Clinical Studies on Presbycusis Part Ⅰ: Relationship between the hearing in old age and the results of examinations of systemic functions Part Ⅱ Relationship between results of automatic audiometry and those of systemic examinaminations Part Ⅲ Relationship between the hearing in old age and electroencephalogram

For the purpose of carrying on studies on presbycusis from clinical standpoint the author conducted precise examinations of 137 cases over 40 years old visiting the Okayama National Hospital by conducting various systemic examinations, audiometry, electroencephalogram and automatic audiometry in some. In the pilot study, by classifying the hearing-loss into five new steps and by pursuing the relationship between the hearing in old age and various functions of different organs, the author odtained the following results. 1. The majority of hearing-loss show high tone-loss, and in the age range of forty and fifty years the disorders are more frequeutly of a mild degree, showing no marked difference in the two groups. However, in the age over 60 years these disorders increase in intensity and iu the age over 70 years this tends to become quite marked. 2. The aortensclerosis (as revealed by roentgenograms), urine protein content, and arteriosclerosis of retina are more frequently pathological along with the progress of hearing-loss clinicaly suggesting the relationship between the hearing disorders in old age and arteriosclerosis. 3. No relationship can be recognized between the hearing-loss and snch findings as the systemic blood pressures, blood pressure of fundus, the ratio detween the systemic blood pressure and that of fundus, cold pressure test, renal function, urine sugar content, heart muscle disturbances as revealed by electrocardiogram and hypertensive changes in the fundus, 4. The majority of the hearing type belong to abrupt type of high tone-loss, followed in the descending order of gradual type, horizontal type and dip type. In the age over 60 years the gradual type tends to increase as compared with the age range in forty and fifty years. In examining 38 cases with presbycusis out of those examined in the part Ⅰ by means of automatic audiometer, the author studied mainly the amplitude in the automatic audiogram, and odtained the following results. Moreover, the classification of the amplitude in the 26 ears of normal adults is divided into the amplitude decreasing type under 4 db, normal type between 5 db to 17 db, and the amplitude increasing type over 18 db. 1. Those showing the amplitude decreasing type amounted to 23 cases (60.5%); normal type 12 cases (31.5%); and the amplitude increasing type 3 cases (7.9%); and the majority of the amplitude decreasing type showed the decrease in the high tone area. 2. The amplitude decreasing type was found mostly in those with mild disorders, and it decreased along with the progress in hearing disorders. 3. The amplitude decreasing type was found mostly in high: while the increasing type in the abrupt type of high-tone-loss, gradual type and in the horirizontal type. 4. The amplitude decreasing type decreased, though slightly, along with the advance in age. 5. The tinnitus had no special association with the amplitude in the audiogram. 6. The amplitude decreasing type decreased along with the advance in the degrees of arteriosclerosis of retina and hypertensive changes. In the electroencephalographic examinations of 130 cases previously mentioned in the Part Ⅰ, the author studied the relationship between the electroencephalogram and the hearing in old age, and obtained the following results: 1. (Irregularity in) the wave legnth and the amplitude of α-wave as well as the breakdown in the wave fomation are revealed more markedly along with the advance in the hearingloss. 2. Of the abnormal waves, slow wave and spike appear in a direct proportion to the degree of hearing-loss. 3. As the hearing-loss in the age range of forty and fifty years are milder, the same holds true of the changes in electroencephalogram in the majority of cases. In the age range over sixty years both tend to be more marked. 4. Most of those belonging to the amplitude decreasing type reveal a milder degree of electroencephalographic changes,