Otopathology in Congenital Toxoplasmosis

Objective: To describe the temporal bone histopathology in children with congenital toxoplasmosis. Background: Toxoplasmosis is a parasitic infection caused by Toxoplasma gondii. If fetal infection occurs early in gestation, severe inflammation and necrosis can cause brain lesions, chorioretinitis, and hearing loss. Hearing loss in congenital toxoplasmosis may be preventable with early diagnosis and treatment. Materials and Methods: The temporal bones of 9 subjects with congenital toxoplasmosis were removed at autopsy and studied under light microscopy. Cytocochleograms were constructed for hair cells, the stria vascularis, and cochlear neuronal cells. Results: Three (33%) of 9 subjects were found to have parasites in the temporal bone. The organism was identified in the internal auditory canal, the spiral ligament, stria vascularis, and saccular macula. The cystic form of the parasite was not associated with the inflammatory response seen in the active tachyzoite form. Conclusion: We infer that the hearing loss of toxoplasmosis is likely the result of a postnatal inflammatory response to the tachyzoite form of T. gondii. Our findings have implications for the early identification and management of Toxoplasmosis.