Sensorineural hearing loss is an important complication of mumps. Audiologic tests of 26 children with mumps meningoencephalitis, 25 uncomplicated mumps cases and 20 control cases were performed, and hearing level thresholds at speech and high frequencies were determined. The mean hearing level thresholds in the mumps meningoencephalitis group were higher than those of mumps cases at frequencies from 6000 to 18 000 Hz in the right ear and at 250 and from 4000 to 18 000 Hz in the left ear (P < 0.05). Mumps meningoencephalitis cases had higher mean hearing thresholds than did control groups at all frequencies other than 125 and 250 Hz in the right ear and 10 000 Hz in the left ear. The mean hearing thresholds of mumps cases were higher than those of control group at frequencies of 1000 and 4000 Hz in the right ear and 1000 and 10 000 Hz in the left ear (P < 0.05). These results show that mumps meningoencephalitis causes a higher risk of hearing loss than does mumps.
Mumps is one of the common causes of acquired sensorineural hearing loss. 1 The risk of hearing loss in mumps infections is from 1 per 2000 to 1 per 30 000 cases. 2–4 Hearing loss after mumps infection is usually mild or moderate, and severe or bilateral hearing loss is rare. 3 Although it is suggested that development of hearing loss is not related to the clinical form of mumps infection, 3–5 there are a few reports in the medical literature about hearing loss associated with mumps meningoencephalitis. 4, 5 This study was designed to investigate whether mumps meningoencephalitis is more prone to cause hearing loss than mumps without central nervous system complications.
Materials and methods.
The audiologic tests were performed in 3 groups of cases. The first group consisted of 26 cases of mumps meningoencephalitis diagnosed and hospitalized in Hacettepe University Children’s Hospital between 1990 and 2000. The criteria for the diagnosis of mumps meningoencephalitis were: presence of parotid swelling together with fever, headache, vomiting and/or any sign of disturbance in consciousness; and findings of meningeal irritation by physical examination with the presence of pleocytosis in cerebrospinal fluid (CSF) determined by lumbar puncture. Also diagnosis was supported by negative bacteriologic studies including CSF cultures, CSF Gram-stained smears and latex agglutination test for bacterial antigens. The second group included 25 children with mumps who did not develop signs of meningoencephalitis during the same period. Both were recalled for audiologic testing between January and May 2001. The third group was the control group consisting of 20 healthy children who had negative serology by enzyme-linked immunosorbent assay for mumps. All 3 groups were similar in terms of age and sex. Informed written consent was obtained from each child’s parent.
The audiologic tests were performed by an Intraacoustic AC-5 and AC-30 clinical audiometer and and Interacoustic AS-10 high frequency audiometer in a standard sound-proof room manufactured by Industrial Acoustic Co. Specialized audiologists who were blind in terms of patients performed the tests. The pressure of middle ear and acoustic reflexes were determined by Intraacoustic AZ-7 and AT-22 electroacoustic impedence meter. Patients who had any pathologic condition related to middle and external ear were excluded from the study. The hearing level thresholds of both ears in decibel hearing level were determined by both air and bone conduction at frequencies of 125, 250, 500, 1000, 2000, 4000, 6000, 8000, 10 000, 12 000, 14 000, 16 000 and 18 000 Hz. The mean hearing level thresholds of mumps meningoencephalitis cases were compared with those of mumps and control cases.
Statistical analysis was performed with SPSS for Windows Release 6. 0 program. For statistical significance the P value was accepted to be 0. 05 or less.
The mean ages of control, mumps and mumps meningoencephalitis subjects were 7.01, 6.60 and 6.62 years, respectively. There were 9 girls of 20 cases in the control group, 12 girls of 25 cases in the mumps group and 11 girls of 26 cases in the mumps meningoencephalitis group. There was no age or sex difference in our study groups.
The mean hearing level thresholds at each frequency are given in Table 1. The mean hearing level thresholds in the mumps meningoencephalitis group were higher than those of mumps cases at frequencies of 6000, 8000, 10 000, 14 000, 16 000 and 18 000 Hz in the right ear and 250, 4000, 6000, 12 000, 14 000 and 18 000 Hz in the left ear (P < 0.05). Mumps meningoencephalitis cases had higher mean hearing level thresholds than did the control group at all frequencies other than 125 and 250 Hz in the right ear and 10 000 Hz in the left ear (P < 0.05). The mean hearing level thresholds of mumps cases were higher than those of the control group at frequencies of 1000 and 4000 Hz in the right ear and 1000 and 10 000 Hz in the left ear (P < 0.05).
Hearing loss caused by mumps infection can occur before, after or together with parotid swelling and even in the absence of swelling. 1, 2, 6, 7 The medical literature suggests that sensorineural hearing loss might develop irrespective of the severity of the mumps infection. 3–8 Azimi et al. 5 reported that there were no cases with hearing loss in 50 children with mumps meningoencephalitis. Garthy and Danon 4 determined hearing loss at a frequency of 3.5% among 79 cases of mumps meningoencephalitis during an epidemic in Israel. Mumps infection directly involving the endolymphatic systems of the cochlea and thus influencing the organ of Corti, tectorial membrane and myelin sheath of the eighth nerve could lead to hearing loss. 7, 9
In our study the hearing thresholds of mumps meningoencephalitis cases were higher than those in mumps and control groups at almost all frequencies. This could be a result of cochlear damage, although hearing level thresholds were not at the level of clinical hearing loss. Westmore et al. 10 detected mumps virus in the perilymphatic fluid, which supports the concept of direct cochlear damage. In mumps meningoencephalitis cochlear damage can constitute a risk for functional hearing loss especially together with superimposing conduction-type problems of the middle ear, which are very common in childhood. 11
The results of the study revealed that the mean hearing level thresholds of mumps meningoencephalitis cases were higher than those of mumps cases at both speech and high frequencies and higher thresholds than those of control cases at almost all frequencies. It might be advisable to perform audiologic tests on mumps cases routinely. Children with mild and unilateral hearing loss might remain undiagnosed unless audiologic tests are performed.
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