Epidemiological Study of Toxoplasmosisand Cytomegalovirous among Children with Idiopathic Sensorineural Hearing Loss

Abstract

Infections are an important cause for sensorineural hearing loss just after genetic causes especially in developing countries. Congenital CMV is a common cause for sensorineural hearing loss. Burden of congenital CMV related hearing loss is not well estimated and needs further studies. The current retrospective study is an attempt to study relation between CMV and toxoplasmosis in occurrence of sensorineural hearing loss.This study was conducted on 82 children, 40 males and 42 females. Their age ranged from 1 to 15 years. Fifty two of these children (study group) had sensorineural hearing loss with unknown etiology (no risk factors), 20children(controlsubgroup I) had sensorineural hearing loss but with a risk factor (possible etiology) and10 children (control subgroup II) had conductive hearing loss. ELISA is used to detect IgG and IgM antibodies for CMV and toxoplasmasois. The percent of seropositive CMV cases was high either in study or control groups. IgG seropositive titer shows significant difference between study and control groups. Also there was significant difference between possible active cases in study and control groups. Cases with possible active infection and hearing loss of unknown risk factor increase our suspicion for possible congenital CMV related hearing loss. As regard toxoplasmosis, small number of cases is seropositive with no statistical significant difference between study and control groups. We suspect congenital CMV related hearing loss in possible active cases as theories for CMV related hearing loss incriminate ongoing virus replication and host immune response to presence of the virus. This may explain the late onset and progressive course of cytomegalovirus related hearing loss. The delayed onset of hearing loss in some patients suggests chronic persistence of the virus and/or inflammation in the inner ear and/or auditory pathway. The prevalence of toxoplasmosis differs across countries.Toxoplasmosis as a cause of sensorineural hearing loss may be not as common as CMV. May be it is decreasing due to the increase of awareness about disease especially among pregnant females and availability of effective treatment. The understanding and prevention of CMV related SNHL remain a challenge and we need further research for further understanding of CMV related hearing loss.