Facial neuroma of the cerebellopontine angle and the internal auditory canal

Four cases of facial neuroma confined to the cerebellopontine angle and internal auditory canal are presented. Prior to surgery, three of these were diagnosed as an acoustic tumor. At operation the true diagnosis of facial neuroma was made. The operative procedure was recorded on film and videotape. The magnetic resonance imaging (MRI) and computed tomography (CT) scans were reviewed retrospectively. In the first three cases the tumor was not centered on the axis of the internal auditory canal (IAC), as would be typical of an acoustic neuroma, but instead occupied a position eccentric to this axis. In one case, this eccentricity was marked. A similar appearance in the fourth case enabled the true diagnosis of facial neuroma to be made before surgery. The postoperative behavior of the tumors was unpredictable. The patient with the largest tumor, which was debulked at operation, did not develop a facial palsy. However, a patient with a small tumor which was not biopsied, developed a delayed but complete paralysis from which she subsequently recovered. This small series suggests that it may be possible, by use of the appropriate imaging technique, to diagnose, preoperatively, a cerebellopontine angle facial neuroma which is otherwise indistinguishable from an acoustic neuroma.     

Distance from acoustic neuroma to fundus and a postoperative facial palsy.

OBJECTIVE/HYPOTHESIS: Generally, patients with small acoustic neuroma have less facial palsy after its removal. The middle cranial fossa approach is mainly applied to the small acoustic neuroma and tumor size does not influence the prognosis of facial palsy. The internal auditory canal cannot be fully opened in the middle cranial fossa approach, and the facial nerve is tightly attached in the fundus. According to these anatomical factors, we hypothesized that acoustic neuromas located away from the fundus might be removed with less facial nerve damage. We investigated the distance between the acoustic neuroma and fundus and its clinical relationship. STUDY DESIGN: Retrospective study of 45 patients with acoustic neuroma who underwent a middle cranial fossa approach. METHODS: The distance between the acoustic neuroma and fundus and the tumor diameter were measured on T2-weighted and contrast-enhanced magnetic resonance images, respectively. These data were compared with the postoperative facial nerve function. RESULTS: The mean distance was 3.0 +/- 1.8 mm (range, 0-10 mm), and the mean diameter was 11.3 +/- 3.7 mm (means +/- standard deviation; range, 4-20 mm). Neither the distance nor the diameter had any correlation to the degrees of postoperative facial palsy either immediately or at 3 months after surgery. CONCLUSIONS: As far as the nerve was anatomically preserved, postoperative facial nerve function seemed to be influenced by factors other than surgical manipulation among small acoustic neuromas. Although the tumor fills in the fundus, it may not influence postoperative facial nerve function and also may not interfere with indication of the middle cranial fossa approach for removal of the acoustic neuroma.     

Diagnosis of retrocochlear and central vestibular disease by magnetic resonance imaging

Magnetic resonance imaging has become the study of choice for the diagnosis of retrocochlear and central vestibular disease. Three groups of lesions, each characterized by a specific site of origin, have been recognized: 1) petrous apex lesions such as congenital cholesteatomas and cholesterol granulomas involving the eighth cranial nerve within the internal auditory canal; 2) cerebellopontine angle tumors, mainly acoustic neuromas and meningiomas; and 3) CNS disease involving the brain stem and the central auditory and vestibular pathways such as tumors, multiple sclerosis, infarcts, and hemorrhage.     

Retrosigmoid approach for acoustic tumor removal.

The retrosigmoid technique has evolved from the traditional suboccipital operation and, when combined with removal of the posterior wall of the internal auditory canal, affords a wide exposure of the cerebellopontine angle. This approach may be used for acoustic neuromas of all sizes, from intracanalicular to more than 4 cm from the porus acusticus. Hearing preservation may be attempted and is generally successful in a substantial minority of cases. The facial nerve is readily visualized at the lateral end of the internal auditory canal and is at no greater risk than in the translabyrinthine operation. We use this approach for all hearing preservation surgery as well as for tumors of more than 3 cm, regardless of hearing.     

Extended middle fossa and retrolabyrinthine approaches in acoustic neuroma surgery: case reports.

Hearing conservation surgery for small acoustic neuromas is well accepted. At present, two approaches are primarily used: the suboccipital and the middle fossa. The middle fossa approach to the internal auditory canal has the advantage of using bony landmarks to identify and protect the facial nerve. Because of anatomic constraints presented by the superior semicircular canal however, its uses are limited to intracanalicular tumors or tumors protruding only slightly into the cerebellopontine angle. By extending the approach through the superior semicircular canal, a wide access to the cerebellopontine angle can be safely obtained. In this study three procedures, two through the superior semicircular canal and one through the posterior semicircular canal, were utilized for hearing conservation surgery. By immediately sealing off the canal ends, hearing preservation was accomplished in two out of three of these cases. The dictum that labyrinthine opening invariably leads to anacusis should be reconsidered. By utilizing approaches through the semicircular canal, it is possible that morbidity from this surgery may be reduced.     

Approach design and closure techniques to minimize cerebrospinal fluid leak after cerebellopontine angle tumor surgery.

OBJECTIVE: The purpose of the study was to identify specific aspects of surgical approach design and closure technique aimed at reducing the incidence of cerebrospinal fluid leak after cerebellopontine angle tumor surgery. STUDY DESIGN: Retrospective case review. SETTING: Tertiary referral center. PATIENTS: All patients undergoing cerebellopontine angle tumor surgery at the study institution from January 1996 through September 2004. MAIN OUTCOME MEASURE: The presence or absence of cerebrospinal fluid leak after various surgical approaches for a wide variety of cerebellopontine angle tumors. RESULTS: Three hundred forty three patients underwent surgery for cerebellopontine angle tumors at the study institution during the study period. Tumor types in descending order of frequency were as follows: acoustic neuroma, 244; cerebellopontine angle meningiomas, 33; petroclival meningiomas, 32; foramen magnum meningiomas, 10; epidermoid tumors, 9; facial nerve tumors, 6; hemangiopericytomas, 3; schwannomas of glossopharyngeal/spinal accessory nerves, 3; and unusual internal auditory canal tumors, 3. Surgical approaches used for tumor resection included translabyrinthine, retrosigmoid, combined transpetrosal, far lateral/transcondylar, middle cranial fossa, and extended middle cranial fossa. During the nearly 8-year study period, four postoperative cerebrospinal fluid leaks were encountered, resulting in a leak rate of 1.2%. Two of these patients required surgical repair of their leaks; the other two stopped spontaneously. The authors describe specific aspects of approach design and closure that appear to have a positive impact on postoperative cerebrospinal fluid leak rates. CONCLUSION: Attention to specific aspects of surgical approach design and wound closure results in a reduced incidence of cerebrospinal fluid leak after surgery for cerebellopontine angle tumors.     

Intratemporal facial nerve neuroma: anatomical location and radiological features

OBJECTIVES: To present the imaging findings and anatomical locations of a series of 88 facial nerve neuromas from two centers over a 30-year period. We describe the salient radiological features of neuromas in each anatomical location and outline the ways in which modern imaging techniques have altered our perception of this entity. STUDY DESIGN: A retrospective review of tumors presenting to two tertiary care referral institutions since 1970. METHODS: The charts and available imaging of patients with the diagnosis of facial neuroma were reviewed. These patients presented to the House Ear Clinic between 1970 and 1994 and to the University of Utah Medical Center (Salt Lake City, UT) between 1986 and August 2000. We examined anatomical location to determine patterns of tumor presentation and compared the findings before and after the era of magnetic resonance imaging (MRI). RESULTS: All segments of the facial nerve were represented. Overall, multiple-segment tumors were almost twice as common (63.6%) as single-segment tumors (36.4%). Before the advent of MRI, all segments of the nerve from the cerebellopontine angle to the tympanic portion were almost equally represented (29.5%-36.3%). After MRI, the geniculate ganglion (68.2%) and labyrinthine portion (52.3%) were by far the most commonly affected areas. Before MRI, there were, on average, 1.89 segments involved per tumor. After MRI, this average number increased to 2.57 segments per tumor. Radiologically, the high-resolution computed tomography and MRI features cannot be generalized. Rather, the imaging features depend on which segments are involved. This is because of the variation in the surrounding anatomical landscape of the facial nerve in its course through the temporal bone. CONCLUSION: The more sensitive imaging provided by newer radiological techniques has altered our perception of facial neuroma. It has provided us with an increased ability to diagnose and fully evaluate this neoplasm preoperatively, allowing improved patient counseling and surgical planning.     

Facial nerve neuroma: diagnosis and management

Facial neuroma is a condition of insidious onset. Prior to the introduction of modern imaging techniques (computerised tomography, magnetic resonance imaging) delays between presentation and diagnosis were common place. Atypical facial paralysis and hearing loss are the most common presenting features. This combination is very suggestive of a facial neuroma and is an indication to proceed to computed tomography. This investigation can reveal expansion of the Fallopian canal at any point through the temporal bone. A few facial neuromas occur in the cerebello-pontine angle alone or in the parotid. Resection and grafting are always worthwhile as facial neurones seem to persist in the tumour mass keeping muscle alive until the facial nerve graft becomes functional. The presentation, management and results of treatment of 15 such cases is presented.     

Acoustic neuromas after failed radiation therapy: challenges of surgical salvage

OBJECTIVES: As stereotactic radiation has emerged as a treatment option for acoustic neuromas, cases that require surgical salvage after unsuccessful radiation have emerged. We present a comparison of the technical challenges faced by the surgeons in the treatment of irradiated versus nonirradiated acoustic neuromas. STUDY DESIGN: Matched case-control series. METHODS: We identified nine patients with acoustic neuromas that required surgical resection after radiation therapy. Cases were performed with suboccipital and translabyrinthine approaches. Nine nonirradiated case-control subjects matched for age, sex, tumor size, and surgical approach were identified for purposes of general comparison. Operative findings and outcomes were compared for the two groups. RESULTS: Surgical removal was found to be significantly more difficult after radiation therapy because of increased fibrosis and adhesion to adjacent nervous structures, particularly at the porus acousticus. Excessive scarring hindered identification of the facial nerve and added uncertainty as to the completeness of tumor removal. Decompression of the internal auditory canal (IAC) dura and resection of neoplasm in the IAC before cerebellopontine angle dissection was required for facial nerve identification. Operative time was significantly longer for irradiated cases, and facial nerve outcomes tended to be poorer, particularly when facial nerve dysfunction prompted the salvage procedure. CONCLUSIONS: Surgical salvage of acoustic neuromas after radiation therapy is feasible, but it presents technical challenges beyond that associated with primary surgical therapy. Poorer outcomes of postoperative cranial nerve status were caused primarily by anatomic changes at the nerve/tumor interface. As surgical experience with the irradiated acoustic neuroma grows, operative observations should be incorporated into the counsel provided to patients with acoustic neuromas as they weigh different management options.     

Primäres B-Zell-Non-Hodgkin-Lymphom des inneren Gehörgangs

A primary non-Hodgkin lymphoma (NHL) of the internal auditory canal or the cerebellopontine angle is an absolute rarity, even among the unusual lesions encountered there. Schwannomas or meningiomas account for approximately 90-95% of the tumors of the cerebellopontine angle and the internal auditory canal. Atypical symptoms, such as facial nerve palsy or rapid progression, require differential diagnostics to identify less frequent entities. However, clinical symptoms or the image morphology cannot confirm the diagnosis of a lymphoma. If a malignant process is suspected during surgical exploration, an immediate intraoperative biopsy can give important clues for appropriate treatment. The course, diagnostics, and therapy of a rare case of primary B-cell NHL of the internal auditory canal are reported here.     

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.     

Facial neuroma in the internal auditory canal

Authors presented two cases of facial neuromas in the internal auditory canal, one without facial palsy and the other with facial palsy. In both cases neuromas were occult and undiagnosed. Although in the first case neuroma was greater than the other, facial palsy was not developed. The mechanism of the facial palsy due to neuromas could not be clearly clarified.     

扩大迷路径路切除经枕下径路手术后复发的听神经瘤

目的：探讨听神经瘤经枕下径路手术后复发、后经扩大迷路径路再次切除肿瘤的方法及效果。方法：对5例复发的听神经瘤患者，采用扩大迷路径路手术，在经典迷路径路的基础上，通过充分切除岩骨骨质扩大手术视野，将复发的肿瘤组织完全切除。结果：5例听神经瘤直径为2．5～4．0cm，均全部切除，无死亡病例，未发生颅内感染及脑脊液漏；面神经功能与术前一致；术后CT和MRI复查均显示无肿瘤残存，小脑、脑干位置恢复正常。经0．5～2年7个月的随访，至今未见复发，患者已恢复正常生活和工作。结论：枕下径路手术容易残留内听道内的肿瘤，再次手术采用扩大迷路径路可直接暴露肿瘤并到达脑干，既可避免瘢痕粘连区，方便定位面神经，又能全部切除复发的肿瘤，且具有创伤小、面神经功能保存完好等优点。     

Cerebellopontine angle tumors

Acoustic neuromas account for approximately 80 to 90 per cent of cerebellopontine angle tumors. Useful imaging studies include (1) high-resolution CT of the internal auditory canals using extended scale and "bone algorithm" techniques, (2) infusion study of the cerebellopontine cisterns, (3) gaseous or opaque CT cisternography, and (4) MRI.     

Meningioma of the internal auditory canal

The great majority of tumors that arise in the internal auditory canal are schwannomas of the eighth cranial nerve (acoustic neuromas). Meningiomas constitute the second largest group of posterior fossa tumors. Meningiomas arise from arachnoid villae, the apparatus responsible for cerebrospinal fluid absorption, in proximity to a major vein or dural sinus in most cases. Arachnoid villae are also present along neural foramena at the base of the skull. They have been observed histologically in the internal auditory canal (IAC), and are the probable site of origin of meningiomas in this location. Larger cerebellopontine angle meningiomas occasionally possess a significant intracanalicular component; however, these lesions usually originate from the meningeal lining of the posterior petrous face adjacent to the sigmoid, superior petrosal, or inferior petrosal sinuses and prolapse into the IAC. Two meningiomas have recently been observed that extensively involved the IAC, one of which arose from the lining of the IAC. The clinical manifestations of these meningiomas mimicked those of acoustic neuromas. Preoperative radiographic studies, including magnetic resonance imaging, were unable to differentiate these from acoustic neuromas. Meningiomas have a higher rate of recurrence than acoustic neuromas and should be excised with surrounding dura and several millimeters of subjacent bone. Meningiomas that extensively involve the IAC have a tendency to invade the inner ear and the deeper portions of the temporal bone. In meningiomas that involve the lateral portion of the IAC, consideration should be given to exenteration of the cochlea and semicircular canals.     

Cavernous hemangioma of the internal auditory canal arising from the inferior vestibular nerve: case report and review of the literature

OBJECTIVE: To describe a case of cavernous hemangioma arising from the inferior vestibular nerve, limited to the internal auditory canal. STUDY DESIGN: Retrospective case review and review of literature. SETTING: A tertiary referral clinic. INTERVENTIONS: Extended middle cranial fossa surgery. RESULTS: The hemangioma was completely resected through the extended middle cranial fossa approach. No serious complications occurred, and the hearing and the facial nerve function were preserved. CONCLUSIONS: Originating from the capillary plexus surrounding Scarpa's ganglion, this hemangioma has to be differentiated from intratemporal hemangioma at the geniculate ganglion. Because of extrinsic growth pattern, the potential for preservation of the facial nerve function is high if surgery is performed early. Complete resection through the extended middle fossa approach is the treatment of choice for cavernous hemangioma with limited extension into the cerebellopontine angle. It remains difficult to distinguish preoperatively from the more common tumors, and surgery is usually planned on assumption of vestibular schwannoma.     

面神经瘤的诊断与处理

目的探讨面神经鞘瘤和面神经纤维瘤的临床和病理特点以及影像学表现,为面神经瘤的早期诊断和不同类型面神经瘤的治疗提供经验。方法采用回顾性方法,对20例面神经鞘瘤和2例面神经纤维瘤的诊断和治疗过程进行分析。面神经瘤的手术入路为：颅中窝入路2例,乳突径路8例,乳突腮腺联合径路10例,腮腺径路2例。17例面神经瘤切除后同期进行面神经移植。其中耳大神经颞内段移植3例,颞内外联合移植1例;腓肠神经颞内段移植5例,颞内外联合移植8例。2例后期行面肌悬吊术。结果面神经瘤完全切除21例,20例术后无复发,失访1例。次全切除1例,次全切除者术前和术后接受1刀治疗,随访无复发。影像学表现：CT示面神经鞘瘤为呈膨胀性改变面神经管缺损。面神经纤维瘤主要表现为面神经管增粗,行走于面神经骨管内。磁共振成像可以显示所有面神经行走途经径,并显示面神经瘤从乳突扩展到腮腺的情况。病理诊断面神经鞘膜瘤20例,面神经纤维瘤2例。结论虽然面神经瘤的发生率低,但是只要了解其临床特点,借助影像学手段,可以早期诊断。对面神经瘤治疗可考虑不同径路摘除肿瘤并行面神经移植手术。     

Normal auditory brainstem response in patients with acoustic neuroma

Auditory brainstem response testing has been a major breakthrough in audiologic screening for acoustic neuroma because of its high degree of sensitivity. Although it is not uncommon for other cerebellopontine angle masses to present with normal ABR findings, reports of eighth nerve tumors with false-negative auditory brainstem response tests are quite rare. A series of 120 acoustic neuromas resected at the University of Michigan was reviewed and revealed two such patients. These two patients presented with asymmetric sensorineural hearing loss and unilateral tinnitus and were found to have completely normal auditory brainstem response. The diagnosis of acoustic neuroma would have been delayed if a comprehensive evaluation had not been pursued.     

Facial nerve paralysis and meningioma of the internal auditory canal

Pathological lesions confined to the internal auditory canal (IAC) commonly present with cochleovestibular symptoms; sensorineural hearing loss, tinnitus and balance disturbance. The commonest lesion of the IAC is vestibular schwannoma. Other lesions include meningioma, facial neuroma, cavernous haemangioma, lipoma and arachnoid cyst. Presentation with facial palsy and an intracanalicular lesion is suggestive of pathology other than acoustic neuroma. Magnetic resonance imaging (MRI) cannot reliably distinguish intracanalicular vestibular schwannomas from meningiomas. Particular care is required for surgery of these lesions: the facial nerve typically does not lie in a protected anterior position within the IAC.     

A case of Mobius syndrome--radiological and electrophysiological findings

Mobius syndrome is characterized by congenital bilateral facial palsy and abducens nerve paralysis, but reports of radiological and electrophysiological findings are scarce. A 4-year-old boy presented with mask-like facies noted at birth after a 34-week pregnancy. Examination revealed bilateral facial and abducens nerve paralysis with no other neurological abnormalities. Computed tomography revealed bilateral absence of facial nerve canal in the middle ear. Brain magnetic resonance imaging indicated a narrow than expected nerve in the internal auditory canal (IAC). Evoked electromyography and blink reflex testing to evaluate facial nerve function yielded no responses bilaterally. Facial palsy thus appears to be caused by facial nerve dysplasia or aplasia.