2001 年 60 巻 2 号 p. 105-112
The effects of surgical manipulation to the vestibular system have not fully been elucidated and this study was designed to investigate the effects of tympanoplasty and cochlear implant on positional nystagmus.
Materials and methods: (1) Tympanoplasty: A total of 42 patients were included in this study and the etiological diagnosis of the patients were 26 cases of cholesteatoma and 22 cases of chronic otitis media. Types of tympanoplasty were type I, 12 cases; type III, 26 cases; type IV, 7 cases; and first-stage operation, 3 cases. The positional nystagmus was monitored and video-recorded using an infrared CCD camera before surgery, one day and every several days after surgery until it disappeared.
(2) Cochlear implant: The etiological diagnoses of these patients were 5 cases of progressive hearing loss, 4 cases of meningitis, 2 cases of sudden deafness and 6 cases of unknown etiology. Vestibular function was evaluated before and after surgery using the caloric test and the positional nystagmus.
Results: (1) Tympanoplasty: Postoperative positional nystagmus was observed in 19 out of the 42 cases (45.2%), all of which showed no nystagmus prior to surgery. The direction and type of the nystagmus varied and it was toward the surgical side in 13 cases, downbeat nystagmus in 4 and apogeotropic direction-changing positional nystagmus in 2. Postoperative nystagmus disappeared 4 to 68 days after surgery.
(2) Cochlear implant: Postoperative positional nystagmus was observed in 6 out of 11 cases (54.5%), all of which showed no nystagmus prior to surgery. The type of nystagmus was toward the surgical side in all cases. Postoperative nystagmus disappeared 8 to 26 days after surgery. Reduced results of caloric testing after surgery were found in 3 of 14 cases with residual vestibular function.
Conclusions: Tympanoplasty and cochlear implant have a significant effect on the vestibular system. However, vestibular changes after these surgeries were considered to be reversible.