Takashi Tsuiki

Audiologic features of hearing loss due to the 1,555 mutation of mitochondrial DNA

We proved a 1,555 mutation of mitochondrial DNA in one member of each of three families with familial streptomycin hearing loss, and report the pedigrees and audiologic features. DNA was extracted by the standard method. The 1,555 A to G mutation was identified in all three patients and confirmed by direct sequencing of the polymerase chain reaction products by a cycle sequencing method. On audiograms, the hearing loss was sensorineural, bilateral, and symmetric, showing a high-tone loss or a profound loss particularly in the high-tone range, and the “symmetry law” of Langenbeck was applicable. The superimposed audiograms of members of one family did not cross themselves, proving the applicability of the “never-cross principle of audiograms.”

Clinical study of audiograms in the initial stage and fixed stage of sudden deafness.

Audiograms in the initial stage and the fixed stage of sudden deafness were analyzed in 79 cases using the following 5 criteria; i) the onset is sudden and time of onset definite, ii) hearing loss at 1 kH is more than 35 dB, iii) the course of hearing recovery is clear, iv) unaffected ear has normal hearing, and v) the first examination and treatment is within 15 days after onset. Consequently, at least in cases receiving treatment within 6-15 days after onset, it was considered that the prognosis of hearing recovery could be established rather than the pattern of hearing loss than by the period of treatment after onset.

HEARING TEST FOR EIGHTEEN THOUSAND SCHOOL CHILDREN

A scheduled survey was carried out to obtain the incidence of children with defective hearing and individual records of the auditory function of all school children living in Morioka City. Almost all the children of all primary schools in Morioka City were surveyed. The program consisted of four steps: the first step was a group pure tone screening test, the second and third were individual screening tests and the fourth was ordinary pure tone audiometry. The first and second steps were performed at each school and the third and fourth at Iwate Medical University Hospital. In the first step, the authors employed a new test method for group screening, in which 40 testees were tested at the same time. Among 18,422 school children tested, 388 were judged as having defective hearing. The incidence was 2.1 %. No essential difference was found among school grades one (6 years old) to six (11 years old). Two notable findings were (1) a prevalence of perceptive against conductive hearing loss and (2) relatively high incidence of 4 KHz dip.

Study on Self-Recording Audiogram of Sudden Deafness

Self-recording audiograms of sudden deafness in 54 patients were studied for the relationship between type of Jergers classification, hearing loss at the initial examination, and prognosis of hearing loss. Type I of Jergers classification was shown in patients with slight to profound hearing loss, whereas Type II + IV was shown more frequently in cases with profound hearing loss. Many patients of Types I and II were among those who recovered completely or markedly, while patients of Type II + IV were found more frequently among those who recovered or had unchanged hearing.