THE SYSTEM OF MODIFIED TRANSCOCHLEARAPPROACHES FOR INTRADURAL SKULL BASE LESIONS

SANDEEP KARMARKAR, Clinical Research Fellow,Gruppo Otologico, Piacenza, ItalySANJAYA BHATIA, ENT Surgeon, Bombay, IndiaESSAM SALEH, Dept. of ENT, Alexandria University, EgyptABDELKADAR TAIBAH, ALESSANDRA RUSSO, ANTONIO MAllONI,MARIO SANNA, Gruppo Otologico, Piacenza, Italy.

The modified transcochlear approach was used to manage 27 patients with intraduraltumours of petroclival region and prepontine cistern. Total tumour removal was possiblein 21 cases. Planned subtotal removal was done in 2 elderly patients; one was a chordomawith involvement of the cavernous sinus and extending upto the optic chiasma while theother was a petroclival meningioma involving the cavernous sinus with normal abducentnerve function. The remaining 4 cases are awaiting their second stage. The modifiedtranscochlear approach is systematized and further classified into types A, B, C and Ddepending upon its extensions. The basic surgical technique with its extensions, detailsof the classification, indications of each type and results are presented in this report.

INTRODUCTION

Although surgery of the median skull basestill represents an enigma involving diversespecialities, it is increasingly being recognizedas a peculiar area possessing both uniquediagnostic and surgical challenges. House andHitselberger (1976) were the first to be accred-ited for their description of the transcochlearapproach for such lesions. Since then, the evolutionof this classical approach has seen severalmodifications (Jenkins and Fisch, 1980; Sekharand Estonillo, 1986; Horn et al., 1991; Daspitet al., 1991; Thedinger et al., 1992). We areusing the modified transcochlear approach (MTCA)in the management of various extra, intra and/or transdural lesions like petrous bonecholesteatoma (Sanna et al., 1993; Sanna etal., 1994), meningiomas (Sanna et al., 1994;Saleh et al., 1994) and chordomas (Sanna etal., 1993).

The aim of this paper is to present ourclassification and systematization of the MTCAbased on the surgical technique, limits and theextensions of this approach and to report our

results in intradural tumours managed by thesystem of MTCA.

SURGICAL TECHNIQUE

The surgical steps about to be describedbelow are a summary of the technique detailedbefore (Sanna, M et al., in press). Under generalanaesthesia, the patient is placed in supineposition with the head turned to the oppositeside. Continuous facial nerve monitoring usingthe NIM -II facial nerve monitor (Xomed Treace,Jacksonville, Florida) and the Myo Alarm(OtolabTM, Italy) is done. A postaural C-shapedincision is given starting 3 cm above the auricle,coursing 5 cm posteriorly and extending 1 cmbelow the mastoid tip. The skin and the musculo-periosteal flap is elevated to expose the mastoid,temporalis muscle, zygomatic arch and part ofthe temporal squama. A cul-de-sac closure ofthe external auditory canal (EAC) is performed.After removing the remaining EAC skin, tym-panic membrane and the ossicles; an extendedcanal wall down mastoidectomy is accomplishedso as to expose the middle fossa dura and the

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posterior fossa dura in front and 2-3 cm behindthe sigmoid sinus. The sigmoid sinus is skeletonisedto the jugular bulb, taking utmost care duringthe removal of the thin shell of bone over thesestructures. A high jugular bulb, if encountered,is managed using the technique previouslydescribed (Saleh et al., 1994). A labyrinthectomy

dissection with a beaver knife so as to cut itsstrongfibrous attachments. The tympanic portionis then mobilised using an angled pick. Directsuction trauma over the nerve should be avoid-ed by protecting it with cottonoids or alterna-tively by using Brackmann fenestrated suctiontips. Once the nerve is liberated, it is cautiously

Fig. 1. A Schematic representation of the exposure afforded (shaded and outlined region) by the type A approach.TS=transverse sinus, SS=sigmoid sinus, JB=jugular bulb, IJV=internal jugular vein, vL=Labbe's vein, ev=emissaryvein, sps=superior petrosal sinus, MMA=middle meningeal arery, V3 and V2=mandibular and maxillary division ofthe fifth cranial nerve, gspn=greater superficial petrosal nerve, vii= facial nerve, ix/x/xi/xii=lower cranial nerves,AFL=anterior foramen lacerum,Sph=sphenoid sinus, pc=postenor clinoid, ICA=internal carotid artery,ET=eustachian tube, za=zygomatic arch, M=mandible, pp=pterygoid process, Co=cochlea, oc=occipital condyle,Cl=atlas, TP=transverse process, Pcn=posterior communicating artery, PCA=posterior cerebralartery,SCA=superior tere bellar artery, BA=basilar artery, AICA=anterior inferi or cerebellar artery,PICA=posterior inferior cerebellar artery, VA=vertebral artery (c=contralateral, cx=cervical part). The structuresincluded in the vertical columns on either side of the figure can be controlled by this approach (unshaded=totalcontrol, shaded=partial) while those outside cannot be controlled.

with wide exposure of the internal auditory canal(IAC) is performed as detailed before (Naguibet al. 1994). The facial nerve is then skeletonisedfrom the stylomastoid foramen till the fundusof the IAC, with due care in uncovering it atthe geniculate ganglion and labyrinthineportion. Sufficient bone removal is necessaryin this step to avoid trauma to the nerve duringits posterior transposition. The greater super-ficial petrosal nerve is then exposed, coagu-lated and transected. Using an angled pick, thegeniculate and the labyrinthine portion of thenerve are separated from the underlying bone.The mastoid segment is liberated using sharp

rerouted posteriorly. The dura of the anteriorwall of the IAC is dissected and reflectedposteriorly alongwith all the contents of theIAC till the level of the meatus so as to protectthe delicate intracanalicular portion of thefacial nerve. The mobilised portion of thenerve is then protected by fixing it to theposterior fossa dura just anterior to the sigmoidsinus and posterior to the jugular bulb usingfibrin glue. Further bone removal is accom-plished by drilling off the cochlea, the remain-ing fallopian canal and the anterior wall ofthe IAC. The vertical portion of the internalcarotid artery (ICA) is then identified using

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a large diamond burr. For achieving near totalcircumferential control over the ICA, the man-dibular condyle is displaced anteriorly. Thehomolateral petrous apex and the middle clivus

of the tumour are identified, carefully dissectedand then the intracapsular debulking is donewith extreme caution taking care of the anteriorinferior cerebellar artery (AICA), posterior

Fig. 2. Exposure and extent of neurovascular structures in the MTCA type A. Vl=sixth cranial nerve, fn=postenorlyfacial nerve.

is then drilled . The inferior petrosal sinus canat this step bleed notoriously and if so, shouldbe packed with surgicel (Johnson & JohnsonCo., New Brunswick,NJ). The dura is then openedin a triangular fashion between the superiorpetrosal sinus superiorly and the inferior pet-rosal sinus and jugular bulb inferiorly. Due careis taken to avoid damage to the facial nervewhile opening the dura in front of the IAC meatus.the intracisternal part of the facial nerve, if notalready displaced back by the tumour, is re-leased posteriorly and thus the nerve is actuallytransposed behind from the stylomastoid fora-men till its origin at the brain stem. The clivaldura is then separated form the overlying clivalbone and the incision is extended anteriorly.this step of dissection and opening of the clivaldura has to be done carefully, as it should beresected when infiltrated by tumours likemeningiomas and chordomas and at same timetaking care not to damage the sixth nerve atits entrance into the Dorello's canal.

Tumour removal is then commenced usinga bipolar cautery and continuous suction irri-gation. The superior, inferior and posterior poles

inferior cerebellar artery (PICA), superior cer-ebellar artery (SCA) or the cranial nerves whichmay be embedded in the tumour. The tumourcapsule is further separated away meticulouslyfrom these surrounding neurovascular struc-tures by always staying in the arachnoid plane.The lower cranial nerves are dissected awaycarefully. Attention and optimal dissection isrequired hereto avoid the effects of vagal stimulationwhich manifest as hypotension and bradycar-dia. The facial-vestibulocochlear nerve com-plex is in many instances pushed posteriorlyand can be easily identified. However, it canbe sometimes engulfed by the tumour and needsa careful dissection for the preservation of thefacial nerve and its vasculature. Further, dis-section of the abducent nerve which may bepushed antero-inferiorly by the tumour is car-ried out and this nerve is followed distally. Thetrigeminal nerve, in many instances, is variablybut intimately related to the tumour and ispushed cranially, anteroinferiorly and rarelyposteriorly. At times, the tumour may extendinto and beyond the Meckel's cave which shouldbe opened and the tumour gradually separated

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taking care of the three subsequent finger likedivisions of the trigeminal nerve.

The tumour is then dissected gently from

ing a precise dissection to separate the tumourfrom them. The tumour is then gently removedfrom the brain stem area by alternatively working

Fig. 3. A schematic representation of the additional anterior exposure afforded by the type B approach. The whole ICA is exposed.

the basilar artery, vertebrobasilar junction andfrom the homolateral vertebral artery. Thehomolateral vertebral artery may be often encasedand the basilar artery with its perforating branches,generally pushed to the opposite side warrant-

from all around the tumour. The dissection, asfar as possible is always done by staying inthe arachnoid plane which in some extensivelesions may be lost compelling the surgeon todo partial removal so as to avoid damage to

Fig. 4. Exposure and extent of neurovascular structures in the MTCA type B. V=fifth cranial nerve.

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the brain stem.

Once the tumour removal is accomplished,the eustachian tube is obliterated using muscle

plug and bone wax. Because of a large oper-ative defect, a single large piece of abdominal

fat, rather than small strips as in extended

EXTENSIONS OF MICA AND THEIRTECHNIQUES

The basic approach (MICA Type A) givesa good access to the mid clivus, homolateralpetrous apex, anterior CPA and the prepontinecistern.

Fig. 5. A schematic representation of the exposure possible by the type C approach.

translabyrinthine surgery, is used alongwith fibringlue to avoid slipping into the cerebello-pontineangle (CPA). After reposing the myoaponeuroticalflap, the wound is tightly closed in two layers.Figures 1 and 2 show the exposure facilitatedby the basic MTCA type A.

The concept of staging the operations is.vitaland is practised by us whenver necessary. Incases with large supratentorial extensions aMTCA is done in the first stage followed by thesubtemporal transtentorial approach in secondstage through the previous operative site andin addition sectioning the tentorium. Tumoursextending anteriorly with close relation to thenasopharyngeal areas are first tackled by theinfratemporal fossa approach of Fisch (1978)to remove the extradural part and the MTCAis performed in the second stage to managethe intradural part. In certain lower clival tumoursextending downwards into paravertebral andneck spaces a first stage MICA followed bya second stage Transcervial-extreme lateralapproach is used.

We further extended the approach depend-ing on the tumour location. The MTCA type Bis the combination of the basic approach withthe type B infratemporal fossa approach of Fisch(1978). The additional features of this approach.are the inferior displacement of the mandibularcondyle, drilling of the glenoid fossa and di-vision of the middle meningeal artery and themandibular nerve. This allows anterior exten-sion of the basic approach and in addition,permits control of the parapharyngeal areas aswQlI as the horizontal portion of the ICA uptothe anterior foramen lacerum (Figures 3 & 4).

The MTCA type C is nothing but a superior ,

extension of the basic approach and is thusused for transtentorial tumours. The superiorpetrosal sinus (SPS) is opened and packed withsurgicel. The middle fossa dura is incised parallelto. and few mm above the SPS. The tentoriumis then cut beginning posteriorly, coursing antero-medially uptill the tentorial incisura. Care shouldbe taken to avoid injury to the fourth cranialnerve which pierces the tentorium and is so

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intimately related to it. This upward extension,as seen in figures 5 & 6, allows the removalof the supratentorial tumour component keep-

The MTCA type D is a combination of thebasic approach with the petro-occipital trans-sigmoid approach (Mazzoni and Sanna; 1992).

Fig. 6. Exposure and extent of neurovascular structures in the MTCA type C. lll=third cranial nerve, IV= fourth cranial nerve

ing under good control the superior cerebellarartery (SCA), posterior cerebral artery and thethird and fourth cranial nerves, without anysignificant temporal lobe retraction.

The highlights of the MTCA type D are theopening of the sigmoid sinus and packing iswith large pieces of Surgicel, first extraluminallyand then intraluminally. The internal jugular vein

Fig. 7. A schematic representation of the exposure afforded by the type D approach after transection of the sigmoid sinus and

ligation of the IJV.

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is ligated at the end of the procedure as thebulb is blocked by the tumour in most cases.Also, the occipital condyle can be drilled if needed.This approach is adopted for the intra and/ortransdural tumours involving the lower and midclivus which usually extend into the jugular bulb,occipital condyle and around the intradural vertebralartery. The total exposure and amount ofneurovascular control which can be obtainedin this approach is shown in figures 7 & 8.

achieved in 21 cases (either at one or morestages), planned subtotal in 2, while 4 othersare awaiting their second stage. In the 2 patientswith subtotal removal, one had invasion of thecavernous sinus with tumour extending upto theoptic chiasma with good vision while the otherhad tumour extending into the cavernous sinuswith normal cranial nerve function. Thus, sinceboth these patients were elderly a preoperativedecision to remove the tumour subtotally was

Fig. 8. Exposure and extent of neurovascular structures in the MTCA type D. Icn=lower cranial nerves (IX-XI), Xll=twelfthcranial nerve

PATIENTS, METHODS AND RESULTS

This series consists of 27 intradural lesionsoperated using the MTCA. Table I shows thevarious lesions tackled by using the system ofMTCA; petroclival meningiomas constituted about48% of all cases. The basic type A approach(Figures 9a and 9b) was done in 18 cases(66.66%) while the MTCA types B (Figures 10aand 10b), C (Figures 11 a and 11 b) and D (Figures12a, 12b and 12c) were performed in cases 4(14.81%), 2 (7.40%), and 3 (11.11%) casesrespectively. Table II gives a summary of thesecases.

We had 12 males and 15 females with ageranging from 12 to 71 years (mean age 44years). Tumour size measured as the largestintradural diameter, ranged from 3.5 to 7 cmwith mean of 4.5 cm. Total tumour removal was

taken weighing the anticipated morbidity thatcould be caused by total tumour removal againstthe prospective expected life of these patients.In none of the patients was the tumour subtotallyremoved for lack of exposure.

Two patients pre-operatively, had mildconductive hearing loss, two moderate senso-rineural hearing loss (SNHL) and twelve hadprofound ipsilateral SNHL. The remaining elev-en cases had normal hearing.

Pre-operatively, 20 (74.07%) cases had normalfacial nerve function, 2 partial while 5 had completeparalysis. Of the 20 patients with mormal pre-operative facial nerve function, 14 (70%) caseswith a follow up of more than a year are includedfor assessment of the post-operative facial nervefunction according to the House-Brackmann gradingsystem (1985). The eventual outcome of facial

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nerve function in these 14 cases is shown intable III.

One case had postoperative sixth nerve paresiswhile four had post-operative VI nerve palsy,with histopathologic evidence of nerve infiltra-tion by meningioma in one case Similarly, therewere two cases in whom the IV nerve was sacrificed

removed in a third stage surgery. There are nomore recurrences as yet.

DISCUSSION

Tumours in the vicinity of the median skullbase always represent a difficult surgical task.Due to the deep seated location of the clivus,

Fig. 9A. Preoperative MR! (coronal TIW, gadolinium) of o ni'al chordoina

due to meningioma invasion. Fifth nerve wasinjured in one case during removal of chordomafrom around it. Finally, one patient showed post-operative paresis of IX and X nerves, but hascompensated well without significant problem.The vertical ICA was accidentally intraoperativelylacerated and uneventfully repaired in one case.We had two mortalities. The first had a largesphenopetroclival meningioma with supratentorialextension and died 20 days after surgery dueto brain stem infarction secondary to suspectedinjury to the anterior inferior cerebellar artery(AICA). The second was an extensive chordomainvolving the whole clivus and reaching the C1 -C2 through the foramen magnum. This 12 yearboy died of unexplained acute brain oedemaand breathing difficulty, one day after surgery.All the remaining cases have done well andhave returned to work. Excluding the cranialnerve deficits, there were no other neurologicalcomplications. There was no patient with cere-brospinal fluid leakage and\or meningitis. Onecase with chordoma had a recurrence along thehorizontal part of the ICA which was completely

petrous apex, anterior cerebellopontine angleand the prepontine cistern, access has alwaysbeen a major surgical problem for tumourssituated in these areas, more so in intradurallesions. This is further complicated by the variabilityof lesions arising there and the multiplicity ofapproaches advocated (midline or lateral,neurosurgical or otological, single or combined,one or more staged). In our series of intradural

^ TABLE—f

Lesions addressed by the system of MTCA

2 cases of Neurofibromatosis-2.

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tumours, meningiomas and chordomas were thecommonest lesions encountered and both ofthem are not only known to have significant

An ideal approach is the one which gives adirect access to this area, allows total removalwith a simultaneous good control over the

Fig. 9B, Postoperative MR! (coronal, TIW) 0/ the same patient with enhancement of the fat in the detect sand completeremoval by the MTCA type A

dural and bony invasion but also to have a highrecurrence rates, unless totally removed

Various approaches have been describedand are being practised for petroclival tumours,

neurovascular structures and entails minimummorbidity The middle fossa transpetrous ap-proach (House etal , 1986; Hitselbergeretat.,1993)allows the possibility of preservation of facial

Fig. 10A. Preoperative MRI (axial TIW, gadolinium showing a 4 cm right sided lesion surrounding the basdar artery.

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nerve function and hearing. It also permits theresection of involved dura and bone. However,this approach neither allows good access to the

transtentorial approach (RLTTA). This approach(RLTTA) as described by Hakuba et al. (1987),as well as its modifications (Samii and Ammirati,

Fig. 10B. Postoperative CT scan of the patient after under going a MTCA type B

region inferior to the IAC nor does it permit thecontrol of vertical ICA and lower aspect of hor-izontal portion of the ICA. A somewhat similarsituation is encountered when such tumours aremanaged by using the retrolabyrinthine-

1988; Al -Mefty et al., 1988; Canalis et al., 1991),has the possibility of preserving facial nervefunction and hearing. Nevertheless, it warrantsa significant amount of temporal lobe retraction.Moreover, it gives a restricted view of the petroclival

Fig. 1 1A. Preoperative MRI (coronal, TIW, gadolinium) showing a 3 7 cm left petroclival meningioma.

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region, does not allow control of ICA, does notpermit total resection of involved dura/bone andendangers the neurovascular structures as theyare interposed between the surgeon and tumour.

The transcochlear approach enables a di-rect lateral access to the anterior CPA andprepontine cistern. Further, the MTCA allowsbetter visualization of the anterior CPA and alsopermits nearly total circumferential control overthe ICA which is critically involved in manytransdural tumours. It also gives a much widerexposure with nearly no temporal or cerebellar

The MTCA type B is an anterior extensionof the basic approach to tackle the tumoursinvolving the parapharyngeal spaces and isgenerally used for transdural tumours in thisarea (chordomas, chondromas, chondrosarcomas).However, in tumours closely related to thenasopharynx a staged procedure is performedwith the removal of the extradural comport It

using the type B infratemporal fossa approachat the first stage foilowed by a MTCA for theintradural part at the second stage. This is downto avoid the risk of meningitis and CSF rhinorrhoea.

Fig. 1 1B. Postoperative CT scan (axial) of same patient showing extent of bone removal in the MTCA type C and no evidence)

of residual tumour

retraction. Moreover, the removal of involveddura/bone is possible and thus the MTCA allowsthe radical surgery required for the treatmentof these aggresive lesions. By combining theseadvantages of the MTCA with various exten-sions as in the system of MTCA; it was realisedthat the potential to tackle difficult lesions inthese area has widened.

We have systematized and further classifiedthe MTCA into four types depending on its extensionso as to simplify the understanding of the indicationsand the drawbacks of this approach. The basicapproach or the MICA type A is indicated forlesions involving the mid clivus, petrous apexand the prepontine cistern. It allows a goodcontrol over the cranial nerves IV through Xand partial control over the XI and XII cranialnerves.

The MTCA type C is a superior extensionof the basic approach and is indicated mainlyfor petroclival tumours with supratentorial ex-tension. The type C approach gives good exposureof the upper and mid clivus and a good controlover the ICA, the posterior cerebral artery andover cranial nerves III-IX. In patients with alarge supratentorial extension, we usually pre-fer a staged removal.

The MTCA type D is suitable for tumoursinvolving the mid and lower clivus and is aninferior extension by combination of the basicwith the POTS approach. It affords a good controlover the lower cranial and the XII cranial nerve.If the tumour is extending extracranially, a stagedprocedure is preferred so as to avoid the highchances of CSF leak in the neck.

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TABLE—II

Summary of 27 patients operated by the system of the modij.ed transcochlear approach

No Age Sex Pathology Location Clinical status Approach Complications Facial nerve

1 44 F Meningic 'a Petroclival Recurrent tumour. MTCA A None Grade III

Good Hearing

2 63 M Meningioma Petroclival Dead ear MTCA A None Grade IV

3 51 M Meningioma sphenopetro V, VI, cn palsy MICA A Death-Brain Stem-clival with Good hearing infarction

supratentorial

4 60 F Meningioma Petroclival V cn paresis MICA A' VI cn cut Grade IIIsupratentorial Dead ear ST-TTT Transient hemiparesis2

5 55 M Meningioma Petroclival Good hearing MICA A None Grade i il

6 44 F Meningioma Petroclival IV, VI, cn paresis MICA A None Grade IlMild CHL

7 47 F Meningioma Petroclival V cn paresis MICA C IV cn cut Grade III

supratentorial Good hearing Transient diploplia

8 57 F Meningioma Petroclival V cn paresis MICA A None Grade III

Moderate SNHL

9 24 F Meningioma Enplaque Recurrent tumour MICA D' Transient Dysphagia Grade VI*

Petroclival V-XII cn paresis Transcervical2

Neck extension Dead ear

10 36 F Meningioma Enplaque VI cn paresis MICA D' Transient Trigeminal Grade VI§

Petroclival IX-XI cn paresis Far laterale neuralgia

Neck extension Good heanng

11 30 F Meningioma Petroclival Good hearing MICA A' None Grade IV^

transtentorial Awaited'

12 35 F Meningioma Petroclival good hearing MICA B' None Grade VI§

transtentorial Awaited'

13 59 F Meningioma Petroclival Moderate SNHL MICA A Planned subtotal Grade IV§

intracavemous IV cn cutVI cn paresis

14 57 M Chordoma Upper, mid Clivus Profound SNHL IIF-C' VI cn palsy Grade III

Cavernous sinus Ophthalmoptegia MICA Al

Transdural V3 cn hypoaesthesia

15 12 M Chordoma Upper, mid lower Mild CHL ITF-C' Death-? brain edema

clivus, Foramen X, XII cn palsy MICA A2

Magnum and CI-C2Transdural

16 65 M Chordoma Middle clivus VI cn paresis MICA A None Grade III

Transdu ral IncontinenceGood hearing

17 38 F Chordoma Mid clivus Good hearing MICA A Transient diploplia Grade V

Prepontinecistern &CP angle

18 33 M Chordoma Upper, mid Recurrent tumour MTCA C' None Grade VI*

lower clivus Ophthalmoplegia Awaited'

Cavernous sinus V-X cn palsy

Parapharyngeal Dead ear

Transdural

19 46 F Chordoma Middle clivus Recurrent tumour MICA A' None Grade VI'§

Prepontine VI, VII cn palsy Midline

cistern; CP suboccipital

angle; Inter and MFTPZ

cerebellar tonsiltransdural

20 63 F Chordoma Middle clivus Dead ear MICA B Subtotal Grade III

Cavernous sinusContd.

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Optic chiasma

21 20 M Chordoma Middle ck'us Good hearing MICA B VI cn cut Grade III§22 35 M NF2-Acoustic CP angle Recurrent tumour MICA A None Grade VI'

neuroma Prepontine VII cn palsycistern Dead ear

23 41 F NF2-Acoustic Cp angle Recurrent tumour MICA A None Grade VI'neuroma Prepontine VII cn palsy

cistern Dead ear

24 71 M Acoustic CP angle Recurrent tumour MICA A VI cn Palsy Grade VI'neuroma Prepontine VII cn palsy

cistern Dead ear

25 29 M Jugular CP angle XII cn palsy MICA D None Grade IIIforamen Lower, mid Dead earneuroma clivus

26 49 F Glomus CP angle VII cn paresis MICA A None Grade V'Jugulare & Mid, lower IX, X; XII cn palsyVagale clivus Dead ear

27 33 M Epidermoid Prepontine Diploplia MICA 8 1 IX, X cn paresis Grade VICyst cistern, CP Somnolence Awaited'

angle R hemiparesisTranstentorial Good hearing

HL = hearing loss; cn = cranial nerve, ITF = infratemporal fossa; MFTP = middle fossa transpetrous1 = first stage, 2 = second stage

= cases with preoperative facial nerve dysfunction; = cases with follow up less than one year# House Brackmann grading system (1985)

After understanding this system of the MTCA areas. Other specific indications for this ap-and its ability to address the lesions situated proach are large transdural tumours with ex-

in these previously inaccessible areas, it is in tensive clival, temporal bone and/or ICA in-

no way unclear that it is an extensive and time volvement. Recurrent cases, previously irradi-consuming skull base approach. We reserve the ated patients as well as the cases with vertebralMTCA to large extra and/or intradural lesions and/or basilar artery encasement can be dealt

of the petroclival area, prepontine cistern and very well by the system of MICA.anterior CPA withor without extension to adjacent The success of avoiding a CSF leak in our

Lig. 12A, Preoper tive MR? (coronal, TIW. gadolinium) of a left meningsoma en-plaque.

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patients is attributed to the blind sac closureof the EAC, removal of all cell tracts of thetemporal bone, obliteration of the eustachiantube, to the utilization of a single large pieceof fat to fill in the defect and lastly to avoidthe communication of the operative cavity withthe neck spaces. The most important reasonof not having a CSF leak is the single largepiece of tat which is plugged in the defect ina way that it's one end lies partially in theprepontine cistern /CP angle and the other larger

part in the cavity.The two obvious disadvantages of the MTCA

are the total loss of hearing and facial dysfunction.Twenty six patients had a grade VI facial nervefunction in the immediate postoperative periodwhile one had grade IV. However, at the endof one year 64% (9/14) had a grade III and 1patient had grade II facial nerve function. Asimilar observation has been reported by others(Thedinger et al., 1992). We correlate this fact

Fig. 12B. Postoperative CT scan after first stage MICA type C showing residual tumour involving lower clivus

TABLE—IllFacial nerve outcome as seen at one year

follow up in patients with normal preoperativefunction (N=14) #

Facial nerve function* Number Percentage

Grade 1 - 0%

Grade II 1 7.14%

Grade Ill 9 64.28%

Grade IV 2 14.28%

Grade V 1 7.14%

Grade VI 1 7.14%

# Cases with follow up less than one year andwith abnormal preoperative facial nerve functionare excluded* According to House-Brackmann grading system

to the inevitable sacrifice of blood supply to thegeniculate ganglion, intracisternal part and partiallyto the mastoid portion during the posterior reroutingof the facial nerve. The second unavoidablefeature of this approach is the sacrifice of hearing.Nevertheless, nearly 50% of our patients hadunserviceable hearing preoperatively. On weighingthese unavoidable demerits against the significantand wide exposure afforded by the MTCA, webelieve that it is a small price to pay when itcomes to complete removal of turnouts with satecontrol over vital neurovascular structures atthe skull base. Moreover, a very low incidenceof morbidity as regards lower cranial nerve damage,cerebellar/temporal lobe embarrasment and CSFleakage in our series, has encouraged us toimplement the system of the modified transcochlearapproach in increasing number of lesions affectingthe median skull base.

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The System of Modified Transcochlear Approaches for Intradural Skull Base Lesions—Sandeep Karmarkar er al.

CONCLUSIONS

The system of modified transcochlear approachoffers wide, direct and safe access to the entireclivus, anterior cerebellopontine angle andprepontine cistern with no cerebellar and/or brainstem retraction. The basic approach can be

extended superiorly, inferiorly and anteriorly toenable total tumour removal. This system ofMTCA afforded excellent control over all themajor neurovascular structures of the medianskull base. Inevitable hearing loss and resultingfacial paresis are main drawbacks of this approach.

Fig. 12C. Postoperative CT scan after second stage far lateral approch with total tumour exclsron

REFERENCES

1. Al-Mefty, 0., Fox, J.L., Smith, R.R. (1988) : Petrosal approach for petroclival meningiomas.Neurosurgery 22:510-517.

2. Canalis, R.F., Black, K., Martin, N. et al. (1991) : Extended retrolabyrinthine transtentorial approachto petroclival lesions. Laryngoscope 101:6-13.

3. Daspit, C.P., Spetzler, R.F., Pappas, , C.T.E. (1991) : Combined approach for lesions involving thecerebellopontine angle and skull base : Experience with 20 cases—Preliminary report.Otolaryngology-Head & Neck Surgery 105:788-796.

4. Fisch, U. (1978) : Infratemporal fossa approach to tumours of the temporal bone and baseof the skull. The Journal of Larynogology and Otology 92 : 949-967.

5. Hakuba, A., Nishimura, S., Tanaka, K et al. (1977) : Clivus meningioma : six cases of total removal.Neurologica Medica Chirurgica (Tokyo) 17:63-77.

6. Hitselberger, W.E., Horn, K.L., Hankirtfon, H.L et al. (1993) : The middle fossa transpetrous ap-proach for petroclival meningiomas. Skull Base Surgery 3:130-135.

7. Horn, K.L., Hankinson, N.L., Erasmus, M.D. et al. (1991) : The modified transcochlear approach tothe cerebello-pontine angle. Otolaryngology-Head & Neck Surgery 104 : 37-41.

8. House, J.W., Brackmann, D.E. (1985) : Facial nerve grading system Otolaryngology-Head & NeckSurgery 93:146-147.

9. House, W.F., Hitselberger, W.E., Horn, K.L. (1986) : The middle fossa transpetrous approach to theanterior superior cerebellopontine angle. American Journal of Otology 7 : 1-4.

IJO & HNSNOL.47 NO.4,Oct -Dec, 1995 zbc

The system of modidied transcochlear Approaches for Intradural Skull Base Lesions—Sandeep Karmakar at al

10. House, W.F., Hitselberger, W.E. (1976) : The transcochlear approach to the skull base. Archivesof Otolaryngology 102 : 334-342.

11. Jenkins, H.A., Fisch, U. (1980) : The transotic approach to resection of difficult acoustic tumoursof the cerebellopontine angle. American Journal of Otology 2:70-76.

12. Mazzoni, A., Sanna, M. (1992) : The petro-occipital trans-sigmoid approach to the postero-lateralskull base. Presented at third annual meeting of the North American Skull Base Society. Acapulco,Mexico. February 15-20. Abstract Skull Base Surgery 2:47.

13. Naguib, M.B., Saleh, E., Cokkeser, Y et al. (1994): The enlarged translabyrinthine approach forremoval of large vestibular schwannomas. The Journal of Laryngology and Otogogy 108:545-550.

14. Saleh, E., Aristegui, M., Taibah, A. et al. (1994) : Management of high jugular bulb in thetranslabyrinthine approach. Otolaryngology-Head & Neck Surgery (in press).

15. Saleh, E.A., Taibah, A.K., Achilli, V et al. (1994) : Posterior fossa meningioma : Surgical strategy.Skull Base Surgery (in press).

16. Samii, M., Ammirati, M. (1988) : The combined supra-infra tentorial pre-sigmoid sinus avenue to thepetroclival region. Surgical technique and clinical applications. Acta Neurochirurgica 95: 6-12.

17. Sanna, M., Saleh, E., Russo, A., Taibah, A. (in press) : Atlas of Temporal bone and Skull basesurgery, Stuttgart, New York, Georg Thieme Verlag.

18. Sanna, M., Mazzoni, A., Landolfi, M et al. (1994) : Tratamiento del colesteatoma intrapetroso (CIP).Acta Otorrinolaringologica Espanola 3:201-213.

19. Sanna, M., Mazzoni, A., Saleh, E., Taibah, A., Russo, A. (1994) : Lateral approaches to the medianskull base through the temporal bone : The System of the modified transcochlear approach. TheJournal of Laryngology and Otology 108:1035-1043.

20. Sanna, M., Mazzoni, A., Shaan, M. (1993) : Surgical strategy and complications in skull basechordomas. Presented at fourth annual meeting of the North American Skull Base Society.Scottsdale, Arizona. February 12-14. Abstract Skull Base Surgery 3:11.

21. Sanna, M., Zini, C., Gamoletti, R et al. (1993) : Petrous bone cholesteatoma. Skull Base Surgery3: 201-213.

22. Sekhar, L, Estonillo, R. (1986) : Transtemporal approach to the skull base : An anatomical study.Neurosurgery 19:799-808.

23. Thedinger, B.A., Glasscock, M.E., Cueva, R.A. (1992) : Transcochlear transtentorial approach forremoval of large cerebellopontine angel meningiomas. American Journal of Otology 13:408-415.

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