clinical use of the laser in otology can be traced back to 1980 with Dr. Perkins when he used argon lasers and the microscope-mounted manipulators to vaporize the stapedial tendon, the posterior crus and to create a small fenestrain a rosette pattern as shown here in this figure on the stapes footplate of 11 patients with otosclerosis which show that laser stapedotomy can achieve excellent clinical outcome with a closure of air/bone gap to 0‑10 decibels in all patients at six weeks with minimal vestibular complaints. In the same year Dr. DiBartolomeo and Ellis also showed that using argon laser in various procedures such as tympanoplasty, myringotomy, lysis of adhesions, stapedectomy and external auditory canal osteoma excision. They showed satisfactory outcome in six out of seven tympanoplasty patients and nine out of ten stapedectomy patients at a three month followup time. The original laser stapedotomy as proposed by Dr. Perkinsinvolves the vaporization of stapedial tendon and posterior crus with laser, therefore, minimizing chance of footplate fracture and mobilization at the time of stapes super structureremoval. He reported using laser to create a small fenestration in a footplate enables better control in power delivery, therefore, resulting in improved precision and minimizes raumatic vibration into the vestibule. There is some controversy as to whether or not lasers stapedectomy or stapedotomy is superior to the conventional methods. McGee and others in 1983 conducted a study compared a 100 argon laser stapedotomy with 139 conventional small fenestra stapedotomy or stapedectomy. There is a comparable closure of air-bone gap to within 10 decibel at six months and also he showed comparable results in speech discrimination score to within 10% at six months. The study did show a statistically significant reduction in the length of stay in the laser group compared to that of the conventional method group. 70% of the laser group were discharged on postoperative day #1 versus that of 50% in conventional method group. He also reported subjectively that he observed fewer postoperative symptoms of vertigo in the laser group compared to that of conventional group. Compared to the primary laser stapedotomy the revision stapedectomy or stapedotomy offers more of a challenge to otologists. These are usually indicated when there are greater than 20 decibels of persistent conductive hearing loss in the speech frequencies and also when the presence of oval window perilymph fistula is suspected. There has been significant postoperative sensorineural hearing loss in these types of surgery, between 3-20% reported and up to 14% of these have been reported to be profound. The challenges of revision surgery involved the need to identify the ossicular chain mobility and the status of the oval window and needing to establish a precise relation of the failed prosthesis to the entrance of the vestibule. However, it is difficult to visualize often the depth and lateral margin of the oval window due to scar tissue, as well as surrounding granulation tissue and also palpation in this case can be misleading secondary to the lateralization of the neomembrane to the oval window floor. Laser has been shown to be particularly useful in meeting these challenges and there has been more of a consensus over the advantage of using laser in revision casescompared to the primary cases. Wiet et al in 1997 conducted a metanalysis comparing 1147 conventional revision stapedectomies to 170 laser revision stapedectomies and saw a statistically significant advantage with the laser group compared to that of conventional group. A postoperative air/bone gap closure to less than 10 decibels was seen in 64% of the laser group compared to 51% in the conventional group. Now, this study obviously has its limitations given the unequal sample size between the two groups. Also it does not discriminate among different laser types within the laser group. However, it does appear that laser can be used to safely vaporize the soft tissue scar oblitering the oval window in revisioncases and compared to conventional revision stapedectomy the laser appears to minimize prosthesis manipulation and therefore trauma to the vestibule. Given the advantage of laser, there has always been a concern regarding the use of laser in ear surgeries. Gantz and others first in 1982 reported the use of argon laser stapedotomy in eight cat ears and they saw perforation of three saccular membrane in direct line with the laser fenestration. Dr. Coker in 1986 conducted a similar experiment using CO2 laser stapedectomy in 11 cat ears with various laser settings and the group saw that photothermal injury was seen in the membranes of labyrinthsecondary to the laser heat dissipation in 10 out of the 11 ears and these effects included discoloration, reactive hemorrhage and also dehiscence of the utricular and saccularwall and seen in this figure is an example figure from the paper showing reactive hemorrhage in the saccularwall. However, it was also noted in the paper that since the clinical effect associated with the vestibularinjury such as dizziness and other phenomenon are rarely reported clinically that we should be cautious about extrapolating these animal research data to humans due to anatomic differences in the species. The two primary effects of absorption in laser as mentioned before are photothermal and photoacoustic and these have been further studied. Photothermal affects as reported by Dr. Coker in 1985 where a CO2 laser stapedectomy was performed on 14 cats and observed temperature elevation ranges from 0-4.4 degrees Celsius in the vestibule and directly correlates with the power and the duration of laser beam. It was concluded that the conversion of laser energy to heat in the vestibule represents the greatest potential risk to the inner ear. The photoacoustic effect has been studied by Gardner and others in 2002 where they used a CO2 laser on the human temporal bone model. They did not detect any significant sounds below the power of 4 volts in the continuous modes or 16 millijoules on the superpulse mode. However, on a high energy they did observe sounds greater than 90 decibels resulting from the vaporization of perilymph leading to a bubble burst and then generation of pressure wave or sounds. So the questionthen becomes which laser is the best one to use in laser stapedectomy and stapedotomy procedure. In the US the KTP, CO2 and argon laser are the most commonly used for these procedures. Vernick in 1996 conducted a prospective study of 100 consecutive laser primary stapedectomies comparing KTP and CO2 lasers and he did not see any statistical difference in the outcome measured by hearing results. Antonelli and others in 1998 conducted a similar type of study with a smaller sample and again did not see any significant difference in the cochlear function postoperatively. Buchman et al in year 2000 compared argon and the CO2 lasers and they also found there is a similar hearing results in frequency and complications between these two particular types of lasers. The erbium YAG is less frequently used here in the States, however, is much more commonly used in the Europe for laser stapedectomies and stapedotomies and most of the literature has been from Europeanliterature. There has been some initial concern regarding the temporary worsening of hearing and high incidence that was observed of a transient tinnitus with the use of erbium YAG laser in laser stapedectomy and stapedotomies. However, long-term followup data on these patients shows that there is no significant risk to inner ear function when the energy used on this laser is kept to the necessary minimum. Therefore, it appears that there is comparable safety and efficacy between these four commonly used types of lasers and the choice depends more on personal training, preference and the laser availability. Now laser has been used in other types of middle ear surgery as well. In chronic ear surgery laser is use to divide adhesion with reduced mechanical trauma and it also offers the chance to simultaneously vaporize and coagulate the cholesteatoma matrix. Thedinger in 1990 reported data of 277 chronic ear surgery cases mostly tympanomastoidectomies. 103 of these were done with KTP laser and he found there was a comparable postoperative results in the hearing outcome and the complication rates between the laser and non-laser group. Laser has also been extended to use in the inner ear surgery as well particularly in treatment of benign paroxysmal positional vertigo. The pathophysiology of which is thought to be due to loosened otolithin the posterior semicircular canal as shown in this figure. Money and Scott back in 1962 first showed that occlusion of posterior semicircular canal in a cat causes loss of reactivity to rotational motion. Parnes and McClure later in 1990 showed that mechanical occlusion of the posterior semicircularcanal with drilling and bone wax in humans can give a good control over BPPV symptoms. Anthony in 1991 conducted a study using laser to achieve posterior canal occlusion, which he termed labyrinth partitioning where he bluelined the posterior semicircular canal and then lased it with argon laser to create fiber bands. He theorized that this results in the coagulation of semicircular canal membrane coating, therefore, causing a contraction and eventually a constriction occlusion of the membranous semicircular canal and henceforth resulting in a trapped otolyth. He saw the resolution of BPPVsymptoms in all 14 patients in the study 8 weeks postop. However, he did see a transient sensorineural hearing loss in six patients and permanent hearing loss in one. He also observed that location of the lasing did notseem to affect the outcome and his results are since been reproduced by others as well. Some of the other laser applications include use of laser for malleus, incus, and fixation release. Seidman and Babu in 2004 conducted study where 20 patients with bony effusion was released with a KTP laser and resulting in a good closure air/bone gap. They reported that there is an advantage over incus intrapositional graft in the treatment of malleus incus fixation. CO2 laser has also been used in myringotomy as well, the OtoLam hand-held CO2 laser was introduced in 1997 for this use and however, there has been no significant advantage over traditional myringotomy and PE tubes for otitis media with effusion using OtoLam compared to the traditional methods. Laser has also been extended to use in tumor ablation as well such as acoustic neuroma, bone tumor and other skull-based tumors. However, the advantage of laser in these cases had been limiteddue to the slow rate of ablation and also the adjacent tissue damage from the photothermal energy spread. Some of the future applications of laser for example involve the use of laser to irradiate the basilar membrane where a pulse-dye laser was used to irradiatea guinea pig cochlea resulting in change of collagen organization within the basilar membrane and therefore results in the change within the basilar membrane stiffness and therefore affects cochlear tuning by shifting the resonant frequency and this has a potential of therapeutic application such as high frequency cochlear hearing loss. Ultrashort pulse laser is another new laser that is being developed and for these types of lasers, the laser pulsed duration are in ultra short range, in the range of microseconds or trillionth of a second. When a laser pulse is this short, it actually changes the laser tissue interacting physics. So instead of molecules absorbing the lasers, in these cases are electrons are actually what is absorbing the laser energy and what this means is that ablation of tissue becomes independent of the tissue type and there results in minimal to no surrounding mechanical or thermal trauma and shown here is a scanning electron micrograph of the lesion impact on the human incus bone from the ultra short pulse laser. In conclusion, the laser like any other surgical tool is capable of performing some tasks with greater precision and less trauma and the clinical observations in humans suggested that laser applications in the middle and inner ear surgery can cause minimal trauma and physiological disturbance when it is applied within the recommended settings. Finally successful use and the choice of laser type depend on the operator technique experience of knowledge in addition to the type of laser that is used. Case Presentation: V.C. is a 44-year-old female who presented to the Methodist Hospital Otology Clinic on 3/9/04 for evaluation of right-sided hearing loss. She reports progressive hearing loss in the right ear for the past 13 years that had recently worsened. She had previously been given the diagnosis of right otosclerosis by an outside otolaryngologist but she was not interested in intervention at that time. She denies any history of otitis media, head trauma, vertigo, or tinnitus. She denies any significant past medical history and is not taking any medication. Family history is notable for paternal hearing loss of unknown etiology. On otoscopic exam her external auditory canal and tympanic membrane are clear bilaterally. The visualized portion of the malleus is mobile. There is no evidence of promontory hyperemia. The rest of the head and neck exam is within normal limits. The audiogram performed on the day of visit shows severe mixed hearing loss with air-bone gap of 30 – 40 dB across all frequencies for the right ear. The left ear is notable for a mild SNHL. Speech audiometry reveals good speech discrimination bilaterally. Acoustic immittance measures show normal tympanogram with absent acoustic reflexes. She was given the working diagnosis of right otosclerosis. Treatment options including hearing aids were discussed with patient who wished to proceed with right middle ear exploration with possible CO 2 laser stapedotomy. Intra-operative palpation of the ossicular chain revealed mobile malleus and incus with fixed stapes footplate. CO 2 laser was used to vaporize the stapedius tendon and posterior crus. A 0.6 mm fenestration on the footplate was created with both laser and perforator. A Causse piston was then used for reconstruction with the temporalis fascial graft placed over the oval window. 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A comparison of the results of KTP and CO2 laser stapedotomy. Am J Otol 1996;17:221-224. Vrabec JT, Coker NJ. Stapes surgery in the United States. Otol Neurotol 2004;25:465-469. Wenzel GI, Pikkula B, Choi CH, Anvari B, Oghalai JS. Laser irradiation of the guinea pig basilar membrane. Lasers Surg Med 2004;35:174-180. Wiet RJ, Kubek DC, Lemberg P, Byskosh AT. A meta-analysis review of revision stapes surgery with argon laser: Effectiveness and safety. Am J Otol 1997;18:166-171. 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. Yung MW. A study of the intra-operative effect of the Argon and KTP laser in stapes surgery. Clin Otolaryngol Allied Sci 2002;27:279-282. Grand Rounds Archive | Department Home page BCM Public | BCM Intranet | Privacy Notices | Contact BCM | BCM Site Map | ©2001-2006 Baylor College of Medicine |