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

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%).

Atrial natriuretic peptide (ANP) suppresses acute atrial electrical remodeling in the canine rapid atrial stimulation model.

OBJECTIVES: Atrial electrical remodeling is considered to play an important role in the appearance of atrial fibrillation. The effect of atrial natriuretic peptide (ANP) on atrial electrical remodeling was evaluated in a canine atrial stimulation model. METHODS: In 15 beagle dogs, electrodes for pacing and recording were fixed on the atrial surface. In 10/15 dogs, rapid atrial stimulation (400 bpm) was performed for 7 h at the right atrial appendage (RAA) and the remaining 5 were used as the sham without rapid pacing. In 5/10 dogs with rapid pacing, human atrial natriuretic peptide (ANP) was infused (1.0 microg/kg/min). The effective refractory period (ERP) and the monophasic action potential duration (MAP) were evaluated at 0, 3, and 7 h after rapid pacing. The expression levels of mRNAs of ion channels or transporters were evaluated from the atrial samples of sham and after a 7 hour pacing. RESULTS: In the control group with rapid pacing (n=5), the atrial ERP and MAP duration were shortened at all atrial sites, e.g., ERP from 148+/-14 ms to 109+/-8 ms at RAA, P=0.006. In contrast in the ANP group, neither the ERP nor MAP duration showed a significant shortening and the effect of ANP on hemodynamic parameter was relatively small. Expression levels of the mRNA were not significantly different between the control and ANP groups. CONCLUSIONS: Administration of ANP prevented the shortening of the ERP and MAP duration in the rapid atrial stimulation model. The effect of ANP on atrial electrical remodeling was considered to be due to its direct action on the myocardium.

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 sternoclei-domastoid muscles of humans.