Comparative Histopathologic Analysis of Inner Ear Damage in Meningitis: Otogenic Versus Meningogenic Routes

Abstract

Objective: To distinguish the patterns of inner ear changes between meningogenic and otogenic routes in meningitis cases. Our hypothesis is that pinpointing distinct patterns linked to each route could aid in the development of diagnostic strategies and targeted therapies.

Methods: Temporal bones (TBs) from patients with a history of meningitis and histopathological evidence of labyrinthitis were divided into two groups (otogenic and meningogenic). Inner ear histopathological examination was performed to identify qualitative and semi-quantitative changes. This assessment encompassed inflammation patterns, indications of early ossification, hair cell loss, and alterations in the lateral wall, round window membrane, cochlear aqueduct and vestibular aqueduct.

Results: Thirty-six TBs were included in the study (otogenic, 21; meningogenic, 15). Generalized labyrinthitis was more common in otogenic cases (100% vs. 53%, p < 0.001). Early signs of cochlear ossification were exclusively observed in otogenic cases (9 TBs). The spiral ligament of otogenic cases has shown a uniform loss of fibrocytes across all cochlear turns, while meningogenic cases showed more severe loss in the apical turn. Otogenic cases exhibited a higher prevalence of severe inflammation of the cochlear aqueduct and endolymphatic sac. Meningogenic cases showed more severe loss of vestibular hair cells in the otolithic organs.

Conclusion: Otogenic cases displayed a higher prevalence of changes in the spiral ligament and signs of early ossification, whereas meningogenic cases were associated with a higher degree of vestibular damage. Our findings emphasize the importance of considering the infection route and its implications for timely diagnosis and development of pathology-oriented treatment strategies.

Level of evidence: NA Laryngoscope, 135:864-872, 2025.

Keywords: human temporal bone; labyrinthitis; meningitis; otopathology.

Fig. 1

Two representative temporal bone sections showing middle ear changes. (A) Otogenic meningitis case displaying middle ear changes, like thickened mucosa, granulation tissue (*), purulent effusion, and polymorphonuclear infiltration. (B) Meningogenic case with no significant finding in the middle ear. FN = facial nerve; IAC = internal auditory canal; LSCC = lateral semicircular canal; M = malleus. [Color figure can be viewed in the online issue, which is available at www.laryngoscope.com.]

Fig. 2

Representative temporal bone sections showing cochlear changes. (A) Otogenic meningitis case; arrows: eosinophilic precipitate; *, purulent material. (B) Meningogenic case; arrows: eosinophilic precipitate. SL = spiral ligament; SM = scala media. [Color figure can be viewed in the online issue, which is available at www.laryngoscope.com.]

Fig. 3

Three representative temporal bone sections showing different patterns of purulent labyrinthitis. (A) Localized labyrinthitis; arrows: polymorphonuclear cells. (B) Generalized labyrinthitis, acute stage; arrows: polymorphonuclear cells. (C) Generalized labyrinthitis, fibrous stage; arrows: polymorphonuclear cells; *: fibrous tissue. CA = cochlear aqueduct; RW = round window; RWM = round window membrane. [Color figure can be viewed in the online issue, which is available at www.laryngoscope.com.]

Fig. 4

Representative temporal bone sections showing the visual scale used to assess changes in the spiral ligament (SL) and stria vascularis (SV). (A) Normal SL; arrow: SV with edema. (B) SL with mild loss of fibrocytes; arrow head: areas of loss of fibrocytes. (C) SL with moderate loss of fibrocytes; arrow head: areas of loss of fibrocytes; (D) SL with severe loss of fibrocytes; arrow: atrophic SV; arrow head: areas of loss of fibrocytes. [Color figure can be viewed in the online issue, which is available at www.laryngoscope.com.]

Fig. 5

Representative sections showing the semi‐quantitative assessment of loss of vestibular hair cells in the saccule. (A) Normal macula. (B) Mild loss of hair cells; arrows: areas of cell loss. [Color figure can be viewed in the online issue, which is available at www.laryngoscope.com.]