Identification of the exact stimulated site in transcranial magnetic stimulation of the facial nerve.
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Electric Stimulation↗
Biomedical subjects
R Shiobara
Publications and source records attributed to R Shiobara.
Middle fossa transpetrosal-transtentorial approaches for petroclival meningiomas. Selective pyramid resection and radicality.
Forty-two patients with petroclival meningioma were operated upon by the middle fossa transpetrosal-transtentorial approaches since 1977. Half of those showed tumour extension into the middle fossa and one-third in the cavernous sinus. Seventeen (40%) had a large tumour of 40 mm in diameter or larger, and 8 of those had a broad attachment from the clivus to petrous pyramid of the temporal bone. The site of pyramid resection was selected from three types, depending on the tumour location and the patients' pre-operative hearing. There was no surgical mortality. Significant risk of lower cranial nerves palsy was minimal and useful hearing was preserved in 18 out of 21 patients. The follow-up, an average of 4 and a half years, showed tumours were completely eradicated in 32 patients (76%) and there was regrowth in 3 (7%). Thirty-four patients (81%) were independent, 3 disabled and only one died of rapid tumour regrowth. The most influential factor on surgical results was the extent to which the tumour had invaded the brain stem. The presence or absence of arterial encasement and of peritumoural oedema on MRI were important in the selection for radical surgery.
Adolescent↗
Hearing preservation by the extended and nonextended middle cranial fossa approach for acoustic neuroma.
The results of 248 cases of acoustic neuroma surgery carried out mainly by the extended middle cranial fossa approach during a 16-year period from 1976 to 1991 are analyzed. Hearing preservation was attempted in 69 cases and successfully achieved in 35 (51%) cases. Hearing was preserved in 24 (57%) of 42 cases in which a tumor was 20 mm or smaller in diameter, pure-tone hearing level was 50 dB or lower, and speech discrimination score was 50% or higher. The hearing preservation rate (76%) in the cases with a tumor extending 3 mm or less from the internal auditory canal was much higher than in cases with a larger tumor. Hearing was preserved in three of seven cases with a tumor of 21 mm or larger and in two of four cases of neurofibromatosis type 2. The evaluation of postoperative hearing is also discussed.
Journal Article↗
[Transcranial magnetic stimulation of the facial nerve--identification of the actual excitation site in the cat].
The site where transcranial magnetic stimulation excites the facial nerve was studied in 6 cats. Transcranial magnetic stimulation of the facial nerve was recorded from the left mentalis muscle. A figure-of-eight shaped magnetic coil was used, and coil induction direction had more influence on the facial nerve evoked compound muscle action potentials (CMAPs) than the coil position. No change could be detected in the CMAPs before and after craniotomy, after cerebellar lobectomy and after exposure of the facial nerve in the facial canal. The facial nerve was stimulated electrically at the porus, meatal portion, geniculum and horizontal portion. The latencies of the CMAPs for each portion were measured and compared with the magnetic response, which was coincidental with that of the meatal portion. The facial nerve was then transected distally from the porus, and CMAPs following magnetic stimulation were recorded at each step. The CMAPs disappeared when the nerve was transected at the fundus. The results of both approaches in this study led to the conclusion that transcranial magnetic stimulation excites the facial nerve at the meatal portion.
Action Potentials↗
Classification of the extended middle cranial fossa approach.
There are several possible operative approaches to acoustic neuroma surgery. Ideally, there should be no need to select among approaches according to tumor size or indications for hearing preservation. The ideal approach should also allow otologists and neurosurgeons to work as a team using the same operative field and achieve functional preservation (facial nerve function and hearing) in a high percentage of cases. In 1977, the authors first reported on the extended middle cranial fossa (EMCF) approach for AN surgery. Based on our 15-year experiences of this approach, we have classified it into 3 types and describe their indications and techniques in the present paper. In addition, we examine the advantages and disadvantages and emphasize its excellent applicability as a team approach for otologists and neurosurgeons.
Cerebellum↗
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.
Adolescent↗
Hearing preservation in acoustic neuroma surgery by the extended middle cranial fossa method.
The results of attempted hearing preservation were investigated in 160 cases of acoustic neuroma surgery carried out by a team of otologists and neurosurgeons at Keio University Hospital during a 14-year period from 1976 to 1989. Surgery was carried out by the middle cranial fossa (MCF) approach in the earlier cases and by the extended middle cranial fossa (EMCF) approach in the more recent cases. Measurable postoperative hearing was preserved in 20 of the 160 cases. Preoperatively, 22 cases had tumors of 20 mm or smaller in diameter, hearing levels (HL) of 50 dB or lower, and speech discrimination scores (SDS) of 50% or higher; 8 (36%) met these conditions postoperatively. Among those cases with hearing preserved postoperatively, hearing was unchanged from the preoperative level in 9 cases and changed in 11 cases. Total tumor removal was achieved in 19 cases. In one case, part of the tumor was left in order to preserve hearing, but MRI and CT have revealed no change in hearing or tumor enlargement to date, at 4 1/2 years after surgery. Hearing was preserved but progressively deteriorated postoperatively in one case in which the tumor was believed to have been totally removed but there was recurrence and in another case of total resection of neurofibromatosis II. Postoperatively, there were increased incidences of absence of the stapedius reflex, Type V by Békésy audiometry, and prolongation of the IT5, disappearance of Wave V, and no response in measurements of the ABR.
Adolescent↗
Preservation of facial nerve function in acoustic neuroma surgery by the extended middle cranial fossa approach.
The anatomical preservation rates of the facial nerve and postoperative facial nerve function were investigated in cases of initial operation for acoustic neuroma by the middle cranial fossa or extended middle cranial fossa approach. The cases were divided chronologically into three groups according to the date of surgery. The rate of anatomical preservation was 93% in the most recent period, compared to 82.4% for the entire series. This was attributable to higher preservation rates being achieved in cases with medium or large tumors with increased experience. Also regarding postoperative facial nerve function, the number of cases with no paralysis or only partial paralysis increased and the number of cases requiring sacrifice of the facial nerve decreased as experience was accumulated in the series. Even when the facial nerve was preserved anatomically, however, facial-hypoglossal anastomosis was carried out actively if facial nerve function did not recover satisfactorily one year after surgery. For this reason, as many as 33% of the patients underwent anastomosis. This high percentage, however, is attributable to anastomosis ultimately being carried out in 47.7% of the patients in the early period; 22.2% of the patients in the most recent period underwent anastomosis.
Adolescent↗
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.
Adolescent↗
Intracranial reconstruction of the facial nerve. Clinical observation.
Nine cases of intracranial facial nerve reconstruction are reviewed in this paper. All patients underwent this procedure for severe injury or disruption of the facial nerve during surgery for acoustic neruroma through the modified extended middle cranial fossa approach (1). Satisfactory recovery of facial function was obtained in 4 patients. Three patients underwent hypoglossal-facial nerve anastomosis 1.3-1.5 years later for no or poor recovery of the facial function. One patient refused any further surgical treatment despite unsatisfactory recovery. The remaining 1 patient, during a telephone interview, stated that facial function had not returned at all 1 year and 5 months postoperatively. Although some degree of associated movement or mass movement was unavoidable, facial movement and mimetic facial expression were better in the patients with satisfactory recovery, as compared with those after hypoglossal-facial nerve anastomosis (2). Fibrin glue, which we used in the latest 3 cases instead of suture, seemed to possibly solve the technical difficulty in placing a suture. Facial function after intracranial reconstruction with fibrin glue was as good or better than that after repair by suturing.
Adult↗
Anterior transpetrosal-transtentorial approach for sphenopetroclival meningiomas: surgical method and results in 10 patients.
This report presents a new surgical method and the results in 10 patients with petroclival meningiomas extending into the parasellar region (sphenopetroclival meningiomas). Minimal but effective extradural resection of the anterior petrous bone via a middle fossa craniotomy offered a direct view of the clival area with preservation of the temporal bridging veins and cochlear organs. The dural incision was extended anteriorly to Meckel's cave, and in cases with invasion of the cavernous sinus, Parkinson's triangle was enlarged by mobilization of the trigeminal nerve. This approach offered an excellent view from the mid-clivus to the cavernous sinus. Extra-as well as intradural tumor masses and dural attachments could be cleared under direct view of the pontine surface. The risk of injury to the lower cranial nerve and of retraction damage to the temporal lobe and brain stem were kept minimal by this approach. Total tumor resection was achieved in 7 patients, with no resultant mortality. Eight patients had a satisfactory postsurgical course, extraocular paresis being their main complaint. The extent of tumor resection depended on the degree of tumor adhesion to the carotid artery, and operative morbidity on the degree of tumor invasion of the brain stem. Of the 3 patients in whom subtotal tumor removal was achieved, only one experienced regrowth of the tumor and underwent a second operation during the follow-up period (6 months-6 years).
Adult↗
Ceruminoma with intracranial invasion--case report.
Ceruminous gland tumors (ceruminomas), which usually involve the external auditory canal, are rare. A case of ceruminoma invading the temporal bone and histologically proven to be papillary adenoma is presented. The tumor recurred and invaded intracranially after subtotal removal and was finally diagnosed as adenocarcinoma. The importance of early diagnosis and radical treatment is stressed.
Adenocarcinoma↗
[Intraoperative monitoring of facial nerve evoked electromyography. Accurate identification of the facial nerve during surgery of cerebellopontine angle tumors].
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Cerebellar Neoplasms↗
[Intraoperative monitoring of facial nerve evoked electromyography during surgery for cerebellopontine angle tumors. Usefulness in prognosis of postoperative facial nerve function].
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Cerebellar Neoplasms↗
A modified extended middle cranial fossa approach for acoustic nerve tumors. Results of 125 operations.
During the past 10 years, 125 operations for acoustic nerve tumors were performed on 114 patients at the authors' institution using a modified extended middle cranial fossa approach. This approach is based on a combination of King and Morrison's translabyrinthine-transtentorial approach and on the extended approach through the middle cranial fossa described by Bochenek and Kukwa. There were two hospital deaths (operative mortality 1.6%). In 102 operations on the initial tumor, total removal was performed in 89 cases (87%), and in 71 (80%) of these the facial nerve was anatomically preserved. Intracranial end-to-end anastomosis was performed on five of the 18 sacrificed facial nerves; a facial-hypoglossal anastomosis was carried out in the remaining 13 patients and in five (7%) of the 71 patients whose anatomically preserved facial nerve functioned poorly. In seven (39%) of the 18 patients in whom an attempt to preserve hearing was made, postoperative hearing was saved. In 23 operations on 17 patients for recurrent tumors, most of which had previously been removed subtotally via the suboccipital approach, total removal was accomplished in 13 (57% of the 23 reoperations and 76% of the 17 patients). At reoperation, the facial nerve was preserved in six (55%) of the 11 patients in whom the facial nerve had not been sacrificed. Postoperative leakage of cerebrospinal fluid occurred in 11 cases (8.8%), with rhinorrhea in 10 cases and otorrhea in one. Five of the fistulas were corrected by surgery and the rest healed spontaneously. Other complications were not significant.
Adolescent↗
[Intraoperative electrophysiological monitoring for hearing preservation in acoustic neurinoma surgery].
Five acoustic neurinomas have been operated with hearing preservation as a goal. We monitored intraoperative brainstem auditory evoked potentials (BAEP) in all five cases, electrocochleogram (ECoG) using needle electrode in external auditory meatus in four, and compound action potentials directly recorded from the cochlear nerve (CAP VIII) in three. In all five cases the tumor was totally resected and cochlear nerve was anatomically preserved. However, in only one case useful hearing was preserved with preservation of all wave forms of the BAEP. Another patient with preservation of all wave forms of BAEP and the ECoG showed postoperative severe hearing loss. Other three patients showed postoperative severe hearing loss: only Wave I of BAEP and ECoG were preserved without preservation of the CAP VIII in one whose cochlear nerve was thought to be damaged in cerebellopontine angle cistern; Wave I of BAEP, ECoG and CAP VIII were preserved in one in whom it was suggested cochlear nerve near brainstem or cochlear nucleus was damaged; none of the BAEP, ECoG and CAP VIII was preserved in one in whom it was suggested distal cochlear nerve, or internal auditory artery was damaged. These different patterns of changes suggested that different causes for the hearing loss and difficulties in hearing preservation during acoustic neurinoma surgery. Having identified the putative mechanism of the hearing loss by monitoring those potentials, suggestions are made about how such hearing loss might be avoided. For preservation of the hearing in acoustic neurinoma surgery, all of those potentials including all wave forms of BAEP, ECoG and CAP VIII should be preserved during surgery.(ABSTRACT TRUNCATED AT 250 WORDS)
Action Potentials↗
[Monitoring of antidromic facial nerve action potentials in cerebello-pontine angle tumor operations].
A method of recording the antidromic facial nerve compound potential (AFNAP) is presented. When the facial nerve is stimulated, a compound action potential is propagated in both directions from the stimulating site. We recorded AFNAP's in 6 cases of cerebello-pontine angle (CP angle) tumors (5 acoustic neuromas and one epidermoid) using a bipolar silver ball-type electrode directly put on the facial nerve in CP angle by stimulation of the peripheral facial nerve at the stylomastoid foramen. It was necessary to use needle electrodes instead of surface ones for stimulation to keep the artefacts from stimulating currents within reasonable bounds. Good contact of the electrode tips with facial nerve was required to get clear action potential. By stimulation with needle electrodes AFNAP's were recorded without averaging and had a good reproducibility. AFNAP's were typical triphasic potentials and the major negative peak latencies were observed from 1.5 to 3.4 msec except one case of recurrent epidermoid whose major negative peak latency was 7.6 msec. It was verified that these potentials were the results of facial activity, because they were recorded exclusively on the facial nerve, they could not be recorded at the proximal end of the sectioned facial nerve, and alterations of latency were observed with changing the position of recording electrode along the facial nerve. A calculated conduction velocity was about 50 m/sec. It was thought that recording AFNAP facilitated the identification of the facial nerve on the surface of the CP angle tumor, because the amplitude of AFNAP decreased immediately when the recording electrodes were off from the facial nerve.(ABSTRACT TRUNCATED AT 250 WORDS)
Action Potentials↗
Results of surgery by the modified extended middle cranial fossa approach in 100 patients with acoustic neuroma.
The results of surgery by the middle cranial fossa (MCF) approach or the modified extended MCF approach in 100 patients with acoustic neuroma are reported. The rates of facial nerve preservation, tumor removal, and hearing preservation were reported and discussed. This surgical procedure can be applied to tumors of any size, from tumors confined to the internal auditory canal to those extending into the posterior fossa.
Adult↗