The jugular foramen (JF) lesions, once thought to be one of the most difficult surgically unapproachable ones, are now becoming safely manageable with reasonable morbidity and mortality rates.  This recent achievement has been accomplished by the extraordinary efforts put forth in the understanding of the microsurgical techniques and instrumentations and by the most exciting and promising innovations in cranial base surgery.  Added to this revolutionary neuro-surgical armamentarium, the parallel advances in the field of neuroradiology,  neuroanesthesiology, neuroelectrophysiology and neuro-intensive care, in fact, paved the way for the successful management of these lesions as seen today.  But the highly complex nature of the jugular foramen and even more perplexing morphological organization of its surrounding neurovascular structures coupled with the plethora of pathological conditions encountered in this region still pose a major challenge to the neurosurgeon.  From the pre-microsurgical era to the microsurgical era various safe approaches have been established.  A proper patient selection, a thorough pre-operative work-up, choosing the ideal surgical approach, and the interdisciplinary team work involving neurosurgeon, otologist, neuroradiologist and plastic surgeon, has made the now preferred single stage procedure feasible in dealing with these bewildering lesions.

 In this article, we review the salient anatomical, pathological radiological and clinical features of JF lesions and indications, these discuss the techniques, merits, demerits and the complications of the major approaches to the JF based on our experience of 9 cases. 

ANATOMICAL CONSIDERATIONS:

Since the neural, arterial, venous, muscular and osseous relationships are exhaustive, only the salient features related to jugular foramen and mentioned here.  The jugular foramen is located at the posterolateral skull base with its long axis obliquely directed from posterolateral to anteromedial direction and is formed by the petrous temporal bone anterolaterally and by the jugular process of condylar part of the occipital bone postermedially.  It is configured around the sigmoid sinus and the inferior petrosal sinus. The junction where the transverse sinus continues as the sigmoid sinus is indicated externally by the asterion at which point the vein of Labbe enters the sinuses. 

The right foramen is larger than the left in 68%, equal in 12% and smaller than the left in 20%, possibly due to the difference in the size of the sigmoid sinus and the jugular bulb.  On the intracranial side the jugular foramen is related inferior to the porus acoustics and superolateral to the intracranial orifice of the hypoglossal canal.  On the extracranial side it is Iocated just behind the carotid cannal separated by the carotid ridge, lateral to anterior half of the occipital condyle, antermedial to the stylomastoid foramen and posteromedial to the styloid process.

The jugular foramen is traditionally divided into a large posterolateral compartment (pars venosa) and a smaller anteromedial compartment (pars nervosa).  This view has been recently challenged by Katsura et al who has divided the jugular foramen into three compartments : two venous compartments and one neural intrajugular compartment in between.  The venous compartments include a large posterolateral sigmoid part and a small anteromedial petrosal part.  At the junction of these two compartments there are two bony prominences (intrajugular processes) arising from the temporal and occipital bones joined by a fibrous or less commonly osseous bridge forming the intrajugular septum.

The dura over the intrajugular septum has two characteristic performations : the glosso-pharyngeal meatus for IX nerve and larger vagal meatus for X and XI nerves.  Both of the meati are located on the medial side of the intrajugular processes and septum, being consistently separted by a dural septum.  Over the upper and lateral margin of the intrajugular part of the jugular foramen the dura is thickened forming a roof or lip that projects inferiorly and medially to partially cover the IX and X nerves meati.  This thick dural fold is called plica occipitals oblique or jugular dural fold.  The lip projects most prominently over the IX nerve meatus whereas the lip over the X nerve is less prominent.

The inferior petrosal sinus (IPS) joins the jugular bulb in 90%, passing between IX nerve superolaterally and X and XI nerves inferomedially.  In 10% it drains directly into the internal jugular vein.  The occipital condyle (OC) contains condylar emissary vein in 70% of cases.  This posterior condylar vein enters the jugular foramen at its posteromedial part and serves as a landmark to the foramen for the posterior approaches.  The hypoglossal canal contains a venous plexus, called anterior condylar vein in addition to XII nerve.  The IX nerve enters the jugular foramen just below the cochlear aqueduct piercing the dura at the pyramid fossa, expands at the site of the superior and inferior ganglia and courses forwards along the medial side of the intrajugular ridge before turning downward.  The X nerve enters jugular foramen below the IX nerve.  Its superior ganglion is located at the level of dural roof of the JF and the inferior ganglion is located below the JF at the level of atlanto-occipital (AO) joint.  The X nerve after piercing the dura quickly turns downwards without having the forward course within the JF.  The XI nerve bundle blends into lower margin of X nerve at the level of JF.

The relationships between lower cranial nerves (LX-XII) and the major vessels (internal) carotid artery (ICA), internal jugular vein (IJV), external carotid artery (ECA) and branches of vertebral artery (VA) are extremely complex at the level of JF and in the upper neck.  At the level of the skull base the IJV courses just posterior to the ICA being separated by the carotid ridge.  At this level both the artery and the vein are surrounded by a thick fibrous attachment of the carotid sheath to the periosteum of the skull base.  The styloid process with the muscles attached to it separates the ECA laterally from ICA medially.  The IX, X, XI and XII nerves at the exit from their respective foramina, first lie medially to both the ICA and the IJV with IX being most lateral and XII most medial; then IX, XI and XII nerves pass laterally between ICA and IJV; later the IX and XII descend forward along the lateral surface of ICA while XI descends backward along the lateral surface of IJV.  The posterior branches of ECA (occipital and ascending pharyngeal) supply the meninges around the Jf and are the main feeding arteries of the JF lesions.  The vertebral branches that are encountered near the JF region include the meningeal and posterior spinal arteries and posterior inferior cerebellar artery (PICA) having close relationship with IJV, which lies just anterior to the transverse process of the atlas. 

PATHOLOGY:

The jugular foramen lesions are rare in clinical practice.  Owing to the presence of osseous, muscular, neural, vascular, dura and connective issue elements in the jugular foramen region lesions arising from these elements are encountered in this region, some are more common then others.  They are broadly classified into intrinsic and extrinsic or neoplastic and nonneoplastic.  Table I lists the lesions involving the jugular foramen region.  Since the choice of the surgical approaches is dependent on the site of the origin, size and extent of the lesion, attempts were made to classify these lesions into various types or classes, for example Fisch’s and Glasscock and Jacobson’s classification for glomus jugular tumours and Keye’s and Franklin’s classification for schwannoma. 

The one proposed by Bertalanffy and Ulrich Sure is applicable to any type of lesion, which is as follows : 

Type  I           -  Small lesions confined to jugular foramen 

Type II           -  Intrinsic lesions of lower brainstem located in the vicinity of the jugular foramen 

Type III          -  Lesions of jugular foramen with predominant intradural extension located above the level of foramen magnum

Type IV          -  Lesions of Jugular foramen with intradural extension beyond the level of foramen magnum into the spinal canal.

Type V           -  Lesions of Jugular foramen with intra and extradural extension into the petrous bone. 

Type VI          -  Lesions of Jugular foramen with predominant extradural extension.

Neoplastic: Paraganglioma ,Schwannoma, Meningioma & Metastisis (hematogenous, nasopharyngeal ca) are the common ones.    

Exophytic brainstem glioma,  Choroid plexus papilloma,  Hemangioblastoma, Hemangiopericytoma, Chordoma, Chondroma, Chondroblastoma, Chondrosarcoma, Chondromyxoid fibroma, Osteoblastoma, Plastacytoma, cavernoma, Rhabdomyosarcoma, Ca of tympanic cavity and neuroeneteric cyst are  uncommon.    

Non neoplastic: Internal jugular vein thrombosis, Large jugular bulb pseudomass(included because of radiological importance) are the common non-neoplastic jugular foramen lesions.

Aneurysm,Osteomyelitis, Malignant external otitis,Cholesterol granuloma, and Amyloidoma are uncommon.                            

 CLINICAL MANIFESTATIONS:

The clinical presentation of jugular foramen lesions is dependent on size, extent and pathology of the tumour.  Typically they produce the jugular foramen syndrome (Vernet’s syndrome) and depending on their extension produce other related syndrome (Table 2).  The patients with IX, X and XI cranial nerves dysfunction may present with dysphagia, dysarthria, hoarseness of voice, dystphonia, nasal regurgitation, ipsilateral trapezius and sternomastoid muscle weakness and atrophy, depressed gag reflex, palatal droop on affected side with ipsilateral vocal cord paralysis and loss of taste on the posterior 1/3^rd of the tongue, paresis of soft palate, uvula, pharynx and larynx.  Some patients may present with neuralgic pain in IX and X nerves distribution.  Because of slow expansile growth of these lesions, the lower cranial nerves dysfunction is of gradual onset and in most patients, they are well tolerated as a result of gradual compensation.  As a result, though imaging studies reveal extensive involvement of these neural structures, patients may have only subtle manifestation of their dysfunction.  Even though a positive correlation exists between cranial nerve palsy and tumour invasion, lack of preoperative nerves dysfunction does not correlate with degree of nerve invasion found at the time of surgery (15).  The anterior extension encasing cavernous sinus and internal carotide artery may produce Horner’s syndrome and III, IV, V and VI nerves palsy.  Intracranial extension can produce posterior fossa symptoms as nystagmus, ataxia, hemiparesis and increased intracranial tension (16).  The extracranial extension along the internal jugular vein can produce a visible mass in the oropharynx or a palpable mass in the neck.  The intraluminal growth can block venous drainage and occlude the sigmoid sinus and if present bilaterally, increased intracranial tension can occur.  The intracranial extension superiorly can produce the cerebollopontine angle syndrome (deafness, tinnitus, VII nerve palsy) and those extending still laterally can produce bloody otorrhoea, a visible mass through tympanic membrane and a bruit over the mastoid. 

THE JUGULAR FORAMEN AND RELATED SYNDROMES:

 NEUROIMAGING:

The cornerstone in the successful management of the jugular foramen lesions is the preperative high quality and multimodiality neuroimaging.  Advances in this field have led the surgeon to select the most appropriate surgical approach and technique, to anticipate the possible complications and to prevent or manage them.  CT, MRI and Angiography of brain must be done in all cases to get the maximum information preoperatively.

The plain and contrast CT scan of the brain with 1.5mm cuts, bone window algorithm and coronal cuts help to reveal the normal bony variation and the pathological bony involvement, at the site of jugular foramen and extension into the nearby osseous structures and also the type of involvement, either expansile (compressive) or invasive (destructive) enlargement.  The presence of obstructive hydrocephalus is also visualized.  If spiral CT scan is available, this, with a bolus of contrast medium will give additional information  like three dimensional visualization of the skull base and the relationship between the lesions, vessels and skull base.

MRI brain images are extremely useful in delineating the exact location, origin, size, limits, margins, vascularity and extent of the lesions, degree of involvement of the important neurovascular structures and also to some extent the pathological diagnosis.  For the latter purpose, a dynamic, high dose Gd-study with creation of time intensity curves is found to be particularly useful.  With this technique glomus jugulare tumors can be differentiated from schwannoma, meningioma and metastases.  MRI venography is highly predictive in differentiating pseudomas (large and high lying jugular bulb) from the pathological lesions.  Octerotide scintigraphy, if available, is helpful in the diagnosis of multifocal paragangliomas since these tumor above 1.5cm size take up the radiosotope.

Lt.Glomus tumor-MRI axial	Lt.Glomus tumor-MRI coronal	Lt.Glomus tumor-MRI sagital	Lt.Glomus tumor-angio

Finally the bilateral cerebral angiography with cross-compression or balloon occlusion test will demonstrate enlarged feeding arteries, degree of vascularity, dominance and pathology of sigmoid sinus, jugular bulb and internal carotid artery.  If the tumor is highly vascular, then a preoperative super-selective endovascular embolization can also be undertaken to assist in safe surgical removal. 

SURGICAL APPROACHES:

Since the first reported exploration of the jugular bulb for a completely intraluminal mass by Sieffert in 1934, many surgical approaches, their modifications and combinations have been developed and utilized by neurosurgeons and otologists to deal with the jugular foramen lesions.  Historically a sequence in developing these approaches with the aim to improve surgical management can be distinguished, for example, realizing the need for VII nerve mobilzation, packing of sigmoid sinus, ligation of major vessels, resection of the skull base and so on.  As a result, numerous approaches are now available, which vary in skin incision, soft tissue dissection and bone removal, having specific indications depending upon the site, size, extend and vascularity of the tumor, involvement of the surrounding neural (cranial nerves, brainstem and cerebellum), vascular (internal carotid artery, vertebral artery, sigmoid sinus, jugular bulb, internal jugular vein and cavernous sinuses) and osseous (petrous, clivus, condylar part of occipital bone) structures and finally upon the patient’s clinical condition (hearing).  The choice of the most appropriate surgical approach to a particular lesion in a particular patient has to be individualized and is dictated by the morphology of the lesion and the surgeon’s experience and preference.

The surgical approaches used for JF lesions, although not always directed primarily to the jugular foramen, include the suboccipital retrosigmoid, presigmoid and transsigmoid, retrolabyrinthine and translabyrithine, transcochlear and subcochlear, trans-supra and juxtacondylar, far lateral suboccipital, lateral skull base, infratemporal fossa and middle cranial fossa approaches. 

These approaches can be broadly grouped into posterior, lateral, anterior, superior and inferior approaches and further subdivided into limited, extended and combined approaches.  In general the limited approaches are useful for small lesions and extended and combined approaches for the larger lesions.

Major groups: 

THE LATERAL APPROACHES:

These are the most commonly used access routes for the jugular foramen lesions having large extracranial extensions.  These involve basically a mastoidectomy and more often, anterior re-routing of the VII nerve to drill the bone inferior to the labyrinth to acess to JF.  The exposure can be widened anteriorly, by sacrificing the external auditory canal and midline ear structures or medially by drilling away the otic capsule (translabyrinthine) or cochlea (transcochlear).  When combined with the upper neck dissection it provides a satisfactory exposure of JF, mastoid air cells, tympanic cavity and extracranial structures.  The removal of styloid process with transposition of VII nerve facilitates wide opening of extracranial orifice or JF and provides access to lower part of petrous portion of ICA.  Still wider exposure of extracranial tumour is achieved by removing the transverse process of atlas or dislocating or resecting the mandibular condyle.  However, these approaches cannot be used for the removal of large intradural extensions which require combination of the posterior approaches.

The classification of Lateral approaches: Juxtacondylar  and   lateral skull base approaches.

Lateral skull base approaches may further be grouped into

                    -Approaches sacrificing otic capsule (translabyrinthine and transcochlear)

        -Approaches conserving otic  Capsule (extra-labyrinthine)    

                         a) Passing above otic capsule (supralabyrinthine)                                                                                                 1) middle cranial fossa                                                                                         2) extended middle cranial fossa                                                                                     3) middle fossa transpetrous                                                                                       b) Passing behind the otic capsule (retrolabyrinthine)                                                                                     1) Retrosigmoid                                                                                      2) Retrolabyrinthine                                                                                     3) Retrolabyrinthine transtentorial

                                                           C) Passing anterior to otic capsule (prelabyrinthine)

                                                                         1) Infratemporal fossa type B & C (Fisch’)                                                                                      2) Preauricular subtemporal – infratemporal

                                                           d) Passing inferior to otic capsule (infralabyrinthine)

                                                                         1) Approaches to jugular foramen

                                                                              – infra temporal fossa type A & petro-occiptal transsigmoid (POTS)

                                                                          2) extreme lateral approach

 THE POSTERIOR APPROACHES:           

These are the most suitable approaches for the predominantly intradural lesions and for the Jesions extending down to foramen magnum and medially to lower and midclivus.  The retro-sigmoid approach provides access to the cere-bellopontine angle and the intracranial orifice of JF.  Its transcondylar modification and the far lateral approach access the foramen magnum and lower clival regions by opening the posterolateral quadrant of foramen magnum and by drilling away the posterior part of occipital condyle.  The posterior and posterolateral margin of the JF is approached by removing the part of jugular process of the occipital bone behind the JF and the portion of the mastoid just behind the mastoid segment of VII nerve and the stylomastoid foramen.  This provides an upward view from below but to get a flatter view toward the midclivus, an additional drilling of jugular tubercle is required.

THE ANTERIOR APPROACHES:

These use the pathway anterior to the external auditory canal and through the tympanic bone, exposed by removal or displacement of the glenoid fossa and temporomandibular joint.  The subtemporal-infratemporal fossa approach alone can access anterior part of JF after reflecting the petrous portion of ICA anteirorly.  Further drilling exposes the midline and upper clivus anteriorly.  However, more commonly this approach has to be combined with lateral approaches to access the anterior extension of the pathology.  These combined procedures are designated by Fisch as infratemporal fossa type B and C approaches.

Since reviewing all the approaches is impossible in this article only the approaches used in our series are described here. 

SUBOCCIPITAL RETROSIGMOID APPROACH:

This is a limited and posterior approach pioneered by Sir Charles Balance in 1894 and refined by Cushing and Dandy in 1920, and is frequently, one component of the more extensive exposures.  The main indications are type A schwannomas of lower cranial nerves, epidermoid cyst and acoustic neuroma extending down into jugular foramen.

This is an important standard neurosurgical approach to posterior fossa and hence does not need elaboration.  The retroauricular skin incision exposes suboccipital region including the asterion and medial portion of the mastoid process and reaches but does not extend inferiorly to the supracondylar fossa.  Usually the lateral rim of foramen magnum is life in place.  The mastoid air cells are usually opened, taking care of the emissary veins draining into the sigmoid sinus.  The intracranial part of jugular foramen is exposed by dissecting the arachnoid around IX, X, XI nerves.

It is technically simply, familiar and associated with few complications and can be easily combined with other skull base procedures to gain further exposure.  But, it has limited applicability in that, only intradural portion of the tumor could be removed and does not allow removal of either intrajugular pathology or extracranial extensions.

SUBOCCIPITAL TRANSCONDYLAR APPROACH:

Termed by Seeger (1978) and refined by Gilsbach (1987) and by Bertalanffy et al, this approach is an extended modification of the retrosigmoid approach providing more extended lateral and inferior exposure than the latter.  This is not synonymous to the far lateral approach for the foramen magnum (FM) lesions, which requires the resection of only the medial 1/3^rd of the occipital condyle.  The indications are intrinsic lesions of the lower brainstem upto pontomedullary junction, tumors located anterior or anterolaterally to the lower brainstem, extradural pathology from lower clivus, occipital condyle, anterolateral rim of foramen magnum and jugular process of occipital bone and aneurysm of vertebrobasilar complex.

Technique : Initial procedure is like that of the standard suboccipital retrosigmoid approach.  In addition to suboccipital craniotomy the bone resection extends to include posterior and medial portion of the occipital condyle and part of the jugular process superior to the condyle to expose hypoglossal canal and the jugular foramen from dorsally and inferiorly.  The distal extradural vertebral artery is exposed upto the point where it pierces the atlanto-occipital membrane and dura.  While making the dural incision it is desirable to leave a cuff around the vertebral artery, which aids in the watertight dural closure at the end of the procedure to prevent postoperative CSF leak.  The posterior emissary vein when present is a useful landmark in the identification of the jugular foramen.

It provides a straight line view to anterior rim of foramen magnum and lower clivus, an excellent exposure of lower brainstem without the necessity of retracting brainstem or overstretching of lower cranial nerves with an excellent control of vertebral artery in its extradural and intradural course.  It can be extended laterally to expose JF lesions either from intradural or from extradural approach.  The ligation and division of the sigmoid sinus to expose the intradural portion is done according to the surgeon’s preference.

There is a potential risk of injury to vertebral artery (VA), lower cranial nerves and a risk of craniocervical instability, if the atlanto-occipital joint is opened.  For the predominant extradural growth with a lateral extension into the JF, Sen and Sekhar used this approach from a lateral direction by combining lateral exposure of foramen magnum with a partial mastoidectomy.  Though useful for the above indication, the mastoidectomy and extensive OC resection is not necessary for the predominant intradural growth. 

SUPRACONDYLAR APPROACH:

Described by Gilsbach et al, this is a limited variation of the transcondylar approach and is indicated for small lesions confined to hypoglossal canal and to the medial rim of jugular foramen.

Technique : Initial procedure is like that of the standard suboccipital approach.  Then the suboccipital craniotomy is extended down to supracondylar fossa while preserving the foramen magnum and occipital condyles.  The jugular tubercle is drilled away extradurally, exposing the medial aspect of jugular foramen laterally and hypoglossal canal inferiorly.  The advantage of this approach is the low morbidity and the disadvantage is that the radical excision is not possible and is adequate only for biopsy and for small intradural lesions confined to the hypoglossal canal.

JUXTACONDYLAR APPROACH:

Developed by Geroge et al, it is an important limited and lateral approach and one of the primarily targeted approaches to the JF.  The prime indication is the extradural tumors confined to the jugular foramen like lower cranial nerve schwannoma, meningioma etc.

Technique : The skin incision starts from superior nuchal line behind the mastoid, extends along the medial border of the sternomastoid muscle to 6cm below the mastoid tip.  The IJV and XI nerves are exposed after resecting the muscles attached to the mastoid.  The transverse process of atlas is freed of it muscles attachment and VA above and below the transverse foramen is exposed.  The transverse process of atlas is removed and VA can be transpositioned, if necessary.  The posterolateral aspects of the atlantooccipital and atlanto-axial joints are exposed.  The posterior belly of diagstric muscle is resected and occipital artery is ligated.  External and internal carotid arteries are exposed only if necessary.  Then a partial mastoidectomy is done, which is continued medially to expose the distal SS.  The remaining posteroinferior wall of the jugular bulb is drilled away which opens the jugular foramen posteriorly and inferiorly.  The exposure of VII nerve at its exit at stylomastoid foramen and at its petrosal segment and the dural opening is done only if necessary, in cases of large tumors.

 provides a wide exposure of  posterolateral aspect of the jugular foramen with out the extensive petrous bone drilling and hence preserves hearing and VII nerve functions.  There is no risk of CSF leak because dura is usually not opened.  It can be combined with supracondylar exposure, which is mainly indicated for intradural pathology or with infratemporal fossa approach Type A.

But this is a limited exposure of JF with the potential risk of venous bleeding around the VA within the foramen transversorium of atlas.

Samii and Bini advocated a combined lateral suboccipital-infralabyrinthine approach Hirsch, Sekhar and Kamerer proposed a transtemporal and infratemporal approach for the benign tumors with both extra and intradural extensions with an excellent control of the vertebral artery.

Post operative CSF leak may need repair. Watertight closure with grafts, packing of the cavity with fat, and use of vascularized muscle flap are used to prevent CSF leak and its complications. Vascular, and  Cranial nerve injuries may be avoided by choosing the right approach, meticulous technique with attention to preoperative image studies, and intraoperative physiological monitoring. Preoperative embolization and radiotherapy will help.

Hydrocephalus, craniocervical instability, trismus and incorrect dental occlusion, and eustachian tube function  rarely occur.      

PETRO-OCCIPTAL TRANS-SIGMOID (POTS) APPROACH

It is one of the lateral infralabyrinthine skull base approaches primarily targeting the jugular foramen, described by Mann et al.

It is primarily indicated for jugular foramen, lesions especially, the lower cranial nerves schwannoma with intracranial extensions, meningioma of jugular bulb and some cases of glomus jugulare tumors with predominant posterior extension.  It is also indicated in small petroclival meningioma lying anterior to internal auditory canal (IAC) with preserved hearing.

Technique : A shaped skin incision 4cm posterior to postauricular sulcus with its lower limb extending inferiorly 2cm below the mastoid up is used.  An inferiorly based ‘U’ shaped musculoperiosteal flap is then raised extending from 1-2cm above the zygomatic arch superiorly to the level of mastoid tip inferiorly.  Anteriorly a strip of periosteum is left a few mm posterior to EAC to allow re-suturing of this flap during closure.  The sternomastoid muscle is retracted posteriorly.  The lateral process of atlas is identified and the IJV anterior to this is dissected free and ligated.  Following a complete mastoidectomy the mastoid portion of VII nerve and JB are identified and the bone over SS and JB and posterior fossa dura in front of SS are removed.  A 4 X 4 cm suboccipital craniotomy is performed limited anteriorly by SS and superiorly by TS.  The infralabyrinthine petrous bone is drilled away taking care not to injure the posterior semicircular cannal or VII nerve.  The occipital condyle is partially drilled upto hypoglossal canal.  The vertical segment of the JCA is exposed by drilling the inferior tympanic bone while preserving the EAC wall.  The proximal part of the SS is compressed extraluminally and SS is then opened and packed distally and proximally.  A horizontal dural incision is made starting posterior to SS, coursing anteriorly transversing the medial wall of the SS.  Then arachnoid is removed from neurovascular structures, exposing IV-XI nerves and the superior cerebellar artery, AICA and PICA.

The removal of lateral wall of JF and if necessary of its medial wall fully exposes the intracranial part of IX-XI nerves.  The dura over the drilled part of OC is excised exposing the hypoglossal canal.  When needed IX-XI nerves are retracted or sacrificed if invaded by the tumor.  If necessary, drilling is continued to ipsilateral lower clivus and to lower border of foramen magnum.  If control of vertical portion of ICA and of the infralabyrinthine compartment is needed, the mastoid segment of VII nerve is mobilized as far as the stylomastoid foramen.  Only if the tumor extends to hypotympanum, an extended posterior tympanotomy is performed and facial nerve is rerouted.  The retrosigmoid posterior fossa dura should be closed.  The resected cavity is filled with the abdominal fat graft and the wound is closed.

The advantages are that the middle ear and VII nerve functions are preserved and it can be combined with transtentorial approach for tumors with supratentorial extension or with translabyrinthine  approach for tumours involving IAC in absence of preperative serviceable hearing (and if hearing is preserved then the posterior and inferior wall of IAC is drilled away without sacrificing the labyrinth) or with extreme lateral approach for tumors extending downwards to involve CV junction ventral to the brainstem.

The disadvantages are that it only provides limited control of ICA (dorsal and lateral aspects) and hence extensive involvement of IAC is contraindication to POTS approach for which either modified transcochlear or infratemporal fossa type A approach is indicated.  Injury to the lower cranial nerves and CSF leak are the potential complications.  Also this is not useful in highly vascular and invasive glomus jugulare tumour for which infratemporal fossa type A approach is preferable. 

INFRATEMPORAL FOSSA APPROACH TYPE A:

Described by Ugo Fisch in 1970, it is one of the most important combined approaches to jugular foramen lesions, belonging to the lateral group of approaches.

Indications : The jugular foramen lesions especially the large glomus jugulare tumours, some lower cranial nerves neurinomas and meningiomas and the lesions of infralabyrinthine and apical portion of petrous temporal bone like cholestaetoma, chordoma of lower clivus and carcinomas invading this regions and extensive facial nerve neurinomas.

Technique : A postauricular skin incision extending superiorly to temporal region and inferiorly along the anterior border of sternomastoid muscle 5-6 cm below the mastoid tip with a preaauricular limb is used.  A small anteriorly based musculoperiosteal flap is raised and the cul-de-sac closure of the external auditory canal is done.  Through the neck dissection, the VII nerve as its exits at stylomastoid foramen is identified and its main trunk is traced into parotid gland till the proximal parts of temporal and zygomatic brances.  The lower cranial nerves the ECA, ICA and IJV are exposed in upper neck.  After dividing the sternomastoid muscle and the posterior belly of digastric muscle, the ECA is ligated distal to its lingual branch.  The skin of external auditory canal, tympanic membrane, malleus and incus are removed.  A radical mastoidecomy is done.  The VII nerve is freed from the fallopian canal from genigulate ganglion to stylomastoid  formamen and transposed anteriorly and fixed to the new bony canal drilled in the root of zygoma superior to Eustachian tube and to the tunnel created in parotid gland to lodge the nerve.  The hypotympanum is drilled completely to expose the vertical portion of ICA.  The ascending mandibular ramus is displaced anteriorly and the mandibular condyle is resected is case of large tumors.  The SS is either packed or doubly ligated and if necessary, its lateral wall is removed upto the level of jugular bulb and lateral wall of jugular bulb is opened taking care to pack the IPS and condlar emissary veins entry into it.  The IJV is doubly ligated and cut in the neck and elevated superiorly taking care not to injure the XI nerve.  In case of limited intradural extension of the tumor, the dura is opened with out injuring endolymphatic sac.

Advantage : It offers wide exposure anterior to JF and to infratemporal fossa upto petrous apex.

Disadvantage : Apart from hearing loss, facial paralysis and numbness and malocclusion, this is not suitable for large intracranial tumor extension and for the large tumors reaching the foramen lacerum or cavernous sinuses.  For this infratemporal fossa Type B or C (anterior approaches) has to be combined with this type A (lateral approach).

Modifications of this approach since the hearing could not be preserved in Type.  A Fisch’s infratemporal fossa approach for the patients with the JF tumor with preserved hearing, Pensak and Jackler in 1997 advocated an approach that preserves external auditory canal and middle ear structures and allows working anterior and posterior to descending segment of VII nerve which is not re-routed.  But this is possible only in tumors that do not erode the carotid genu.

Sekhar and Schramm advocated a combined lateral and posterior cranial base approach (preauricular subtemporal-infratemporal fossa) for large tumors, which differs from Fisch’s approach in that the VII nerve is not displaced from the temporal bone.

The type B infratemporal fossa approach is mainly designed for extradural petrous apex and midclival tumors, with preservation of the inner ear function.  It is used in associated with type A infratemporal fossa approach for the extensive glomus tumors involving petrous and the midclivus.   This involves the reflection of zygomatic arch inferiorly and division of middle meningeal artery and mandibular branch of V nerve.  This gives exposure upto foramen lacerum, petrous apex and clivus.

The type C approach involve an orbitozygomatic reflection, sectioning of some branches of the facial nerve in parotid area, resection of the pterygoid process and sectioning of V3 nerve.  This gives wider exposure to the carotid artery in cavernous sinus. 

MODIFIED TRANSCOCHLEAR APPROACH

One of the lateral skull base approaches described by Mario Sanna, provides better visualization of ventral brainstem and vertebrobasilar junction by removing the petrous apex and clivus and the excellent control of vertical and horizontal segments of ICA.  It is classified into Types A-D.  The Type A is the basic approach upon which other types are extended, but by itself, it provides only a limited access to tumors extending into jugular bulb and down to foramen magnum. It is indicated for extradural lesions involving petrous apex with VII nerve and inner ear compromise (eg. : petrous bone cholestaetoma, extensive VII nerve neurinoma, recurrent VIII nerve neurinoma), intradural recurrent VIII neurinomas, large petroclival meningiomas and for the transdural lesions invading the petrous bone, like residual glomus tumor, chordoma etc.

Type a modified transcochlear approach

Technique : A-C shaped postauricular skin incision is made.  The blind sac closure of external auditory canal, extended mastoidectomy, posterior re-routing of VII nerve after its complete mobilization from stylomastoid foramen up to geniculate ganglion and labyrinthectomy are done.  The greater petrosal nerve and vessels are sacrificed.  The internal auditory canal is not opened.  The fallopian canal, cochlear and anterior wall of IAC are drilled and the vertical segment of the internal carotid artery is exposed.  Then pertrous apex and anterior wall of EAC are drilled.  The mandibular condyle is anteriorly displaced.  The petrous apex is drilled upto midelius to get the full control of horizontal part of ICA.  The dura is incised in front of internal auditory canal taking care not to injure VII nerve.

Its disadvantages includes risk of injury to VI nerve while incising the dura of petrous apex and injury to VII nerve while its mobilization.

Type B modified transcochlear approach incorporate Fisch’s type B or C infratemporal fossa approach into type A modified transcochlear and is used for the lesions extending into the parapharyngeal space.
Type C modified transcochlear approach allows control of both infratentorial and supratentorial parts of tumor lying ventral to pons and midbrain and is indicated for the petroclival tumors with supratentorial extension.

Type D modified transcochlear approach incorporates either POTS or extreme lateral approach Type A modified transcochlear.  This is indicated in the mid and low clival lesions, petroclival meningiomas and extensive lower cranial nerve neurinomas.  If it is necessary to get excellent control of the caudal part of the medulla, the VII nerve may be transposed anteriorly.

POSTOPERATIVE COMPLICATIONS

Many of the complications are related to the size, vascularity and extent of the tumor choice of the surgical approach, skill of the surgeon and the preoperative condition of the patient.  Some complications )eg. Infarct) that are related to preoperative endovascular embolization can also occur in the post operative period.  The possible complications, their prevention and management are listed in Table-4.  In general, if there are no neurovascular deficits pre-operatively then meticulous care I to be taken in order to preserve their functions.  In preventing the postoperative CSF leak, which is the most frequent complication, a lumbar drain is preferred to intraventricular drain since the latter is fraught with the risk of intraventricular hemorrhage, which may prove fatal.  Excessive CSF drainage is also to be avoided to prevent the low intracranial pressure and subsequent subdural hemorrhage.  Special mention should be made on the cranial nerves dysfunction.  This is the most serious complication.  The size of the lesion is generally correlated with the dysfunction and their recovery.  In smaller lesions the postoperative morbidity is minimal and the chance for long term improvement is excellent.  There are reports of excellent long-term recovery in patients in whom the nerves were sectioned.  But more commonly the functional recovery is dependent on the nerve continuity after the surgery.  Another important point is that if lower cranial nerves dysfunction is already present preoperatively the patients will be usually compensated for this deficit and so an aggressive surgical strategy can be undertaken without producing any increase in their preoperative deficit.  In general the complications can be avoided by carefully scrutinizing, the preoperative images, selecting the most appropriate approach or its modification tailored according to the need and by giving enormous attention to the technical details.

SUMMARY OF OUR EXPERIENCE

In our series, the suboccopital retrosigmoid approach was used in two cases (NO. 1 and 2) of the large acoustic schwannomas extending intradurally into the jugular foramen and total excision was achieved.  For another large acoustic schwannomas (No.3) extending inferiorly to the jugular and hypoglossal canal, medially into the petrous bone, clivus, foramen lacerum and petrous apex and superiorly upto V nerve level, the modified transcochlear type A approach was used and total excision was done.  In one patient (No. 4) with medium sized dumbbell shaped vagal schwannoma with a posterior parapharyngeal space-extension, the combined supracondylar and transcondylar (extended retromastoid) approaches was used and total excision was done.  In case No. 5, the POTS approach was chosen because the large vagal schwannoma was extending into the parapharyngeal space, CP angle and eroding the jugular plate, occipital condyle and near total excision was achieved  For the totally extradural vagal schwannoma (Case No. 6) the juxitacondylar approach was performed and total excision was achieved.  For the small hypoglossal nerve schwannoma the supracondylar approach was found to be sufficient for the total removal (No. 9). For the large glomus jugulare tumors (No. 7 and 8) the infratemporal fossa type A approach was used and total excision was done, in one case preoperative embolization was used in another case the preoperative irradiation, to reduce vascularity of the tumor.  The details re given in Table 5. 

There was no mortality in our series and no postoperative CSF leak (we used fibrin glue and fat graft in selected cases).  There were two instances of new postoperative cranial nerve palsy.  Left VII nerve in case No. 7 and left X nerve in case No. 1.  The temporary deterioration of preoperative nerves dysfunction (VII, VIII, X, XI) was seen in almost all cases and most of them improved after two to three months.  There are no other significant complications occurred in our cases.   In all cases the postoperative CT and / or MRI were done for the follow up study and there was not recurrence or residual tumor seen. 

 DETAILS OF AUTHORS’ CASES

CONCLUSION

It is true that the outcome in patients with jugular foramen lesions has dramatically improved during the last two decades, owing to the sophisticated technical advances in imaging techniques and micro neurosurgical tools which, in turn, made the surgeon to get maximum information regarding the detailed morphology of the lesions and to achieve the principle of minimal invasive surgery, respectively.  Equally important is the surgeons’ ability in selecting the patient and tailoring the surgical approach based on the morphological and biological criteria of the lesions and on the preoperative clinical status of the patient, and more importantly in applying the good old principle of ‘to do no more harm’ to the patient and finally in showing an intense quest for gaining more knowledge and acquiring never surgical skills to aid in the patient’s management.  In spite of these achievements we still see some patients suffering from the disabling morbidity either due to the disease per se or to the postoperative sequealae.  Interestingly and also unfortunately, we have yet to get the benefit from the basic neurosciences research work (neurobiology,molecular genetics, cloning, neurochemistry etc.,) because of its slow pace of progression for the obvious ethical issues and technological inadequacy.  If it becomes available then we can think of successful neural grafting or microelectrode implantation for cochlea, pharyngeal and laryngeal muscle ‘pacing’ etc and ultimately of a 100% success rate in the management of the jugular foramen lesions. 

That day will come soon ! we hope!!