Retrolabyrinthine Approach Research Articles

Utility of three-dimensional computed tomographic angiography for assessment of relationships between the vertebrobasilar system and the cranial base.

The optimal surgical exposure for basilar tip aneurysms is dictated by the relationship of the basilar bifurcation to the cranial base. This study was designed to evaluate three-dimensional computed tomographic angiography as a means of obtaining detailed anatomic information on the basilar artery and the surrounding cranial base in individual patients before surgery. We studied 30 patients using three-dimensional computed tomographic angiographic reconstructions from 1-mm computed tomographic slices. Detailed anatomic measurements were performed to define the relationship between the basilar artery and the cranial base. Particular attention was paid to the height of the dorsum sellae and its relationship to the basilar bifurcation. The heights of the basilar apex and the vertebrobasilar junction, relative to the cranial base, were extremely variable. Considerable asymmetries in the heights of the left and right posterior clinoid processes were identified; in one case, this difference was more than 1 cm (mean difference in height, 0.9 mm; range, 0-10.3 mm). The heights of the posterior clinoid processes above the sellar floor ranged from 5.8 to 14.1 mm (mean height, 9.5 mm). We were able to determine the feasibility of the pterional/orbitozygomatic, middle fossa/ anterior petrosal, and presigmoid retrolabyrinthine approaches to an individual basilar bifurcation. We also estimated the amount of bone removal required and determined the operative distances via those approaches. Three-dimensional computed tomographic angiography is a useful tool for assessing critical anatomic relationships and represents an adjunct to conventional angiography in the planning of individualized, precisely tailored, cranial base approaches to the vertebrobasilar system.

Classification and quantification of the petrosal approach to the petroclival region

The petrosal approach to the petroclival region has been used by a variety of authors in various ways and the terminology has become quite confusing. A systematic assessment of the benefits and limitations of each approach is also lacking. The authors classify their approach to the middle and upper clivus, review the applications for each, and test their hypotheses on a cadaver model by using frameless stereotactic guidance. The petrosal approach to the upper and middle clivus is divided into four increasingly morbidity-producing steps: retrolabyrinthine, transcrusal (partial labyrinthectomy), transotic, and transcochlear approaches. Four latex-injected cadaveric heads (eight sides) underwent dissection in which frameless stereotactic guidance was used. An area of exposure 10 cm superficial to a central target (working area) was calculated. The area and length of clival exposure with each subsequent dissection was also calculated. The retrolabyrinthine approach spares hearing and facial function but provides for only a small window of upper clival exposure. The view afforded by what we have called the transcrusal approach provides for up to four times this exposure. The transotic and transcochlear procedures, although producing more morbidity, add little in terms of a larger clival window. However, with each step, the surgical freedom for manipulation of instruments increases. The petrosal approach to the upper and middle clivus is useful but should be used judiciously, because levels of morbidity can be high. The retrolabyrinthine approach has limited utility. For tumors without bone invasion, the transcrusal approach provides a much more versatile exposure with an excellent chance of hearing and facial nerve preservation. The transotic approach provides for greater versatility in treating lesions but clival exposure is not greatly enhanced. Transcochlear exposure adds little in terms of intradural exposure and should be reserved for cases in which access to the petrous carotid artery is necessary.

Posterior fossa vestibular nerve section for the management of peripheral vertigo.

Patients with vertigo resistant to conservative treatment require surgical management. Between March 1991 and August 1996, vestibular nerve sections were performed in 108 patients with peripheral vertigo not responding to conservative treatment. The diagnoses were classic Ménière's disease in 96 patients and recurrent vestibulopathy in 12 patients. Combined retrosigmoid retrolabyrinthine (n = 106) and retrolabyrinthine (n = 2) approaches were used. Patients were grouped according to follow-ups of less than 2 years and more than 2 years. In the former group (n = 49), hearing preservation and vertigo control were achieved in 93.9% and 100%, respectively. In the latter group (n = 59) the rates were 89.8% and 96.6%, respectively. Overall complications were uncommon. Three patients had cerebrospinal fluid leakage and one had total hearing loss. According to our results, posterior fossa vestibular nerve section was found to be an effective treatment for the management of patients with intractable vertigo.

Endoscopy of the posterior fossa and endoscopic dissection of acoustic neuroma

The objective of this study was to evaluate the importance of endoscopes in eliminating the disadvantage of posterior fossa approach--that is, the lack of adequate visualization obtained of the lateral aspect of the internal acoustic canal (IAC). Over a 10-year period 32 patients underwent removal of acoustic neuroma (AN) via a combined retrosigmoid retrolabyrinthine approach (CRSRL). Endoscopes were used at different stages of the operation, and their use was evaluated with regard to elimination of the disadvantages of the posterior fossa approach. All patients in whom AN had been diagnosed underwent surgery. A standard combined retrosigmoid retrolabyrinthine approach was performed. Standard sinus endoscopes of 0, 30, and 70° were introduced into the cerebellopontine angle before debulking the tumor, and the IAC was inspected at the end of the operation. Neurovascular integrity as well as the relationship between AN and surrounding structures were evaluated. The IAC was inspected for residual tumor, and if any was found, endoscopic tumor dissection was performed. Endoscopes have facilitated the understanding of the relationship between AN and neighboring neurovascular structures. The disadvantage of posterior fossa approach can be eliminated by using endoscopes. In surgery in which the posterior fossa approach is performed, endoscopes can be used to make operations safer. In addition to allowing inspection of the fundus, it is possible to perform tumor dissection within the IAC by using the endoscopes.

Endoscopic anatomy of the cerebellopontine angle: a study in cadaver brains

The increasing trend toward performing minimally invasive neurosurgery may benefit from recent progress in using neuroendoscopic techniques to reduce trauma in patients who have undergone operations. Arterial and venous vessels, especially loops, may compress the central segment and cause hyperactive dysfunction of the nerves. Relationships of the anterior inferior cerebellar artery to the facial and vestibulocochlear nerves and the anterior inferior, and superior cerebellar arteries to the trigeminal nerve were studied. The authors report findings from an endoscopic study performed in cadaver heads via the retrosigmoid and retrolabyrinthine approaches. Arteries and veins were colored by injection of red and blue silicon rubber. The cerebellopontine angle (CPA) was examined using 2.7-mm and 4-mm-diameter rigid endoscopes at viewing angles of 0š, 30š, and 70š. Well-known structures could be identified endoscopically without prior dissection, and the entire CPA could be explored. However, with a retrosigmoid or a retrolabyrinthine approach, the cerebellum had to be retracted to some extent to view the CPA. Moreover, wide dural exposure was required to maneuver the endoscope freely in the CPA. Use of the rigid fiberoptic endoscope is not yet superior to standard surgical techniques for approaching and exploring the CPA.

Retrolabyrinthine Vestibular Nerve Section: A Current Appraisal

We report our experience (1987-1993) with Meniere's disease patients treated with a retrolabyrinthine vestibular neurectomy. The current literature was reviewed and our results have been compared with those of previous reports. The overall success rate for vertigo relief was 96.7%, with no serious or permanent complications resulting from the procedure. The technical elements of the operation, as they apply to our approach and those of others, have been analyzed, with special attention given to the anatomical features of the region and their influence on success or failure. We conclude that the retrolabyrinthine approach for vestibular nerve section remains a safe and highly successful technique which merits continued use.

V-4-55 - Disrupted and migrated microcatheter in the vertebrobasilar system in endovascular embolization of cerebellar AVM: Failure in endovascular and microneurosurgical retrieval

To evaluate the use of the retrolabyrinthine approach (RLA) combined with endoscopy with particular reference to preservation of cranial nerve function and completeness of excision in surgery of epidermoid cysts.A retrospective study was performed on a series of 8 consecutive patients of whom 7 have undergone surgery.Measures include audiological and neurological status preoperatively and postoperatively, size of the lesion, the surgical approach, completeness of excision, and operative morbidity.The tumors were all large, ranging from 2 × 3 cm to 6 × 6 cm. Presenting symptoms were headache (75%), dysequilibrium (62%), trigeminal nerve palsy (38%), abducens nerve palsy (25%), and, rarely, auditory symptoms. Seven patients underwent surgery, 5 by the RLA, 1 by a translabyrinthine approach (TLA), and 1 by a transcochlear approach. Complete excision was achieved in 5 of the 7 patients. A transtentorial approach was combined in 2 cases (1 RLA, 1 TLA). Endoscopy was used in 3 cases. It allowed a complete tumor excision. One case of keratinous meningitis was observed. Trigeminal nerve function returned to normal in all patients. Postoperative facial nerve function was grade I in 5 cases and grade III in 2 cases. Hearing was preserved in 3 cases as class A, 1 case as class B. In the 2 cases presenting with abducens nerve palsy preoperative symptoms were initially aggravated before returning to normal function by 1 year postoperatively. The RLA with endoscopy allowed less invasive surgery and preservation of hearing in 4 of the 5 cases where it was attempted. Tumor control appeared better than with the suboccipital approach. Mortality and postoperative morbidity also appear reduced.RLA combined with endoscopy should be considered as the standard approach for excision of epidermoid cysts. Extension of this approach into a TLA or transcochlear approach will depend on preoperative difficulties and preoperative hearing.

V-4-54 - Intraoperative bleeding in early surgery of vertebral artery aneurysms

To evaluate the use of the retrolabyrinthine approach (RLA) combined with endoscopy with particular reference to preservation of cranial nerve function and completeness of excision in surgery of epidermoid cysts.A retrospective study was performed on a series of 8 consecutive patients of whom 7 have undergone surgery.Measures include audiological and neurological status preoperatively and postoperatively, size of the lesion, the surgical approach, completeness of excision, and operative morbidity.The tumors were all large, ranging from 2 × 3 cm to 6 × 6 cm. Presenting symptoms were headache (75%), dysequilibrium (62%), trigeminal nerve palsy (38%), abducens nerve palsy (25%), and, rarely, auditory symptoms. Seven patients underwent surgery, 5 by the RLA, 1 by a translabyrinthine approach (TLA), and 1 by a transcochlear approach. Complete excision was achieved in 5 of the 7 patients. A transtentorial approach was combined in 2 cases (1 RLA, 1 TLA). Endoscopy was used in 3 cases. It allowed a complete tumor excision. One case of keratinous meningitis was observed. Trigeminal nerve function returned to normal in all patients. Postoperative facial nerve function was grade I in 5 cases and grade III in 2 cases. Hearing was preserved in 3 cases as class A, 1 case as class B. In the 2 cases presenting with abducens nerve palsy preoperative symptoms were initially aggravated before returning to normal function by 1 year postoperatively. The RLA with endoscopy allowed less invasive surgery and preservation of hearing in 4 of the 5 cases where it was attempted. Tumor control appeared better than with the suboccipital approach. Mortality and postoperative morbidity also appear reduced.RLA combined with endoscopy should be considered as the standard approach for excision of epidermoid cysts. Extension of this approach into a TLA or transcochlear approach will depend on preoperative difficulties and preoperative hearing.

P-3-376 - Thermal monitoring system during drilling with a high speed drill in skull base surgery

Novel audiovisual feedback methods were developed to improve image guidance during skull base surgery by providing audiovisual warnings when the drill tip enters a protective perimeter set at a distance around anatomic structures (“distance control”) and visualizing bone drilling (“virtual drilling”).To benchmark the drill damage risk reduction provided by distance control, to quantify the accuracy of virtual drilling, and to investigate whether the proposed feedback methods are clinically feasible.In a simulated surgical scenario using human cadavers, 12 unexperienced users (medical students) drilled 12 mastoidectomies. Users were divided into a control group using standard image guidance and 3 groups using distance control with protective perimeters of 1, 2, or 3 mm. Damage to critical structures (sigmoid sinus, semicircular canals, facial nerve) was assessed. Neurosurgeons performed another 6 mastoidectomy/trans-labyrinthine and retro-labyrinthine approaches. Virtual errors as compared with real postoperative drill cavities were calculated. In a clinical setting, 3 patients received lateral skull base surgery with the proposed feedback methods.Users drilling with distance control protective perimeters of 3 mm did not damage structures, whereas the groups using smaller protective perimeters and the control group injured structures. Virtual drilling maximum cavity underestimations and overestimations were 2.8 ± 0.1 and 3.3 ± 0.4 mm, respectively. Feedback methods functioned properly in the clinical setting.Distance control reduced the risks of drill damage proportional to the protective perimeter distance. Errors in virtual drilling reflect spatial errors of the image guidance system. These feedback methods are clinically feasible.

The widened retrolabyrinthe approach: a new concept in acoustic neuroma surgery.

For many years, the retrolabyrinthine approach has been limited to functional surgery of the cerebellopontine angle (CPA). As a result of the increased surgical exposure, particularly the opening of the internal auditory meatus (IAM), the widened retrolabyrinthine technique permits tumor excision from both the CPA and the IAM, regardless of the histological nature of the tumor. The authors have treated 60 acoustic neuromas of varying sizes via this approach (6% intrameatal tumors; 30% > 25 mm in diameter). The postoperative mortality rate was 0%. The risk of fistula formation was 3.3%, and 3.3% of the patients suffered from postoperative meningitis. The results for facial nerve function were equivalent to those obtained previously via a widened translabyrinthine approach and those in a series treated via a suboccipital approach (80% with Grades I and II, 15% with Grade III, and 5% with Grades V and VI). One patient (1.7%) required a secondary hypoglossal-facial nerve anastomosis and had attained a Grade IV result 6 months later. Postoperatively 21.7% of these patients maintained socially useful hearing and 20% had mediocre hearing. Socially useful hearing was preserved in 50% of a subgroup of 20 patients who had both good preoperative hearing and a tumor that involved less than half of the IAM regardless of its volume. Additionally, 15% had mediocre hearing that could be improved with hearing aids. Because of its efficacy in preserving hearing, the authors favor the retrolabyrinthine over the occipital approach, with the latter being considered less subtle and more aggressive.

Aneurysms of the vertebro-basilar junction area: preliminary experience in endovascular and surgical management.

Aneurysms of the vertebro-basilar junction area have been considered the most difficult to be surgically treated because of their deep location, the proximity of the brain stem and the cranial nerves. However, at present, new endovascular techniques and new transbasal surgical approaches offer valuable management strategies. This paper concerns six consecutive patients whom we managed either endovascularly or surgically during a period of eighteen months. Direct surgical treatment was offered to two young patients with relatively small aneurysms in good neurological condition, whereas the other four patients initially underwent an endovascular attempt at aneurysm obliteration using the Guglielmi detachable coil system. Unfortunately, interventional neuroradiology failed in three cases, and surgery had to be re-considered. Accordingly, a total of five patients underwent surgical clipping through the combination of a transmastoid retrolabyrinthine approach with the suboccipital lateral approach. This combination of approaches provided a good control of both vertebral arteries and basilar artery, and allowed the aneurysm to be correctly clipped in all cases. Good long-term results were achieved in all cases but one. Based on this preliminary experience, we would stress the importance of multidisciplinary approach with a treatment calibrated for each single case. Furthermore, if surgery is to be performed, the combination of transmastoid-retrolabyrinthine and suboccipital lateral approaches provides a wide exposure of the whole vertebro-basilar junction area and allows good access to the lesion.

The Middle Fossa Transpetrous Approach: Experience With 13 Cases

Surgical access to lesions of the temporal bone anterior to the internal auditory canal and medial to the petrous carotid artery has concerned surgeons for nearly a century. A variety of approaches have been developed to gain access to this region. We report our experience with the middle fossa transpetrous approach for the treatment of a variety of petroclival and/or prepontine lesions. Tentorial transection and the retrolabyrinthine approach to extend this technique is also discussed. In properly selected cases, the middle fossa transpetrous approach is successful in maintaining hearing, labyrinthine and facial function without compromising surgical exposure.

Video Endoscopy-Assisted Vestibular Neurectomy: A New Approach to the Eighth Cranial Nerve

Disequilibrium, ranging from lightheadedness to severe vertigo, is frequently of great concern to the patients with a variety of inner ear diseases, and may cause occupational and social disability. Vestibular nerve section may be considered when vestibular symptoms are resistant to medical therapy and associated with serviceable hearing in the involved ear. During the last century, numerous authors described several routes for intracranial section of the eighth nerve, such as lateral suboccipital craniotomy, middle cranial fossa approach, and retrolabyrinthine approach to the vestibular fossa. Control of vertigo by all routes to the vestibular nerve has a success rate of 80% to 90%. The potential for endoscopic approach to intracranial cavities was recognized early in this century but, due to technical limitations, was largely abandoned after a few attempts. Advances in optics, and the introduction of very fine instruments made endoscopy worth reconsideration. Since the early 1980s, rigid endoscopes have been used in otorhinolaryngology for paranasal sinus surgery and the visualization of the facial and vestibulocochlear nerves during acoustic tumor surgery. We performed endoscopic section of the vestibular nerve through a retrolabyrinthine approach in two cadavers and in two patients with the symptoms of disequilibrium. In the literature survey, we could find no reports on vestibular neurectomy performed by endoscopic technique. We describe technical details of the approach, and conclude that the technique is safe and effective.

Transsigmoid and extreme lateral approaches for removal of jugular foramen tumors

Neoplasms arising in the jugular foramen may involve the posterior fossa, skull base, and cervical region. The infratemporal approach allows single-stage removal of tumor involving the posterior fossa, jugular foramen, and cervical region. The transient facial palsy and permanent conductive hearing loss associated with this approach led Mann et al to develop the transsigmoid approach. This technique, which combines the suboccipital and retrolabyrinthine approaches, provides access similar to the infratemporal fossa approach without rerouting the facial nerve or obliterating the middle ear. The extreme lateral approach is an inferior extension of the transsigmoid approach and may be used for jugular foramen lesions that extend inferiorly to the foramen magnum. The surgical technique and use of these approaches are discussed. Neoplasms arising in the jugular foramen may involve the posterior fossa, skull base, and cervical region. The infratemporal approach allows single-stage removal of tumor involving the posterior fossa, jugular foramen, and cervical region. The transient facial palsy and permanent conductive hearing loss associated with this approach led Mann et al to develop the transsigmoid approach. This technique, which combines the suboccipital and retrolabyrinthine approaches, provides access similar to the infratemporal fossa approach without rerouting the facial nerve or obliterating the middle ear. The extreme lateral approach is an inferior extension of the transsigmoid approach and may be used for jugular foramen lesions that extend inferiorly to the foramen magnum. The surgical technique and use of these approaches are discussed.

The widened transcochlear approach

The petrous pyramid may be considered as an assemblage of four segments whose boundaries are well defined. According to this way of looking, the different transpetrous approaches proposed consist in drilling away one or several of these four segments. Thus, the transpetrous approaches are not different operative techniques, but a single operative technique made up of successive operative stages whose deployment can be continued until complete or interrupted at each stage according to the demands of the resection. The retrolabyrinthine, translabyrinthine, and transcochlear approaches constitute different stages of one and the same technique. The widened transcochlear approach consists of the transcochlear approach and dissection of the infratemporal and superior cervical regions. It simultaneously exposes the cerebellopontine angle (CPA) and the infratemporal regions, which allows a perfect operative management of anatomic elements passing through these two regions (internal carotid artery, sigmoid sinus-jugular vein axis, and lower cranial nerves) and total removal of saddlebag-shaped tumors encountered in these regions. In connection with 17 operated cases, the authors describe the widened transcochlear technique, detail the operative indications, and analyze their results.

To Abandon or Not Abandon: Antesigmoid Craniotomy with Retrolabyrinthine Vestibular Nerve Section

Increasing popularity of the retrosigmoid approach would have one believe this is the preferred posteriorfossa approach for a vestibular nerve section. The authors take issue with this. The antesigmoid posterior lateral retrolabyrinthine approach is a gentle craniotomy, easily performed and with low morbidity. A review of 70 consecutive cases revealed no procedural alteration because of surgical exposure, an absence of meningitis, no VIIth nerve weakness, minimal headache, average hospital stay of five days, and only one patient with a significant CSF leak. Hyperventilation anesthesia, patience during delicate VIIIth nerve exposure, incorporation of abdominal fat into dural closure sutures and prophylactic antibiotics have made this operation easy for the patient...and the surgeon. Don't abandon it!

Surgical Treatment of Meniere's Disease

Surgical treatment is used only for patients with Menière's disease in cases that do not respond to medical therapy. At the present time, the endolymphatic sac shunt operation is performed in cases where the auditory threshold is fluctuant around 30 dB. When the auditory threshold is between 40 and 70 dB we use the vestibular neurectomy by the retrosigmoid approach. In patients with Menière's disease with profound hearing loss the translabyrinthine neurectomy is used. The advantages of the vestibular neurectomy by the retrosigmoid approach compared to the retrolabyrinthine and middle fossa approaches will be described.

VESTIBULAR NEURECTOMY IN THE UNITED STATES???1990

During the last decade, vestibular neurectomy has become a more frequently performed procedure to cure symptoms of inner ear vertigo while preserving hearing. In an effort to determine the results of vestibular neurectomy across the country, a questionnaire was prepared and sent to the 350 members of the American Otologic Society and the American Neurotology Society. Results of that survey indicated that 2,820 vestibular neurectomy procedures were performed by 58 surgeons. Ninety-two percent (2,590 cases) were performed through the posterior fossa approach. Of these, 1149 cases (44%) were through the retrolabyrinthine approach, 940 cases (36%) were through the retrosigmoid approach, 307 cases (12%) were through the combined retrolabyrinthine-retrosigmoid approach, and 194 cases (8%) were unspecified as to which posterior fossa approach was used. The remaining 230 cases (8%) were through the middle fossa approach. Sectioning of the vestibular nerve was done by the otologist in 58 percent of cases, by the neurosurgeon in 12 percent, and by either surgeon in 30 percent. Classic Meniere's disease, the most common indication for vestibular neurectomy, resulted in the best cure rate of 91 percent. Other inner ear diseases such as traumatic labyrinthitis and vestibular neuronitis had a lower cure rate of 74 to 81 percent. Hearing was preserved to within 20 dB of the preoperative pure-tone thresholds in 87 percent. There were no deaths, 11 cases of meningitis and 16 cases of facial paralysis, 15 of which occurred after middle fossa surgery, representing a 7 percent incidence of facial paralysis after middle fossa surgery. Eleven of the 15 cases resulted in permanent paralysis and four in temporary paralysis.(ABSTRACT TRUNCATED AT 250 WORDS)

Retrolabyrinthine approach to the vestibular nerve

Vestibular nerve section is an accepted modality for treating disabling vertigo and disequilibrium in patients with peripheral labyrinthine disorders. The procedure provides a reliable denervation of the diseased ear, while preserving residual hearing in the great majority of cases. Although several surgeries are available including the middle fossa, suboccipital and retrolabyrinthine approach, we prefer the latter, given its demonstrated efficacy and low rate of associated complications. In this review we detail the surgical technique of the retrolabyrinthine vestibular section and survey vestibular and hearing results. Postoperative results are highly dependent on careful preoperative evaluation and accurate identification of the offending ear.

Lower basilar artery aneurysm に対する transpetrosal approach

The lower basilar artery aneurysm is one of the most difficult to approach surgically because of its anatomy. The microsurgical anatomy which is encountered while dissecting cadaver specimens with a transpetrosal approah is presented in this paper. The routes used for this approach are 1) subtemporal approach, 2) retrolabyrinthine approach and 3) supra- and infratentorial approach which combines a retrolabyrinthine approach with a retromastoid-posterior subtemporal approach. With this approach, direct visualization of the lower basilar artery and its vicinity are possible with minimum distance and with minimum brain retraction. However, the surgical field is limited and there exists a risk of disturbing the vestibulocochlear function. So, a thorough knowledge of the anatomy of the petrous portion of the temporal bone and skilful drilling of this bone are indispensable. The landmarks which are the most useful for these approaches are the greater petrosal nerve for a subtemporal approach, and anterior margin of the sigmoid sinus, the superior petrosal sinus and the vestibular aqueduct for a retrolabyrinthine approach.