The influence of pneumococcal otitis media on the cochlear lateral wall

The cochlear influence of otitis media was investigated in order to identify damaged regions causing cochlear malfunction. BALB/c mice were challenged with viable Streptococcus pneumoniae into the middle ear cavity and were killed 1 day to 1 month later for immunohistochemical analysis. Otitis media was induced in all of the animals, and some showed inflammatory cells in the cochlea. Although other changes were not obvious by hematoxylin and eosin staining, immunohistochemistry showed the presence of fibrinogen in the cochlea, mainly in the lower portion of the spiral ligament and in the spiral limbus. Immunostaining for connexin 26 was decreased in the spiral ligament, accompanied by marked fibrinogen staining. Immunostaining for sodium-potassium-adenosine triphosphatase in the stria vascularis and in the type II fibrocytes of the spiral ligament was not affected obviously. The presence of fibrinogen in the cochlea suggests disruption of the blood-labyrinth barrier caused by the middle ear inflammation. Changes in connexin 26 staining suggest the possibility that the spiral ligament could be among the regions responsible for the cochlear malfunction. (C) 1999 Elsevier Science B.V. All rights reserved.