LABYRINTHITIS

   Labyrinthitis or otitis interna is an inflammation of the inner ear that may involve one or more labyrinthine compartments.  Clinically it may be manifested by a wide variety of symptoms, ranging from the full-fledged violent disease in which the patient is incapacitated and has loss of hearing and balance, to the more insidious disease in which transient or permanent loss of cochlear function are the only symptoms present.  Labyrinthitis may be of tympanogenic hematogenic or meningogenic in origin.  Tympanogenic spread generally occurs due to passage of microorganisms, toxins or pharmacologic agents from the middle to inner ear through the round window membrane.  It may be localized to the area of the scala tympani near the round window membrane, the perilymphatic or endolymphatic scala, or diffusely spread throughout.  Labyrinthitis has been histologically divided into 4 classifications: serous, purulent, fibrous, and labyrinthitis ossificans with an overlap of types not uncommon.

    Serous labyrinthitis

    The classification of serous labyrinthitis is based on the presence of eosinophilic staining of the inner ear fluids (Figure 1).  The labyrintitis may be localized to the area of the round window membrane or diffusely distributed thoughout the inner ear.  The irritative agents may be bacterial toxins, mediators or biproducts of inflammation or metabolic products of neoplastic growth in the temporal bone.  Histopathologic characterization is based on eosinophilic staining of the inner ear fluids with or without serofibrinous strands.   Eosinophilia of the fluids of the inner ear can also be seen during maturation of the fetal temporal bone and may occur secondary to post-mortem autolysis.  Nystagmus is often directed toward the affected ear and function of the inner ear is generally preserved after treatment.

Figure 1