Hearing disturbances in hypertrophic cardiomyopathy. Is the sensorineural disorder neurogenic or myogenic?
BACKGROUND
In a previous study, we demonstrated that a hidden hearing defect is present in about 50% of patients with hypertrophic cardiomyopathy (HCM). Such defects were found significantly less frequently in age and clinical stage-matched patients with dilated cardiomyopathy (DCM), and were practically absent in patients with valvular aortic stenosis, and in patients taking beta-receptor blockers for different reasons (such as hypertension, ischemic heart disease, etc.). The hearing disturbances were first examined by means of brain-stem evoked response audiometry (BAEP). This method permitted only a rough differentiation between the origins of cochlear (myogenic) and retrocochlear (neurogenic) hearing disturbances, and did not allow us to establish their myogenic or neurogenic nature with certainty.


OBJECTIVE
Our present aim was to determine whether the hearing disturbances present in HCM and DCM patients are myogenic or neurogenic in origin.


METHODS
The neurogenic function of the inner ear was examined by BAEP as before, and the myogenic function by the distortion product otoacoustic emission technique.


RESULTS
Myogenic abnormalities were found in 39/69 ears (57%) and neurogenic abnormalities in 19/69 (28%) ears among the HCM cases, as compared with 14/39 (36%) and 8/39 (21%) ears respectively among the DCM cases (p<0.005). Healthy controls displayed the lowest incidence of both types of hearing abnormalities.


CONCLUSIONS
Our results lead us to conclude that myogenic lesions are more frequent than neurogenic lesions in patients with HCM. Both myogenic and neurogenic lesions are more frequent in HCM patients than in DCM patients or healthy controls. It may be hypothesized that abnormal sarcomeric proteins present in the muscular structures of the inner ear in HCM are possibly responsible for the hearing disorders in these patients, and that this is not merely a neurological defect.
Csanády
Miklós
M
2nd Department of Medicine and Cardiology Center, Albert Szent-Györgyi Medical and Pharmaceutical Center, Medical Faculty, University of Szeged, Szeged Korányi fasor 6, H-6720, Hungary. csanady@in2nd.szote.u-szeged.hu
Tóth
Ferenc
F
Hogye
Márta
M
Vass
Andrea
A
Sepp
Róbert
R
Csanády
Miklós
M
Czigner
Jeno
J
Kiss
József G
JG
Jóri
József
J
Forster
Tamás
T
D000293:Adolescent; D000328:Adult; D000368:Aged; D002312:Cardiomyopathy, Hypertrophic / Q000150:complications*; D002648:Child; D006319:Hearing Loss, Sensorineural / Q000145:classification* / Q000175:diagnosis / Q000209:etiology*; D006801:Humans; D008875:Middle Aged; D024510:Muscle Development; D017084:Otoacoustic Emissions, Spontaneous