Extended middle cranial fossa approach for vestibular schwannoma: technical note and surgical results of 896 operations.

From 1976 to 2006, 896 vestibular schwannomas were operated on using an extended middle cranial fossa approach. With this approach, the operative field can be extended according to tumor size and the facial and cochlear nerves can be preserved more easily with cooperation between the neurosurgeon and ENT surgeon. The mortality rate among 896 vestibular schwannoma patients was 0.3%. In the 760 initially operated vestibular schwannomas with total removal of the tumor, facial nerves were anatomically preserved in 715 or 94.1% of the cases. In 61.0% of 270 cases in which hearing preservation was attempted, hearing was preserved, and in 46.7% of those 270 cases useful hearing was preserved postoperatively. However, in the last 10 years the useful hearing preservation rate of the 140 attempted cases was 53.6%. Most of the complications of this approach were cerebrospinal fluid leakage; by using fat tissue, fibrin glue and spinal drainage from 1992 to 2005, cerebrospinal fluid leakage occurred in 59 or 10.6% of 569 cases, with 13 or 2.3% being repaired surgically. Moreover, in the last 10 years, the surgical results have improved along with improved surgical experience, improved instruments and better monitoring methods.

Medial (intra-cisternal) acoustic neuromas.

The clinical characteristics of "medial" or "intra-cisternal" acoustic neuroma (AN) treated in our institute were reviewed. Among 466 patients with ANs in our series during the last 20 years, 6 patients (1.3%) were considered to fill the criteria of medial AN definition. Compared with those with non-medial ANs, the patients with medial ANs show a tendency to have cerebellar and/or cranial nerve dysfunction (especially trigeminal and/or facial nerves) in addition to hearing loss at the time of initial presentation. On magnetic resonance imaging, medial AN is visualized as a multi-cystic mass lesion in the cerebello-pontine cistern without extension into the internal auditory canal in most cases. Although total removal of tumor was achieved in all cases, the results of preservation of facial nerve function were not satisfactory. Medial AN can be considered as a clinical, but not pathological, subtype in terms of the functional outcomes of the facial nerve and hearing.

The long-term outcome of hearing preservation following vestibular schwannoma surgery.

OBJECTIVE: The aim of this study is to describe the long-term outcome of preserved hearing after vestibular schwannoma surgery. METHODS: Subjects are 20 unilateral vestibular schwannoma patients whose class A hearing of the AAO-HNS classification was preserved successfully after tumor removal. Hearing preservation surgery was attempted via the middle cranial fossa (MCF) or the extended MCF approach. The follow-up periods ranged from 2 to 16 years. The outcome measures included the pure tone average (PTA) and speech discrimination score (SDS). RESULTS: PTA was maintained in less than 30 dB in 11 out of 20 patients within 2 years follow-up, six out of 13 patients within 4 years follow-up, and two out of five patients within 6 years follow-up, respectively. SDS was maintained in more than 70% in 17 out of 20 patients within 2 years follow-up, ten out of 13 patients within 4 years follow-up, and three out of five patients within 6 years follow-up, respectively. CONCLUSIONS: The preserved hearing maintained about more than 40% of the patients with the class A hearing in every 2 years follow-up. From this result, we can conclude that the hearing preservation surgery could be one of the best treatments for vestibular schwannoma patients with class A hearing. However, further study will be needed to clarify the mechanism of the deterioration in hearing after hearing preservation surgery.

Use of the ultrasonically activated scalpel in acoustic neuroma surgery: preliminary report.

Recently, the ultrasonic activated scalpel (the Harmonic Scalpel, HS) has been introduced in laparoscopic surgery. We have applied the HS in debulking the tumor in the posterior fossa and concluded that this is useful in acoustic neuroma surgery. Fifteen patients with a tumor extending more than 20 mm into the posterior fossa were included in this study. The extended middle cranial fossa approach type II was used in 13 patients and type III (hearing preservation surgery) was used in 2 patients. In one of two patients, hearing was preserved. Postroperative facial nerve function according to the House-Brackmann method was grade I in 12 patients, grade II in 2 patients, and grade III in 1 patient. Compating the technique of using HS to a pair of bipolar forceps and/or ultrasonic cavitational aspirator, the former can result in better preservation of the facial nerve function.

Glomus jugulare tumor presenting with intracerebellar hemorrhage.

What is believed to be the first case of a glomus jugulare tumor presenting with intracerebellar hemorrhage is described. A 25-year-old normotensive man suddenly suffered from severe headache, nausea, vomiting, vertigo, and ataxia due to an intracerebellar hemorrhage. Magnetic resonance imaging and angiography revealed a highly vascular jugulare foramen tumor extending into the intracranial space adjacent to the hematoma. Total removal of the tumor was performed successfully via the combined pre- and retrosigmoid approach, and the histologic diagnosis was a glomus jugulare tumor. We concluded that one of the numerous draining veins on the surface of intracranial tumor, which were observed during the operation, was the origin of the intracerebellar hemorrhage.

Long-term prognosis of profound facial nerve paralysis secondary to acoustic neuroma resection.

The long-term prognosis of profound facial nerve paralysis was reviewed in 107 patients who, despite preserved nerve continuity, showed no facial movement after acoustic neuroma resection. Spontaneous recovery occurred in 77 patients. However, there was no apparent recovery in 30 patients. Twenty-two of these patients underwent hypoglossal-facial nerve anastomosis 7-33 months after tumor resection. When spontaneous recovery occurred, the first sign of remission was observed between 3 and 4 months after surgery in nearly half of the patients. Such a sign did not appear after 12 months. The recovery of facial movement deteriorated depending on how long remission onset was delayed. However, the quality of facial movement in patients with such delayed remission was still identical or better than that in those after hypoglossal-facial nerve anastomosis. These results showed that hypoglossal-facial nerve anastomosis should be performed approximately 1 year after tumor resection if no sign of remission has been observed by then.

Anterior transpetrosal approach to the prepontine epidermoids.

We have operated on nine patients with a prepontine epidermoid extending to the bilateral cistern or the unilateral middle fossa using the anterior transpetrosal approach since 1986. The preoperative symptoms were unilateral trigeminal neuralgia, hearing disturbance, gait disturbance, double vision, facial hypesthesia, hemifacial spasm, and dysphagia. The most common neurological sign was unilateral trigeminal nerve disturbance. In two patients with useful hearing preoperatively lost, the labyrinth and mastoid air cells as well as the petrous apex were resected to extend the surgical field. Tumors were totally removed, except for capsules that were tightly adhered to the brain stem, cranial nerve, and vessels. The trigeminal neuralgia, hemifacial spasm, and dysphagia disappeared, but double vision improved only one out of three cases, and facial hypesthesia was unchanged in all cases. There were no postoperative deaths. New abducens palsy appeared in four cases and cerebrospinal fluid (CSF) leakage appeared in three cases postoperatively, but later these symptoms disappeared. In one case, postoperative chemical meningitis developed, and a ventricular shunt was required later to treat hydrocephalus. Postoperative follow-up, an average of 5,7 years, did not show any increases in any of the tumors. Based on our experience, we conclude that the anterior transpetrosal approach is more useful than the retromastoid suboccipital approach to resect the epidermoid located mainly in the prepontine cistern.

Quality of hearing preservation in acoustic neuroma surgery.

OBJECTIVE: This study aimed to investigate the factors affecting the quality of postoperative hearing in acoustic neuroma. STUDY DESIGN: The study was designed as a retrospective case review. SETTING: The study was performed at the Department of Otolaryngology, School of Medicine, Keio University, Tokyo, Japan. PATIENTS: The subjects were 94 patients with unilateral acoustic neuroma. INTERVENTION: Hearing preservation surgery was performed in the subjects via the extended cranial fossa approach or the middle cranial fossa approach. MAIN OUTCOME MEASURES: The outcome measures included patient's age and gender, hearing level, speech discrimination score, tumor size, and surgical approach. The relationship between the qualities of preoperative and postoperative hearing and the long-term prognosis of preserved hearing also was investigated. RESULTS: In 94 subjects, there were 47 patients whose hearing was preserved (HP group) and 47 patients whose hearing was not preserved (non-HP group). Overall, hearing preservation rate was 50%. There were no significant differences in age, gender, and tumor size between the two groups. The hearing preservation rate was significantly higher in patients with an intracanalicular tumor than that with a larger tumor. The better the preoperative quality of hearing was, the higher the postoperative one. Although the preserved hearing deteriorated after surgery in 4 patients, no significant hearing deterioration was observed in the other 43 patients. CONCLUSIONS: The results of this study indicated that the diagnosis for acoustic neuroma in the early stage with serviceable hearing is the most important to improve the quality of postoperative hearing.

[Cooperative multicentre study on posttraumatic epilepsy].

A multicentre cooperative prospective study have been conducted to investigate the factors influencing posttraumatic epilepsy (PTE) and to evaluate the prophylactic effect of anticonvulsants. Since April 1994, patients with head injury have been observed following our protocol as follows; anticonvulsants are administered only to the patients with brain parenchymal injury for one month just after head trauma and no anticonvulsants are administered after one month after trauma to any patients except those with posttraumatic epilepsy (PTE). Brain parenchymal injury included traumatic subarachnoid hemorrhage, acute subdural hematoma, contusion, intracerebral hematoma, and diffuse axonal injury. To April 1996, 635 patients with head injury have been registered and analyzed. During the follow-up period, 14 patients (2.2%) developed PTEs, which had only been observed in patients with brain parenchymal injury. Multiple regression analysis revealed that two factors, early epilepsy and brain parenchymal injury, could contribute to the prediction of PTE. The frequency of PTE in this study was compared with that in our previous retrospective study (Nakamura, 1995), in which anticonvulsants were administered to the patients with head injury. There was no significant difference in the percentage of patients having PTE between the group treated without anticonvulsants in this study and the untreated group in previous retrospective study. Anticonvulsants treatment after head injury was not likely to have a prophylactic effect against the development of PTE.

Electromyographic analysis of profound facial nerve paralysis following acoustic neuroma resection.

The aim of our retrospective study was to determine whether electromyographic findings (motor unit action potentials, MUAPs) can be used in long-term prognosis for profound facial nerve paralysis in patients whose nerve continuity is preserved during surgery for acoustic neuroma. The orbicularis oris, frontal, and orbicularis oculi muscles were examined for the occurrence of MUAPs in 48 such patients. In 30 patients who recovered from complete paralysis within 10 months after surgery, MUAPs in the first two muscles tended to precede the first sign of facial movement. MUAPs appeared in the orbicularis muscle in 80% of these patients at 1 month and in all at 5 months. In the frontal and orbicularis oculi muscles, MUAPs occurred in only 0-20% of these patients in the first month; within 3-5 months the number increased rapidly, and MUAPs were present in 95% of these patients at 10 months. In the remaining 18 patients with long-term complete paralysis (at least 1 year), MUAPs appeared solely in the orbicularis oris muscle: in 20% of these patients in the first month after surgery. While this number slowly rose, there was no period of rapid increase later. We conclude that the occurrence of MUAPs in the orbicularis oris and frontal muscles within 3 months of surgery indicates a good prognosis for reversal of facial nerve paralysis.

Hearing preservation surgery in acoustic neuroma patients with normal hearing.

Acoustic neuroma (AN) patients who had normal hearing accounted for 7% of all our AN cases. It is important to identify AN patients who have normal hearing but are suffering from tinnitus, dizziness, or vertigo, or a combination of these symptoms (without hearing loss), in order to make an early diagnosis. Patients who experience sudden hearing loss and recover completely should also be thoroughly examined in order to rule out AN. In this article, we describe an investigation of the clinical features and results of hearing preservation surgery in AN patients with normal hearing. The overall hearing preservation rate was 57%. The hearing preservation rate did not depend on the auditory brainstem response (ABR) pattern, tumor size, or the origin of the tumor. We think that patients must be properly informed concerning all aspects of the surgery, including the possibility that hearing and/or facial nerve function cannot be preserved.

Accidentally detected brain tumors: clinical analysis of a series of 110 patients.

The clinical records of 1,155 patients with 1,159 brain tumors who drained on Keio University Hospital between 1983 and 1994 were reviewed. Apparently asymptomatic patients and those whose complaints or neurological deficits were not caused by the brain tumors were defined as accidental cases. For example, patients with a headache which was considered to be unrelated to the presence of a tumor were included in this series. One hundred and ten (9.5%) of the 1,155 cases were found to be accidental. Since three accidental cases had multiple meningiomas, there were 113 accidental brain tumors which involved 63 meningiomas, 22 pituitary adenomas, 9 gliomas, 7 metastatic carcinomas. 5 acoustic neurinomas and 7 miscellaneous. Meningiomas occurred significantly more frequent than other types of accidentally identified tumors. Convexity meningiomas and falx meningiomas accounted for 53.9% of the accidental meningiomas, whereas parasagittal meningiomas were less frequent. It is of note that three out of four cases with multiple meningiomas were accidental. Comparison between the present results and the previously reported incidence of asymptomatic brain tumors in postmortem studies suggest that a substantial number of pituitary adenomas, acoustic neurinomas and small parasagittal meningiomas without suggestive symptoms are likely to be missed by routine neuroradiological examinations.

Developmental patterns and characteristic symptoms of petroclival meningiomas.

Thirty-six cases of petroclival meningiomas with clearly defined anatomical features were selected to analyze the site of tumor attachment and the displacement of the trigeminal nerve. The tumors were classified into four categories according to the origin and extension of the tumor: clival origin medial to the trigeminal nerve (upper clivus type), clival origin with dumbbell extension to the cavernous sinus (cavernous sinus type), tentorial origin over the trigeminal nerve (tentorium type), and petrous apex origin lateral to the trigeminal nerve (petrous apex type). Patients with tumors in each category had characteristic neurological symptoms. Patients with the upper clivus type had oculomotor nerve paresis as a single symptom, if suprasellar tumor extension was present. Patients with the cavernous sinus type commonly presented with abducens nerve paresis caused by epidural tumor invasion around Dorello's canal. Dumbbell tumor extension along the venous drainage of the cavernous sinus was a significant problem for surgical removal in this type. Half of the patients with the tentorium type had a characteristic symptom of trigeminal neuralgia caused by retrograde tumor invasion into Meckel's cave from its orifice, but the cavernous sinus was not involved. The main complaint of patients with the petrous apex type was hearing disturbance, but no epidural or parasellar extension was present. Clinical symptoms and magnetic resonance imaging provide important information about the origin and extension patterns of these tumors, especially the presence or absence of tumor extension into the cavernous sinus. Abducens nerve paresis or trigeminal neuralgia suggests tumor invasion into the cavernous sinus or Meckel's cave, respectively.

Surgical approaches for vertebro-basilar trunk aneurysms located in the midline.

Fourteen cases of midline vertebro-basilar trunk aneurysms were operated on by four routes of surgical approach: middle fossa anterior transpetrosal approach (ATP), presigmoid transpetrosal approach (PTP), conventional lateral suboccipital approach (LSO) or suboccipital transcondylar approach (STC). There was no mortality, but the morbidity was different depending on the surgical approach. In basilar trunk aneurysms located higher than the internal auditory canal, excellent results were obtainable by ATP, especially in the case of posteriorly projecting aneurysms. For midline vertebral aneurysms located lower than the internal auditory canal, STC resulted in less surgical complications than LSO. Extradural resection of the jugular tubercle was necessary for aneurysms located on the distal vertebral artery at or close to the vertebro-basilar junction. For vertebro-basilar junction aneurysms located at the level of the internal auditory canal, hearing was preserved by STC, but not by ATP or PTP. However, choice of the surgical approach may depend on the direction of the aneurysm and the technical accessibility of the skull base. All these skull base approaches reduced surgical complications of retraction damage to the cranial nerves and the brain stem. This holds true for all aneurysms arising from the midline vertebro-basilar trunk.

[Cooperative multicentric study on posttraumatic epilepsy].

A multicenter cooperative study was conducted to investigate factors influencing posttraumatic epilepsy (PTE) and to evaluate the prophylactic effect of anticonvulsants. A retrospective study of 102 PTE patients revealed the following typical clinical features: occurrence in young males, traffic accidents, contusion and/or cerebral hematoma. The latent period after the injury was longer in children. The percentage of EEG paroxysmal activity gradually increased as the generalized abnormality diminished. A retrospective-prospective study of 1998 patients who suffered a head injury between 1984 and 1988 was conducted till 1994. During the follow-up period, 62 patients (3.1%) developed PTE. The drop-out cases were excluded, and the 154 cases followed at least two years were analyzed. Statistical analysis of differences between patients with and without PTE suggested following factors: young, immediate early epilepsy (within 24 hours after injury; IMEE) and early epilepsy (within one week after injury). The risk with the highest relative risk rate was early epilepsy. Multiple regression analysis revealed that three factors, IMEE, early epilepsy and young age, contributed to the prediction of PTE. There was no significant difference in the percentage of patients having PTE in the group treated with anticonvulsants and the untreated group. Anticonvulsant treatment after head injury was unlikely to have a prophylactic effect on the development of PTE.

Unusual location of intracranial vagus neurinoma--case report.

A 55-year-old male presented with hearing disturbance and tinnitus in the left ear. Computed tomography (CT) and magnetic resonance imaging demonstrated a well-defined, homogeneously enhanced mass in the left cerebellomedullary cistern without extension close to the jugular foramen. A three-dimensional image reconstructed from thin-slice CT scans demonstrated that the mass was clearly separated from the jugular foramen. The mass lesion was totally removed surgically. At surgery the tumor was found to originate from one rootlet of the vagal nerve just after its exit from the medulla oblongata. The histological diagnosis was neurinoma. Intracranial neurinomas of the glossopharyngeal, vagal, or accessory nerve usually originate within or close to the jugular foramen. This unusual location made it difficult to achieve a correct preoperative diagnosis.

[Usefulness of 3-dimensional image analysis of skull base lesions].

We have evaluated three-dimensional (3D) images of the skull base lesions for planning cranial base surgery. Fifty 3D images were reconstructed from computed tomographies (CT), and/or magnetic resonance (MR) images or MR angiographic images of 30 patients with skull base lesions. These images have provided useful information for pre-operative evaluation. The 3D image reconstructed from CT provides clear information concerning the bone. Conversely, the 3D image from MR images demonstrates soft tissue very clearly, and that from MR angiography provides a detailed description of the vasculature. For skull base lesions, it is essential to evaluate 3D images from the different modalities, especially CT scan and MR image.

Accumulation of nerve growth factor in cerebrospinal fluid and biological activity following neurosurgery.

Perioperative nerve growth factor (NGF) levels in cerebrospinal fluid (CSF) of patients with acoustic neurinoma (14 cases), tentorial meningioma (1 case), or subarachnoid hemorrhage (1 case) were examined. Preoperative NGF levels in CSF were below the level of detection in all patients. However, NGF was found to accumulate transiently in CSF following neurosurgery. Pre- and postoperative CSF obtained from a patient with acoustic neurinoma enhanced the proliferation of astrocytes in neuronal cell cultures derived from embryonic rat cortex grown in serum-free defined medium, and increased choline acetyltransferase activity of cholinergic neurons derived from embryonic rat septal area and brainstem. The effect of postoperative CSF on septal and brainstem neurons was more potent than that of preoperative CSF. These results indicate that NGF and non-NGF-type neurotrophic activities accumulate in the CSF following neurosurgery. These neurotrophic activities are probably important in the regeneration of damaged neural networks in the central nervous system.