Histopathology update: otomycosis

Analysis of a purely conductance-based stochastic nerve fibre model as applied to compound models of populations of human auditory nerve fibres used in cochlear implant simulations

The study presents the application of a purely conductance-based stochastic nerve fibre model to human auditory nerve fibres within finite element volume conduction models of a semi-generic head and user-specific cochleae. The stochastic, threshold and temporal characteristics of the human model are compared and successfully validated against physiological feline results with the application of a mono-polar, bi-phasic, cathodic first stimulus. Stochastic characteristics validated include: (i) the log(Relative Spread) versus log(fibre diameter) distribution for the discharge probability versus stimulus intensity plots and (ii) the required exponential membrane noise versus transmembrane voltage distribution. Intra-user, and to a lesser degree inter-user, comparisons are made with respect to threshold and dynamic range at short and long pulse widths for full versus degenerate single fibres as well as for populations of degenerate fibres of a single user having distributed and aligned somas with varying and equal diameters. Temporal characteristics validated through application of different stimulus pulse rates and different stimulus intensities include: (i) discharge rate, latency and latency standard deviation versus stimulus intensity, (ii) period histograms and (iii) interspike interval histograms. Although the stochastic population model does not reduce the modelled single deterministic fibre threshold, the simulated stochastic and temporal characteristics show that it could be used in future studies to model user-specific temporally encoded information, which influences the speech perception of CI users.

Pathologic Findings of the Cochlea in Labyrinthitis Ossificans Associated with the Round Window Membrane

OBJECTIVE

To quantitatively demonstrate and classify the histopathologic changes in the cochlea of the human temporal bones with labyrinthitis ossificans (LO).

STUDY DESIGN

Comparative human temporal bone study.

SETTING

Tertiary academic medical center.

SUBJECTS AND METHODS

We compared 23 temporal bone specimens from 19 deceased donors with LO associated with the round window membrane (RWM) and 27 age-matched specimens from 20 deceased donors without any otologic diseases. We focused on the location of LO in the inner ear, the intensity of endolymphatic hydrops, the number of spiral ganglion cells and cochlear hair cells, and the areas of the stria vascularis and spiral ligament. In addition, we created a new pathologic grading system for temporal bone specimens from deceased donors with LO associated with the RWM.

RESULTS

We most often observed LO in the scala tympani of the basal cochlear turn. In the LO group (as compared with the control group), the intensity of endolymphatic hydrops was significantly increased; the number of spiral ganglion cells was significantly decreased in all segments; the loss of outer and inner hair cells was significantly increased in all turns of the cochlea; the atrophy of the stria vascularis was significantly greater in all turns of the cochlea; and atrophy of the spiral ligament was significantly greater in the basal and middle cochlear turn.

CONCLUSION

LO was associated with significant cochlear damage (to the spiral ganglion cells, cochlear hair cells, stria vascularis, and spiral ligament) and with increased intensity of endolymphatic hydrops.

Fungal infections of the ear in immunocompromised host: a review

Otomycosis is a fungal infection of the external ear; middle ear and open mastoid cavity.1 Meyer first described the fungal infection of the external ear canal in 1884. External ear canal has an ideal warm humid environment for the proliferation of fungus.2 Although this disease is rarely life threatening, it can presents a challenging and frustrating situation for the otologist and patients due to long term treatment and high rate of recurrence.3 Otomycosis is seen more frequently in immunocompromised patients as compared to immunocompetent persons. Recurrence rate is high in immunocompromised patients and they need longer duration treatment and complications are more frequent in immunocompromised patients.In the recent years; opportunistic fungal infections are gaining greater importance in human medicine as a result of possibly huge number of immunocompromised patients.4 In immunocompromised patients, it is important that the treatment of otomycosis be vigorous, to minimize complications such as hearing loss, tympanic membrane perforations and invasive temporal bone infection.5 Fungal cultures are essential to confirm the diagnosis.Hematological investigations play a very important role in confirming the diagnosis and immunity status of the patients. In diabetic patients with otomycosis, along with antifungal therapy, blood sugar levels should be controlled with medical therapy to prevent complications.

Cutaneous infections due to opportunistic molds: uncommon presentations

Molds are quite more often suspected as pathogens by the public than by the medical care community. Molds may, however, cause serious medical problems, and mold infections can develop incognito. Among the mycoses caused by opportunistic molds, alternariosis and fusariosis together with aspergillosis are of particular importance. They are more common than other groups with pathological characteristics. The aim of our presentation is to demonstrate the important role of common molds as causative agents in skin and ear infections. The clinical picture, etiology and pathogenesis, diagnosis and treatment, and course and prognosis of cutaneous infections will be given. The spectrum of clinical symptoms ranges from eczemalike lesions to chronic erythematous, verrucous lesions of the skin or multiple acute infiltrations of the dermis, occasionally forming abscesses. The mycologic direct preparation of the specimens, particularly with optical brighteners, and a histological examination of a skin biopsy are strongly recommended. The outbreak of cutaneous infections is triggered by weakened host defense mechanisms. A review of the literature regarding immunosuppressed and immunocompetent patients will be given.

Mycological and histological investigations in humans with middle ear infections

The aim of our investigations was to characterize fungal colonization of the ear in immunocompetent patients. From 1993 to 2000, 128 patients supposed to suffer from otomycosis were included. Mycological examination conducted by direct microscopy and fungal cultures was performed on 139 specimens. Among these, 115 patients suffered from chronic otitis media with persisting tympanum perforation and otorrhea. A further 13 patients had clinical signs of an otitis externa only. Out of 139 samples, fungi were identified in the auditory canal (n = 54), on the tympanic membrane (n = 5), and in the middle ear (n = 5). Two-thirds were as moulds and one-third yeasts. The dominating species were Aspergillus niger and Candida parapsilosis. Samples from 15 patients supposed to have mastoiditis or cholesteatoma were examined histologically. Fungal hyphae were observed in the middle ear cavity and/or between horny lamellae of cholesteatoma in four patients. In the middle ear of immunocompetent patients chronic-hyperplastic (polypoid) inflammation was detected with increased production of mucus, which probably promotes colonization by pathogenic fungi in the middle ear as well as in the auditory canal. Invasive fungal growth into the subepithelial connective tissue was not observed.

[Histologic studies on otomycosis]

Fungal infections of the ear are mostly described as mycoses of the auditory canal. The aim of our investigations was to find out how fungi colonize the ear in immunocompetent patients. In the years from 1993 to 2000, 128 patients suspected of having otomycosis were examined. Of these 115 patients suffered from chronic otitis media with persisting tympanum perforation and otorrhea. A further 13 patients had clinical signs of otitis externa only. In 54 out of 139 samples, fungi were found in the auditory canal, in five on the tympanic membrane, and in five in the middle ear. Two-thirds were isolated as moulds and one-third as yeasts. Dominating species were Aspergillus niger and Candida parapsilosis. Samples of 15 patients suspected of having mastoiditis or cholesteatoma were examined histologically. Fungal hyphae were observed in the middle ear cavity and/or between horny lamellae of cholesteatoma in 4 patients. In the middle ear of immunocompetent patients chronic-hyperplastic (polypous) inflammation was detected with increased production of mucus, which probably promotes the colonization with pathogenic fungi as in the middle ear just like in the auditory canal.