Yoshio Masaki

The prevalence of superior canal dehiscence syndrome as assessed by temporal bone computed tomography imaging

Abstract Conclusion: When a diagnosis of superior canal dehiscence syndrome (SCDS) was made based solely on CT scans, 80% of cases assessed were false positive. This stresses the importance of diagnosing SCDS on the basis of both CT findings and clinical symptoms. Objectives: All the coronal computed tomography (CT) scans of the temporal bones retained in this clinic were reviewed to determine how many of these examined ears have dehiscence(s) of the superior semicircular canal (SSCC). We also determined how many of the ears with a dehiscence of SSCC could also be diagnosed clinically on CT scans as having SCDS. Methods: CT scans of 82 patients, covering 164 ears, were reviewed to determine how many of these ears had dehiscence of SSCC. Of the ears found to have a dehiscence of SSCC in the above procedure, it was determined how many ears could also be diagnosed clinically as having SCDS. Results: Dehiscence of SSCC was demonstrated in 5 (3%) of the 164 ears assessed. Of the five ears noted to have a dehiscence of SSCC, the condition was also considered clinically to be SCDS in only one ear (0.6%).

Cervical reflex induced by click stimuli in cats.

We studied click-evoked potentials in the anterior horn of the spinal cord in 17 cats. A concentric needle electrode was inserted into the anterior horn of the spinal cord at levels C3-C6. Potentials evoked with 105 dB SPL clicks were recorded with a peak latency of 4.89-5.10 ms only at the C3 level. These responses were observed 45-60 dB SPL above the auditory brainstem response (ABR) threshold, and no potentials were evoked by stimulation of the contralateral ear. Average was performed 100 times with changes in stimulation frequency of 1-20 Hz. The amplitude of the potentials decreased with increasing stimulus frequency, but there were no changes in ABRs. The responses disappeared after destruction of the medial vestibulospinal tract at the obex level, but ABRs were still recorded. The spinal nucleus of the accessory nerves was located in the anterior horn of the spinal cord at levels C1-C6, and the sternocleidomastoid muscle motoneurons were found at levels C1-C3. The click-evoked potentials recorded in this study reflect responses of the spinal nucleus of accessory nerves through the vestibulospinal tract to click stimulation. The responses have the same characteristics as vestibular-evoked myogenic potentials that can be recorded using surface electrodes over the sternocleidomastoid muscles of humans.

A study on cervical reflex induced by click stimuli in cats

UNLABELLED The effects of click stimuli on the cervical muscle have been wildly studied, but no information is available on what reaction click stimuli elicit from the cervical cord. We studied the effects of click stimuli on the cervical cord in cats. PURPOSE To determine the response of the cervical cord to click stimuli in cats. MATERIALS AND METHODS Subjects were ten adult cats confirmed to have normal tympanic membranes. Cats were placed on artificial ventilation by tracheal incision. Auditory brainstem response (ABR) of both ears was measured to determine its threshold. Following the cervical incision, the dorsal vertebrae were removed, the cervical cord was exposed at C3 to C6, and bipolar needle electrodes were inserted. The reference electrode was attached to the forehead. Click stimuli were presented using 1-20 Hz clicks. RESULTS Responses peaking at 4.89-5.10 ms were induced by click stimuli of 105 dBSPL (1 Hz) at C3. Latencies tended to be prolonged with decreasing sound pressure. No response was confirmed at of C4 to C6. The responses to clicks of 20 Hz or more disappeared when 100 responses were summed. After the experiment, we confirmed that accessory nerves showed a response to electrical stimuli applied by bipolar needle electrodes. The cervical cord was removed to make sure that the electrode had been passed into the spinal nucleus of the accessory nerve. DISCUSSION Spinal nuclei of accessory nerves exist at C3 to C5 of the cervical cord, and are associated with the movement of the sternocleidomastoid muscle at C3 in particular. Click stimuli are reported to affect the sternocleidomastoid muscle. The results of our study appear to reflect the response of the spinal nucleus of the accessory nerve to click stimuli. The fact that responses to clicks of 20 Hz or more disappeared when 100 responses were summed suggests that the response was induced via a pathway other than the auditory pathway.

Neuro-otological Examination of Olivo-Ponto-Cerebellar Atrophy.

The main clinical findings of OPCA include cerebellar symptoms, extrapyramidal symptoms, autonomic nerve symptoms, in addition to various oculo-motor disturbances. We reported a case of OPCA where neuro-otological examination facilitated the diagnosis. Neuro-otological examination was carried out in 6 cases of OPCA, and duration of illness and experimental findings were compared.Subject: Neuro-otological examination was undertaken in 6 OPCA patients over a 5 year period 1993-1997. The mean patient age was 53.8 years, and the ratio of males to females was 2:4. Duration of illness was 3 years for 2 patients, 4 years for 2 patients, 6 years for 1 patient and 8 years for 1 patient.Method: For all patients, the following examinations were carried out. (1) audiogram, ABR (2) nystagmus (3) eye tracking (4) optokinetic nystagmus, saccade (5) visual suppression.Results: Smooth pursuit eye movement impairment was independent of the duration of illness. Nystagmus findings, saccadic eye movement and the visual suppression test revealed that impairment increased in patients whose duration of illness was more than around 4 to 6 years. The oculo-motor disturbances of OPCA start with impairment of cerebellar and smooth pursuit eye movement, and eventually result in brainstem disorders such as saccadic eye movement and visual suppression. As the duration of illness lengthens, the oculo-motor system itself will no longer function and response to all of the examinations will be lost. Neuro-otological examinations were found to be valuable for the diagnosis of OPCA.