For the patient, sudden deafness can be terrifying. For the specialist, this disorder can be most challenging for the cause of sudden deafness cannot be readily determined by use of the most advanced diagnostic tests.
Several complementary tests are used, such as audiological, biochemical, otoneurological, and imaging studies. Now a research team has elected to choose Magnetic resonance imaging (MRI) for a detailed study of the structures of the inner ear, the internal auditory meatus (IAM), and the cerebellopontine angle, the angle formed at the junction of the cerebellum, pons, and medulla, and most likely location of an acoustic neuroma.
Past research has revealed that in an MRI examination of 495 sudden deafness cases, 22 showed evidence of intra-axial lesions. This gave a research team a central etiologic basis for the deafness; the possibility of lesions in the audiovestibular pathway has been considered by other researchers to be one of the principal causes of sudden hearing loss.
A new study reports on the abnormalities found after an MRI examination of patients with sudden deafness. The authors of “Magnetic Resonance Imaging in Sudden Deafness,” are Hugo Valter Lisboa Ramos MD, Flávia Alencar de Barros, Hélio Yamashita MD PhD, Wellington Yugo Yamaoka MD, Ana Cláudia Valério de Souza MD, and Norma de Oliveira Penido MD PhD, all from the Federal University of São Paulo - Paulista Medical School, São Paulo, Brazil. findings are being presented at the American Academy of Otolaryngology-Head and Neck Surgery Foundation Annual Meeting & OTO EXPO, being held September 19-22, 2004, at the Jacob K. Javits Convention Center, New York City, NY.
This prospective study examined 49 patients, 23 male and 26 female, ranging in age from 15 to 91 years (average 45.4 years). Thirty-four were racially white, ten were mixed-race, two black, and three Asian. Only five of the 49 patients studied had MRI performed before clinical treatment with prednisone and pentoxiphylline. In 23 patients, the deafness was on the left side, 26 on the right side.
An audiometric test and acoustic impedance audiometry were performed on patients who complained of a sudden loss of hearing. Sudden deafness was defined as a sensorineural loss of audition greater than or equal to 30 dB in at least three contiguous audiometric frequencies occurring within three days or less.
The patients studied underwent MRI of the temporal bone and brain. The test was complemented with use of axial slices of the cranium in concentrated sequences obtained by a Fluid Attenuation Inversion Recovery (FLAIR) system with the objective of evaluating the encephalic mass. The researchers determined peripheral alterations to be those limited to the inner ear, and central alterations to be those located in the internal auditory meatus or in the central nervous system. The results were analyzed descriptively.
Of a total of 49 patients studied, 23 (46.9 percent) presented abnormalities on MRI. Among those patients with such abnormalities, the mean age was 55.1. Eleven (47.8 percent) patients were male and 12 (52.2 percent) were female. There were 24 abnormalities because one patient presented two abnormalities. Two tumors suggestive of meningioma were found in the near the sella turcica region that extended towards posterior fossa; three tumors with were identified with characteristics of vestibular schwannoma, two of them intracanalicular. Another patient presented dilatation of the fourth cerebral ventricule, but the most frequent abnormality was the presence of subcortical and periventricular lesions, found in 13 patients.
Five (21.7 percent) patients presented peripheral abnormalities, and all were on the same side as the deafness. Two types of such abnormalities were found: vestibulocochlear gadolinium-enhanced changes in two patients; and a hyperintense vestibulocochlear signal observed without gadolinium enhancement, in three patients.
Sudden deafness should be approached as a symptom common to different diseases. Our study showed abnormalities on MRI in 46.9 percent of patients with SD, and 10.2 percent of cerebellopontine angle tumors. The MRI is becoming more and more recognized as useful in the etiological investigation of SD patients. This imaging technology could identify and define etiologic bases or suggest a possible course treatment for sudden onset of deafness.