Minako Yamamoto

The Growth Rate of Acoustic Neuromas

Growth rate of acoustic neuromas (AN) was studied in 43 patients. The growth rate was analyzed using tumor increasing size (IS) and tumor volume doubling time (VDT). The growth rate of unilateral AN was lower than that of bilateral AN associated with neurofibromatosis2 (NF2). The growth rate of recurrent tumors was higher than that of non-operative tumors. The relationships between growth rate and age and tumor size were also analyzed. The younger the patient or the greater the tumor size, the higher the growth rate. Several factors, i.e. age and sex of patients, tumor pathology and tumor size, should be considered together for predicting the growth rate on AN.

Evaluation of Hearing Recovery in Patients with Sudden Deafness

It is still difficult to evaluate the efficacy of treatment of sudden deafness. Effective methods of therapy have been reported in some studies and other studies have reported spontaneous recovery. In the present study, we assessed the correlation between hearing recovery and various parameters measured during recovery. We used three parameters: hearing gain, relative hearing gain, and recovery rate. We found that the recovery rate during recovery and the parameters measured on the 7th treatment day demonstrated the greatest correlation. The recovery rate on the 7th day of treatment was found to be useful for predicting the final hearing recovery. Comparison of the recovery rate on the 7th day of treatment may be useful for the evaluation of the efficacy of treatment of sudden deafness.

Endoscopic diagnosis of idiopathic perilymphatic fistula

The usefulness of endoscopic examination for the diagnosis of idiopathic perilymphatic fistula (IPLF) was investigated. Eight patients presenting with unilateral sensorineural hearing loss and vertigo underwent endoscopic examination by the transtubal or transtympanic approach. In 5 out of the 8 patients, transtubal endoscopy was carried out using a superfine flexible endoscope. With this approach, no abnormal findings were visualized. A perilymphatic leak from the round window was observed in 2 patients by means of transtympanic examination using a needle scope. These findings were confirmed in both patients by microscopic observation during tympanotomy. In one patient who was finally diagnosed with IPLF, the transtympanic endoscopy failed to detect perilymphatic leakage. Although incision of the tympanic membrane is necessary for the examination, transtympanic endoscopy is useful for the diagnosis of IPLF. Further improvement of the superfine flexible fiberscope is necessary before transtubal observation of the tympanic cavity can be effectively conducted.

Postoperative complications in acoustic neuroma surgery by the extended middle cranial fossa approach

The complications of acoustic neuroma (AN) surgery by the extended middle cranial fossa approach were studied in 160 cases. Death during surgery occurred in 3 cases (1.9%); 2 of these involved large tumors and the third was a case of recurrence. Transient temporal lobe symptoms were seen in 24 cases (15.3%); the average tumor diameter in these cases was 36.0 mm. Beside symptoms of 7th and 8th nerve disturbance, hemiparesis was seen 7.6%; 3rd, 4th, and 6th cranial nerve symptoms in 7.0%; and cerebellar symptoms in 7.6% of the patients. The incidence of these disturbances increased with tumor size. Cerebrospinal fluid (CSF) leakage occurred in 20.4% of the cases and this necessitated surgical treatment in 5% of the cases.

Hearing recovery and vestibular symptoms in patients with sudden deafness and profound hearing loss

Audiometric data from 76 patients with unilateral sudden deafness and hearing loss of 80 dB or more were studied to statistically assess the relationship between vestibular findings (vertigo and/or dizziness, nystagmus, canal paresis) and hearing recovery in various frequency ranges. Hearing recovery in patients with vertigo and/or dizziness (V(+)) was much poorer than in patients without such findings (V(-)). Concerning hearing recovery in the high frequency range, a significant statistical difference was evident between the V(+) and V(-) group. There were no statistically significant differences in hearing recovery between patients with spontaneous nystagmus or canal paresis and those without.

Psychological aspects of psychogenic deafness in children

Twenty-nine children with psychogenic deafness were investigated from audiological and psychological aspects. ABR and Békésy audiometry were useful for diagnosing psychogenic deafness. The elapsed time from the start of treatment to audiometric recovery was significantly shorter in patients receiving psychological treatment, indicating that treatment by a team of otologists and counselors was able to hasten recovery in children with psychogenic deafness. The pattern of hearing recovery in the treated group was classified into 3 types and in the control group into 4 types. Counseling seemed to have a positive effect on patients with fluctuating improvement. In the patients in the treated group, the elapsed time to audiometric recovery from the beginning of psychological treatment was 7.5 months; however, in the control group recovery it took 17.1 months. Psychological treatment revealed that the clinical course of psychogenic deafness in children seemed to have some relation to the patients personality and psychological stresses.

Audiological Findings in Acoustic Neuroma

Audiological examinations are vital in the diagnosis of acoustic neuroma. In interpreting their results, however, it is necessary to consider the patients hearing level. The most sensitive audiological examination is auditory brain stem response (ABR) audiometry. Its most useful parameter is the IT5. A U-shaped audiometric configuration suggests AN, since it is seen in 10% of patients with small tumors. Psychological audiometric tests can be excluded from the battery of screening tests since they have low rates of positive diagnosis. The stapedius reflex (SR) test also has a low positive diagnostic rate in cases of small tumors. Even with the parameters of absence of reflex, elevated threshold, and decay combined, the overall SR test has a lower positive diagnostic rate than ABR audiometry. Nevertheless, the SR test can be employed as a screening device in cases in which the hearing level at 2 kHz and lower is 70 dB or lower, even if it is 71 dB or higher at 4 kHz and 8 kHz. At present, ABR audiometry is applicable in only about half of AN cases. Therefore, the need for early diagnosis must be further emphasized.

Results of acoustic neuroma surgery by the extended middle cranial fossa approach

The results of surgery in 160 cases of AN are reported. Surgery was carried out by the extended middle cranial fossa (EMCF) approach in 138 cases and by the middle cranial fossa (MCF) approach in 22 cases. The tumor extended an average of 28.9 mm into the posterior cranial fossa; 42% of the tumors extended 31 mm or more. Mortality was 1.9%. Of the 3 cases of death, two had large tumors of 45 mm and 52 mm each, and one was a case of recurrence. Total tumor removal was achieved in an average of 78.8% of the cases. When the cases were classified by date of operation, the total tumor removal rate in the 60 most recent cases was 93.3%. The rate of facial nerve presentation was 82.4% on average and 93% in the recent cases. Hypoglossal-facial nerve anastomosis was performed in 33% of the cases in which facial nerve function failed to recover for an extended period of time. Among recent cases, however, anastomosis has been carried out in 22% of the cases. Hearing was preserved in 20 cases. Useful hearing was preserved in 8 (38%) of 22 cases. Recurrence was confirmed through surgery in 3 cases. Recurrence was suspected but was unconfirmed in 3 cases.

Acoustic neuromas with normal hearing

We report on 10 patients with surgically proven acoustic neuroma (AN) who have normal hearing, and their clinical features have been investigated. The results obtained in this study were as follows: The clinical features of AN patients with normal hearing involved 1) predominance in younger adults, 2) predominance in small tumors with short duration after onset, 3) subjective hearing loss accompanied with tinnitus was the most common symptom, and 4) vertigo or dizziness without any cochlear symptoms was also a frequently seen symptom. We conclude that in order not to overlook AN among patients with normal hearing, transorbital X-ray and ABR tests should be performed on these patients for the screening purpose.

Surgical Anatomy for the Extended Middle Cranial Fossa Approach

The surgical anatomy of the temporal bone and the cerebellopontine angle was studied in cadavers, by performing simulated surgery via the extended middle cranial fossa approach. This approach is classified into 3 types according to extension of the drilling area of the temporal bone. In this paper, the surgical anatomy visualized by the EMCF type II and type III is described. In the EMCF type II, mastoidectomy and labyrinthectomy are performed completely through the middle cranial fossa, and in the EMCF type III permitting hearing preservation surgery, sections of the middle cranial fossa dura and the cerebellar tentorium are added to Houses middle cranial fossa approach. The comprehension of these anatomical structures is essential for surgeons in performing acoustic neuroma surgery. We believe that this study will serve to expand our knowledge of surgical anatomy, and that as a result the EMCF approach for acoustic neuroma surgery will become more popular.