When the electric current was applied, the patient had a sensation of vibration but not sound, which indicated severe to total atrophy of the cochlear nerve. Promontory stimulation tests 9 were performed on the right ear, using a needle electrode placed on the promontory mucosa through the ear drum. Auditory brainstem response tests also showed a normal response in the left ear but no response in the right ear. On click evoked electrocochleography, action potentials were not recorded in the right ear, whereas they were normally evoked in the left ear. Repeated distortion product otoacoustic emission and transiently evoked otoacoustic emission studies confirmed normal responses in the left ear, but very poor or no responses in the right ear, indicating severe cochlear impairment. In the frequency range of 500 to 1000 Hz, at higher tone levels above 100- to 105-dB hearing level (HL), the patient had a feeling that her whole head was shaking as though she were experiencing an earthquake. Thresholds for sound sensation were unmeasurably high in the right ear. Pure-tone audiometry revealed a profound sensorineural hearing impairment in the right ear and normal hearing in the left ear. On T1-weighted images, the right eighth cranial nerve was thin, and the 3 branches were not clearly identified, indicating the thinning of these branches or the absence of certain branches.Ī summary of the imaging studies is shown in Table 1. However, the route for the cochlear nerve was clearly identified to its entrance to the cochlea, which, paradoxically, suggests the atrophy of the nerve, because of the sufficient fluid space in the stenotic canal. This was probably because of the little fluid space between the stenotic canal wall and the nerve. On T2-weighted images, routes for the facial, superior vestibular, and inferior vestibular nerves were not identified. At the cerebellopontine angle, where the seventh and eighth cranial nerves leave the brainstem, the right eighth nerve was obviously smaller in diameter than the other side. On the right side, the cochlea, vestibule, and semicircular canals were normal. On the left side, the inner ear structures were normal, and the 4 nerves in the IAM were clearly identified. T2-weighted magnetic resonance images were more informative than T1-weighted images ( Figure 2). The roof of bone overlying the superior canal was intact on both sides. However, the right IAM was very narrow, and small, branched canals for the 4 nerves were identified at the periphery. The inner ear structures were also normal on the right side. The IAM, cochlea, vestibule, and semicircular canals were normal on the left side. ![]() High-resolution computed tomography revealed no abnormalities in the external auditory meatus or in the middle ear on either side ( Figure 1). Shared Decision Making and Communication.Scientific Discovery and the Future of Medicine.Health Care Economics, Insurance, Payment.Clinical Implications of Basic Neuroscience.Challenges in Clinical Electrocardiography.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |