| 1. |
- Hansson, Annika, 1979-
(författare)
-
The effects of plasminogen deficiency on the healing of tympanic membrane perforations
- 2007
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The healing of tympanic membrane (TM) perforations is a complex wound healing process including inflammation, migration of keratinocytes and tissue remodelling. Most TM perforations in human heal spontaneously, however some perforations become chronic, and the reason to why is still largely unknown. In cutaneous wound healing plasminogen (plg) has been shown to play an important role. Plg is converted into the protease plasmin regulated by two plasminogen activators (PA), urokinase type PA (uPA) and tissue-type PA (tPA). The aim of the present thesis was to evaluate the role of plg in healing of TM perforations, both in vivo and in vitro. The main objectives were to determine the healing capacity of the TM, the involvement of keratinocytes, fibrin(ogen) and inflammatory cells in the healing process. The studies were performed in plg deficient and uPA deficient mice, with littermate wild type (wt) mice as controls It was shown that myringotomies of the TMs in plg deficient mice still remained open 143 days following a perforation. The wound area was characterized by an abundant recruitment and accumulation of inflammatory cells; mainly macrophages and neutrophils, an arrested keratinocyte migration and a fibrin deposition covering the surface of the TM. The TM perforations in the wt mice all healed within 11 days. Interestingly, the myringotomies of the plg deficient mice could be closed by reconstitution with systemic injections of plg, whereas injections of PBS had no affect on the healing. To characterize mechanisms involved in the development of persistent TM perforations in plg deficient mice after a myringotomy the early inflammatory response during the first 48 hours was studied. The recruitment and accumulation of inflammatory cells in the perforated TMs was found to be similar between the plg deficient and the wt mice. Myringotomized TMs in uPA deficient mice healed similar to perforations of wt controls. Neither did the keratinocyte migration nor the occurrence of inflammatory cells differ between these genotypes. In the in vitro experiments TMs from plg deficient and wt mice, were dissected out, perforated and cultured in absence or surplus of plg. A decrease in perforation size was seen in all groups regardless of genotype or amount of plg in the medium. In conclusion, the present studies show: • Plg is essential for the healing of TM perforations in mice. • The altered healing process after a myringotomy in plg deficient mice involves a disturbed keratinocyte migration, a massive deposition of fibrin and an abundant accumulation of inflammatory cells in the wound area. • Plasminogen deficiency does not alter the early inflammatory response, following a myringotomy. • Deficiency of uPA does not influence the healing of TM perforations. • During in vitro conditions healing of TM perforations is initiated irrespectively of genotype of the explant (plg deficient or wt) or supply of plg. The increased knowledge of the involvement of plg in the healing of TM perforations may open therapeutical possibilities in the treatment of chronic TM perforations in humans.
|
|
| 2. |
- Rönnblom, Anton, 1981-
(författare)
-
Middle ear mechanics : using temporal bone experiments to improve clinical methods
- 2022
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- BackgroundThe middle ear transmits and amplifies sound vibrations from the tympanic membrane via three ossicles to the inner ear. Moreover, it contains two muscles, the stapedius muscle (SM) which protects the inner ear from loud noise, and the tensor tympani (TT) whose function is still debated. The majority of hearing loss caused by disruption of the ossicular chain is a result of chronic otitis media and cholesteatoma. Variations in pathology, surgical skill and individual healing conditions make objective evaluation of ossicular replacement prosthesis in vivo difficult. Prosthesis development and the investigation of trauma mechanisms are affected by the same challenges. With few changes postmortem, the temporal bone (TB) is suitable for studies of middle ear mechanics and allows a controlled environment. Equally important, it allows theories to be tested without patient risk. In this thesis we used human TBs to find factors associated with optimal sound transfer in the two types of ossicular replacement prostheses. Furthermore, we investigated the mechanism and forces involved in rare cases of isolated malleus fractures. We also investigated the morphology, fibre phenotype composition and vascularization of the human middle ear muscles in order to better understand their roles.Materials and MethodsLaser Doppler vibrometry (LDV) is an established method of measuring sound transfer in human TBs. We have further developed a surgical model that allows testing of a wide range of prostheses and their placements. In Paper I beneficial factors in partial ossicular replacement prostheses (PORPs) were tested. In Paper II we evaluated different types of total ossicular replacement prostheses (TORPs) including an experimental prosthesis inspired by the single ossicle system of birds. In Paper III the negative pressure trauma typically associated with isolated malleus fractures, produced by a finger being withdrawn from a wet ear canal after a shower or bath, was simulated in TBs. Based on measurement from control persons the forces involved were calculated and measured in models developed for this purpose. The force of the TT was estimated by comparing its cross-sectional area and fibre composition with those reported in published references. In Paper IV we used immunohistochemical, enzyme histochemical, biochemical and morphometric techniques on TT, SM and human orofacial and limb muscle control samples.ResultsOf the prostheses, PORPs and TORPs with lateral contact with both the tympanic membrane and the malleus handle performed best, and TORPs with distal malleus contact proved superior. Our experimental bird-type prosthesis was the most stable in such placement and performed equally to or better than other prostheses. In Paper III the application of negative pressure via the ear canal did not fracture the malleus shaft, with only a passive counterforce from support structures, although the force exceeded that required for a malleus shaft fracture. We estimate that when adding calculated counteracting forces from the TT muscle, sufficient force is generated to cause a malleus fracture. Both human middle ear muscles are predominated by fast type 2 fibres, and have rich capillarization and nerve innervation compared with limb muscles. Muscle spindles were found in the TT but not the SM.ConclusionsWhere possible, an ossicular replacement prosthesis should be placed to allow distal contact with both the TM and the malleus handle. The sound transfer capabilities combined with the stable placement of our experimental prostheses suggest room for improvement. The combination of a negative pressure created by a finger being withdrawn from a wet ear canal and a simultaneous counteracting reflexive force by the TT muscle was found to be sufficient to cause an isolated malleus fracture. The finding of muscle spindles in TT, but not in SM, suggests a difference in regulatory control; furthermore, it indicates that the TT can be activated by a sudden stretch reflex as described in the malleus fracture trauma. The human middle ear muscles have a highly specialized muscle morphology, which is more similar to orofacial than to limb muscles. The fibre phenotype composition suggests capability for fine-tuned, fast, strong and relatively sustainable contractions. Based on fibre type patterns the TT is among the fastest muscles in the human body.
|
|
| 3. |
- Berling Holm, Katarina
(författare)
-
The Chorda Tympani Nerve : Role in Taste Impairment in Middle Ear Disease and after Ear Surgery
- 2017
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The chorda tympani nerve, also known as the taste nerve, runs uncovered through the middle ear cavity, a localization that exposes the nerve to pathological processes and surgical trauma in the middle ear. People operated on for otosclerosis tend to complain more about postoperative taste disturbances than those operated on for chronic otitis media. It has been suggested that this difference may be explained by gradual deterioration of chorda tympani nerve function caused by chronic otitis media infection and that further impairment caused by surgery is less noticeable in these patients.This thesis aimed to evaluate the function of the chorda tympani nerve, the effects of middle ear disease on taste and complications resulting from ear surgery for chronic otitis media or otosclerosis. This information will help to improve the ear surgeon’s ability to predict the prognosis of iatrogenic taste disturbances in patients with middle ear disease and after ear surgery.Taste was assessed using electrogustometry and the filter paper disc method before and after surgery for chronic otitis media or otosclerosis. Patients also completed questionnaires about symptoms and quality of life. The status of the chorda tympani nerve upon surgical opening of the ear and grading of the trauma to the nerve during the surgery were recorded. The ultrastructure of the chorda tympani nerve from healthy ears and from ears with chronic otitis media was examined. Electrogustometry and the filter paper disc method were evaluated.The results of electrogustometry and the filter paper disc method were highly reproducible, although their correlation was moderate. Patients with chronic otitis media, patients with a more traumatized nerve, female patients and younger patients were more likely to report postoperative taste disturbances. Most of the patients recovered their taste after 1 year. The quality of life study showed only minor changes after surgery. Electron microscopic observations of nerves from ears with chronic otitis media showed signs of structural degeneration, although signs of regeneration, such as sprouting were also observed. This results may explain the recovery of taste postoperatively and indicate that the nerve should be carefully handled during surgery.
|
|
| 4. |
- Niklasson, Anders, 1967-
(författare)
-
Malleus fracture : experimental and clinical aspects
- 2019
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Background: Patients with malleus fractures are described as rare in the literature. The cause of these fractures are most commonly trauma and digital manipulation of the ear canal, while in some cases the causes are unknown. At our clinic we record one new case every year, which leads to an incidence of approximately 40-50 new cases every year in Sweden. Different treatments have been proposed for this condition. However, since the condition is rare, no consensus has been reached regarding the best treatment. Additionally, it remains unclear whether malleus fractures can heal.Aim: To get a deeper understanding of how malleus fractures occur, how they should be treated surgically, and if the malleus shows any sign of bone healing.Materials and methods: Paper I. We carried out both a retrospective study of the medical records of nine Swedish patients with isolated malleus fractures, and a literature review of this condition. Symptoms, clinical findings and patients’ history were collected.Paper II. Ossiculoplasty on human temporal bones was performed in the presence of a malleus fracture. We developed a surgical model from freshly frozen human temporal bones, and we performed Laser Doppler vibrometry (LDV) measurements on this model both before and after ossiculoplasty.Paper III. We performed ossiculoplasties with different types of partial ossicular replacement prostheses (PORP) on human temporal bones and we measured the results with LDV.Paper IV. We performed an in vivo animal study on Merino sheep, in which we produced isolated malleus fractures. We then compared the bone healing of these fractures with that of the nasal bone and the mandible. Bone healing was detected with micro-CT.Results: Paper I. The most common cause of isolated malleus fractures was found to be a so-called “digital” trauma, which occurred when the patients had removed a finger from the wet ear canal after bath. The hearing loss was occasionally accompanied by tinnitus and transient pain. Pneumatic otoscopy and tympanometry showed a hypermobile tympanic membrane, while audiometry showed a conductive hearing loss that increased towards higher frequencies.Paper II. Our LDV measurements indicated that fixation of an isolated malleus with bone cement may give the best results after surgery.Paper III. The best LDV measurements were obtained when ossiculoplasty was done using a PORP in lateral contact with both the tympanic membrane and the malleus handle.Paper IV. In our animal study we found no signs of bone healing at micro-CT four weeks after producing the malleus fractures. In contrast, both the nasal bone and the mandible showed bone healing. This indicates that the bone healing properties of the ossicles probably differ from those of other bones in the body.Conclusion: Digital trauma is the major cause of isolated malleus fractures. Pneumatic otoscopy and tympanometry showed a hypermobile tympanic membrane, while audiometry showed a conductive hearing loss increasing towards the higher frequencies. We developed a method to employ freshly frozen human temporal bones and we used LDV for detecting optimal results. This method allows to evaluate and develop otosurgery, aimed to restore hearing after an interrupted ossicular chain. The animal study indicates that malleus fractures will not heal spontaneously.
|
|
