Clinical application of virtual endoscopy as a support system for endoscopic sinus surgery.

CONCLUSIONS: Computer processing of conventional CT images can provide virtual endoscopic images (VEIs). Surgeons observing these images feel as if they are observing the lesion using an endoscope. Simulation based on animated VEIs before endoscopic sinus surgery (ESS) is useful for the improvement of surgical safety and surgeons' education. Although the production of VEIs requires certain surgical experience, after the production of VEIs, surgeons can repeat simulation of a surgical procedure and have confidence in the actual operation. OBJECTIVE: We investigated the clinical application of CT-reconstructed VEIs as a support system for ESS. MATERIALS AND METHODS: A GE Light Speed Ultra 16 as a 16-slice CT scanner and Advantage Workstation 4.2 were used. Software called Navigator in this workstation allows the production of CT-reconstructed VEIs. We applied simulation based on VEIs to endoscopic operations for mucocele or sinusitis. RESULTS: In nine cases of mucoceles and sinusitis, simulation based on animated VEIs was applied. According to the simulation, surgeries were performed, and the mucoceles and obstructed sinuses could be opened readily and safely. This system was more effective when there were landmarks such as polyps or irregular mucosal surfaces allowing macroscopic confirmation ahead of the viewpoint.

Clinical significance of vertical component of caloric response including its second phase in vertiginous patients.

CONCLUSIONS: Up-beating vertical component recorded in the caloric first phase was attributed mainly to the inhibitory endolymph flow in the anterior canal. Down-beating vertical component recorded in the caloric second phase provoked by a positional change could be explained by a reversed endolymph flow in vertical canal(s). OBJECTIVE: To investigate the origin of a vertical component in caloric response. MATERIALS AND METHODS: We analyzed electronystagmography (ENG) of caloric responses, which had measurable horizontal component in the caloric first phase in both ears in 200 ears of 100 vertiginous patients. A caloric first phase was provoked by cold water in the supine position with the lateral semicircular canal earth-vertical. A caloric second phase was provoked by re-orienting the lateral canal from the earth-vertical to earth-horizontal after the cessation of the first phase (provoked second phase). The nystagmus of the whole procedure was recorded by two-dimensional ENG. RESULTS: We recorded the vertical component in 103/200 ears in the caloric first phase, which was directed mostly upward (92/103 ears). We also recorded the vertical component in 91/200 ears in the provoked second phase, which was directed almost exclusively downward (90/91 ears).

Vertical component of the caloric response, including a caloric second phase provoked by positional change: a preliminary report.

We measured the horizontal and vertical components of caloric nystagmus in 120 ears of 60 vertiginous patients who had moderate to vigorous caloric first-phase response in both ears, no spontaneous nystagmus, and no severe disorders in the central nervous system. We provoked a caloric first phase in the supine position with 5 ml of water at 20 degrees C for 15 seconds. We provoked a caloric second phase by changing the position of a patient from supine to sitting after the end of the first phase. The horizontal component of the caloric second phase was recorded in 108 of 120 ears (90%). The vertical component was recorded in 57 of 120 ears (48%) during the caloric first phase and in 51 of 120 ears (43%) during the caloric second phase. We suspected that the vertical component of the caloric first phase was mainly due to the inhibition of the anterior semicircular canal.

The clinical significance of the caloric second phase provoked by positional change in vertiginous patients.

The reversal phase of caloric nystagmus is provoked when the lateral semicircular canal in a patient is reoriented from a vertical to a horizontal plane at the cessation of the caloric first phase, which we called the provoked caloric second phase. In investigating the clinical significance of the provoked caloric second phase, we recruited 102 vertiginous patients who had measurable caloric responses in both ears but no disorders of the central nervous system. We recorded the provoked caloric second phase in 188 (92%) of 204 ears in 102 patients. The average maximum slow-phase velocity of the caloric first phase was 26.9 degrees per second, and that of the provoked caloric second phase was 5.0 degrees per second. The maximum slow-phase velocity of the provoked caloric second phase correlated with that of the foregoing caloric first phase (r = -.84). Thus, we consider that the provoked caloric second phase is influenced largely by the foregoing caloric first phase. Furthermore, in the patients who responded normally to caloric stimulation, the directional preponderance of the provoked caloric second phase correlated with the directional preponderance of optokinetic after-nystagmus (r = .64). Hence, we conclude that the provoked caloric second phase reflects central vestibular asymmetry in patients with normal peripheral vestibular function.