Advantages of the enlarged middle cranial fossa approach in acoustic neurinoma surgery. A review.

Acta Oto-Laryngologica

ISSN: 0001-6489 (Print) 1651-2251 (Online) Journal homepage: http://www.tandfonline.com/loi/ioto20

Advantages of the Enlarged Middle Cranial Fossa Approach in Acoustic Neurinoma Surgery C. T. Haid & M. E. Wigand To cite this article: C. T. Haid & M. E. Wigand (1992) Advantages of the Enlarged Middle Cranial Fossa Approach in Acoustic Neurinoma Surgery, Acta Oto-Laryngologica, 112:3, 387-407 To link to this article: http://dx.doi.org/10.3109/00016489209137419

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Acta Otolaryngol (Stockh) 1992; 1 1 2 387-407

Advantages of the Enlarged Middle Cranial Fossa Approach in Acoustic Neurinoma Surgery A Review C. T. HAID and M. E. WIGAND

Acta Oto-Laryngologica 1992.112:387-407.

From the Department of Oto-Rhino-Loryngology, University of Erlangen-Nuremburg, Germany

Haid CT, Wigand ME.Advantages of the enlarged middle cranial fossa approach in acoustic neurinoma surgery. A review. Acta Otolaryngol (Stockh) 1992; 112 387-407. Utilizing an enlarged middle cranial fossa approach to the cerebello-puntineangle without destruction of the labyrinth or cochlea the authors have since 1981 operated on 263 unilateral acoustic neurinomas. Tumour sizes ranged between 3 mm intrameatal and 35 mm within the cerebella-pontine angle. Complete tumour removal was accomplished in 96%. There was one postoperative mortality, and only rarely neurologicalcomplications.Excellent function of the facial nerve was obtained in 78% (in small and medium sized neurinomas 90% House I and 11) and severe paralysis persisted,in only 6%. Preservation of hearing was possible in 70% of the small tumours, and in 50% of the total group. Against this background comparable data of the literature are reviewed, and the indications for the enlarged midfossa approach analyzed. Key words: acoustic neurinoma, enlarged middle cranial fossa approach, cerebellopontine angle, internat auditory canal, hearing preservation.

INTRODUCTION The first publications on the middle cranial fossa approach to the internal auditory meatus were published by Perry & Panse as early as in 1904 and by Chavanne & Troullier in 1905. The pioneer in micro-otoneurosurgery was William House in the early 1960's. During recent years there has been much controversy about the advantages and disadvantages of different approaches for removal of acoustic neurinomas, e.g. the middle cranial fossa approach (House 1961 and 1963; Fisch 1970), the translabyrinthine approach (House 1961, 1963, 1964 and 1979; Glasscock 1968; Tos & Thomsen 1982 and 1991; Sterkers et al. 1984), the transcochlear approach (House & Hitselberger 1976), the retrolabyrinthine approach (Hitselberger & Pulec 1972; Silverstein & Norell 1977), the transotic approach (Jenkins & Fisch 1980; Fisch 1988; Fisch & Mattox 1988), the retrosigmoid approach (Sterkers 1980 and 1981), the suboccipital approach (Cushing 1917; Dandy 1925; Olivecrona 1940; Rand & Kurze 1967; Samii & Penkert 1984; Samii et al. 1985; Fahlbusch et al. 1991) and modifications of transtemporal approaches (Rosomoff 1971; Morrison & King 1973 and 1984; Bocheneck & Kukwa 1975; Kanzaki et al. 1977 and 1989; Wigand et al. 1982, 1985, 1989 and 1991, Haid & Wigand 1992). The interest has been focussed on 1) total removal and recurrence rates, 2) complication rates, and 3) functional results concerning the facial nerve and the possibility to preserve the hearing function. Our technique of choice is the enlarged middle cranial fossa approach (Wigand et al. 1982; Haid & Wigand 1992) which allows a Function preserving surgery of the facial nerve, cochlear nerve and cerebral structures including a total removal even in cases of acoustic neurinomas with an extrameatal diameter of up to 3-4 cm. MATERIAL AND METHODS From 1981 until October 1991, 263 patients with a unilateral acoustic neurinoma were operated on via the enlarged middle cranial fossa approach in our ENT Department.


388 C. T. Haid and M. E. Wigand

Acta Otolaryngol (Stockh) 112

Thirty-five tumours were classified as small, 117 as medium sized and 111 as large. The average age of the patients was 48 years. The youngest patient was 16 years old, and the oldest 83. The most probable value of the age distribution was located between 51 and 60 years. There was a slight predomination of females without any side preference. With regard to surgical relevance we distinguish between three different classes of tumour size: Type A (a small strictly intrameatal tumour); Type B (a medium sized neurinoma extending not more than a maximum of I5 mm into the cerebella-pontine angle but without adhesion to the brain stem); Type C (a large tumour with broad contact with the brain stem and cerebellum corresponding to a size of 16 mm up to 30-40 mm in the cerebello-pontine angle. Larger lesions (giant tumours) were not submitted to the enlarged middle cranial fossa approach. The surgical procedure starts with a temporal skin incision forming a caudally pedicled flap over the sleeve with the root of the zygomatic arch in its center. The temporal muscle is transsected by a Y-shaped incision. Thereafter an osteoplastic craniotomy (4 x 5 cm bone flap) is performed. The floor of the middle cranial fossa is exposed, the middle meningeal artery (anterior region of the petrous bone), the posterior crest of the petrous bone (posterior part) and the medial crest of this bone with the region of the petrous apex and superior petrosal sinus (medial region). In cases of large acoustic neurinomas (3-4cm) the middle meningeal artery and the superior petrosal sinus are usually resected for additional mobilization of both the temporal and the cerebellar dura blades. Important landmarks can be utilized (House 1961; Aurbach 8z Wigand 1987; Wigand et al. 1991) consisting of the “grey line” of the superior semicircular canal (below the eminentia arcuata) and of the superior petrosal nerve, which together form an angle of about 130”. Bisection of this angle usually corresponds to the axis of the internal auditory meatus. The enlarged middle cranial fossa approach consists of an ample bone resection, using a diamond burr in front of, above and behind the internal auditory canal. The otoneuro-surgeon has to be very careful not to injure the cochlea, the labyrinth or the Fallopian canal with the facial nerve. By this excision of the petrous bone, a broad exposure into the internal auditory canal, the cerebello-pontine angle and the brain stem can be achieved (Fig. 1). In the internal auditory meatus the tumour can be exposed from the fundus to the porus acusticus internus. Incision of the cerebellar dura usually allows the exposure of the anterior, posterior and superior poles of the tumour (Fig. 2a-d) and on its superior anterior surface the facial nerve can be identified. On its superior posterior part the superior vestibular nerve can be visible if it is not completely infiltrated by the tumour. In some rare cases in which the seventh cranial nerve is dislocated by the neurinoma it is possible to identify this nerve from the Fallopian canal or geniculate ganglion. A complete tumour removal is performed by intracapsular debulking of the neurinoma, and by careful mobilization or dissection of the surrounding arachnoidal tissue and cauterization of smaller tumour vessels. The neurinoma often has a close connection to the cerebellum, brain stem, vessels and nerve structures from which it has to be mobilized cautiously. The facial nerve has to be m o b i l i d very carefully from the neurinoma inside the fundus to its root entry zone in the brain stem depending on the size of the space occupying lesion. The cochlear nerve, which can even be localized from the fundus into the cerebello-pontine angle and brain stem via this approach, can be preserved in a considerably high percentage. It is of advantage to perform an intraoperative monitoring of the seventh and eighth cranial nerves (brain stem auditory evoked potentials BAEP for hearing preservation, and direct electrical facial nerve stimulation and transcranial facial nerve stimulation for the function of the facial nerve). At last, the acoustic neurinoma is resected on the proximal healthy stump of the vestibular nerve in the region of the brain stem. After the complete tumour removal the dural flaps are replaced.


Acla Otolaryngol (Stockh) 112

Enlarged middle cranial fossa approach 389

Fig. 1. This figure demonstrates the broad surgical exposure of the enlarged middle cranial fossa approach of a patient (W.W., 42 years, male) with Meniere’s disease on the left side before neurectomy of the vestibular nerve and neuro-vascular decompression (neurolysis). There exists an excellent identification of the seventh and eighth cranial nerves from the fundds of the internal auditory meatus, the cerebello-pontine angle and to their root entry zone in the brain stem. A = Artery; B = Brain stem; E = Eminentia arcuata with the grey line of the superior semicircular canal; F = Facial nerve; V = Vestibular nerve (superior branch).

One or two layers of free. muscle fascia flaps together with fibrin glue (Tissucol@)produce a safe reconstruction of the dural defect above the internal auditory meatus and over the cerebello-pontine angle. The extradural space below the craniotomy is filled out with gelfoam soaked in fibrin glue instead of fixation of the dura by sutures. A complete hemostasis during this kind of surgery is extremely important. The bone flap is refixed by Vicryl sutures and bone pate together with fibrin glue. After the suture of the temporal muscle a Redon drain has to be inserted. The surgery is finished by a double layer skin suture. We keep the patient approximately 2 to 3 days in intensive care. RESULTS In a series of 263 retrospectively studied patients operated on for unilateral acoustic neurinomas via the enlarged middle cranial fossa approach a complete tumour removal was achieved in 96% of the cases (Table I). In 4% an incomplete excision was performed due to tight adhesion to important vessels or extreme vulnerable nerval structures. Until now our approach has not been the reason for insufficient exposure. In bilateral cases of acoustic neurinomas or “last ear hearing” our strategy is a planned incomplete tumour resection (Wigand et al. 1991). which is not considered in this paper. The first postoperative computerized tomography (CT) or magnetic resonance imaging (MRI) follow-up is always performed one year after surgery. Only in one patient of 154



A*a otdupgol (Smckh) 112

Fig. A. Magnetic resonance imaging (MRI)after administration of gadolinium-DTPA of a patient (F.R., 45 years, female) demonstrates an acoustic neurinoma in the cerebello-pontine angle on the left side with a size of about 2 cm.

Fig. 2b. The surgery of the same patient as in Fig. 2a shows the enlarged middle cranial fossa approach on the left side. The acoustic neurinoma has a large extension inside the internal auditory canal and into the cerebello-pontine angle. On its superior anterior surface the facial nerve can be identified. AN = Acoustic neurinoma; E = Eminentia arcuata with the grey line of the superior semicircular canal; F = Facial nerve.


Acta

Otolaryngol (Stockh) I I2

Enlarged middle crmiol fosso opprooch 391

Fig. 2.This figure of the same patient as in Figs. 20 and 26 demonstrates the situation after total removal of the large acoustic neurinoma by the enlarged middle cranial fossa approach. An instrument points to the facial nerve inside the cerebello-pontine angle. E = Brain stem; E = Eminentia arcuata with the grey line of the superior semicircular canal; F = Facial nerve.

Fig. W.This figure of the same patient as in Figs. h - c shows the neurinoma after its total removal via the enlarged middle cranial fossa approach. The size of the tumour is approximately 2.5 cm.Postoperatively the function of the facial nerve was absolutely normal and even the hearing function could be preserved.

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Table I. Results of 263 patients with a unilateral acoustic neurinoma after surgery via the enlarged middle cranial fossa approach Small


Operations (no.) Complete tumour removal (no.) Facial nerve anatomically preserved (no.) , Reoperative hearing loss 1 year after surgery) Transitory neurologic deficit

S d l

Medium

Large

Total

35 0% 0% 3%

117

0% 3% 3%

111 1Yo 3% 4%

263 0.4% 2% 3 yo

3%

3%

I%

2%

0%

1%

4%

2%

0% 6%

4% 4%

11% 6%

6% 5Yo




could start their business a few months after surgery. Only 8% of the patients had reduced vestibular compensation. No patient has suffered invalidity caused by the surgery. Via the enlarged middle cranial fossa approach for acoustic neurinoma surgery no damage to the fifth-, sixth- or caudal cranial nerves has occurred. In nearly half of the cases operated on the facial nerve function was slightly disturbed immediately after surgery or a few days after. However, after a few weeks, months or (no more than) one year, a high percentage of full recovery of the facial nerve was obtained. The facial nerve could be preserved anatomically in 98% of 263 cases. In 4 large cases the facial nerve was sacrificed and initially grafted. A late poor functional facial nerve function and cosmetic result (House VI) occurred in only 6%. In follow-up examinations of 154 unselected patients (including CT or MRI follow-up) one year or more after surgery there existed a House I and I1 in 78% of the cases (grading system according to House & Brackmann 1985). In small and medium sized tumours this index climbed to 90%' (Table 111). A further important goal of this enlarged middle cranial fossa approach is the possibility of preserving the hearing function in a relatively high percentage, even in larger acoustic neurinomas. The cochlear nerve could be preserved anatomically in 78% of the cases. In some cases this nerve had to be sacrificed because of tumour infiltration. In small tumours (Type A) the hearing function could be preserved in 70% of 33 cases with a preoperative hearing loss not exceeding 90 dB, in medium sized tumours (Type B) in 58% and in large neurinomas (Type C) in 34% (Tables I and IV). In summary it was possible to preserve the hearing function in 50% of all patients in 110 out of 220 cases with a preoperative hearing function. In many cases the hearing level was stable. In a few cases the hearing function improved and sometimes it deteriorated. A careful audiometry including an adequate masking was always performed in order to evaluate the hearing function exactly. Seventy-fivepercent of 255 operated patients including 35 persons with total deafness on the diseased side in which the pure tone thresholds could be followed after an adequate postoperative period, had a preoperative hearing level of 60 dB hearing loss or better (Table IV). This range of the hearing level was obtained preoperatively in 83% of the patients with a small acoustic neurinoma. In 51% of these small cases this could still be maintained postoperatively. Seventy-two percent of the patients with a medium-sized tumour had this hearing range

Table 111. Facial nerve function (House I - V I ) of 154 patients with a unilateral acoustic neurinoma operated via the enlarged middle cranial fossa approach (all patients with simultaneously CT or MRI follow-up 2 I year)

mall

medium sized

tunour size

394

c. T. Haid and M . E.

Wimnd


Table IV. Pure tone threshold results in 255 patients before and after acoustic neurinoma surgery via the enlarged middle cranial fossa approach Reoperative (no.)

Postoperative (no.)

Heating 10s

Small

Medium


0-30 dB 16 37 31 -60 dB 13 47 61 -90 dB 4 15 Totaldeafness 2 18 Average of 0,5, 1.2, 4 kHz

Large 34 44 10 I5

Total

Small

Medium

Large

17 30 10 60

19 4 73

87

11

104

I

29 35

5 12

I

Total 35 56 19 145

preoperatively and it could be preserved in 40% after the surgery. Even in 76% of the patients with a large acoustic neurinoma there existed a preoperative hearing level of 60 dB or better; however, it could be maintained in only 25% after surgery. This range between 0 dB up to 60 dB could be saved in 36% of all cases (in 91 out of 255 cases including 35 patients with total deafness on the diseased side preoperatively). In 34% of the cases the preoperative hearing level was as good as 30 dB or better. This level could be preserved in 14% of these cases especially in those with the smaller sizes (in 11 cases out of 35). Our hearing level was averaged for the frequencies of 0.5, 1.0, 2.0 and 4.0 kHz (Table IV). Usually the 4.0 kHz frequency is not considered in the threshold scores reported in the literature. The scores of speech reception within a range of 0 to 60 dB (83%) could be maintained in 47% of the patients, who had a preoperative hearing function (Table V). The speech discrimination loss was preoperatively within a range of 0-30% in 49% of our patients. In 32% this range could be maintained postoperatively, which shows the favourable effect of the enlarged middle cranial fossa approach. The hearing function was usually stable over years (a follow-up of 10 years in many patients). A few cases developed hearing impairment on the operated side. Interestingly, the tinnitus disappeared or decreased in about 50% of the cases especially in patients in whom the hearing function could be preserved. Only in a few cases did this symptom occur postoperatively or start to be more intense. Table V. Results of the speech audiometry before and after acousiic neurinoma surgery by the enlarged midd[e cranial fossa approach Postoperative (YO)

Reoperative (%) Medium sized

Hearing loss

Small

Speech reception 0-30 dB 31-60dB 61 -90 dB 90-120dB

threshold (50% numbers) 66 51 64 24 5 5

25 7 I1

Large

19 6 11

Total

Small

Medium sized

Large

Total

61 22 6 I1

30 40 0 30

32 19 10 39

11 19 3 67

25 22 7

46

49 13 10 28

45 9 9 37

38 5 10 47

19 6 6 69

32 6 9 53

Speech discriminalion loss (monosyllables) O-M% 31 -60% 61 -90% Totally deaf

37 18 27 18

48 16 9 27

53 8 8 31

Acta Otolaryngol (Stockh) I12



CASE REPORT In order to demonstrate the advantages of the enlarged middle cranial fossa approach for total removal of large acoustic neurinomas together with hearing preservation a case report (F. H., 40 years, male, Fig. 3a-e) is given. As cardinal symptom the patient had been complaining of vertigo for half a year prior to operation. There was no complaint of hearing loss and tinnitus. This patient came with an already diagnosed acoustic neurinoma (Fig. 3a) for surgery. Interesting was the fact that there had been an increase of the size of the tumour during the waiting period for surgery compared with the MRI examination 6 months before. In our department the pure tone threshold was objectified normal. The results of the brain stem audiometry pointed to a retrocochlear Lesion. In the caloric reaction there existed a hypoactivity on the diseased side. A total removal of the acoustic neurinoma was performed via the enlarged middle cranial fossa approach (Figs. 3b-d). Postoperatively the facial nerve function was absolutely normal (House I) and the hearing function could be preserved at the same level as preoperatively. The patient was free of vertigo only a few weeks after surgery. A vestibular index of “8” denoted good vestibular compensation. He did not feel any headache and was able to resume his job just a short time after the intervention. A MRI follow-up one year after surgery did not reveal any sign of recurrence of the tumour (Fig. 3e). DISCUSSION Since the introduction of the microscope, special microinstruments and equipment, intraop erative monitoring, enhancement of anesthesia, and improvement of intensive care, the

Fig. 30. Magnetic resonance imaging (MRI)after administration of gadolinium-DTPA of a patient (F.H., 40 years, male) shows an acoustic neurinoma in the cerebello-pontine angle on the left side with a size of approximately 2 cm.


3%

C. T. Haid and M. E. Wigand

A*o otoluyngol (Stoclrh) I 12

Fig. 3.The surgery of the same patient as in Fig. 30 is performed by the enlarged middle cranial fossa approach on the k R side. The acoustic neurinoma has a large extension inside the internal auditory canal and into the arrbello-pontine angle. On its superior anterior surface the facial nerve can be identified. AN = Acoustic neurinoma; E = Eminentia arcuata with the grey line of the superior semicircular canal; F = Facial nerve.

complication rates and mortality rates in the treatment of acoustic neurinomas have been lowered immensely. Usually they are dependent on the size of the tumour and on the patient’s preoperative state of health. Further important facts for success of the surgery are the experience and skill of the surgeon, as well as patience and a good physical condition. Centralization of patients for successful surgery is furthermore a point that has to be stressed. Comparing the possibility of tow rPm0v.l of acoustic neurinomas with different sizes by different procedures, there exist many publications with a high success rate between 93% and 99.4% (Rand 1982; Glasscock et al. 1986; Tos & Thomsen 1989; Pellet et al. 1989; Samii 1991). Kanzaki et al. (1986) reported a complete removal of neurinomas in 81% by the extended middle cranial fossa approach. In contrast to other authors (House 1961; House & Hitselberger 1969; House & Luetje 1979; Gantz et al. 1986; Sanna et al. 1987; Sterkers & bwdler 1988; Glasscock et al. 1988; Shelton et al. 1990; Tos & Thomsen 1991; Helms 1991; Zini et al. 1991; Jackler & Pitts 1991), our experience has shown that it is possible not only to perform a total removal of intrameatal, that is, smaller acoustic neurinomas, or medium sized tumours not exceeding more than 10 to 15 mm into the cerebello-pontine angle, but also of larger tumours (1 11 cases out of 263) up to a size of 30 to 40 cm vii the enlarged middle cranial fossa approach. Complete tumour removal has been achieved in 96% of our cases. Comparing the complication .rate of the different approaches the mortality rate by the translabyrinthine approach lies between 0% and 5% (House 1968; Morrison & King 1982; Glasscock et al. 1986; Fisch 1988; Pellet et al. 1989; Tos & Thomsen 1991), via the


Acta Otolaryngol (Lockh) 112


Fig. k. This figure of the same patient as in Figs. 3a and 3b demonstrates the exposure of the superior, posterior and anterior poles of the neurinoma, after beginning with the intracapsular debulking of the tumour by the enlarged middle cranial fossa approach. The tumour has extensions to the cerebellum and to the brain stem, which are visible. A N = Acoustic neurinoma; E = Eminentia arcuata with the grey line of the superior semicircular canal, F = Facial nerve.

suboccipital or retrosigmoid approach between 0% and 4% (Rand 1982; Samii 1989; Pfaltz et al. 1991) but even as high as 8.5% and 12% (Charabi et al. 1991; Lumenta et al. 1991). In centres removing even large acoustic neurinomas (more than 200 cases) by the enlarged middle cranial fossa approach there the mortality Lies between 0.4% and 0.9% (Wigand et al. 1991; Haid & Wigand 1992; Kanzaki et al. 1991; Shiobara et al. 1991). In small and medium sized tumours the mortality and the risk of invalidity is lower than 1% (Wigand et al. 1982 and 1991; Haid and Wigand 1992; Fisch 1988; Samii 1991; Tos & Thomsen 1991). Improved surgical technique is also reflected in the rate of postoperative complications. The chance of a postoperative Cerebro-spinaI h i d leak (Table 11) is usually ranged between 2% and 5% in centres of acoustic neurinoma surgery irrespective of procedure (Yasargil 1978; Morrison & King 1982; Glasscock et al. 1986; Gantz 1988; F i s h 1988; Sterkers & Bowdler 1988; Pellet et al. 1989; Tos & Thomsen 1991; Calabrese et al. 1991; Wigand et al. 1991; Haid & Wigand 1992). There is a close relationship between cerebro-spinal fluid leaks and the origin of meningitis (Table 11) which can occur in between 2.6% and 6% (Morrison & King 1982; Nadol et al. 1987; Pellet et al. 1989; Calabrese et al. 1991; Pfaltz et al. 1991; Wigand et aI. 1991; Haid & Wigand 1992). The critique that the middle cranial fossa approach induces complications like temporal lobe seizure, aphasia and intracranial haemorrhage is not correct. The risk of a tmpod lobe seizure, which is usually of transitory character, is reported to be between 0% and 6% (Glasscock et al. 1987; Gantz 1988). In the meantime, in more than 500 enlarged middle cranial fossa procedures in our department, e.g. acoustic neurinoma surgery, neurectomy of


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Acta OloLyagol (Stockh)112

Fig. M. This f i p of the same patient as in Figs. 30-c demonstrates the situation after total removal of the large acoustic neurinoma by the enlarged middle cranial fossa approach. On the right side the facial and cochlear nerves are visible and on the left side the cerebellum. The function of the facial and d e a r nerves were absolutely normal postoperatively as well as preoperatively. C =Cerebellum; C.N.= Cochlear nerve; E = Eminentia arcuata with the g ~ line y of the superior semicircular canal; G = Ground of the internal auditory meatus; F = Facial nerve.

the vestibular nerve, neuro-vascular decompression and facial nerve surgery, this symptom has occurred as a single incident in only 2% of the cases. A further important advantage of our procedure is the fact that postoperative pain like bedache occurred in only 5% of our patients. They were never of intolerable character, such as has been reported by Schessel et al. (1991) in about 20% of their patients operated on by the suboccipital approach. To preserve the facial llccvc fnwtion is an extremely important goal in acoustic neurinoma surgery. The use of intraoperative monitoring of the facial nerve during acoustic neurinoma surgery can improve the rate of normal function. In contrast to other authors (Samii et al. 1991; Glasscock et al. 1988) it should be emphasized that the facial nerve and the eighth cranial nerve usually can be identified very exactly via the enlarged middle cranial fossa approach (Wigand et al. 1982; Haid & Wigand 1992). A broad surgical exposure of the internal auditory canal and cerebello-pontine angle is required, just as to keep important landmarks in mind. It is difficult to compare different authors’ material and results directly. Comparing the four Merent approaches (middle cranial fossa approach, translabyrinthine approach and suboccipital and retrosigmoid approach) the facial nerve was anatomically preserved in 98% out of 263 cases via our enlarged middle cranial fossa approach. Kanzaki et al. (1986) was able to preserve this nerve anatomically in 83.4% operated via the same approach. As far as we know the Erlangen and Tokyo centres are the only ENT departments in the world removing even large acoustic neurinomas via the enlarged middle cranial fossa approach. By


Aced Ololaryngol (Stockh) I12


Fig. 3e. Magnetic resonance imaging (MRI) after administration of gadolinium-DTPA of the same patient as in Figs. 30 -d shows no sign of a recurrence of an acoustic neurinorna one year after surgery.

the translabyrinthine route the success rate is between 89% and 98% (House & Luetje 1979; Tos & Thomsen 1984; Sterkers & Bowdler 1988; Pellet et al. 1989; Piazza et al. 1991). In other centres of acoustic neurinoma surgery the facial nerve could even be preserved anatomically in a high percentage of patients operated on by the suboccipital or retrosigmoid approach, that is to say between 79% and 97% (Yasargil & Fox 1974; Nadol et al. 1987; Samii & Draf 1989; Harner et al. 1990, Jiiiiskelainen et al. 1990, Calabrese et al. 1991). It should be mentioned that via this approach the risk of sacrificing the nerve (350/-550/,) increased considerably if the patients were not centralized for surgery. These persons needed facial nerve reconstruction surgery (Devriese et al. 1984; Sabin et al. 1990, Charabi et al. 1991) because the nerve could not be preserved anatomically during the surgery. The facial nerve function according to the grading system by House & Brackmann (1985) was maintained postoperatively (House I and 11) via the middle cranial fossa approach in between 77% and 95% of cases (Brackmann 1979; Wade & House 1984; Glasscock et al. 1988; Gantz 1988). Usually these neunnomas were classified as small and medium sized. In 78% of our 154 unselected patients operated on via the enlarged middle cranial fossa approach including all sizes the function of the facial nerve was excellent (House I and 11). This percentage would be considerably higher if we did not consider patients with synkinesis but without any facial nerve weakness as House Ill. For our small and medium-sized turnours House I and I1 was as high as 90% (Table 111, Wolf et al. 1992). Only in 2% of all our 263 cases the seventh cranial nerve had to be grafted, and in 6% a late poor facial nerve function occurred (House VI) as a sign of a paralysis. Tos & Thomsen (1991) classified the facial nerve function operated on via the translabyrinthine approach as House I and I1 in 68% out of 504 cases. Patients with


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an acoustic neurinoma smaller than 2cm (135 cases) climbed to 92%. A facial nerve paralysis occurred in 10% of all their cases. Fisch (1988) succeeded in an absolutely normal facial nerve function via the same route in 65% out of 114 cases. A paralysis of the seventh cranial nerve happened only in 4%. Using the retrosigmoid approach Uziel & Benezech ( 1991) reported a House I and I1 in 94% out of 95 operated cases one year after the surgery. Pfaltz et al. ( 1991) reported a success rate of 53% out of 93 large cerebello-pontine angle tumours operated on via the same approach. Glasscock et al. (1988) reported a House I and I1 via the suboccipital procedure in 85%. A facial nerve paralysis ( H o w W)occ~rredvia the suboccipital or retrosigmoid approach in between 2% and 17.5% (YasarGl et al. 1977; Rand 1982; Nadol et al. 1987; Sterkers & Bowdler 1988) and even as high as in up to 57% (Charabi et al. 1991). As for the probability of postoperative hearing preservation, the probability of preservation of normal facial nerve function is related to the size of the acoustic neurinoma. The chance of preservation of the facial nerve function drops considerably for larger tumours of about 2.0 to 3.0 cm in size (House & Luetje 1979; Rand 1982; Glassock et al. 1986; Kanzaki et al. 1986; Fisch 1988; Tos & Thomsen 1991). This implicates the indication to remove acoustic neurinomas at an early stage with an approach that is believed to preserve facial nerve function. in constrast to our experience, Clemis (1984), Gardner & Robertson (1988) and Tos & Thomsen (1991) have reported that only a small percentage of acoustic turnour patients are suitable candidates for attempted hearing preservation. Via the middle cranial fossa approach Sterkers (1981) was able to preserve the hearing function in 8 out of 20 cases (40%) and 54% in small turnours, Gantz (1988) in 18 out of 33 intracanalicular tumours (55%), Shelton et al. (1989) in 59% out of 106 neurinomas, Kanzaki et al. (1991) in 45% (in 59 cases out of 130 cases), Jenkins (1991) in 67% (8 of 12 surgeries), Brackmann (1979) in 45% (in 5 out of 1 1 intracanalicular tumours), Glassock et al. (1987) in 10 out of 32 neurinomas (31%), Cannoni et al. (1989) in 6 out of 13 intracanalicular tumours (46%). There is a remarkable chance of preservation of hearing function (Tables I, IV and V) in surgery by our enlarged middle cranial fossa approach (in 110 out of 220 unselected patients with a preoperative hearing sensation = SOYO)especially in small neurinomas (70%) but even in larger neurinomas (34%). This fact underlines the importance of early diagnosis and treatment of smaller acoustic neurinomas. Favourable for the patient was the fact that the scores of the speech reception could be maintained within a range of 0-60 dB in 47% of the cases after the treatment. In 32% of our operated cases the speech discrimination loss could be preserved in the range of between 0-30%, which once more reveals the advantages of the enlarged middle cranial fossa approach. Samii et al. (1991) has reported a successful hearing preservation in 57% of 16 intracanalicular acoustic neurinomas treated via the suboccipital approach. Samii & Draf ( 1989) were able to preserve the hearing function in 40% of the cases via this approach, if the tumour was smaller than 3 cm.Cohen et al. (1986) succeeded in hearing preservation in I 1 out of 18 neurinomas (61%) smaller than 2 cm,Calabrese et al. (1991) in 50% (in 30 out of 60 attempted cases smaller than 2 an),Kernink et al. (1991) in over two-thirds of 30 selected cases with tumours of less than 1.5 cm,Fahlbusch et al. (1991) in 29% (in 18 out of 56 cases). Nadol et al. (1987) were able to preserve the hearing function in 8 out of 1 1 cases (73%) via the suboccipital approach, if the extension into the posterior fossa was smaller than 0.5 cm,and in 2 of 9 patients if the extension was greater than 2.5 cm. Altogether the success rate of hearing preservation was 36% (24 out of 66 attempted cases). The retrosigmoid approach is a further useful approach to attempt hearing preservation. Sterkers & Bowdler (1988) succeeded in 20% out of 131 acoustic neurinomas to preserve the


Actd Otoldryngol (Stockh) 112

Enlarged middle cranial fossa avproach 401

hearing function, which increased to 38% in 58 selected patients. Harner (1991) reported a success in 53 out of 221 patients (24%) and 51% in tumours smaller than 2 cm,Pfaltz et al. (1991) in 25% of the cases not exceeding 20-30 mm of size, Smith (1988) in 23 out of 47 selected patients (49%) and Beaumont & Fagan (1988) in 11 out of 22 neurinomas (50%). Gardner & Robertson ( 1988) have reviewed studies that reported 585 patients in whom hearing preservation was attempted. Altogether they were successful in 185 cases (31.6%). Via our enlarged middle cranial fossa approach this was possible in I10 out of 220 attempted cases (50%). One of the great disadvantages of the translabyrinthine approach is its function-destroying effect of the cochlear and vestibular functions immediately after destruction of the labyrinth. This approach is still considered in many otoneurosurgical centres even in cases with a serviceable hearing capacity (House 1964, Morrison & King 1982; Tos & Thomsen 1984; Glasscock et al. 1986; Sterkers & Bowdler 1988; Pellet et al. 1989; Mercke et al. 1991). Intraoperative monitoring of the eighth cranial nerve (BAEP) may be advantageous in hearing preservation surgery. However, even if evoked potentials are preserved during surgery, the hearing function may sometimes be completely lost during the immediate or delayed postoperative period (Strauss et al. 1991; Fahlbusch et al. 1991; Maniglia 1991; Wigand et al. 1991). Preservation of the blood supply to the inner ear and cochlear nerve is the most challenging task in hearing preservation surgery. Vessels arising from the anterior inferior cerebellar artery (AKA) feeding the tumour capsula may also nourish the hearing organ and the cochlear nerve. Mechanical trauma to the cochlear nerve during tumour removal can be attributed to disturbances of the microcirculation in endoneuraI vasa nervorum (Strauss et al. 1991). Further causes can be vasospasm of the internal auditory artery, edema in the cochlear nerve, compression inside the internal auditory meatus or growth of scar tissue. Even a cerebellar retraction or escape of cerebro-spinal fluid can result in hearing deterioration. In some cases the hearing function will impair after years in relation to the non operated ear (Jannetta et al. 1984; Palva et at. 1985; Rosenberg et al. 1987; Sterkers & Bowdler 1988; Shelton et al. 1991). The postoperative auditus (Table IV) has usually been related to the size of the tumour and to the preoperative hearing capacity. There is a small chance to preserve the hearing function beyond a tumour size of 2.5-3.0cm (Nadol et al. 1987; Gardner & Robertson 1988; Samii 1989). In contrast to other authors (Wade & House 1984; Smith & Lagger 1984; Gantz et al. 1986; Glasscock et a]. 1986; Sterkers & Bowdler 1988; Jenkins 1991; Calabrese et al. 1991; Bynke et al. 1991; Kemink 1991; Tos & Thomsen 1991) it should be stressed that even in cases of larger tumours and reduced hearing it is justified to try to preserve the cochlear nerve anatomically. This was possible in 78% of all our cases. Thus there exists a possibility of more or less hearing ability in some cases (Wigand et al. 1989; Samii 1990, Haid & Wigand 1992). It can be of value not only for conversation but even for directional hearing capacity (Hiinig & Berg 1991). In our experience the tinnitus can be reduced or even made to disappear in approximately 50% of the patients, especially in cases in whom hearing preservation has been successful. It has to be mentioned that even the vestibular compensation after acoustic neurinoma surgery via the enlarged middle cranial fossa approach was quite satisfactory irrespective of the size of the tumour and of the patient's age if the central vestibular pathways were not disturbed, e.g. in cases with a large tumour compressing the brain stem or cerebellum, after cranial injury or in patients with severe internal diseases (Haid et a]. 1991). Furthermore, in contrast t o the suboccipital approach, the enlarged middle cranial fossa approach does not touch the cerebellum at all which contains important neural structures for vestibular compensation. An important fact for the efficiency of the patients' vestibular compensation, which begins immediately within days after surgery, is to start as soon as possible with a




special training programme. Only 8% of our patients with an acoustic neurinoma complained of a strong vertigo caused by reduced vestibular compensation. So far we have not observed a single case of tumonr regrontb in 154 postoperative follow-up examinations (MIU-follow up 2 1 year post-operatively) in unilateral acoustic neurinomas following a planned total removal. It has to be stressed that the enlarged middle cranial fossr approach (Wigand et al. 1982; Wigand, Haid & Berg 1991; Haid & Wigand 1992) is the procednre of first eboice with an extremely low postoperative complication rate (Table 11) and mortality rate even for larger acoustic neurinomas. In the last years, the number of detected small and medium sized acoustic neurinomas as a sign of an early diagnosis has increased. One hundred and fifty-two out of 263 operated unilateral tumours could be classified as smaller or medium sized (58%). Disadvantages are surely that this procedure is very time consuming and sophisticated requiring exact knowledge of the microanatomy of the petrous bone and surrounding structures. But it also has to be stressed that the advantages are unique (Fig. 1): Excellent exposure of the fundus, internal auditory meatus, pons acusticus internus, cerebello-pontine angle to the brain stem, good identification of the facial nerve, cochlear nerve, superior and inferior vestibular nerve, retractor in extradural position, avoidan& of compression to the cerebellum and the possibility of total removal even of large acoustic neurinomas. The enlarged middle cranial fossa approach represents a function preserving surgery. In fact this exposure allows more direct visualization of the seventh and eighth cranial nerves which the two standard techniques, the translabyrinthine and suboccipital approaches cannot provide. These two classical procedures for acoustic neurinoma surgery, have some important disadvantages which have to be considered. The translabyrinthine approach represents a function destroying procedure for the eighth cranial nerve resulting in obligatory total deafness on the operated side. By the suboccipital procedure it is necessary more or less to compress the cerebellum intradurally. Furthennore, it is not always possible to accomplish an exposure into the fundus of the internal auditory meatus without destroying the inner ear because of its topographic position of the superior and posterior semicircular canal and the endolymphatic sac (Domb & Chole 1980; Stennert 1986; Aurbach & Wigand 1987; Roland et al. 1988). Samii et al. (1991) do not agree with this statement. Beside removal of cerebello-pontine angle tumours via the enlarged middle cranial fossa approach it is also possible to perfom other otonertrosm@eal interventions e.g. a neuro-vascular decompression in patients with hemifacial spasm or Meniere’s disease and/or neurectomy of the vestibular nerve in patients with Meniere’s disease (Haid & Wigand 1985) by the same approach. It is sometimes necessary to do a simple exploration of these regions without damaging the hearing and vestibular function and to be precise in unclarified findings of CT-scan or MRI (Glass et al. 1991). Furthermore, even extradurally located diseases of the middle cranial fossa can be treated via this approach, e.g. to decompress or to graft the facial nerve or to repair an extensive cerebro-spinal fluid fistula in fractures of the petrous bone and to remove pseudotumours like cholesterol granulomas or penetrating cholesteatomas. These facts indicate once more the advantages of the enlarged middle cranial fossa approach. An early diagwsis of acoustic neorinomas or other space occupying lesions in the internal auditory meatus or cerebello-pontine angle is of great advantage for the patient’s postoperative neural and neurological functions. This early diagnosis is based on a general tendency of otologists to submit every case of unilateral sensorineural hearing loss, including sudden deafness, to a diagnostical procedure, including brain stem audiometry and advanced vestibular testing consisting of both the positional test and the caloric reaction. If these functional tests gke a suspicion of retrolabyrinthine lesion, MRI or CT with air-meatography are indicated (Haid 1987, 1990 and 1991), verifying or excluding a space occupying lesion in the intrameatal auditory canal or cerebello-pontine angle.



ACKNOWLEDGEMENTS This work was supported by the J. and F. Marohn Foundation.


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Hearing preservation in acoustic neuroma surgery by the extended middle cranial fossa method.

Translabyrinthine surgery of acoustic neurinoma.

Subtemporal-anterior transtentoral approach to middle cranial fossa microsurgical anatomy.

Calcified Middle Cranial Fossa Mass.

Arachnoid cysts of the middle cranial fossa.

Acoustic neurinoma surgery in Belfast 1986-1989.

Meningeal melanocytoma of the middle cranial fossa (the Meckel's cave).

Endoscopic endonasal approach to the middle cranial fossa through the cavernous sinus triangles: anatomical considerations.

Three-dimensional Anatomical Analysis of Surgical Landmarks for the Middle Cranial Fossa Approach.

A Middle Cranial Fossa Dermoid Cyst Treated by an Endonasal Endoscopic Approach.

Landmark structures to approach the internal auditory canal: a dimensional study related to the middle cranial fossa approach.

Piezosurgery for the repair of middle cranial fossa meningoencephaloceles.

Arachnoid cyst in the middle cranial fossa presenting with pulsatile exophthalmos: case report and literature review.

Cerebrospinal Fluid Leakage from Tegmen Tympani Defects Repaired via the Middle Cranial Fossa Approach.

Traumatic dislocation of intact mandibular condyle into middle cranial fossa.

Cerebrospinal fluid rhinorrhea following acoustic neurinoma surgery. Technical note.

Cerebellopontine angle facial schwannoma relapsing towards middle cranial fossa.

Retrosigmoidal approach to the posterior cranial fossa. An anatomical study.

Dislocation of a mandibular condyle in the middle cranial fossa, diagnosed 54 years after trauma.

The significance for postoperative hearing of preserving the labyrinth in acoustic neurinoma surgery.

An extended approach through the middle cranial fossa to the internal auditory meatus and the cerebello-pontine angle.

Arachnoid cysts of the middle cranial fossa: a clinical, radiological and follow-up study.

The middle cranial fossa approach to the internal auditory canal -- an anatomical study stressing critical distances between surgical landmarks.

The first calcified acoustic neurinoma identified in China: a case report and literature review.