Infratemporal fossa approaches to the lateral skull base

The infra-temporal fossa approach is one of the lateral approaches to the skull base. It is indicated for the treatment of tumors such as glomus tumor, petrous apex cholesteatoma, chondroma, lower cranial nerve neuroma and nasopharyngeal cancer. In the present paper, we described the surgical anatomy of the lateral skull base and the indications for the infra-temporal fossa approach with its variants. We showed the hints and pitfalls in the procedures. Five illustrative cases are also presented.

No cerebrospinal fluid leaks in translabyrinthine vestibular schwannoma removal: reappraisal of 200 consecutive patients

OBJECTIVE

The objective of this study was to validate measures taken to reduce the number of cerebrospinal fluid (CSF) leaks after removal of vestibular schwannomas to 0.

STUDY DESIGN

This study was a retrospective case review.

SETTING

The study was conducted at an otology/neurotology tertiary referral center (Gruppo Otologico, Piacenza, Italy).

PATIENTS

Three hundred thirty-one vestibular schwannoma patients were studied.

INTERVENTIONS

The enlarged translabyrinthine approach (TLA) was used in all cases, with a number of modifications in the last 200 patients. It was extended in 22 patients with blind sac closure of the external meatus, removal of the posterior bony canal wall, and obliteration of the Eustachian tube and middle ear.

MAIN OUTCOME MEASURES

Whether patients had a leak through the wound, the nose (rhinoliquorrhea), or the ear (otoliquorrhea) was assessed.

RESULTS

In an early group, the percentage of CSF leaks was 6.9%. On the basis of the evaluated causes, as time went by, technical modifications evolved. They consisted of 1) the total conservation of the fascioperiosteal flap, 2) obliteration of all petrosal cells possibly communicating with the middle ear, 3) removing the incus in a correct way, 4) closing the attic with periosteum, 5) obliterating the surgical cavity, leaving strips of abdominal fat with their medial ends inside the cerebellopontine angle, 6) suturing the musculo-periosteal layer in a correct way, and 7) fixing the skin flap to the underlying surface. The application of these modifications resulted in a total absence of CSF leaks in 200 consecutive patients thereafter. Also, no cases of meningitis were encountered.

CONCLUSIONS

To our knowledge, this is the first series of 200 consecutive vestibular schwannoma patients operated by means of the enlarged TLA without a single CSF leak. When the appropriate measures are taken, the number of CSF leaks after removing tumors through the enlarged TLA must and can be reduced to 0.

Subtemporal exposure of the intrapetrous internal carotid artery. An anatomical study with surgical application

This work describes the exposure of the intrapetrous internal carotid artery (ICA) through the subtemporal approach. The anatomical details of 25 fresh temporal bones were studied and provided the initial background for this procedure. Bone drilling in the meatal plane anterior to the internal auditory canal could create a four-sided quadrangular area. The exposure of the ICA through this area was applied on three occasions. It proved safe as regards the surrounding structures and also provided an ample working space for the extirpation of tumours surrounding the artery.

Further observations on the presence of ganglion cells in the oculomotor nerves of mammals and fish: number, origin and probable functions

The oculomotor nerves (3rd, 4th and 6th) of some species of fish and mammals have been studied to establish the presence, number, true topography and probable functional role of the ganglion cells located along the trunk. The finding of typical pseudo-unipolar ganglion cells is always unpredictable and extremely variable, from an inter- and intra-specific point of view, in members of the two zoological classes studied.

[Facial nerve identification in the translabyrinthine approach: an alternative method]

Since the abrupt drop in the mortality rate as a result of the introduction of microsurgical dissection techniques in the treatment of acoustic neuromas, surgeons have concentrated their efforts on preserving hearing and facial nerve function. In the translabyrinthine approach, identification of the facial nerve at the fundus of the internal auditory canal is an important step for subsequent dissection. However, the identification techniques available to date carry with them some potential risk of facial nerve injury when performed by inexperienced surgeons. In addition, they are time-consuming procedures. The authors present an alternative method for identification of the facial nerve at the fundus of the internal auditory canal during the translabyrinthine approach. The superior ampullary nerve is interrupted at the superior cribrosa area where it is not in intimate relationship with the facial nerve. Medial reflection of the superior ampullary nerve and the superior vestibular nerve facilitates identification of the facial nerve and preparation of a vestibulo-facial dissection plane.

[Coexistence of vestibular schwannoma and glomus tympanicum tumor]

Simultaneous occurrence of a vestibular schwannoma and a glomus tympanicum tumor has been reported only once in the international literature. The authors present a second case: a 72-year-old woman having a glomus tympanicum tumor and an ipsilateral lesion confined to the internal auditory canal, radiologically diagnosed as an acoustic neuroma. Due to the patient's age, symptoms, hearing threshold and the small size of both tumors the decision was made not to perform surgery. The patient will be regularly followed-up through computerized tomography and magnetic resonance imaging.

Anatomic relationships between surgical landmarks in type b and type c infratemporal fossa approaches

Anatomic relationships of the structures exposed in type B and C infratemporal fossa approaches were studied in 20 temporal bones. The intrapetrous carotid artery (ICA), cochlea (CH), eustachian tube (ET), foramen spinosum (FS), foramen ovale (FO) and anterior foramen lacerum (AFL) were exposed by drilling of the glenoid fossa and base of middle cranial fossa. The relationships of the ICA with the cochleariform process (CP), CH, ET, FS, FO and AFL were noted along with associated measurements. The CP was lodged at a mean distance of 9.2 mm from the ICA genu. The ET was found to intersect the ICA. The mean distance of the ICA to the CH was 1.6 mm. The carotid canal was dehiscent on its horizontal portion in 30% of the bones studied and on its vertical portion in 5%. The periarterial venous plexus was found in 70% of the bones. No obvious branch was observed emerging from the vertical portion of the ICA. The FS was found to be a canal having a mean length of 5.8 mm.

Myringoplasty in children: factors influencing surgical outcome

Age, size, and site of perforation, condition of the ear, status of the contralateral ear, grafting materials, and more are considered factors influencing the success rates in myringoplasties in children. The ambivalence in results is mainly due to nonhomogeneous patient groups. In an effort to compose groups as homogeneous as possible for analysis of influencing factors, a retrospective study of 51 pediatric myringoplasty cases (51 ears) was undertaken. All patients had perforations caused by simple chronic otitis media. The overall surgical success rate was 82.3% at 18 months, and for young (5 to 10 years) and older (11 to 16 years) children it was 77.2% and 86.2%, respectively. Anterior, central, and total perforations healed without significant differences. Outcome in unilateral perforations was better than bilateral: 96.9% and 55%, respectively (p < 0.01). Discharging ears (100%) healed better compared with dry ears (75%) (p < 0.05). Analysis of the literature also revealed significant difference in success rates of discharging and dry ears: 92.5% and 80.6%, respectively (p < 0.01). We conclude that, contrary to comments in the literature, discharging ears in children favor good outcome and they should be operated on regardless of age and site of perforation. However, in bilateral perforations results may not be so rewarding.

The cochlear aqueduct: an important landmark in lateral skull base surgery

The cochlear aqueduct (CA) is used as a landmark in lateral skull base surgery. In this study anatomic relationships between the CA and adjacent neurovascular structures were examined by dissecting 32 temporal bones. Observations of the relationship of the external opening (EO) of the CA with the ninth, tenth, and eleventh cranial nerves, inferior petrosal sinus (IPS), and intrapetrous carotid artery (ICA) were noted. In addition to the distance of the EO of the CA to the vertical portion of the ICA, the entire length of the CA and the width of the EO were also measured. The ninth nerve was the only structure lodged at the EO of the CA in 34.4% of bones. However, in 40.6% of bones only the IPS crossed the EO of the CA, although the ninth nerve was situated just anteroinferiorly in the vicinity of the EO. In 15.6% of bones it was possible to observe both the ninth nerve and the IPS crossing the EO. In 9.4% of bones the EO of the CA was found to be occupied by the tenth and eleventh nerves. It was also observed that the ICA was located anteriorly on the same sagittal plane with the EO in 15.6% of bones. It was concluded that although in 90% of cases the EO of the CA was in close relation with the ninth nerve, other structures such as the IPS, the tenth and eleventh cranial nerves, and the ICA were also at risk during drilling in this area because of their intimate relationships with the EO of the CA.

[Cerebrospinal fluid leak after translabyrinthine approach in acoustic neuroma excision]

Cerebrospinal fluid (CSF) leak is one of the most dangerous complications that can arise in cases of acoustic neuroma removal. It increases the risk of meningitis, requires longer postoperative recovery and often requires revision surgery. A retrospective analysis was performed on all cases of acoustic neuromas which had undergone translabyrinthine surgery at the Gruppo Otologico, Piacenza, Italy, between April 1987 and December 1997, in the aim of finding the causes of postoperative CSF leaks. The causes found were high pneumatization of the temporal bone and improper execution of some surgical steps. The technique has presently been modified on the basis of the experience gained from cases of CSF leaks. By scrupulously applying these modifications, from July 1994 to December 1997, a total of 160 patients were consecutively treated using the translabyrinthine approach without a single case of postoperative CSF leak. Routine use of this modified technique can and must lower the percentage of CSF leaks after a translabyrinthine surgery to nearly 0%.

Titration streptomycin therapy in Meniere's disease: long-term results

As soon as the use of streptomycin was started for the treatment of tuberculosis, its ototoxic effect was discovered. Initial reports demonstrated that streptomycin was successful in reducing vestibular responses while preserving cochlear activity. Streptomycin sulfate has been used for almost half a century for the treatment of vertigo in patients with Meniere's disease. At the Gruppo Otologico, Piacenza, Italy, between 1987 and 1995 we treated 16 patients with either bilateral Meniere's disease or with Meniere's disease in their only hearing ear, adopting the titration streptomycin therapy protocol of Graham et al. Three patients with follow-up periods of less than 2 years were not included in this study. The ages of the patients ranged from 36 to 64 years with a mean of 49.2 years. The patients were observed for 2 to 8.8 years. The dose of administered streptomycin varied from 14 to 49 gm. Episodic vertigo was totally relieved in all of the patients after initial treatment, whereas hearing remained the same or was improved when compared with the pretreatment levels. Five of the patients experienced recurring vertigo during a period of 4 to 24 months after initial treatment. Oscillopsia persisted in two patients and ataxia in darkness persisted in another two patients. Hearing was unchanged in 14 ears, improved in 2 ears, and worsened in 4 ears at the last follow-up evaluation. The overall outcome indicated that intramuscular titration streptomycin therapy seems to be one of the most important therapeutic options in the treatment of disabling vertigo in patients with either bilateral Meniere's disease or Meniere's disease in an only hearing ear.

The system of the modified transcochlear approach: a lateral avenue to the central skull base

OBJECTIVE

This study aimed to update the authors' experience with the modified transcochlear approach for the management of lesions of the central skull base. The surgical technique, classification, indications, and results also are presented.

STUDY DESIGN

A retrospective review of the charts of 66 consecutive patients treated in our centers by the modified transcochlear approach was conducted.

SETTING

The study was performed in two tertiary referral centers.

PATIENTS

All patients treated by the modified transcochlear approach were included. Thirty-five patients had extradural lesions, whereas 31 lesions were intradural.

INTERVENTION

All patients were treated surgically using the modified transcochlear approach either in its basic form (type A) or with its extensions (types B, C, and D).

MAIN OUTCOME MEASURES

The outcome of surgery is evaluated with particular emphasis on the incidence of morbidity, mortality, and the degree of total tumor removal.

RESULTS

Total tumor removal was accomplished in 58 cases either in single or staged procedures. A second-stage procedure for total tumor removal is planned in five other patients. Subtotal tumor removal was performed in three patients. Mortality occurred in two cases. Ipsilateral hearing loss and immediate facial nerve palsy constituted the major drawbacks of this approach. However, 67.5% recovered to grade III facial function or better 1 year after surgery.

CONCLUSIONS

The modified transcochlear approach provides a relatively safe, wide, and versatile access to large lesions of the central skull base.

Mastoidectomy in noncholesteatomatous chronic suppurative otitis media: is it necessary?

Chronic suppurative otitis media (CSOM) without cholesteatoma, the surgical treatment of which is still controversial, is a common diagnosis in otologic practice. A retrospective analysis of 323 patients who underwent surgery for noncholesteatomatous chronic otitis media in the Gruppo Otologica, Piacenza, Italy, between April 1983 and December 1993 is presented. Cases were separated into three groups according to different surgical treatment modalities and conditions of the ears at the time of operation. Group I (n = 53) consisted of cases of CSOM treated by tympanoplasty without mastoidectomy (TLWOM). Group II (n = 28) included cases of CSOM treated by tympanoplasty with mastoidectomy (TLWM). Intact canal wall technique was used in these cases. The ears in both these groups were discharging severely at the time of surgery. Group III (n = 242) included patients whose ears were dry at the time of surgery but who had had previous recurrent episodes of suppuration and who were treated by TLWOM. At the last follow-up, graft success rates for groups I, II, and III were 90.5%, 85.7%, and 89.2%, respectively, and mean residual gaps were 17.2 dB, 20.1 dB, and 19.4 dB, respectively. There was no statistically significant difference between the three groups either on graft success rates (p > 0.05) or on final functional hearing outcome (p > 0.05). TLWM is the preferable treatment modality for most surgeons in noncholesteatomatous CSOM. Nevertheless, in our experience TLWOM yields comparable results for this group of patients. In addition, we could not find any significant difference in results of graft success and final functional hearing rates between dry and discharging ears (p > 0.05).

Clinical observations on coexistence of sudden hearing loss and vestibular schwannoma

It has long been recognized that sudden hearing loss (SHL) may be a harbinger of vestibular schwannoma (VS). Among 192 VS patients who underwent operation in the Gruppo Otologico, Piacenza, Italy, from April 1987 to October 1995, the charts of 14 (7.3%) cases with a history of SHL were examined. SHL was the first symptom in 8 (4.2%) patients. Eight (57.1%) of 14 VS cases with SHL anamnesis had reported recovery of their previous hearing either totally or partially before establishment of tumor diagnosis. Five (35.7%) cases had recurrent bouts of SHL. SHL was observed less frequently in cases with large tumors (>3 cm). However, the frequency of SHL in patients with small tumors did not differ from that of medium-sized tumors. Awareness about coexistence of SHL and VS, as well as concomitant use of auditory brain stem response and magnetic resonance imaging, is crucial to rule out the diagnosis of VS in a patient with SHL.

[Lateral approaches to the clivus]

Thanks to ongoing development in microsurgical techniques to treat the skull base some clivus lesions, considered inoperable until a few years ago, can now be removed with relatively low mortality and morbidity. The approaches available for the treatment of lesions in this anatomical area can be broken down into anterior and lateral. The latter offer the surgeon several important advantages such as better control over the main vascular structures and the possibility of opening the intradural space without coming into communication with the pharynx. By virtue of their extreme versatility, the lateral approaches may be used in combination in a single operation or can be performed as staged procedures. Each of the lateral routes, however, has its own advantages and drawbacks. These are presented during a brief description of each technique. The main factor in selection of approach is the anatomical limits of the approach itself. Generally speaking, the largest surgical field is offered by the most destructive approaches. Although they do cause such deficits as unilateral hearing loss, these approaches permit greatly improved control over the vital structures. Nevertheless, when such deficits exist prior to surgery, the morbidity of such approaches is negligible. The histological nature of the disease, the variable relationships with the dura, the main neurovascular structures and other factors should all be considered when deciding how to manage each case. The surgeon must, however, have the range of skills required to perform the diversity of approaches to the lateral skull base so as to provide the patient with the best possible care.

Clinical Observations on Coexistence of Sudden Hearing Loss and Vestibular Schwannoma

It has long been recognized that sudden hearing loss (SHL) may be a harbinger of vestibular schwannoma (VS). Among 192 VS patients who underwent operation in the Gruppo Otologico, Piacenza, Italy, from April 1987 to October 1995, the charts of 14 (7.3%) cases with a history of SHL were examined. SHL was the first symptom in 8 (4.2%) patients. Eight (57.1%) of 14 VS cases with SHL anamnesis had reported recovery of their previous hearing either totally or partially before establishment of tumor diagnosis. Five (35.7%) cases had recurrent bouts of SHL. SHL was observed less frequently in cases with large tumors (<3 cm). However, the frequency of SHL in patients with small tumors did not differ from that of medium-sized tumors. Awareness about coexistence of SHL and VS, as well as concomitant use of auditory brain stem response and magnetic resonance imaging, is crucial to rule out the diagnosis of VS in a patient with SHL.

[Modified Body technique in the treatment of epithympanic cholesteatoma. Otologic group, Piacenza]

The Bondy technique is a particular radical, yet conservative, treatment where the intact tympanic-ossicular system is preserved during the operation. This technique was initially introduced by Gustave Bondy in 1910 and has been used at the authors' center since December 1983 with a few modifications. In the twelve years from December 1983 to December 1995 69 cases (66 patients) were treated with this technique: 5.6% of all chronic cholesteatomatose otitis surgically treated during that period. The following indications were applied: purely epitymapnic cholesteatoma, average transmission gap equal to or lower than 25 dB and intact bone chain. During the follow-up no signs of recurrent cholestatoma were found. The average post-operative transmission gap was greater than 25 dB in only 5 of the 54 cases with at least one year of follow-up. When used in selected cases, the modified Bondy technique can be considered an excellent option in the treatment of epitympanic cholesteatoma, making it possible to maintain the good pre-operative hearing without requiring a second operation.

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.

Lower cranial nerve schwannomas involving the jugular foramen

Schwannomas involving the jugular foramen are rare lesions, and no consensus exists on their management. This paper reports on 20 such cases treated in our centers. Nineteen cases were operated on for removal of the tumors, and the remaining case is being managed by watchful expectancy. Fifteen cases were operated on by the petro-occipital trans-sigmoid approach with or without labyrinthectomy, 2 by the infratemporal fossa approach, 1 by the modified transcochlear approach, and 1 by the jugulo-petrosectomy approach. The petro-occipital trans-sigmoid approach allowed single-stage, total tumor removal with preservation of the facial nerve and of middle and inner ear functions. Lower cranial nerve paralysis was the major complication and seemed to be inherent to the disease rather than to the approach used. No cerebrospinal fluid leak or meningitis occurred in the present series. So far, no recurrence has been detected.

Anatomical considerations of high jugular bulb in lateral skull base surgery

In order to study high jugular bulb management in lateral skull base surgery, an anatomical study was conducted on 30 temporal bones by examining the relationship between the internal auditory canal (IAC) and the jugular bulb. The following parameters were measured: 1) Height of the jugular bulb (H)... distance between the level of jugular bulb dome and the line passing through the confluence of the sigmoid sinus with the jugular bulb (SS-JB), 2) Mastoid length (ML)... distance between the mastoid process and middle cranial fossa dura, 3) Distance between the most inferior part of the porus acousticus and jugular bulb dome (A), 4) Distance between the porus acousticus and SS-JB (B). The jugular bulb was defined as high when it occupied more than two thirds of (B). The incidence of a high jugular bulb was 23 per cent in this study. When the jugular bulb was high, the mean (H) and (A) were 9.4 +/- 1.9 mm and 2.7 +/- 0.5 mm, respectively. (H) was higher on the right side than on the left side. No statistically significant difference was found between small and large mastoids (t-test: p > 0.05). It was concluded that when a high jugular bulb was encountered during lateral skull base surgery, the jugular bulb position allows a very small working area inferior to the IAC. In these cases, a 3 or 4 mm depression of the jugular bulb is necessary in order to expose the lower cranial nerves. This can be accomplished by lowering the jugular bulb with the technique already described.

Morphometric evaluation of the infralabyrinthine approach to the internal auditory canal

Morphometric evaluation of the infralabyrinthine approach to the internal auditory canal (IAC) was performed using 20 fresh human temporal bones in order to assess the exposure limitations, inherent risks and technical difficulties that may arise due to common anatomic variations of this region. While performing the infralabyrinthine approach to the IAC, minor problems such as an anteriorly placed sigmoid sinus were easily managed. However, in 50% of the specimens, this approach was limited due to variations of the jugular bulb, restricting access to the IAC. Sacrificing the endolymphatic duct in these specimens did not significantly improve the surgical access to the eighth nerve. Furthermore, it was noted that this approach puts the facial nerve and cochlea under the risk of inadvertent damage during drilling. The authors conclude that vestibular nerve sectioning using the infralabyrinthine approach may be performed only in few selected cases and extreme care is needed in order not to damage the structures that limit this approach.

Measurement of endocochlear DC potentials in ears with acoustic neuromas: a preliminary report

The pathogenesis of hearing loss in acoustic neuromas remains to be elucidated. To obtain more detailed information about inner ear damage in this disease, especially that dealing with the possibility of ischemia of the inner ear due to compression of the blood supply in the internal auditory canal by acoustic neuromas, measurement of endocochlear DC potential (EP) was attempted in three ears with acoustic neuromas during surgical removal of the tumors by the translabyrinthine approach. The size of each tumor was 3.0, 0.8, and 1.8 cm, respectively. An EP with a positive value was recorded in each of the three ears, i.e., 54, 57, and 38 mV, respectively, although the first and third patients were profoundly deaf on the side with a tumor. These findings were interpreted as being evidence of retention of function by the stria vascularis and the existence of blood supply to the inner ear in spite of the presence of tumors. Measurement of the EP seems to provide a new tool with which to analyze the causes of hearing loss in acoustic neuromas. Relatively low EP values may suggest mild dysfunction of the stria vascularis with acoustic neuromas.

Vestibular schwannoma and the only hearing ear

With the recent advances in the management of vestibular schwannomas, it is possible not only to save the facial nerve function but also preserve hearing in a small percentage of cases. Difficulties arise while managing patients with vestibular schwannoma in their only hearing ear. In this article we summarize our experience in managing seven of these patients. We recommended a watch and wait policy with a regular follow-up with audiometric testing and gadolinium-enhanced magnetic resonance imaging (MRI). Gamma knife radiosurgery is advised in cases with deterioration of hearing or increase in tumour size. Surgery is usually avoided unless there are brainstem compression symptoms.