Eur Arch Otorhinolaryngol DOI 10.1007/s00405-014-2884-y

OTOLOGY

Endolymphatic sac involvement in bacterial meningitis Martin Nue Møller • Christian Brandt • Christian Østergaard • Per Caye-Thomasen

Received: 11 November 2013 / Accepted: 3 January 2014 Ó Springer-Verlag Berlin Heidelberg 2014

Abstract The commonest sequelae of bacterial meningitis are related to the inner ear. Little is known about the inner ear immune defense. Evidence suggests that the endolymphatic sac provides some protection against infection. A potential involvement of the endolymphatic sac in bacterial meningitis is largely unaccounted for, and thus the object of the present study. A well-established adult rat model of Streptococcus pneumoniae meningitis was employed. Thirty adult rats were inoculated intrathecally with Streptococcus pneumoniae and received no additional treatment. Six rats were sham-inoculated. The rats were killed when reaching terminal illness or on day 7, followed by light microscopy preparation and PAS-Alcian blue staining. The endolymphatic sac was examined for bacterial invasion and leukocyte infiltration. Neither bacteria nor leukocytes infiltrated the endolymphatic sac during the first days. Bacteria invaded the inner ear through the cochlear aquaduct. On days 5–6, the bacteria invaded the endolymphatic sac through the endolymphatic duct

M. N. Møller (&)  P. Caye-Thomasen Department of Oto-Rhino-Laryngology, Head and Neck Surgery, University Hospital Rigshospitalet/Gentofte, 2100 Copenhagen, Denmark e-mail: [email protected] C. Brandt Department of Infectious Diseases, Copenhagen University Hospital Hvidovre, Kettega˚rd Alle 30, 2650 Hvidovre, Denmark C. Østergaard Department of Clinical Microbiology, Copenhagen University Hospital Hvidovre, Kettega˚rd Alle 30, 2650 Hvidovre, Denmark P. Caye-Thomasen The Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark

subsequent to invasion of the vestibular endolymphatic compartment. No evidence of direct bacterial invasion of the sac through the meninges was found. Leukocyte infiltration of the sac occurred prior to bacterial invasion. During meningitis, bacteria do not invade the endolymphatic sac through the dura, but solely through the endolymphatic duct, following the invasion of the vestibular system. Leukocyte infiltration of the sac occurs prior to, as well as concurrent with bacterial invasion. The findings support the endolymphatic sac as part of an innate immune defense system protecting the inner ear from infection. Keywords Bacterial meningitis  Inner ear  Mb Me´nie`re  Innate immunity

Introduction Inner ear dysfunction following bacterial meningitis is well known. Thus, the most common long-term sequela after this disease is sensorineural hearing loss, affecting up to 54 % of survivors [1, 2]. Vestibular dysfunction often coexists, leading to vertigo and/or balance problems, which are prevalent in up to at least 15 % of patients [1, 3, 4]. The mechanism behind vestibular end organ damage in bacterial meningitis is unknown, although arguably the same as for the frequently occurring hearing loss. The major cause of meningitis-associated hearing loss is cochlear infiltration of inflammatory cells and their production and release of cytotoxic mediators, causing damage to the organ of Corti and spiral ganglion neurons [5–9]. In addition, direct bacterial toxicity may facilitate cochlear damage [10]. Similarly, these factors may lead to damage to the vestibular system, which is supported by reports on vestibular dysfunction, as well as inflammatory

123

Eur Arch Otorhinolaryngol

involvement of the vestibular end organs in clinical and experimental meningitis [1, 3–7, 11, 12]. Immunological studies suggest that the endolymphatic sac is the primary immunological organ of the inner ear [13, 14], representing a reminiscent of mucosa associated lymphoid tissue (MALT) [15, 16]. As such, the endolymphatic sac may provide the first line defense against invading pathogens in the inner ear, subsequently contributing to a secondary immunologic response. However, the involvement of the endolymphatic sac in inner ear infection is poorly understood. A few studies have shown inflammation in the endolymphatic sac [5, 6] in association with meningitis. Whether bacteria actually enter the sac during meningitis is unknown, as is the response of the sac to bacterial invasion of the other compartments of the inner ear. Since direct evidence of bacterial invasion and a corresponding response of the endolymphatic sac are currently lacking, it is unclear whether the previously demonstrated inflammation of the sac occurs secondary to the bacterial invasion from the meninges or the bloodstream, or as a mere bystander phenomenon secondary to adjacent meningeal inflammation. As for the other parts of the vestibular system, bacterial invasion and/or inflammation of the endolymphatic sac is plausibly related to the malfunction encountered at post-meningitic follow-up in the clinic, i.e., vertigo and imbalance. Using a well-established experimental model of pneumococcal meningitis, this report presents an evidence of bacterial invasion of the endolymphatic sac during meningitis. The routes of bacterial invasion, the pathways and temporary pattern of bacterial spreading and the inflammatory response of the endolymphatic sac and vestibular end organs are demonstrated.

Materials and methods The experimental protocol was based on a well-established model of pneumococcal meningitis [17, 18]. The experimental protocol was approved by the Danish Animal Research Inspectorate (Dyreforsoegstilsynet), license no. 1998/561-62. Adult rat model of meningitis A total of 36 adult rats were included in the study. The adult rat model was chosen because the histopathological brain damage observed in this model resembles the findings in human meningitis more accurately than other models of meningitis. Different serotypes were used to determine potential serotype-related differences in inner ear invasion.

123

Before inoculation, all strains were passed several times through CSF, to obtain maximum virulence of the pathogen. A frozen stock of the bacteria was thawed and grown on 5 % blood agar plates for 18 h, suspended in beef broth, and grown to mid-log phase. The bacteria were washed, centrifuged (3,5099g, 4 °C for 10 min) and diluted in cold saline to a final concentration of 0.9–2 9 105 CFU/ml, as confirmed by quantitative cultures. On the day of infection, young adult male Wistar rats (*200 g) were anesthetized subcutaneously with midazolam (1.88 mg/kg; Dormicum; Roche AG) and a combination of fentanyl and fluanisone (0.12 mg/kg; Hypnorm; Janssen Pharmaceutica NV) and infected with one of the serotypes (serotype 1, n = 10, (strain 277/99, Statens Serum Institute, Copenhagen, Denmark [SSI]); serotype 3, n = 10, (strain 68034, SSI); or serotype 9V, n = 10, SSI), by intrathecal inoculation of 30 lL of the bacterial suspension through the cisterna magna. After the bacterial inoculation, the rats were evaluated clinically three times daily and given 2.5 mL of isotonic saline during periods of severe illness, to prevent dehydration. The clinical score was a modification of the method of Leib et al. [19]. and was graded as follows: 0, normal activity; 1, minimal ambulatory activity (turns upright in \5 s); 2, turns upright within 30 s; 3, does not turn upright; 4, spontaneously lying on the back or side; and 5, terminal illness (cyanosis, apnea, coma, and/or opisthotonus/seizures). When terminal illness occurred, a CSF sample was obtained, and rats were killed with an intravenous injection of pentobarbital (200 mg/mL) and perfused with 1.5 % paraformaldehyde (PFA) through the left ventricle of the heart. Rather than studying the pathology at predefined intervals, this approach was chosen to mimic the clinical setting and allow comparability to human temporal bones harvested from patients succumbing to meningitis. Surviving rats and sham-inoculated rats were observed for a total of 166 h, then killed with an injection of pentobarbital after CSF samples were obtained, then perfused with 1.5 % PFA, as described above. CSF was analyzed for bacterial concentration and white blood cell (WBC) count, to confirm meningitis. Preparation for light microscopy After decapitation, the cranium was stored in paraformaldehyde 1.5 % for at least 1 week, followed by right temporal bone dissection and decalcification for 4 weeks in ethylenediaminetetraacetic acid (EDTA) 10 %. The inner ear was subsequently split in two parts by an intended midmodiolar transection of the cochlea. The transection was performed by aligning the scalpel along the axis of Eustachian tube, through the tympanic orifice and the cochlear apex, and cutting towards the center of the cochlear base in one careful

Eur Arch Otorhinolaryngol Fig. 1 In rats infused with sterile saline (sham group), cells occur within the endolymphatic sac in some cases. a Low power micrograph of the posterior semi-circular canal (arrow), as well as the intraosseous and extraosseous part of the endolymphatic sac (framed areas). Bar 200 lm. b Higher magnification of area framed in a, displaying the extraosseous part of the ES, with no evidence of cells in the lumen (asterisk). Bar 20 lm. c Higher magnification of framed area in a, displaying the intraosseous part of the ES, with no cells in the lumen (asterisk). Bar 20 lm. d Low power micrograph of the posterior semi-circular canal (arrow) and a large endolymphatic sac (framed areas). Bar 200 lm. e Higher magnification of the area framed in d. A possible leukocyte is observed (arrow) within the lumen of the ES (asterisk). Bar 20 lm. f Higher magnification of the framed area in d. Cells are observed (arrow) within the lumen of the ES (asterisk). Bar 20 lm

movement. This was followed by paraffin embedding, serial 5–10 lm sectioning, and periodic acid Schiff (PAS)-alcian blue staining. PAS-alcian blue staining is well documented for the identification of bacteria with a capsule containing acid mucopolysaccharides, such as Streptococcus pneumoniae. The stained bacteria appear blue to bluish-green [20]. Light microscopy and photo-documentation A Zeiss Axio Imager M1 microscope was used for light microscopy and a Zeiss Axiocam HRc camera for photodocumentation, using Zeiss Axiovision software for digital image processing.

Results In all but the six sham-inoculated animals (N = 6), meningitis was verified by clinical appearance, as well as CSF pleocytosis and a positive CSF culture for pneumococci. According the occurrence of terminal illness, serotype 3 inoculated rats (N = 10) were killed after 27, 28, 30, 38, 43 (n = 2), 46 (n = 2), 67 and 91 h, respectively. Serotype 1 inoculated rats (N = 10) were killed after 57, 59 (n = 2), 64, 67 (n = 2), 75, 77 and 166 (n = 2) hours, respectively. Serotype 9V inoculated rats (N = 10) were killed after 57, 66, 90 and 138 (n = 7) hours, respectively.

123

Eur Arch Otorhinolaryngol Fig. 2 Overview of the temporal pattern of bacterial invasion and inflammation in the rat endolymphatic sac (ES) during pneumococcal meningitis. a Micrograph of the endolymphatic sac from a serotype 3-inoculated rat on day 2. Note the absence of bacteria and the initial inflammation (arrow) in the lumen of the ES (asterisk). Bar 40 lm. b Micrograph of the ES from a serotype 1-inoculated rat on day 3. Peri-saccular (horizontal arrow), as well as saccular (vertical arrow) inflammation occur at this stage. Bacteria remain absent from the lumen of the ES (asterisk). Bar 40 lm. c Micrograph of the ES from a serotype 9V inoculated rat on day 6. Surrounding massive volumes of pneumococci (horizontal arrow) are abundant leucocytes (vertical arrow), within the lumen of the ES (asterisk). Bar 40 lm

Routes and temporal pattern of pneumococcal invasion of the vestibular system and endolymphatic sac Bacteria may invade the endolymphatic sac directly from adjacent, infected meninges, alternatively indirectly, through the other naturally occurring openings or soft tissue connections between the intracranial space and the inner ear, i.e., the cochlear aqueduct and the internal auditory canal. In addition, invasion may occur through hematogenous spread of bacteria. In the sham group, no bacteria were observed. However, cells in the luminal space of the endolymphatic sac were seen in three of six animals (Fig. 1). The morphological features of these cells were unspecific and a determination of cell types thus impossible. In the inoculated animals, no qualitative differences were observed regarding the route of bacterial endolymphatic sac invasion between serotype 1 and 9V. Serotype 3 did not invade the endolymphatic sac at all, as these animals succumbed relatively quickly to advanced disease.

123

However, the serotype 3-inoculated animals did not differ from serotype 1 and 9V concerning preceding bacterial inner ear invasion characteristics, up to day 4 postinoculation. Following intrathecal inoculation, the pneumococci invaded the inner ear though the cochlear aqueduct in all cases. The bacteria were subsequently observed in scala tympani of the basal turn of the cochlea (the perilymphatic space), spreading towards the cochlear apex and into the scala vestibuli. Bacteria did not invade inner ear through the internal auditory canal or through bony partitions. Thus, in the sections from the first hours and days post-inoculation, no bacteria were seen in the endolymphatic sac (Fig. 2) or other vestibular end organs (not shown). Bacteria invaded the vestibular system around day 5 post-inoculation, from the scala vestibuli of the cochlea. Thus, bacteria in the vestibular system were first observed in the vestibule, infiltrating the saccule and the utricle perilymphatic space (Fig. 3), in a clear continuation from the scala vestibuli of the cochlea. Bacterial invasion of the

Eur Arch Otorhinolaryngol

Inflammatory response and bacterial elimination In serotype 1 and 9V inoculated animals, infiltration of inflammatory cells occurred in the vestibular end organs concurrent to, or slightly after bacterial invasion of the vestibule and semi-circular canals, both in the perilymphatic and endolymphatic compartments (Figs. 3, 4, 5). The perilymphatic compartment displayed somewhat more abundant bacterial invasion and concurrent inflammation, compared to endolymphatic space (Figs. 3, 4, 5). Notably, inflammatory cell infiltration occurred within the endolymphatic sac prior to bacterial invasion in several cases, on days 3–6 (Fig. 2). No retrograde spreading (from the sac towards the vestibule) of either bacteria or inflammation was observed. In sections from animals surviving more than 5 days, increasing numbers of both leucocytes and macrophages with engulfed bacteria were accumulating in especially the perilymphatic space (Figs. 3, 5), consistent with a temporal pattern of bacterial spread, subsequent inflammatory response and finally bacterial elimination by macrophage engulfment. Fig. 3 Overview of the vestibule and vestibular end organs, from a serotype 9V-inoculated rat on day 4 post-inoculation. Bacteria and leukocytes have infiltrated the perilymphatic space, but not the endolymphatic space (asterisk). Bar 40 lm. Insert Higher magnification of framed area: massive amounts of bacteria and leukocytes are observed in the perilymphatic space of the vestibule (VE). PSCC posterior semi-circular canal, SSCC superior semi-circular canal, UT utricule (macula)

endolymphatic space of the vestibular system (Figs. 4, 5) occurred subsequent to invasion of the endolymph of the scala media in the cochlea. The initial step of endolymphatic invasion occurred from the spiral ligament capillary bed, subsequent to hematogenous spread of the bacteria (not shown). Following the invasion of the saccular and utricular endolymphatic space around day 5, bacteria were observed in the semi-circular canals, both in the peri- and endolymphatic space (Fig. 4). The lateral semi-circular canal was infiltrated first in all cases and displayed a more pronounced bacterial accumulation (not shown). At roughly the same time, bacteria were observed in the endolymphatic duct (Fig. 5), through which the endolymphatic sac was invaded around day 6 (Figs. 2 and 6). In animals surviving more than 5 days, abundant bacteria were accumulating in the endolymphatic sac (Fig. 6). However, the epithelium and subepithelial stroma of the sac remained intact and without bacterial invasion from the luminal space (Fig. 6). In a few severe cases with evident hematogenous spread, some bacteria occurred in the dura and/or stroma adjacent the endolymphatic sac, before bacteria had invaded the endolymphatic sac lumen (Fig. 4).

Discussion In the present study, a visual display of the route, pathways and dynamics of Streptococcus pneumoniae invasion of the vestibular system and endolymphatic sac during meningitis is provided for the first time, using a well-proven rat model. In addition, the nature of the concurrent inflammatory response, as well as the occurrence of bacterial engulfment and elimination is documented. The main findings are (1) during pneumococcal meningitis, bacteria invade the endolymphatic sac solely through the endolymphatic duct, subsequent to invasion of the endolymphatic compartment of the cochlea. (2) Bacteria do not invade the sac directly from the adjacent meninges. (3) Frequently, inflammation of the endolymphatic sac occurs prior to bacterial invasion. (4) In severe cases, hematogenous spread leads to bacterial invasion and concurrent inflammation of the connective tissue stroma surrounding the endolymphatic sac, even before bacteria invade the endolymphatic sac lumen through the endolymphatic duct. During the first few days post-inoculation, neither bacteria nor inflammation occur within the endolymphatic sac, as the bacteria firstly invade the inner ear through the cochlear aqueduct and into the scala tympani of the cochlea. The vestibular system is invaded by bacteria after 5–6 days, concerning both the perilymphatic and endolymphatic compartments. At roughly the same time or subsequent thereto, bacteria spread from the vestibule through the endolymphatic duct and into the endolymphatic sac. In the rat model, we found no evidence of

123

Eur Arch Otorhinolaryngol Fig. 4 Overview (top right) of the semi-circular canals and the endolymphatic sac. The micrographs are from a serotype 9V-inoculated rat on day 6. The invading bacteria have not reached the ES at this time point, despite hematogenous spread to the endolymphatic compartment of the vestibular system. Bar 200 lm. a Higher magnification of frame A in the overview image. Multiple image alignment micrograph displaying bacteria in the connective tissue stroma surrounding the endolymphatic sac (arrows), but not within the sac lumen (asterisk), indicating that the sac epithelium is resistant to bacterial breakthrough. Bar 20 lm. b Higher magnification of frame B in the overview image, displaying the perilymphatic space of the semi-circular canal (asterisk), with engulfed bacteria within macrophages (horizontal arrows), as well as free bacteria in the endolymphatic space, surrounded by leukocytes (vertical arrow). Bar 20 lm. c Higher magnification of a semi-circular canal in frame C of the overview image. Massive volumes of bacteria, as well as leukocytes, are observed in the endolymphatic space (asterisk). Bar 10 lm

bacterial spreading directly from the meninges and into the sac, even though bacteria occurred in the stroma surrounding the sac in severe cases, following hematogenous spread. Likewise, we found no evidence of bacterial invasion of the endolymphatic duct or sac through the bony partitions between the intracranial space and the inner ear. Thus, in the rat model, bacteria invaded the endolymphatic sac solely through the endolymphatic duct, subsequent to invasion of the cochlea and the vestibule. As found in prior studies [7, 11], endolymphatic invasion of bacteria to the scala media of the cochlea occur subsequent to hematogenous to the spiral ligament capillary bed. An inflammatory response within the endolymphatic sac occurred prior to bacterial invasion, but a retrograde spread

123

via the endolymphatic duct towards the vestibular end organs was not observed. Massive infiltration of leukocytes occurred concurrent with bacterial invasion of the sac, as the leukocytes followed the route of bacterial invasion, through the described pathways of the inner ear fluid compartments. A thorough description of these pathways of inflammation in the inner ear during pneumococcal meningitis has previously been published [11]. Considering theses dynamics, the utriculo-endolymphatic valve seems to constitute a naturally occurring anatomical barrier against retrograde spreading of bacteria and ensuing inflammation. Since hydrops occurs following inflammation, the utriculo-endolymphatic valve may act as a oneway valve directing endolymphatic fluid, bacteria and

Eur Arch Otorhinolaryngol Fig. 5 Micrographs from a serotype 9V-inoculated rat on day 6, showing bacteria spreading from the endolymphatic space of the vestibular system through the endolymphatic duct to the endolymphatic sac. In addition, bacterial elimination occurs by engulfment by macrophages. a Overview of the vestibule and posterior semi-circular canal in the late phase of disease. Bar 200 lm. b Overview of the vestibule and posterior semicircular canal from a serotype 1-inoculated rat on day 7. Bar 200 lm. c Higher magnification of the framed area in a, displaying massive amounts of bacteria and leukocytes in the perilymphatic space, where bacterial engulfment by macrophages is observed (arrows). ED endolymphatic duct, from which bacteria and leukocytes are absent, PSCC posterior semi-circular canal, also without bacteria and leukocytes. Bar 20 lm. d Higher magnification of framed area in b, displaying bacterial invasion of the endolymphatic space of the posterior semi-circular canal (PCSS) and concurrent bacterial invasion (vertical arrow) of the endolymphatic duct (ED). Macrophages with engulfed bacteria are seen. Bar 20 lm

ensuing leukocytes toward the endolymphatic sac [21], thus preventing retrograde migration of leukocytes from the endolymphatic sac toward the vestibule. The pneumococcal species used in the present study has a poor ability to cross the meninges. This may explain the observed lack of direct spread from the meninges and into the endolymphatic sac, even though bacteria were observed in the stroma surrounding the endolymphatic sac in severe cases. Other bacterial species causing meningitis, such as Listeria and Neisseria, cross the meninges more readily [22, 23], and may possibly invade the endolymphatic sac directly. Immunological capacities of the endolymphatic sac may explain the relative lack of bacterial invasion. As

noted in the introduction, the endolymphatic sac has previously been proposed as the primary immunological organ of the inner ear [13, 14], potentially resembling MALT [15, 16]. Animal studies have implicated the sac in the molecular and cellular innate immune response, as well as the adaptive immune response [24]. In addition, a few papers have described the occurrence of immunecompetent cells in the human endolymphatic sac, without concurrent infection [5, 25].However, this could prove to be an artifact [26]. The present study was not designed to identify specific immune-competent cells in the endolymphatic sac. Nonetheless, the presence of cells in the lumen of the sterile endolymphatic sacs and the occurrence of inflammation prior to bacterial invasion support

123

Eur Arch Otorhinolaryngol Fig. 6 Micrographs from a serotype 9V-inoculated rat on day 6, during which the endolymphatic sac and the meninges are infiltrated by massive amounts of bacteria. a Overview showing an endolymphatic sac filled with massive amounts of invading bacteria and leukocytes. Bar 20 lm. b High power micrograph of the framed area in a. Despite the massive invasion of pneumococci (horizontal arrow), the epithelium remains intact (vertical arrow), without signs of intrusion or disruption. Bar 10 lm. c High power micrograph of the framed area in a. Note the clear distinction between a pronounced invasion and accumulation of bacteria (horizontal arrow) and leukocytes in the sac lumen and simultaneous absence of bacteria in the meninges (asterisk), indicating that the endolymphatic sac epithelium (vertical arrow) is resistant to bacterial penetration and breakthrough. Bar 10 lm

the previous theories of an immunological function. Individual elements of the humoral innate immune defense have been demonstrated in the human endolymphatic sac [27] and in addition, the presence of several immunological mediators has been evidenced recently, by DNA analysis in the rat [28]. An endolymphatic sac function as the major immunological tissue protecting the inner is also supported by other morphological studies [26, 29]. The qualitative and temporal pattern of inflammation following bacterial invasion in the present study have also been observed in experimental studies using keyhole limpet hemocyanin, in sterile conditions [24]. The reason for the inflammatory response may be antigen presentation in the endolymphatic sac, contributing to an enforced secondary immunologic response in the inner ear. Antigens presented in the cochlea have been shown to reach the endolymphatic sac fastly [30, 31]. In addition, studies have shown that the secondary immunological response in the inner ear is greatly diminished in absence of the endolymphatic sac [13, 14].

123

The cause of post-meningitic inner ear dysfunction is supposed to be inflammation and/or bacterial toxins. As previously noted, inner ear infiltration of inflammatory cells has been shown to be a major cause of meningitisassociated hearing loss, due to damage of the organ of Corti and spiral ganglion neurons, conceivably through the production and release of cytotoxic mediators [5–9]. The same mechanisms are likely to be applicable for vestibular end organ damage and dysfunction.

Conclusion During meningitis, bacteria do not invade the endolymphatic sac through the dura, but solely through the endolymphatic duct, following the invasion of the endolymphatic compartment of the cochlea (scala media). Scala media invasion occurs subsequent to hematogenous spread of bacteria to the spiral ligament capillary bed. Leukocyte infiltration of the sac occurs prior to, as well as concurrent with bacterial invasion. The findings support the

Eur Arch Otorhinolaryngol

endolymphatic sac as part of an innate immune defense system protecting the inner ear from infection. Acknowledgments All financial support for this work was funded solely through public institutional funds. Conflict of interest of interest.

The authors declare that they have no conflict

References 1. Rasmussen N, Johnsen NJ, Bohr VA (1991) Otologic sequelae after pneumococcal meningitis: a survey of 164 consecutive cases with a follow-up of 94 survivors. Laryngoscope 101:876–882 2. Worsøe L, Caye´-Thomasen P, Brandt CT, Thomsen J, Østergaard C (2010) Factors associated with the occurrence of hearing loss after pneumococcal meningitis. Clin Infect Dis 51(8):917–924 3. Cushing SL, Papsin BC, Rutka JA et al (2009) Vestibular endorgan and balance deficits after meningitis and cochlear implantation in children correlate poorly with functional outcome. Otol Neurotol 30(4):488–495 4. Zingler VC, Weintz E, Jahn K et al (2009) Causative factors, epidemiology, and follow-up of bilateral vestibulopathy. Ann NY Acad Sci 1164:505–508 5. Merchant SN, Gopen Q (1996) A human temporal bone study of acute bacterial meningogenic labyrinthitis. Am J Otol 17:375–385 6. Bhatt S, Halpin C, Hsu W et al (1991) Hearing loss and pneumococcal meningitis: an animal model. Laryngoscope 101:1285–1292 7. Caye-Thomasen P, Worsoe L, Brandt CT et al (2009) Routes, dynamics, and correlates of cochlear inflammation in terminal and recovering experimental meningitis. Laryngoscope 119(8):1560–1570 8. Osborne MP, Comis SD, Tarlow MJ, Stephen J (1995) The cochlear lesion in experimental bacterial meningitis of the rabbit. Int J Exp Pathol 76:317–330 9. Brandt CT, Caye´-Thomasen P, Lund SP, Worsøe L, Ostergaard C, Frimodt-Møller N, Espersen F, Thomsen J, Lundgren JD (2006) Hearing loss and cochlear damage in experimental pneumococcal meningitis, with special reference to the role of neutrophil granulocytes. Neurobiol Dis 23(2):300–311 10. Winter AJ, Comis SD, Osborne MP, Tarlow MJ, Stephen J, Andrew PW, Hill J, Mitchell TJ (1997) A role for pneumolysin but not neuraminidase in the hearing loss and cochlear damage induced by experimental pneumococcal meningitis in guinea pigs. Infect Immun 65(11):4411–4418 11. Møller MN, Brandt CT, Ostergaard C, Caye-Thomasen P (2013) Bacterial invasion of the inner ear during pneumococcal meningitis. Accepted Otol Neurotol 12. Hausler R, Toupet M, Guidetti G, Basseres F, Montandon P (1987) Menie`re’s disease in children. Am J Otolaryngol 8(4):187–193 13. Tomiyama S, Harris JP (1986) The endolymphatic sac: its importance in inner ear immune responses. Laryngoscope 96:685–691 14. Tomiyama S, Harris JP (1987) The role of the endolymphatic sac in inner ear immunity. Acta Otolaryngol (Stockh) 103:182–188

15. Gloddek B, Arnold W (1998) The endolymphatic sac receives antigenetic information from the organs of the mucosa-associated lymphatic system. Acta Otolaryngol 118(3):333–336 16. Rask-Andersen H, Stahle J (1980) Immunodefence of the inner ear? Lymphocyte-macrophage interaction in the endolymphatic sac. Acta Otolaryngol 89(3–4):283–294 17. Kastenbauer S, Klein M, Koedel U, Pfister HW (2001) Reactive nitrogen species contribute to blood-labyrinth barrier disruption in suppurative labyrinthitis complicating experimental pneumococcal meningitis in the rat. Brain Res 904(2):208–217 18. Brandt CT, Lundgren JD, Lund SP, Frimodt-Møller N, Christensen T, Benfield T, Espersen F, Hougaard DM (2004) Attenuation of the bacterial load in blood by pretreatment with granulocyte-colony-stimulating factor protects rats from fatal outcome and brain damage during Streptococcus pneumoniae meningitis. Østergaard CInfect Immun 72(8):4647–4653 19. Leib SL, Kim YSM, Ferriero DM, Tauber MG (1996) Neuroprotective effect of excitatory amino acid antagonist kynurenic acid in experimental bacterial meningitis. J Infect Dis 173:166–171 20. Fusaro RM, Goltz RW (1960) A comparative study of the periodic acid-schiff and alcian blue stains. J Invest Dermatol 35:305–307 21. Salt AN, Rask-Andersen H (2004) Responses of the endolymphatic sac to perilymphatic injections and withdrawals: evidence for the presence of a one-way valve. Hear Res 191(1–2):90–100 22. Kugelberg E, Gollan B, Tang CM (2008) Mechanisms in Neisseria meningitidis for risistance against complement-mediated killing. Vaccine 26(6):I34–I39 23. Southwick FS, Purich DL (1996) Intracellular pathogenesis of listeriosis. N Engl J Med 334:770–776 24. Satoh H, Firestein GS, Billings PB, Harris JP, Keithley EM (2003) Proinflammatory cytokine expression in the endolymphatic sac during inner ear inflammation. J Assoc Res Otolaryngol 4(2):139–147 25. Rask-Andersen H, Danckwardt-Lilliestro¨m N, Friberg U, House W (1991) Lymphocyte-macrophage activity in the human endolymphatic sac. Acta Otolaryngol Suppl 485:15–17 26. Møller MN, Caye-Tomasen P, Qvortrup K (2013) Oxygenated fixation demonstrates novel and improved ultrastructural features of the human endolymphatic sac. Laryngoscope 123(8): 1967–1975. doi:10.1002/lary.23929 27. Altermatt HJ, Gebbers J, Mu¨ller C, Laissue J, Arnold W (1992) Immunohistochemical characterization of the human endolymphatic sac and its associated cell populations. Acta Otolaryngol (stockh) 112:299–305 28. Friis M, Martin-Bertelsen T, Friis-Hansen L, Winther O, Henao R, Sørensen MS, Qvortrup K (2011) Gene expression of the endolymphatic sac. Acta Otolaryngol 131(12):1257–1263 Epub 2011 Oct 23 29. Wackym PA, Friberg U, Linthicum FH Jr, Bagger-Sjo¨back D, Bui HT, Hofman F, Rask-Andersen H (1987) Human endolymphatic sac: morphologic evidence of immunologic function. Ann Otol Rhinol Laryngol 96(3 Pt 1):276–281 30. Yeo SW, Gottteschilch S, Harris JP, Keithley EM (1995) Antigen diffusion from the perilymphatic space of the cochlea. Laryngoscope 105:623–628 31. Yimtae K, Song H, Billings P, Harris JP, Keithley EM (2001) Connection between the inner ear and the lymphatic system. Laryngoscope 111:1631–1635

123

Endolymphatic sac involvement in bacterial meningitis.

The commonest sequelae of bacterial meningitis are related to the inner ear. Little is known about the inner ear immune defense. Evidence suggests tha...
2MB Sizes 3 Downloads 0 Views